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tumbledemerald-legacy/agbcc/gcc/gcse.c
BRODY MORAN ab32b30591 import from github
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/* CYGNUS LOCAL entire file */
/* Global common subexpression elimination/Partial redundancy elimination
and global constant/copy propagation for GNU compiler.
Copyright (C) 1997, 1998, 1999 Free Software Foundation, Inc.
This file is part of GNU CC.
GNU CC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU CC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU CC; see the file COPYING. If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
/* TODO
- reordering of memory allocation and freeing to be more space efficient
- do rough calc of how many regs are needed in each block, and a rough
calc of how many regs are available in each class and use that to
throttle back the code in cases where RTX_COST is minimal.
- dead store elimination
- a store to the same address as a load does not kill the load if the
source of the store is also the destination of the load. Handling this
allows more load motion, particularly out of loops.
- ability to realloc sbitmap vectors would allow one initial computation
of reg_set_in_block with only subsequent additions, rather than
recomputing it for each pass
*/
/* References searched while implementing this.
Compilers Principles, Techniques and Tools
Aho, Sethi, Ullman
Addison-Wesley, 1988
Global Optimization by Suppression of Partial Redundancies
E. Morel, C. Renvoise
communications of the acm, Vol. 22, Num. 2, Feb. 1979
A Portable Machine-Independent Global Optimizer - Design and Measurements
Frederick Chow
Stanford Ph.D. thesis, Dec. 1983
A Fast Algorithm for Code Movement Optimization
D.M. Dhamdhere
SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
A Solution to a Problem with Morel and Renvoise's
Global Optimization by Suppression of Partial Redundancies
K-H Drechsler, M.P. Stadel
ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
Practical Adaptation of the Global Optimization
Algorithm of Morel and Renvoise
D.M. Dhamdhere
ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
Efficiently Computing Static Single Assignment Form and the Control
Dependence Graph
R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
Lazy Code Motion
J. Knoop, O. Ruthing, B. Steffen
ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
What's In a Region? Or Computing Control Dependence Regions in Near-Linear
Time for Reducible Flow Control
Thomas Ball
ACM Letters on Programming Languages and Systems,
Vol. 2, Num. 1-4, Mar-Dec 1993
An Efficient Representation for Sparse Sets
Preston Briggs, Linda Torczon
ACM Letters on Programming Languages and Systems,
Vol. 2, Num. 1-4, Mar-Dec 1993
A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
K-H Drechsler, M.P. Stadel
ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
Partial Dead Code Elimination
J. Knoop, O. Ruthing, B. Steffen
ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
Effective Partial Redundancy Elimination
P. Briggs, K.D. Cooper
ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
The Program Structure Tree: Computing Control Regions in Linear Time
R. Johnson, D. Pearson, K. Pingali
ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
Optimal Code Motion: Theory and Practice
J. Knoop, O. Ruthing, B. Steffen
ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
The power of assignment motion
J. Knoop, O. Ruthing, B. Steffen
ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
Global code motion / global value numbering
C. Click
ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
Value Driven Redundancy Elimination
L.T. Simpson
Rice University Ph.D. thesis, Apr. 1996
Value Numbering
L.T. Simpson
Massively Scalar Compiler Project, Rice University, Sep. 1996
High Performance Compilers for Parallel Computing
Michael Wolfe
Addison-Wesley, 1996
Advanced Compiler Design and Implementation
Steven Muchnick
Morgan Kaufmann, 1997
People wishing to speed up the code here should read:
Elimination Algorithms for Data Flow Analysis
B.G. Ryder, M.C. Paull
ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
How to Analyze Large Programs Efficiently and Informatively
D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
People wishing to do something different can find various possibilities
in the above papers and elsewhere.
*/
#include "config.h"
#include "system.h"
#include "rtl.h"
#include "regs.h"
#include "hard-reg-set.h"
#include "flags.h"
#include "real.h"
#include "insn-config.h"
#include "recog.h"
#include "basic-block.h"
#include "output.h"
#include "expr.h"
#include "obstack.h"
#define obstack_chunk_alloc gmalloc
#define obstack_chunk_free free
/* Maximum number of passes to perform. */
#define MAX_PASSES 1
/* Propagate flow information through back edges and thus enable PRE's
moving loop invariant calculations out of loops.
Originally this tended to create worse overall code, but several
improvements during the development of PRE seem to have made following
back edges generally a win.
Note much of the loop invariant code motion done here would normally
be done by loop.c, which has more heuristics for when to move invariants
out of loops. At some point we might need to move some of those
heuristics into gcse.c. */
#define FOLLOW_BACK_EDGES 1
/* We support GCSE via Partial Redundancy Elimination. PRE optimizations
are a superset of those done by GCSE.
We perform the following steps:
1) Compute basic block information.
2) Compute table of places where registers are set.
3) Perform copy/constant propagation.
4) Perform global cse.
5) Perform another pass of copy/constant propagation.
Two passes of copy/constant propagation are done because the first one
enables more GCSE and the second one helps to clean up the copies that
GCSE creates. This is needed more for PRE than for Classic because Classic
GCSE will try to use an existing register containing the common
subexpression rather than create a new one. This is harder to do for PRE
because of the code motion (which Classic GCSE doesn't do).
Expressions we are interested in GCSE-ing are of the form
(set (pseudo-reg) (expression)).
Function want_to_gcse_p says what these are.
PRE handles moving invariant expressions out of loops (by treating them as
partially redundant).
Eventually it would be nice to replace cse.c/gcse.c with SSA (static single
assignment) based GVN (global value numbering). L. T. Simpson's paper
(Rice University) on value numbering is a useful reference for this.
**********************
We used to support multiple passes but there are diminishing returns in
doing so. The first pass usually makes 90% of the changes that are doable.
A second pass can make a few more changes made possible by the first pass.
Experiments show any further passes don't make enough changes to justify
the expense.
A study of spec92 using an unlimited number of passes:
[1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
[6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
[12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
It was found doing copy propagation between each pass enables further
substitutions.
PRE is quite expensive in complicated functions because the DFA can take
awhile to converge. Hence we only perform one pass. Macro MAX_PASSES can
be modified if one wants to experiment.
**********************
The steps for PRE are:
1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
2) Perform the data flow analysis for PRE.
3) Delete the redundant instructions
4) Insert the required copies [if any] that make the partially
redundant instructions fully redundant.
5) For other reaching expressions, insert an instruction to copy the value
to a newly created pseudo that will reach the redundant instruction.
The deletion is done first so that when we do insertions we
know which pseudo reg to use.
Various papers have argued that PRE DFA is expensive (O(n^2)) and others
argue it is not. The number of iterations for the algorithm to converge
is typically 2-4 so I don't view it as that expensive (relatively speaking).
PRE GCSE depends heavily on the second CSE pass to clean up the copies
we create. To make an expression reach the place where it's redundant,
the result of the expression is copied to a new register, and the redundant
expression is deleted by replacing it with this new register. Classic GCSE
doesn't have this problem as much as it computes the reaching defs of
each register in each block and thus can try to use an existing register.
**********************
A fair bit of simplicity is created by creating small functions for simple
tasks, even when the function is only called in one place. This may
measurably slow things down [or may not] by creating more function call
overhead than is necessary. The source is laid out so that it's trivial
to make the affected functions inline so that one can measure what speed
up, if any, can be achieved, and maybe later when things settle things can
be rearranged.
Help stamp out big monolithic functions! */
/* GCSE global vars. */
/* -dG dump file. */
static FILE *gcse_file;
/* Note whether or not we should run jump optimization after gcse. We
want to do this for two cases.
* If we changed any jumps via cprop.
* If we added any labels via edge splitting. */
static int run_jump_opt_after_gcse;
/* Element I is a list of I's predecessors/successors. */
static int_list_ptr *s_preds;
static int_list_ptr *s_succs;
/* Element I is the number of predecessors/successors of basic block I. */
static int *num_preds;
static int *num_succs;
/* Bitmaps are normally not included in debugging dumps.
However it's useful to be able to print them from GDB.
We could create special functions for this, but it's simpler to
just allow passing stderr to the dump_foo fns. Since stderr can
be a macro, we store a copy here. */
static FILE *debug_stderr;
/* An obstack for our working variables. */
static struct obstack gcse_obstack;
/* Non-zero for each mode that supports (set (reg) (reg)).
This is trivially true for integer and floating point values.
It may or may not be true for condition codes. */
static char can_copy_p[(int) NUM_MACHINE_MODES];
/* Non-zero if can_copy_p has been initialized. */
static int can_copy_init_p;
/* Hash table of expressions. */
struct expr
{
/* The expression (SET_SRC for expressions, PATTERN for assignments). */
rtx expr;
/* Index in the available expression bitmaps. */
int bitmap_index;
/* Next entry with the same hash. */
struct expr *next_same_hash;
/* List of anticipatable occurrences in basic blocks in the function.
An "anticipatable occurrence" is one that is the first occurrence in the
basic block, the operands are not modified in the basic block prior
to the occurrence and the output is not used between the start of
the block and the occurrence. */
struct occr *antic_occr;
/* List of available occurrence in basic blocks in the function.
An "available occurrence" is one that is the last occurrence in the
basic block and the operands are not modified by following statements in
the basic block [including this insn]. */
struct occr *avail_occr;
/* Non-null if the computation is PRE redundant.
The value is the newly created pseudo-reg to record a copy of the
expression in all the places that reach the redundant copy. */
rtx reaching_reg;
};
/* Occurrence of an expression.
There is one per basic block. If a pattern appears more than once the
last appearance is used [or first for anticipatable expressions]. */
struct occr
{
/* Next occurrence of this expression. */
struct occr *next;
/* The insn that computes the expression. */
rtx insn;
/* Non-zero if this [anticipatable] occurrence has been deleted. */
char deleted_p;
/* Non-zero if this [available] occurrence has been copied to
reaching_reg. */
/* ??? This is mutually exclusive with deleted_p, so they could share
the same byte. */
char copied_p;
};
/* Expression and copy propagation hash tables.
Each hash table is an array of buckets.
??? It is known that if it were an array of entries, structure elements
`next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
not clear whether in the final analysis a sufficient amount of memory would
be saved as the size of the available expression bitmaps would be larger
[one could build a mapping table without holes afterwards though].
Someday I'll perform the computation and figure it out.
*/
/* Total size of the expression hash table, in elements. */
static int expr_hash_table_size;
/* The table itself.
This is an array of `expr_hash_table_size' elements. */
static struct expr **expr_hash_table;
/* Total size of the copy propagation hash table, in elements. */
static int set_hash_table_size;
/* The table itself.
This is an array of `set_hash_table_size' elements. */
static struct expr **set_hash_table;
/* Mapping of uids to cuids.
Only real insns get cuids. */
static int *uid_cuid;
/* Highest UID in UID_CUID. */
static int max_uid;
/* Get the cuid of an insn. */
#define INSN_CUID(INSN) (uid_cuid[INSN_UID (INSN)])
/* Number of cuids. */
static int max_cuid;
/* Mapping of cuids to insns. */
static rtx *cuid_insn;
/* Get insn from cuid. */
#define CUID_INSN(CUID) (cuid_insn[CUID])
/* Maximum register number in function prior to doing gcse + 1.
Registers created during this pass have regno >= max_gcse_regno.
This is named with "gcse" to not collide with global of same name. */
static int max_gcse_regno;
/* Maximum number of cse-able expressions found. */
static int n_exprs;
/* Maximum number of assignments for copy propagation found. */
static int n_sets;
/* Table of registers that are modified.
For each register, each element is a list of places where the pseudo-reg
is set.
For simplicity, GCSE is done on sets of pseudo-regs only. PRE GCSE only
requires knowledge of which blocks kill which regs [and thus could use
a bitmap instead of the lists `reg_set_table' uses].
`reg_set_table' and could be turned into an array of bitmaps
(num-bbs x num-regs)
[however perhaps it may be useful to keep the data as is].
One advantage of recording things this way is that `reg_set_table' is
fairly sparse with respect to pseudo regs but for hard regs could be
fairly dense [relatively speaking].
And recording sets of pseudo-regs in lists speeds
up functions like compute_transp since in the case of pseudo-regs we only
need to iterate over the number of times a pseudo-reg is set, not over the
number of basic blocks [clearly there is a bit of a slow down in the cases
where a pseudo is set more than once in a block, however it is believed
that the net effect is to speed things up]. This isn't done for hard-regs
because recording call-clobbered hard-regs in `reg_set_table' at each
function call can consume a fair bit of memory, and iterating over hard-regs
stored this way in compute_transp will be more expensive. */
typedef struct reg_set {
/* The next setting of this register. */
struct reg_set *next;
/* The insn where it was set. */
rtx insn;
} reg_set;
static reg_set **reg_set_table;
/* Size of `reg_set_table'.
The table starts out at max_gcse_regno + slop, and is enlarged as
necessary. */
static int reg_set_table_size;
/* Amount to grow `reg_set_table' by when it's full. */
#define REG_SET_TABLE_SLOP 100
/* Array, indexed by basic block number for a list of insns which modify
memory within that block. */
static rtx *modify_mem_list;
/* Bitmap containing one bit for each register in the program.
Used when performing GCSE to track which registers have been set since
the start of the basic block. */
static sbitmap reg_set_bitmap;
/* For each block, a bitmap of registers set in the block.
This is used by expr_killed_p and compute_transp.
It is computed during hash table computation and not by compute_sets
as it includes registers added since the last pass (or between cprop and
gcse) and it's currently not easy to realloc sbitmap vectors. */
static sbitmap *reg_set_in_block;
/* Various variables for statistics gathering. */
/* Memory used in a pass.
This isn't intended to be absolutely precise. Its intent is only
to keep an eye on memory usage. */
static int bytes_used;
/* GCSE substitutions made. */
static int gcse_subst_count;
/* Number of copy instructions created. */
static int gcse_create_count;
/* Number of constants propagated. */
static int const_prop_count;
/* Number of copys propagated. */
static int copy_prop_count;
extern char *current_function_name;
extern int current_function_calls_setjmp;
/* These variables are used by classic GCSE.
Normally they'd be defined a bit later, but `rd_gen' needs to
be declared sooner. */
/* A bitmap of all ones for implementing the algorithm for available
expressions and reaching definitions. */
/* ??? Available expression bitmaps have a different size than reaching
definition bitmaps. This should be the larger of the two, however, it
is not currently used for reaching definitions. */
static sbitmap u_bitmap;
/* Each block has a bitmap of each type.
The length of each blocks bitmap is:
max_cuid - for reaching definitions
n_exprs - for available expressions
Thus we view the bitmaps as 2 dimensional arrays. i.e.
rd_kill[block_num][cuid_num]
ae_kill[block_num][expr_num]
*/
/* For reaching defs */
static sbitmap *rd_kill, *rd_gen, *reaching_defs, *rd_out;
/* for available exprs */
static sbitmap *ae_kill, *ae_gen, *ae_in, *ae_out;
static void compute_can_copy (void);
static char *gmalloc (unsigned int);
static char *grealloc (char *, unsigned int);
static char *gcse_alloc (unsigned long);
static void alloc_gcse_mem (rtx);
static void free_gcse_mem (void);
static void alloc_reg_set_mem (int);
static void free_reg_set_mem (void);
static void record_one_set (int, rtx);
static void record_set_info (rtx, rtx);
static void compute_sets (rtx);
static void hash_scan_insn (rtx, int, int);
static void hash_scan_set (rtx, rtx, int);
static void hash_scan_clobber (rtx, rtx);
static void hash_scan_call (rtx, rtx);
static int want_to_gcse_p (rtx);
static int oprs_unchanged_p (rtx, rtx, int);
static int oprs_anticipatable_p (rtx, rtx);
static int oprs_available_p (rtx, rtx);
static void insert_expr_in_table (rtx, enum machine_mode,
rtx, int, int);
static void insert_set_in_table (rtx, rtx);
static unsigned int hash_expr (rtx, enum machine_mode,
int *, int);
static unsigned int hash_expr_1 (rtx, enum machine_mode, int *);
static unsigned int hash_set (int, int);
static int expr_equiv_p (rtx, rtx);
static void record_last_reg_set_info (rtx, int);
static void record_last_mem_set_info (rtx);
static void record_last_set_info (rtx, rtx);
static void compute_hash_table (int);
static void alloc_set_hash_table (int);
static void free_set_hash_table (void);
static void compute_set_hash_table (void);
static void alloc_expr_hash_table (int);
static void free_expr_hash_table (void);
static void compute_expr_hash_table (void);
static void dump_hash_table (FILE *, char *, struct expr **,
int, int);
static struct expr *lookup_set (int, rtx);
static struct expr *next_set (int, struct expr *);
static void reset_opr_set_tables (void);
static int oprs_not_set_p (rtx, rtx);
static void mark_call (rtx);
static void mark_set (rtx, rtx);
static void mark_clobber (rtx, rtx);
static void mark_oprs_set (rtx);
static void alloc_cprop_mem (int, int);
static void free_cprop_mem (void);
static void compute_transp (rtx, int, sbitmap *, int);
static void compute_transpout (void);
static void compute_local_properties (sbitmap *, sbitmap *,
sbitmap *, int);
static void compute_cprop_avinout (void);
static void compute_cprop_data (void);
static void find_used_regs (rtx);
static int try_replace_reg (rtx, rtx, rtx);
static struct expr *find_avail_set (int, rtx);
static int cprop_insn (rtx, int);
static int cprop (int);
static int one_cprop_pass (int, int);
static void alloc_pre_mem (int, int);
static void free_pre_mem (void);
static void compute_pre_data (void);
static int pre_expr_reaches_here_p (int, struct expr *,
int, int, char *);
static void insert_insn_end_bb (struct expr *, int, int);
static void pre_insert (struct expr **);
static void pre_insert_copy_insn (struct expr *, rtx);
static void pre_insert_copies (void);
static int pre_delete (void);
static int pre_gcse (void);
static int one_pre_gcse_pass (int);
static void alloc_code_hoist_mem (int, int);
static void free_code_hoist_mem (void);
static void compute_code_hoist_vbeinout (void);
static void compute_code_hoist_data (void);
static int hoist_expr_reaches_here_p (int, int, int, char *);
static void hoist_code (void);
static int one_code_hoisting_pass (void);
static void alloc_rd_mem (int, int);
static void free_rd_mem (void);
static void handle_rd_kill_set (rtx, int, int);
static void compute_kill_rd (void);
static void compute_rd (void);
static void alloc_avail_expr_mem (int, int);
static void free_avail_expr_mem (void);
static void compute_ae_gen (void);
static int expr_killed_p (rtx, int);
static void compute_ae_kill (void);
static void compute_available (void);
static int expr_reaches_here_p (struct occr *, struct expr *,
int, int, char *);
static rtx computing_insn (struct expr *, rtx);
static int def_reaches_here_p (rtx, rtx);
static int can_disregard_other_sets (struct reg_set**, rtx, int);
static int handle_avail_expr (rtx, struct expr *);
static int classic_gcse (void);
static int one_classic_gcse_pass (int);
static void mems_conflict_for_gcse_p (rtx, rtx);
static int load_killed_in_block_p (int, int, rtx, int);
/* Entry point for global common subexpression elimination.
F is the first instruction in the function. */
int
gcse_main (f, file)
rtx f;
FILE *file;
{
int changed, pass;
/* Bytes used at start of pass. */
int initial_bytes_used;
/* Maximum number of bytes used by a pass. */
int max_pass_bytes;
/* Point to release obstack data from for each pass. */
char *gcse_obstack_bottom;
/* We do not construct an accurate cfg in functions which call
setjmp, so just punt to be safe. */
if (current_function_calls_setjmp)
return 0;
/* Assume that we do not need to run jump optimizations after gcse. */
run_jump_opt_after_gcse = 0;
/* For calling dump_foo fns from gdb. */
debug_stderr = stderr;
gcse_file = file;
/* Identify the basic block information for this function, including
successors and predecessors. */
max_gcse_regno = max_reg_num ();
find_basic_blocks (f, max_gcse_regno, file);
/* Return if there's nothing to do. */
if (n_basic_blocks <= 1)
{
/* Free storage allocated by find_basic_blocks. */
free_basic_block_vars (0);
return 0;
}
/* See what modes support reg/reg copy operations. */
if (! can_copy_init_p)
{
compute_can_copy ();
can_copy_init_p = 1;
}
gcc_obstack_init (&gcse_obstack);
/* Allocate and compute predecessors/successors. */
s_preds = (int_list_ptr *) alloca (n_basic_blocks * sizeof (int_list_ptr));
s_succs = (int_list_ptr *) alloca (n_basic_blocks * sizeof (int_list_ptr));
num_preds = (int *) alloca (n_basic_blocks * sizeof (int));
num_succs = (int *) alloca (n_basic_blocks * sizeof (int));
bytes_used = 4 * n_basic_blocks * sizeof (int_list_ptr);
/* Compute the predecessors and successors for each basic block.
A nonzero return value indicates that edges were split and thus
basic block and preds/succs info must be recomputed. */
if (compute_preds_succs (s_preds, s_succs, num_preds, num_succs, 1) != 0)
{
/* Call find_basic_blocks to compute the new number of basic
blocks and new edge data. */
find_basic_blocks (f, max_gcse_regno, file);
/* This leaks memory until the end of this function. I don't see
a good way to fix this without introducing more complexity in
this code. */
s_preds
= (int_list_ptr *) alloca (n_basic_blocks* sizeof (int_list_ptr));
s_succs
= (int_list_ptr *) alloca (n_basic_blocks * sizeof (int_list_ptr));
num_preds = (int *) alloca (n_basic_blocks * sizeof (int));
num_succs = (int *) alloca (n_basic_blocks * sizeof (int));
bytes_used = 4 * n_basic_blocks * sizeof (int_list_ptr);
/* Now recompute predecessor and successor information. */
compute_preds_succs (s_preds, s_succs, num_preds, num_succs, 0);
/* We split some edges, which introduces labels; run jump optimization
after gcse so that any labels which were not used are deleted so as
not to pessimize loop optimizations. */
run_jump_opt_after_gcse = 1;
}
if (file)
dump_bb_data (file, s_preds, s_succs, 0);
/* We need alias analysis. */
init_alias_analysis ();
/* Record where pseudo-registers are set.
This data is kept accurate during each pass.
??? We could also record hard-reg information here
[since it's unchanging], however it is currently done during
hash table computation.
It may be tempting to compute MEM set information here too, but MEM
sets will be subject to code motion one day and thus we need to compute
information about memory sets when we build the hash tables. */
alloc_reg_set_mem (max_gcse_regno);
compute_sets (f);
pass = 0;
initial_bytes_used = bytes_used;
max_pass_bytes = 0;
gcse_obstack_bottom = gcse_alloc (1);
changed = 1;
while (changed && pass < MAX_PASSES)
{
changed = 0;
if (file)
fprintf (file, "GCSE pass %d\n\n", pass + 1);
/* Initialize bytes_used to the space for the pred/succ lists,
and the reg_set_table data. */
bytes_used = initial_bytes_used;
/* Each pass may create new registers, so recalculate each time. */
max_gcse_regno = max_reg_num ();
alloc_gcse_mem (f);
/* Don't allow constant propagation to modify jumps
during this pass. */
changed = one_cprop_pass (pass + 1, 0);
if (optimize_size)
changed |= one_classic_gcse_pass (pass + 1);
else
changed |= one_pre_gcse_pass (pass + 1);
if (max_pass_bytes < bytes_used)
max_pass_bytes = bytes_used;
/* Free up memory, then reallocate for code hoisting. We can
not re-use the existing allocated memory because the tables
will not have info for the insns or registers created by
partial redundancy elimination. */
free_gcse_mem ();
/* CYGNUS LOCAL hoisting/law */
/* It does not make sense to run code hoisting unless we optimizing
for code size -- it rarely makes programs faster, and can make
them bigger if we did partial redundancy elimination. */
if (optimize_size)
{
max_gcse_regno = max_reg_num ();
alloc_gcse_mem (f);
changed |= one_code_hoisting_pass ();
free_gcse_mem ();
if (max_pass_bytes < bytes_used)
max_pass_bytes = bytes_used;
}
/* END CYGNUS LOCAL */
if (file)
{
fprintf (file, "\n");
fflush (file);
}
obstack_free (&gcse_obstack, gcse_obstack_bottom);
pass++;
}
/* Do one last pass of copy propagation, including cprop into
conditional jumps. */
max_gcse_regno = max_reg_num ();
alloc_gcse_mem (f);
/* This time, go ahead and allow cprop to alter jumps. */
one_cprop_pass (pass + 1, 1);
free_gcse_mem ();
if (file)
{
fprintf (file, "GCSE of %s: %d basic blocks, ",
current_function_name, n_basic_blocks);
fprintf (file, "%d pass%s, %d bytes\n\n",
pass, pass > 1 ? "es" : "", max_pass_bytes);
}
/* Free our obstack. */
obstack_free (&gcse_obstack, NULL);
/* Free reg_set_table. */
free_reg_set_mem ();
/* Free storage used to record predecessor/successor data. */
free_bb_mem ();
/* Free storage allocated by find_basic_blocks. */
free_basic_block_vars (0);
/* We are finished with alias analysis. */
end_alias_analysis ();
/* Record where pseudo-registers are set. */
return run_jump_opt_after_gcse;
}
/* Misc. utilities. */
/* Compute which modes support reg/reg copy operations. */
static void
compute_can_copy ()
{
int i;
rtx reg,insn;
char *free_point = (char *) oballoc (1);
zero_memory (can_copy_p, NUM_MACHINE_MODES);
start_sequence ();
for (i = 0; i < NUM_MACHINE_MODES; i++)
{
switch (GET_MODE_CLASS (i))
{
case MODE_CC :
#ifdef AVOID_CCMODE_COPIES
can_copy_p[i] = 0;
#else
reg = gen_rtx (REG, (enum machine_mode) i, LAST_VIRTUAL_REGISTER + 1);
insn = emit_insn (gen_rtx (SET, VOIDmode, reg, reg));
if (recog (PATTERN (insn), insn, NULL) >= 0)
can_copy_p[i] = 1;
#endif
break;
default :
can_copy_p[i] = 1;
break;
}
}
end_sequence ();
/* Free the objects we just allocated. */
obfree (free_point);
}
/* Cover function to xmalloc to record bytes allocated. */
static char *
gmalloc (size)
unsigned int size;
{
bytes_used += size;
return xmalloc (size);
}
/* Cover function to xrealloc.
We don't record the additional size since we don't know it.
It won't affect memory usage stats much anyway. */
static char *
grealloc (ptr, size)
char *ptr;
unsigned int size;
{
return xrealloc (ptr, size);
}
/* Cover function to obstack_alloc.
We don't need to record the bytes allocated here since
obstack_chunk_alloc is set to gmalloc. */
static char *
gcse_alloc (size)
unsigned long size;
{
return (char *) obstack_alloc (&gcse_obstack, size);
}
/* Allocate memory for the cuid mapping array,
and reg/memory set tracking tables.
This is called at the start of each pass. */
static void
alloc_gcse_mem (f)
rtx f;
{
int i,n;
rtx insn;
/* Find the largest UID and create a mapping from UIDs to CUIDs.
CUIDs are like UIDs except they increase monotonically, have no gaps,
and only apply to real insns. */
max_uid = get_max_uid ();
n = (max_uid + 1) * sizeof (int);
uid_cuid = (int *) gmalloc (n);
zero_memory ((char *) uid_cuid, n);
for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
{
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
INSN_CUID (insn) = i++;
else
INSN_CUID (insn) = i;
}
/* Create a table mapping cuids to insns. */
max_cuid = i;
n = (max_cuid + 1) * sizeof (rtx);
cuid_insn = (rtx *) gmalloc (n);
zero_memory ((char *) cuid_insn, n);
for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
{
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
{
CUID_INSN (i) = insn;
i++;
}
}
/* Allocate vars to track sets of regs. */
reg_set_bitmap = (sbitmap) sbitmap_alloc (max_gcse_regno);
/* Allocate vars to track sets of regs, memory per block. */
reg_set_in_block = (sbitmap *) sbitmap_vector_alloc (n_basic_blocks,
max_gcse_regno);
/* Allocate array to keep a list of insns which modify memory in each
basic block. */
modify_mem_list = (rtx *) gmalloc (n_basic_blocks * sizeof (rtx *));
}
/* Free memory allocated by alloc_gcse_mem. */
static void
free_gcse_mem ()
{
free (uid_cuid);
free (cuid_insn);
free (reg_set_bitmap);
free (reg_set_in_block);
free (modify_mem_list);
}
/* Compute the local properties of each recorded expression.
Local properties are those that are defined by the block, irrespective
of other blocks.
An expression is transparent in a block if its operands are not modified
in the block.
An expression is computed (locally available) in a block if it is computed
at least once and expression would contain the same value if the
computation was moved to the end of the block.
An expression is locally anticipatable in a block if it is computed at
least once and expression would contain the same value if the computation
was moved to the beginning of the block.
We call this routine for cprop, pre and code hoisting. They all
compute basically the same information and thus can easily share
this code.
TRANSP, COMP, and ANTLOC are destination sbitmaps for recording
local properties. If NULL, then it is not necessary to compute
or record that particular property.
SETP controls which hash table to look at. If zero, this routine
looks at the expr hash table; if nonzero this routine looks at
the set hash table. */
static void
compute_local_properties (transp, comp, antloc, setp)
sbitmap *transp;
sbitmap *comp;
sbitmap *antloc;
int setp;
{
int i, hash_table_size;
struct expr **hash_table;
/* Initialize any bitmaps that were passed in. */
if (transp)
sbitmap_vector_ones (transp, n_basic_blocks);
if (comp)
sbitmap_vector_zero (comp, n_basic_blocks);
if (antloc)
sbitmap_vector_zero (antloc, n_basic_blocks);
/* We use the same code for cprop, pre and hoisting. For cprop
we care about the set hash table, for pre and hoisting we
care about the expr hash table. */
hash_table_size = setp ? set_hash_table_size : expr_hash_table_size;
hash_table = setp ? set_hash_table : expr_hash_table;
for (i = 0; i < hash_table_size; i++)
{
struct expr *expr;
for (expr = hash_table[i]; expr != NULL; expr = expr->next_same_hash)
{
struct occr *occr;
int indx = expr->bitmap_index;
/* The expression is transparent in this block if it is not killed.
We start by assuming all are transparent [none are killed], and
then reset the bits for those that are. */
if (transp)
compute_transp (expr->expr, indx, transp, setp);
/* The occurrences recorded in antic_occr are exactly those that
we want to set to non-zero in ANTLOC. */
if (antloc)
{
for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
{
int bb = BLOCK_NUM (occr->insn);
SET_BIT (antloc[bb], indx);
/* While we're scanning the table, this is a good place to
initialize this. */
occr->deleted_p = 0;
}
}
/* The occurrences recorded in avail_occr are exactly those that
we want to set to non-zero in COMP. */
if (comp)
{
for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
{
int bb = BLOCK_NUM (occr->insn);
SET_BIT (comp[bb], indx);
/* While we're scanning the table, this is a good place to
initialize this. */
occr->copied_p = 0;
}
}
/* While we're scanning the table, this is a good place to
initialize this. */
expr->reaching_reg = 0;
}
}
}
/* Register set information.
`reg_set_table' records where each register is set or otherwise
modified. */
static struct obstack reg_set_obstack;
static void
alloc_reg_set_mem (n_regs)
int n_regs;
{
int n;
reg_set_table_size = n_regs + REG_SET_TABLE_SLOP;
n = reg_set_table_size * sizeof (struct reg_set *);
reg_set_table = (struct reg_set **) gmalloc (n);
zero_memory ((char *) reg_set_table, n);
gcc_obstack_init (&reg_set_obstack);
}
static void
free_reg_set_mem ()
{
free (reg_set_table);
obstack_free (&reg_set_obstack, NULL);
}
/* Record REGNO in the reg_set table. */
static void
record_one_set (regno, insn)
int regno;
rtx insn;
{
/* allocate a new reg_set element and link it onto the list */
struct reg_set *new_reg_info, *reg_info_ptr1, *reg_info_ptr2;
/* If the table isn't big enough, enlarge it. */
if (regno >= reg_set_table_size)
{
int new_size = regno + REG_SET_TABLE_SLOP;
reg_set_table = (struct reg_set **)
grealloc ((char *) reg_set_table,
new_size * sizeof (struct reg_set *));
zero_memory ((char *) (reg_set_table + reg_set_table_size),
(new_size - reg_set_table_size) * sizeof (struct reg_set *));
reg_set_table_size = new_size;
}
new_reg_info = (struct reg_set *) obstack_alloc (&reg_set_obstack,
sizeof (struct reg_set));
bytes_used += sizeof (struct reg_set);
new_reg_info->insn = insn;
new_reg_info->next = NULL;
if (reg_set_table[regno] == NULL)
reg_set_table[regno] = new_reg_info;
else
{
reg_info_ptr1 = reg_info_ptr2 = reg_set_table[regno];
/* ??? One could keep a "last" pointer to speed this up. */
while (reg_info_ptr1 != NULL)
{
reg_info_ptr2 = reg_info_ptr1;
reg_info_ptr1 = reg_info_ptr1->next;
}
reg_info_ptr2->next = new_reg_info;
}
}
/* For communication between next two functions (via note_stores). */
static rtx record_set_insn;
/* Called from compute_sets via note_stores to handle one
SET or CLOBBER in an insn. */
static void
record_set_info (dest, setter)
rtx dest, setter;
{
if (GET_CODE (dest) == SUBREG)
dest = SUBREG_REG (dest);
if (GET_CODE (dest) == REG)
{
if (REGNO (dest) >= FIRST_PSEUDO_REGISTER)
record_one_set (REGNO (dest), record_set_insn);
}
}
/* Scan the function and record each set of each pseudo-register.
This is called once, at the start of the gcse pass.
See the comments for `reg_set_table' for further docs. */
static void
compute_sets (f)
rtx f;
{
rtx insn = f;
while (insn)
{
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
{
record_set_insn = insn;
note_stores (PATTERN (insn), record_set_info);
}
insn = NEXT_INSN (insn);
}
}
/* Hash table support. */
#define NEVER_SET -1
/* For each register, the cuid of the first/last insn in the block to set it,
or -1 if not set. */
static int *reg_first_set;
static int *reg_last_set;
/* Perform a quick check whether X, the source of a set, is something
we want to consider for GCSE. */
static int
want_to_gcse_p (x)
rtx x;
{
enum rtx_code code = GET_CODE (x);
switch (code)
{
case REG:
case SUBREG:
case CONST_INT:
case CONST_DOUBLE:
case CALL:
return 0;
default:
break;
}
return 1;
}
/* Used for communication between mems_conflict_for_gcse_p and
load_killed_in_block_p. Nonzero if mems_conflict_for_gcse_p finds a
conflict between two memory references. */
static int gcse_mems_conflict_p;
/* Used for communication between mems_conflict_for_gcse_p and
load_killed_in_block_p. A memory reference for a load instruction,
mems_conflict_for_gcse_p will see if a memory store conflicts with
this memory load. */
static rtx gcse_mem_operand;
/* DEST is the output of an instruction. If it is a memory reference, and
possibly conflicts with the load found in gcse_mem_operand, then set
gcse_mems_conflict_p to a nonzero value. */
static void
mems_conflict_for_gcse_p (dest, setter)
rtx dest, setter;
{
while (GET_CODE (dest) == SUBREG
|| GET_CODE (dest) == ZERO_EXTRACT
|| GET_CODE (dest) == SIGN_EXTRACT
|| GET_CODE (dest) == STRICT_LOW_PART)
dest = XEXP (dest, 0);
/* If DEST is not a MEM, then it will not conflict with the load. Note
that function calls are assumed to clobber memory, but are handled
elsewhere. */
if (GET_CODE (dest) != MEM)
return;
if (true_dependence (dest, GET_MODE (dest), gcse_mem_operand,
rtx_addr_varies_p))
gcse_mems_conflict_p = 1;
}
/* Return nonzero if the expression in X (a memory reference) is killed
in block BB before or after the insn with the CUID in UID_LIMIT.
AVAIL_P is nonzero for kills after UID_LIMIT, and zero for kills
before UID_LIMIT.
To check the entire block, set UID_LIMIT to max_uid + 1 and
AVAIL_P to 0. */
static int
load_killed_in_block_p (bb, uid_limit, x, avail_p)
int bb;
int uid_limit;
rtx x;
int avail_p;
{
rtx list_entry = modify_mem_list[bb];
while (list_entry)
{
rtx setter;
/* Ignore entries in the list that do not apply. */
if ((avail_p
&& INSN_CUID (XEXP (list_entry, 0)) < uid_limit)
|| (! avail_p
&& INSN_CUID (XEXP (list_entry, 0)) > uid_limit))
{
list_entry = XEXP (list_entry, 1);
continue;
}
setter = XEXP (list_entry, 0);
/* If SETTER is a call everything is clobbered. Note that calls
to pure functions are never put on the list, so we need not
worry about them. */
if (GET_CODE (setter) == CALL_INSN)
return 1;
/* SETTER must be an INSN of some kind that sets memory. Call
note_stores to examine each hunk of memory that is modified.
The note_stores interface is pretty limited, so we have to
communicate via global variables. Yuk. */
gcse_mem_operand = x;
gcse_mems_conflict_p = 0;
note_stores (PATTERN (setter), mems_conflict_for_gcse_p);
if (gcse_mems_conflict_p)
return 1;
list_entry = XEXP (list_entry, 1);
}
return 0;
}
/* Return non-zero if the operands of expression X are unchanged from the
start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
static int
oprs_unchanged_p (x, insn, avail_p)
rtx x, insn;
int avail_p;
{
int i;
enum rtx_code code;
char *fmt;
/* repeat is used to turn tail-recursion into iteration. */
repeat:
if (x == 0)
return 1;
code = GET_CODE (x);
switch (code)
{
case REG:
if (avail_p)
return (reg_last_set[REGNO (x)] == NEVER_SET
|| reg_last_set[REGNO (x)] < INSN_CUID (insn));
else
return (reg_first_set[REGNO (x)] == NEVER_SET
|| reg_first_set[REGNO (x)] >= INSN_CUID (insn));
case MEM:
if (load_killed_in_block_p (BLOCK_NUM (insn), INSN_CUID (insn),
x, avail_p))
return 0;
/* There is no conflict for the memory locations. Now check that the
address itself has not changed. */
x = XEXP (x, 0);
goto repeat;
case PRE_DEC:
case PRE_INC:
case POST_DEC:
case POST_INC:
return 0;
case PC:
case CC0: /*FIXME*/
case CONST:
case CONST_INT:
case CONST_DOUBLE:
case SYMBOL_REF:
case LABEL_REF:
case ADDR_VEC:
case ADDR_DIFF_VEC:
return 1;
default:
break;
}
i = GET_RTX_LENGTH (code) - 1;
fmt = GET_RTX_FORMAT (code);
for (; i >= 0; i--)
{
if (fmt[i] == 'e')
{
rtx tem = XEXP (x, i);
/* If we are about to do the last recursive call
needed at this level, change it into iteration.
This function is called enough to be worth it. */
if (i == 0)
{
x = tem;
goto repeat;
}
if (! oprs_unchanged_p (tem, insn, avail_p))
return 0;
}
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
{
if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, avail_p))
return 0;
}
}
}
return 1;
}
/* Return non-zero if the operands of expression X are unchanged from
the start of INSN's basic block up to but not including INSN. */
static int
oprs_anticipatable_p (x, insn)
rtx x, insn;
{
return oprs_unchanged_p (x, insn, 0);
}
/* Return non-zero if the operands of expression X are unchanged from
INSN to the end of INSN's basic block. */
static int
oprs_available_p (x, insn)
rtx x, insn;
{
return oprs_unchanged_p (x, insn, 1);
}
/* Hash expression X.
MODE is only used if X is a CONST_INT.
A boolean indicating if a volatile operand is found or if the expression
contains something we don't want to insert in the table is stored in
DO_NOT_RECORD_P.
??? One might want to merge this with canon_hash. Later. */
static unsigned int
hash_expr (x, mode, do_not_record_p, hash_table_size)
rtx x;
enum machine_mode mode;
int *do_not_record_p;
int hash_table_size;
{
unsigned int hash;
*do_not_record_p = 0;
hash = hash_expr_1 (x, mode, do_not_record_p);
return hash % hash_table_size;
}
/* Subroutine of hash_expr to do the actual work. */
static unsigned int
hash_expr_1 (x, mode, do_not_record_p)
rtx x;
enum machine_mode mode;
int *do_not_record_p;
{
int i, j;
unsigned hash = 0;
enum rtx_code code;
char *fmt;
/* repeat is used to turn tail-recursion into iteration. */
repeat:
if (x == 0)
return hash;
code = GET_CODE (x);
switch (code)
{
case REG:
{
register int regno = REGNO (x);
hash += ((unsigned) REG << 7) + regno;
return hash;
}
case CONST_INT:
{
HOST_WIDE_UINT tem = INTVAL (x);
hash += ((unsigned) CONST_INT << 7) + (unsigned) mode + tem;
return hash;
}
case CONST_DOUBLE:
/* This is like the general case, except that it only counts
the integers representing the constant. */
hash += (unsigned) code + (unsigned) GET_MODE (x);
if (GET_MODE (x) != VOIDmode)
for (i = 2; i < GET_RTX_LENGTH (CONST_DOUBLE); i++)
{
unsigned tem = XINT (x, i);
hash += tem;
}
else
hash += ((unsigned) CONST_DOUBLE_LOW (x)
+ (unsigned) CONST_DOUBLE_HIGH (x));
return hash;
/* Assume there is only one rtx object for any given label. */
case LABEL_REF:
/* We don't hash on the address of the CODE_LABEL to avoid bootstrap
differences and differences between each stage's debugging dumps. */
hash += ((unsigned) LABEL_REF << 7) + CODE_LABEL_NUMBER (XEXP (x, 0));
return hash;
case SYMBOL_REF:
{
/* Don't hash on the symbol's address to avoid bootstrap differences.
Different hash values may cause expressions to be recorded in
different orders and thus different registers to be used in the
final assembler. This also avoids differences in the dump files
between various stages. */
unsigned int h = 0;
unsigned char *p = (unsigned char *) XSTR (x, 0);
while (*p)
h += (h << 7) + *p++; /* ??? revisit */
hash += ((unsigned) SYMBOL_REF << 7) + h;
return hash;
}
case MEM:
if (MEM_VOLATILE_P (x))
{
*do_not_record_p = 1;
return 0;
}
hash += (unsigned) MEM;
x = XEXP (x, 0);
goto repeat;
case PRE_DEC:
case PRE_INC:
case POST_DEC:
case POST_INC:
case PC:
case CC0:
case CALL:
case UNSPEC_VOLATILE:
*do_not_record_p = 1;
return 0;
case ASM_OPERANDS:
if (MEM_VOLATILE_P (x))
{
*do_not_record_p = 1;
return 0;
}
default:
break;
}
i = GET_RTX_LENGTH (code) - 1;
hash += (unsigned) code + (unsigned) GET_MODE (x);
fmt = GET_RTX_FORMAT (code);
for (; i >= 0; i--)
{
if (fmt[i] == 'e')
{
rtx tem = XEXP (x, i);
/* If we are about to do the last recursive call
needed at this level, change it into iteration.
This function is called enough to be worth it. */
if (i == 0)
{
x = tem;
goto repeat;
}
hash += hash_expr_1 (tem, 0, do_not_record_p);
if (*do_not_record_p)
return 0;
}
else if (fmt[i] == 'E')
for (j = 0; j < XVECLEN (x, i); j++)
{
hash += hash_expr_1 (XVECEXP (x, i, j), 0, do_not_record_p);
if (*do_not_record_p)
return 0;
}
else if (fmt[i] == 's')
{
register unsigned char *p = (unsigned char *) XSTR (x, i);
if (p)
while (*p)
hash += *p++;
}
else if (fmt[i] == 'i')
{
register unsigned tem = XINT (x, i);
hash += tem;
}
else
abort ();
}
return hash;
}
/* Hash a set of register REGNO.
Sets are hashed on the register that is set.
This simplifies the PRE copy propagation code.
??? May need to make things more elaborate. Later, as necessary. */
static unsigned int
hash_set (regno, hash_table_size)
int regno;
int hash_table_size;
{
unsigned int hash;
hash = regno;
return hash % hash_table_size;
}
/* Return non-zero if exp1 is equivalent to exp2.
??? Borrowed from cse.c. Might want to remerge with cse.c. Later. */
static int
expr_equiv_p (x, y)
rtx x, y;
{
register int i, j;
register enum rtx_code code;
register char *fmt;
if (x == y)
return 1;
if (x == 0 || y == 0)
return x == y;
code = GET_CODE (x);
if (code != GET_CODE (y))
return 0;
/* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
if (GET_MODE (x) != GET_MODE (y))
return 0;
switch (code)
{
case PC:
case CC0:
return x == y;
case CONST_INT:
return INTVAL (x) == INTVAL (y);
case LABEL_REF:
return XEXP (x, 0) == XEXP (y, 0);
case SYMBOL_REF:
return XSTR (x, 0) == XSTR (y, 0);
case REG:
return REGNO (x) == REGNO (y);
/* For commutative operations, check both orders. */
case PLUS:
case MULT:
case AND:
case IOR:
case XOR:
case NE:
case EQ:
return ((expr_equiv_p (XEXP (x, 0), XEXP (y, 0))
&& expr_equiv_p (XEXP (x, 1), XEXP (y, 1)))
|| (expr_equiv_p (XEXP (x, 0), XEXP (y, 1))
&& expr_equiv_p (XEXP (x, 1), XEXP (y, 0))));
default:
break;
}
/* Compare the elements. If any pair of corresponding elements
fail to match, return 0 for the whole thing. */
fmt = GET_RTX_FORMAT (code);
for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
{
switch (fmt[i])
{
case 'e':
if (! expr_equiv_p (XEXP (x, i), XEXP (y, i)))
return 0;
break;
case 'E':
if (XVECLEN (x, i) != XVECLEN (y, i))
return 0;
for (j = 0; j < XVECLEN (x, i); j++)
if (! expr_equiv_p (XVECEXP (x, i, j), XVECEXP (y, i, j)))
return 0;
break;
case 's':
if (strcmp (XSTR (x, i), XSTR (y, i)))
return 0;
break;
case 'i':
if (XINT (x, i) != XINT (y, i))
return 0;
break;
case 'w':
if (XWINT (x, i) != XWINT (y, i))
return 0;
break;
case '0':
break;
default:
abort ();
}
}
return 1;
}
/* Insert expression X in INSN in the hash table.
If it is already present, record it as the last occurrence in INSN's
basic block.
MODE is the mode of the value X is being stored into.
It is only used if X is a CONST_INT.
ANTIC_P is non-zero if X is an anticipatable expression.
AVAIL_P is non-zero if X is an available expression. */
static void
insert_expr_in_table (x, mode, insn, antic_p, avail_p)
rtx x;
enum machine_mode mode;
rtx insn;
int antic_p, avail_p;
{
int found, do_not_record_p;
unsigned int hash;
struct expr *cur_expr, *last_expr = NULL;
struct occr *antic_occr, *avail_occr;
struct occr *last_occr = NULL;
hash = hash_expr (x, mode, &do_not_record_p, expr_hash_table_size);
/* Do not insert expression in table if it contains volatile operands,
or if hash_expr determines the expression is something we don't want
to or can't handle. */
if (do_not_record_p)
return;
cur_expr = expr_hash_table[hash];
found = 0;
while (cur_expr && ! (found = expr_equiv_p (cur_expr->expr, x)))
{
/* If the expression isn't found, save a pointer to the end of
the list. */
last_expr = cur_expr;
cur_expr = cur_expr->next_same_hash;
}
if (! found)
{
cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
bytes_used += sizeof (struct expr);
if (expr_hash_table[hash] == NULL)
{
/* This is the first pattern that hashed to this index. */
expr_hash_table[hash] = cur_expr;
}
else
{
/* Add EXPR to end of this hash chain. */
last_expr->next_same_hash = cur_expr;
}
/* Set the fields of the expr element. */
cur_expr->expr = x;
cur_expr->bitmap_index = n_exprs++;
cur_expr->next_same_hash = NULL;
cur_expr->antic_occr = NULL;
cur_expr->avail_occr = NULL;
}
/* Now record the occurrence(s). */
if (antic_p)
{
antic_occr = cur_expr->antic_occr;
/* Search for another occurrence in the same basic block. */
while (antic_occr && BLOCK_NUM (antic_occr->insn) != BLOCK_NUM (insn))
{
/* If an occurrence isn't found, save a pointer to the end of
the list. */
last_occr = antic_occr;
antic_occr = antic_occr->next;
}
if (antic_occr)
{
/* Found another instance of the expression in the same basic block.
Prefer the currently recorded one. We want the first one in the
block and the block is scanned from start to end. */
; /* nothing to do */
}
else
{
/* First occurrence of this expression in this basic block. */
antic_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
bytes_used += sizeof (struct occr);
/* First occurrence of this expression in any block? */
if (cur_expr->antic_occr == NULL)
cur_expr->antic_occr = antic_occr;
else
last_occr->next = antic_occr;
antic_occr->insn = insn;
antic_occr->next = NULL;
}
}
if (avail_p)
{
avail_occr = cur_expr->avail_occr;
/* Search for another occurrence in the same basic block. */
while (avail_occr && BLOCK_NUM (avail_occr->insn) != BLOCK_NUM (insn))
{
/* If an occurrence isn't found, save a pointer to the end of
the list. */
last_occr = avail_occr;
avail_occr = avail_occr->next;
}
if (avail_occr)
{
/* Found another instance of the expression in the same basic block.
Prefer this occurrence to the currently recorded one. We want
the last one in the block and the block is scanned from start
to end. */
avail_occr->insn = insn;
}
else
{
/* First occurrence of this expression in this basic block. */
avail_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
bytes_used += sizeof (struct occr);
/* First occurrence of this expression in any block? */
if (cur_expr->avail_occr == NULL)
cur_expr->avail_occr = avail_occr;
else
last_occr->next = avail_occr;
avail_occr->insn = insn;
avail_occr->next = NULL;
}
}
}
/* Insert pattern X in INSN in the hash table.
X is a SET of a reg to either another reg or a constant.
If it is already present, record it as the last occurrence in INSN's
basic block. */
static void
insert_set_in_table (x, insn)
rtx x;
rtx insn;
{
int found;
unsigned int hash;
struct expr *cur_expr, *last_expr = NULL;
struct occr *cur_occr, *last_occr = NULL;
if (GET_CODE (x) != SET
|| GET_CODE (SET_DEST (x)) != REG)
abort ();
hash = hash_set (REGNO (SET_DEST (x)), set_hash_table_size);
cur_expr = set_hash_table[hash];
found = 0;
while (cur_expr && ! (found = expr_equiv_p (cur_expr->expr, x)))
{
/* If the expression isn't found, save a pointer to the end of
the list. */
last_expr = cur_expr;
cur_expr = cur_expr->next_same_hash;
}
if (! found)
{
cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
bytes_used += sizeof (struct expr);
if (set_hash_table[hash] == NULL)
{
/* This is the first pattern that hashed to this index. */
set_hash_table[hash] = cur_expr;
}
else
{
/* Add EXPR to end of this hash chain. */
last_expr->next_same_hash = cur_expr;
}
/* Set the fields of the expr element.
We must copy X because it can be modified when copy propagation is
performed on its operands. */
/* ??? Should this go in a different obstack? */
cur_expr->expr = copy_rtx (x);
cur_expr->bitmap_index = n_sets++;
cur_expr->next_same_hash = NULL;
cur_expr->antic_occr = NULL;
cur_expr->avail_occr = NULL;
}
/* Now record the occurrence. */
cur_occr = cur_expr->avail_occr;
/* Search for another occurrence in the same basic block. */
while (cur_occr && BLOCK_NUM (cur_occr->insn) != BLOCK_NUM (insn))
{
/* If an occurrence isn't found, save a pointer to the end of
the list. */
last_occr = cur_occr;
cur_occr = cur_occr->next;
}
if (cur_occr)
{
/* Found another instance of the expression in the same basic block.
Prefer this occurrence to the currently recorded one. We want
the last one in the block and the block is scanned from start
to end. */
cur_occr->insn = insn;
}
else
{
/* First occurrence of this expression in this basic block. */
cur_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
bytes_used += sizeof (struct occr);
/* First occurrence of this expression in any block? */
if (cur_expr->avail_occr == NULL)
cur_expr->avail_occr = cur_occr;
else
last_occr->next = cur_occr;
cur_occr->insn = insn;
cur_occr->next = NULL;
}
}
/* Scan pattern PAT of INSN and add an entry to the hash table.
If SET_P is non-zero, this is for the assignment hash table,
otherwise it is for the expression hash table. */
static void
hash_scan_set (pat, insn, set_p)
rtx pat, insn;
int set_p;
{
rtx src = SET_SRC (pat);
rtx dest = SET_DEST (pat);
if (GET_CODE (src) == CALL)
hash_scan_call (src, insn);
if (GET_CODE (dest) == REG)
{
int regno = REGNO (dest);
rtx tmp;
/* Only record sets of pseudo-regs in the hash table. */
if (! set_p
&& regno >= FIRST_PSEUDO_REGISTER
/* Don't GCSE something if we can't do a reg/reg copy. */
&& can_copy_p [GET_MODE (dest)]
/* Is SET_SRC something we want to gcse? */
&& want_to_gcse_p (src))
{
/* An expression is not anticipatable if its operands are
modified before this insn. */
int antic_p = oprs_anticipatable_p (src, insn);
/* An expression is not available if its operands are
subsequently modified, including this insn. */
int avail_p = oprs_available_p (src, insn);
insert_expr_in_table (src, GET_MODE (dest), insn, antic_p, avail_p);
}
/* Record sets for constant/copy propagation. */
else if (set_p
&& regno >= FIRST_PSEUDO_REGISTER
&& ((GET_CODE (src) == REG
&& REGNO (src) >= FIRST_PSEUDO_REGISTER
&& can_copy_p [GET_MODE (dest)])
/* ??? CONST_INT:wip */
|| GET_CODE (src) == CONST_INT)
/* A copy is not available if its src or dest is subsequently
modified. Here we want to search from INSN+1 on, but
oprs_available_p searches from INSN on. */
&& (insn == BLOCK_END (BLOCK_NUM (insn))
|| ((tmp = next_nonnote_insn (insn)) != NULL_RTX
&& oprs_available_p (pat, tmp))))
insert_set_in_table (pat, insn);
}
}
static void
hash_scan_clobber (x, insn)
rtx x, insn;
{
/* Currently nothing to do. */
}
static void
hash_scan_call (x, insn)
rtx x, insn;
{
/* Currently nothing to do. */
}
/* Process INSN and add hash table entries as appropriate.
Only available expressions that set a single pseudo-reg are recorded.
Single sets in a PARALLEL could be handled, but it's an extra complication
that isn't dealt with right now. The trick is handling the CLOBBERs that
are also in the PARALLEL. Later.
If SET_P is non-zero, this is for the assignment hash table,
otherwise it is for the expression hash table.
If IN_LIBCALL_BLOCK nonzero, we are in a libcall block, and should
not record any expressions. */
static void
hash_scan_insn (insn, set_p, in_libcall_block)
rtx insn;
int set_p;
int in_libcall_block;
{
rtx pat = PATTERN (insn);
/* Pick out the sets of INSN and for other forms of instructions record
what's been modified. */
if (GET_CODE (pat) == SET && ! in_libcall_block)
hash_scan_set (pat, insn, set_p);
else if (GET_CODE (pat) == PARALLEL)
{
int i;
for (i = 0; i < XVECLEN (pat, 0); i++)
{
rtx x = XVECEXP (pat, 0, i);
if (GET_CODE (x) == SET)
{
if (GET_CODE (SET_SRC (x)) == CALL)
hash_scan_call (SET_SRC (x), insn);
}
else if (GET_CODE (x) == CLOBBER)
hash_scan_clobber (x, insn);
else if (GET_CODE (x) == CALL)
hash_scan_call (x, insn);
}
}
else if (GET_CODE (pat) == CLOBBER)
hash_scan_clobber (pat, insn);
else if (GET_CODE (pat) == CALL)
hash_scan_call (pat, insn);
}
static void
dump_hash_table (file, name, table, table_size, total_size)
FILE *file;
char *name;
struct expr **table;
int table_size, total_size;
{
int i;
/* Flattened out table, so it's printed in proper order. */
struct expr **flat_table = (struct expr **) alloca (total_size * sizeof (struct expr *));
unsigned int *hash_val = (unsigned int *) alloca (total_size * sizeof (unsigned int));
zero_memory ((char *) flat_table, total_size * sizeof (struct expr *));
for (i = 0; i < table_size; i++)
{
struct expr *expr;
for (expr = table[i]; expr != NULL; expr = expr->next_same_hash)
{
flat_table[expr->bitmap_index] = expr;
hash_val[expr->bitmap_index] = i;
}
}
fprintf (file, "%s hash table (%d buckets, %d entries)\n",
name, table_size, total_size);
for (i = 0; i < total_size; i++)
{
struct expr *expr = flat_table[i];
fprintf (file, "Index %d (hash value %d)\n ",
expr->bitmap_index, hash_val[i]);
print_rtl (file, expr->expr);
fprintf (file, "\n");
}
fprintf (file, "\n");
}
/* Record register first/last/block set information for REGNO in INSN.
reg_first_set records the first place in the block where the register
is set and is used to compute "anticipatability".
reg_last_set records the last place in the block where the register
is set and is used to compute "availability".
reg_set_in_block records whether the register is set in the block
and is used to compute "transparency". */
static void
record_last_reg_set_info (insn, regno)
rtx insn;
int regno;
{
if (reg_first_set[regno] == NEVER_SET)
reg_first_set[regno] = INSN_CUID (insn);
reg_last_set[regno] = INSN_CUID (insn);
SET_BIT (reg_set_in_block[BLOCK_NUM (insn)], regno);
}
/* Record memory modification information for INSN. We do not actually care
about the memory location(s) that are set, or even how they are set (consider
a CALL_INSN). We merely need to record which insns modify memory. */
static void
record_last_mem_set_info (insn)
rtx insn;
{
modify_mem_list[BLOCK_NUM (insn)]
= gen_rtx_INSN_LIST (VOIDmode, insn, modify_mem_list[BLOCK_NUM (insn)]);
}
/* Used for communicating between next two routines. */
static rtx last_set_insn;
/* Called from compute_hash_table via note_stores to handle one
SET or CLOBBER in an insn. */
static void
record_last_set_info (dest, setter)
rtx dest;
rtx setter;
{
if (GET_CODE (dest) == SUBREG)
dest = SUBREG_REG (dest);
if (GET_CODE (dest) == REG)
record_last_reg_set_info (last_set_insn, REGNO (dest));
else if (GET_CODE (dest) == MEM
/* Ignore pushes, they clobber nothing. */
&& ! push_operand (dest, GET_MODE (dest)))
record_last_mem_set_info (last_set_insn);
}
/* Top level function to create an expression or assignment hash table.
Expression entries are placed in the hash table if
- they are of the form (set (pseudo-reg) src),
- src is something we want to perform GCSE on,
- none of the operands are subsequently modified in the block
Assignment entries are placed in the hash table if
- they are of the form (set (pseudo-reg) src),
- src is something we want to perform const/copy propagation on,
- none of the operands or target are subsequently modified in the block
Currently src must be a pseudo-reg or a const_int.
F is the first insn.
SET_P is non-zero for computing the assignment hash table. */
static void
compute_hash_table (set_p)
int set_p;
{
int bb;
/* While we compute the hash table we also compute a bit array of which
registers are set in which blocks.
We also compute which blocks set memory, in the absence of aliasing
support [which is TODO].
??? This isn't needed during const/copy propagation, but it's cheap to
compute. Later. */
sbitmap_vector_zero (reg_set_in_block, n_basic_blocks);
zero_memory ((rtx *) modify_mem_list, n_basic_blocks * sizeof (rtx *));
/* Some working arrays used to track first and last set in each block. */
/* ??? One could use alloca here, but at some size a threshold is crossed
beyond which one should use malloc. Are we at that threshold here? */
reg_first_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
reg_last_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
for (bb = 0; bb < n_basic_blocks; bb++)
{
rtx insn;
int regno;
int in_libcall_block;
int i;
/* First pass over the instructions records information used to
determine when registers and memory are first and last set.
??? The hard-reg reg_set_in_block computation could be moved to
compute_sets since they currently don't change. */
for (i = 0; i < max_gcse_regno; i++)
reg_first_set[i] = reg_last_set[i] = NEVER_SET;
for (insn = BLOCK_HEAD (bb);
insn && insn != NEXT_INSN (BLOCK_END (bb));
insn = NEXT_INSN (insn))
{
if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
continue;
if (GET_CODE (insn) == CALL_INSN)
{
for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
if ((call_used_regs[regno]
&& regno != STACK_POINTER_REGNUM
&& ! (regno == ARG_POINTER_REGNUM && fixed_regs[regno])
&& regno != FRAME_POINTER_REGNUM)
|| global_regs[regno])
record_last_reg_set_info (insn, regno);
if (! CONST_CALL_P (insn))
record_last_mem_set_info (insn);
}
last_set_insn = insn;
note_stores (PATTERN (insn), record_last_set_info);
}
/* The next pass builds the hash table. */
for (insn = BLOCK_HEAD (bb), in_libcall_block = 0;
insn && insn != NEXT_INSN (BLOCK_END (bb));
insn = NEXT_INSN (insn))
{
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
{
if (find_reg_note (insn, REG_LIBCALL, NULL_RTX))
in_libcall_block = 1;
else if (find_reg_note (insn, REG_RETVAL, NULL_RTX))
in_libcall_block = 0;
hash_scan_insn (insn, set_p, in_libcall_block);
}
}
}
free (reg_first_set);
free (reg_last_set);
/* Catch bugs early. */
reg_first_set = reg_last_set = 0;
}
/* Allocate space for the set hash table.
N_INSNS is the number of instructions in the function.
It is used to determine the number of buckets to use. */
static void
alloc_set_hash_table (n_insns)
int n_insns;
{
int n;
set_hash_table_size = n_insns / 4;
if (set_hash_table_size < 11)
set_hash_table_size = 11;
/* Attempt to maintain efficient use of hash table.
Making it an odd number is simplest for now.
??? Later take some measurements. */
set_hash_table_size |= 1;
n = set_hash_table_size * sizeof (struct expr *);
set_hash_table = (struct expr **) gmalloc (n);
}
/* Free things allocated by alloc_set_hash_table. */
static void
free_set_hash_table ()
{
free (set_hash_table);
}
/* Compute the hash table for doing copy/const propagation. */
static void
compute_set_hash_table ()
{
/* Initialize count of number of entries in hash table. */
n_sets = 0;
zero_memory ((char *) set_hash_table, set_hash_table_size * sizeof (struct expr *));
compute_hash_table (1);
}
/* Allocate space for the expression hash table.
N_INSNS is the number of instructions in the function.
It is used to determine the number of buckets to use. */
static void
alloc_expr_hash_table (n_insns)
int n_insns;
{
int n;
expr_hash_table_size = n_insns / 2;
/* Make sure the amount is usable. */
if (expr_hash_table_size < 11)
expr_hash_table_size = 11;
/* Attempt to maintain efficient use of hash table.
Making it an odd number is simplest for now.
??? Later take some measurements. */
expr_hash_table_size |= 1;
n = expr_hash_table_size * sizeof (struct expr *);
expr_hash_table = (struct expr **) gmalloc (n);
}
/* Free things allocated by alloc_expr_hash_table. */
static void
free_expr_hash_table ()
{
free (expr_hash_table);
}
/* Compute the hash table for doing GCSE. */
static void
compute_expr_hash_table ()
{
/* Initialize count of number of entries in hash table. */
n_exprs = 0;
zero_memory ((char *) expr_hash_table, expr_hash_table_size * sizeof (struct expr *));
compute_hash_table (0);
}
/* Expression tracking support. */
/* Lookup pattern PAT in the expression table.
The result is a pointer to the table entry, or NULL if not found. */
static struct expr *
lookup_expr (pat)
rtx pat;
{
int do_not_record_p;
unsigned int hash = hash_expr (pat, GET_MODE (pat), &do_not_record_p,
expr_hash_table_size);
struct expr *expr;
if (do_not_record_p)
return NULL;
expr = expr_hash_table[hash];
while (expr && ! expr_equiv_p (expr->expr, pat))
expr = expr->next_same_hash;
return expr;
}
/* Lookup REGNO in the set table.
If PAT is non-NULL look for the entry that matches it, otherwise return
the first entry for REGNO.
The result is a pointer to the table entry, or NULL if not found. */
static struct expr *
lookup_set (regno, pat)
int regno;
rtx pat;
{
unsigned int hash = hash_set (regno, set_hash_table_size);
struct expr *expr;
expr = set_hash_table[hash];
if (pat)
{
while (expr && ! expr_equiv_p (expr->expr, pat))
expr = expr->next_same_hash;
}
else
{
while (expr && REGNO (SET_DEST (expr->expr)) != regno)
expr = expr->next_same_hash;
}
return expr;
}
/* Return the next entry for REGNO in list EXPR. */
static struct expr *
next_set (regno, expr)
int regno;
struct expr *expr;
{
do
expr = expr->next_same_hash;
while (expr && REGNO (SET_DEST (expr->expr)) != regno);
return expr;
}
/* Reset tables used to keep track of what's still available [since the
start of the block]. */
static void
reset_opr_set_tables ()
{
/* Maintain a bitmap of which regs have been set since beginning of
the block. */
sbitmap_zero (reg_set_bitmap);
/* Also keep a record of the last instruction to modify memory.
For now this is very trivial, we only record whether any memory
location has been modified. */
zero_memory ((char *)modify_mem_list, n_basic_blocks * sizeof (rtx *));
}
/* Return non-zero if the operands of X are not set before INSN in
INSN's basic block. */
static int
oprs_not_set_p (x, insn)
rtx x, insn;
{
int i;
enum rtx_code code;
char *fmt;
/* repeat is used to turn tail-recursion into iteration. */
repeat:
if (x == 0)
return 1;
code = GET_CODE (x);
switch (code)
{
case PC:
case CC0:
case CONST:
case CONST_INT:
case CONST_DOUBLE:
case SYMBOL_REF:
case LABEL_REF:
case ADDR_VEC:
case ADDR_DIFF_VEC:
return 1;
case MEM:
if (load_killed_in_block_p (BLOCK_NUM (insn), INSN_CUID (insn), x, 0))
return 0;
/* There is no conflict for the memory locations. Now check that the
address itself has not changed. */
x = XEXP (x, 0);
goto repeat;
case REG:
return ! TEST_BIT (reg_set_bitmap, REGNO (x));
default:
break;
}
fmt = GET_RTX_FORMAT (code);
for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
{
if (fmt[i] == 'e')
{
int not_set_p;
/* If we are about to do the last recursive call
needed at this level, change it into iteration.
This function is called enough to be worth it. */
if (i == 0)
{
x = XEXP (x, 0);
goto repeat;
}
not_set_p = oprs_not_set_p (XEXP (x, i), insn);
if (! not_set_p)
return 0;
}
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
{
int not_set_p = oprs_not_set_p (XVECEXP (x, i, j), insn);
if (! not_set_p)
return 0;
}
}
}
return 1;
}
/* Mark things set by a CALL. */
static void
mark_call (insn)
rtx insn;
{
if (! CONST_CALL_P (insn))
record_last_mem_set_info (insn);
}
/* Mark things set by a SET. */
static void
mark_set (pat, insn)
rtx pat, insn;
{
rtx dest = SET_DEST (pat);
while (GET_CODE (dest) == SUBREG
|| GET_CODE (dest) == ZERO_EXTRACT
|| GET_CODE (dest) == SIGN_EXTRACT
|| GET_CODE (dest) == STRICT_LOW_PART)
dest = XEXP (dest, 0);
if (GET_CODE (dest) == REG)
SET_BIT (reg_set_bitmap, REGNO (dest));
else if (GET_CODE (dest) == MEM)
record_last_mem_set_info (insn);
if (GET_CODE (SET_SRC (pat)) == CALL)
mark_call (insn);
}
/* Record things set by a CLOBBER. */
static void
mark_clobber (pat, insn)
rtx pat, insn;
{
rtx clob = XEXP (pat, 0);
while (GET_CODE (clob) == SUBREG || GET_CODE (clob) == STRICT_LOW_PART)
clob = XEXP (clob, 0);
if (GET_CODE (clob) == REG)
SET_BIT (reg_set_bitmap, REGNO (clob));
else
record_last_mem_set_info (insn);
}
/* Record things set by INSN.
This data is used by oprs_not_set_p. */
static void
mark_oprs_set (insn)
rtx insn;
{
rtx pat = PATTERN (insn);
if (GET_CODE (pat) == SET)
mark_set (pat, insn);
else if (GET_CODE (pat) == PARALLEL)
{
int i;
for (i = 0; i < XVECLEN (pat, 0); i++)
{
rtx x = XVECEXP (pat, 0, i);
if (GET_CODE (x) == SET)
mark_set (x, insn);
else if (GET_CODE (x) == CLOBBER)
mark_clobber (x, insn);
else if (GET_CODE (x) == CALL)
mark_call (insn);
}
}
else if (GET_CODE (pat) == CLOBBER)
mark_clobber (pat, insn);
else if (GET_CODE (pat) == CALL)
mark_call (insn);
}
/* Classic GCSE reaching definition support. */
/* Allocate reaching def variables. */
static void
alloc_rd_mem (n_blocks, n_insns)
int n_blocks, n_insns;
{
rd_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
sbitmap_vector_zero (rd_kill, n_basic_blocks);
rd_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
sbitmap_vector_zero (rd_gen, n_basic_blocks);
reaching_defs = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
sbitmap_vector_zero (reaching_defs, n_basic_blocks);
rd_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
sbitmap_vector_zero (rd_out, n_basic_blocks);
}
/* Free reaching def variables. */
static void
free_rd_mem ()
{
free (rd_kill);
free (rd_gen);
free (reaching_defs);
free (rd_out);
}
/* Add INSN to the kills of BB.
REGNO, set in BB, is killed by INSN. */
static void
handle_rd_kill_set (insn, regno, bb)
rtx insn;
int regno, bb;
{
struct reg_set *this_reg = reg_set_table[regno];
while (this_reg)
{
if (BLOCK_NUM (this_reg->insn) != BLOCK_NUM (insn))
SET_BIT (rd_kill[bb], INSN_CUID (this_reg->insn));
this_reg = this_reg->next;
}
}
/* Compute the set of kill's for reaching definitions. */
static void
compute_kill_rd ()
{
int bb,cuid;
/* For each block
For each set bit in `gen' of the block (i.e each insn which
generates a definition in the block)
Call the reg set by the insn corresponding to that bit regx
Look at the linked list starting at reg_set_table[regx]
For each setting of regx in the linked list, which is not in
this block
Set the bit in `kill' corresponding to that insn
*/
for (bb = 0; bb < n_basic_blocks; bb++)
{
for (cuid = 0; cuid < max_cuid; cuid++)
{
if (TEST_BIT (rd_gen[bb], cuid))
{
rtx insn = CUID_INSN (cuid);
rtx pat = PATTERN (insn);
if (GET_CODE (insn) == CALL_INSN)
{
int regno;
for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
{
if ((call_used_regs[regno]
&& regno != STACK_POINTER_REGNUM
&& ! (regno == ARG_POINTER_REGNUM
&& fixed_regs[regno])
&& regno != FRAME_POINTER_REGNUM)
|| global_regs[regno])
handle_rd_kill_set (insn, regno, bb);
}
}
if (GET_CODE (pat) == PARALLEL)
{
int i;
/* We work backwards because ... */
for (i = XVECLEN (pat, 0) - 1; i >= 0; i--)
{
enum rtx_code code = GET_CODE (XVECEXP (pat, 0, i));
if ((code == SET || code == CLOBBER)
&& GET_CODE (XEXP (XVECEXP (pat, 0, i), 0)) == REG)
handle_rd_kill_set (insn,
REGNO (XEXP (XVECEXP (pat, 0, i), 0)),
bb);
}
}
else if (GET_CODE (pat) == SET)
{
if (GET_CODE (SET_DEST (pat)) == REG)
{
/* Each setting of this register outside of this block
must be marked in the set of kills in this block. */
handle_rd_kill_set (insn, REGNO (SET_DEST (pat)), bb);
}
}
/* FIXME: CLOBBER? */
}
}
}
}
/* Compute the reaching definitions as in
Compilers Principles, Techniques, and Tools. Aho, Sethi, Ullman,
Chapter 10. It is the same algorithm as used for computing available
expressions but applied to the gens and kills of reaching definitions. */
static void
compute_rd ()
{
int bb, changed, passes;
for (bb = 0; bb < n_basic_blocks; bb++)
sbitmap_copy (rd_out[bb] /*dst*/, rd_gen[bb] /*src*/);
passes = 0;
changed = 1;
while (changed)
{
changed = 0;
for (bb = 0; bb < n_basic_blocks; bb++)
{
sbitmap_union_of_predecessors (reaching_defs[bb], rd_out,
bb, s_preds);
changed |= sbitmap_union_of_diff (rd_out[bb], rd_gen[bb],
reaching_defs[bb], rd_kill[bb]);
}
passes++;
}
if (gcse_file)
fprintf (gcse_file, "reaching def computation: %d passes\n", passes);
}
/* Classic GCSE available expression support. */
/* Allocate memory for available expression computation. */
static void
alloc_avail_expr_mem (n_blocks, n_exprs)
int n_blocks, n_exprs;
{
ae_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
sbitmap_vector_zero (ae_kill, n_basic_blocks);
ae_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
sbitmap_vector_zero (ae_gen, n_basic_blocks);
ae_in = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
sbitmap_vector_zero (ae_in, n_basic_blocks);
ae_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
sbitmap_vector_zero (ae_out, n_basic_blocks);
u_bitmap = (sbitmap) sbitmap_alloc (n_exprs);
sbitmap_ones (u_bitmap);
}
static void
free_avail_expr_mem ()
{
free (ae_kill);
free (ae_gen);
free (ae_in);
free (ae_out);
free (u_bitmap);
}
/* Compute the set of available expressions generated in each basic block. */
static void
compute_ae_gen ()
{
int i;
/* For each recorded occurrence of each expression, set ae_gen[bb][expr].
This is all we have to do because an expression is not recorded if it
is not available, and the only expressions we want to work with are the
ones that are recorded. */
for (i = 0; i < expr_hash_table_size; i++)
{
struct expr *expr = expr_hash_table[i];
while (expr != NULL)
{
struct occr *occr = expr->avail_occr;
while (occr != NULL)
{
SET_BIT (ae_gen[BLOCK_NUM (occr->insn)], expr->bitmap_index);
occr = occr->next;
}
expr = expr->next_same_hash;
}
}
}
/* Return non-zero if expression X is killed in BB. */
static int
expr_killed_p (x, bb)
rtx x;
int bb;
{
int i;
enum rtx_code code;
char *fmt;
/* repeat is used to turn tail-recursion into iteration. */
repeat:
if (x == 0)
return 1;
code = GET_CODE (x);
switch (code)
{
case REG:
return TEST_BIT (reg_set_in_block[bb], REGNO (x));
case MEM:
if (load_killed_in_block_p (bb, get_max_uid () + 1, x, 0))
return 1;
/* There is no conflict for the memory locations. Now check that the
address itself has not changed. */
x = XEXP (x, 0);
goto repeat;
case PC:
case CC0: /*FIXME*/
case CONST:
case CONST_INT:
case CONST_DOUBLE:
case SYMBOL_REF:
case LABEL_REF:
case ADDR_VEC:
case ADDR_DIFF_VEC:
return 0;
default:
break;
}
i = GET_RTX_LENGTH (code) - 1;
fmt = GET_RTX_FORMAT (code);
for (; i >= 0; i--)
{
if (fmt[i] == 'e')
{
rtx tem = XEXP (x, i);
/* If we are about to do the last recursive call
needed at this level, change it into iteration.
This function is called enough to be worth it. */
if (i == 0)
{
x = tem;
goto repeat;
}
if (expr_killed_p (tem, bb))
return 1;
}
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
{
if (expr_killed_p (XVECEXP (x, i, j), bb))
return 1;
}
}
}
return 0;
}
/* Compute the set of available expressions killed in each basic block. */
static void
compute_ae_kill ()
{
int bb,i;
for (bb = 0; bb < n_basic_blocks; bb++)
{
for (i = 0; i < expr_hash_table_size; i++)
{
struct expr *expr = expr_hash_table[i];
for ( ; expr != NULL; expr = expr->next_same_hash)
{
/* Skip EXPR if generated in this block. */
if (TEST_BIT (ae_gen[bb], expr->bitmap_index))
continue;
if (expr_killed_p (expr->expr, bb))
SET_BIT (ae_kill[bb], expr->bitmap_index);
}
}
}
}
/* Compute available expressions.
Implement the algorithm to find available expressions
as given in the Aho Sethi Ullman book, pages 627-631. */
static void
compute_available ()
{
int bb, changed, passes;
sbitmap_zero (ae_in[0]);
sbitmap_copy (ae_out[0] /*dst*/, ae_gen[0] /*src*/);
for (bb = 1; bb < n_basic_blocks; bb++)
sbitmap_difference (ae_out[bb], u_bitmap, ae_kill[bb]);
passes = 0;
changed = 1;
while (changed)
{
changed = 0;
for (bb = 1; bb < n_basic_blocks; bb++)
{
sbitmap_intersect_of_predecessors (ae_in[bb], ae_out, bb, s_preds);
changed |= sbitmap_union_of_diff (ae_out[bb], ae_gen[bb],
ae_in[bb], ae_kill[bb]);
}
passes++;
}
if (gcse_file)
fprintf (gcse_file, "avail expr computation: %d passes\n", passes);
}
/* Actually perform the Classic GCSE optimizations. */
/* Return non-zero if occurrence OCCR of expression EXPR reaches block BB.
CHECK_SELF_LOOP is non-zero if we should consider a block reaching itself
as a positive reach. We want to do this when there are two computations
of the expression in the block.
VISITED is a pointer to a working buffer for tracking which BB's have
been visited. It is NULL for the top-level call.
We treat reaching expressions that go through blocks containing the same
reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2 as not reaching. The intent is to improve the probability of finding
only one reaching expression and to reduce register lifetimes by picking
the closest such expression. */
static int
expr_reaches_here_p (occr, expr, bb, check_self_loop, visited)
struct occr *occr;
struct expr *expr;
int bb;
int check_self_loop;
char *visited;
{
int_list_ptr pred;
if (visited == NULL)
{
visited = (char *) alloca (n_basic_blocks);
zero_memory (visited, n_basic_blocks);
}
for (pred = s_preds[bb]; pred != NULL; pred = pred->next)
{
int pred_bb = INT_LIST_VAL (pred);
if (visited[pred_bb])
{
/* This predecessor has already been visited.
Nothing to do. */
;
}
else if (pred_bb == bb)
{
/* BB loops on itself. */
if (check_self_loop
&& TEST_BIT (ae_gen[pred_bb], expr->bitmap_index)
&& BLOCK_NUM (occr->insn) == pred_bb)
return 1;
visited[pred_bb] = 1;
}
/* Ignore this predecessor if it kills the expression. */
else if (TEST_BIT (ae_kill[pred_bb], expr->bitmap_index))
visited[pred_bb] = 1;
/* Does this predecessor generate this expression? */
else if (TEST_BIT (ae_gen[pred_bb], expr->bitmap_index))
{
/* Is this the occurrence we're looking for?
Note that there's only one generating occurrence per block
so we just need to check the block number. */
if (BLOCK_NUM (occr->insn) == pred_bb)
return 1;
visited[pred_bb] = 1;
}
/* Neither gen nor kill. */
else
{
visited[pred_bb] = 1;
if (expr_reaches_here_p (occr, expr, pred_bb, check_self_loop, visited))
return 1;
}
}
/* All paths have been checked. */
return 0;
}
/* Return the instruction that computes EXPR that reaches INSN's basic block.
If there is more than one such instruction, return NULL.
Called only by handle_avail_expr. */
static rtx
computing_insn (expr, insn)
struct expr *expr;
rtx insn;
{
int bb = BLOCK_NUM (insn);
if (expr->avail_occr->next == NULL)
{
if (BLOCK_NUM (expr->avail_occr->insn) == bb)
{
/* The available expression is actually itself
(i.e. a loop in the flow graph) so do nothing. */
return NULL;
}
/* (FIXME) Case that we found a pattern that was created by
a substitution that took place. */
return expr->avail_occr->insn;
}
else
{
/* Pattern is computed more than once.
Search backwards from this insn to see how many of these
computations actually reach this insn. */
struct occr *occr;
rtx insn_computes_expr = NULL;
int can_reach = 0;
for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
{
if (BLOCK_NUM (occr->insn) == bb)
{
/* The expression is generated in this block.
The only time we care about this is when the expression
is generated later in the block [and thus there's a loop].
We let the normal cse pass handle the other cases. */
if (INSN_CUID (insn) < INSN_CUID (occr->insn))
{
if (expr_reaches_here_p (occr, expr, bb, 1, NULL))
{
can_reach++;
if (can_reach > 1)
return NULL;
insn_computes_expr = occr->insn;
}
}
}
else /* Computation of the pattern outside this block. */
{
if (expr_reaches_here_p (occr, expr, bb, 0, NULL))
{
can_reach++;
if (can_reach > 1)
return NULL;
insn_computes_expr = occr->insn;
}
}
}
if (insn_computes_expr == NULL)
abort ();
return insn_computes_expr;
}
}
/* Return non-zero if the definition in DEF_INSN can reach INSN.
Only called by can_disregard_other_sets. */
static int
def_reaches_here_p (insn, def_insn)
rtx insn, def_insn;
{
rtx reg;
if (TEST_BIT (reaching_defs[BLOCK_NUM (insn)], INSN_CUID (def_insn)))
return 1;
if (BLOCK_NUM (insn) == BLOCK_NUM (def_insn))
{
if (INSN_CUID (def_insn) < INSN_CUID (insn))
{
if (GET_CODE (PATTERN (def_insn)) == PARALLEL)
return 1;
if (GET_CODE (PATTERN (def_insn)) == CLOBBER)
reg = XEXP (PATTERN (def_insn), 0);
else if (GET_CODE (PATTERN (def_insn)) == SET)
reg = SET_DEST (PATTERN (def_insn));
else
abort ();
return ! reg_set_between_p (reg, NEXT_INSN (def_insn), insn);
}
else
return 0;
}
return 0;
}
/* Return non-zero if *ADDR_THIS_REG can only have one value at INSN.
The value returned is the number of definitions that reach INSN.
Returning a value of zero means that [maybe] more than one definition
reaches INSN and the caller can't perform whatever optimization it is
trying. i.e. it is always safe to return zero. */
static int
can_disregard_other_sets (addr_this_reg, insn, for_combine)
struct reg_set **addr_this_reg;
rtx insn;
int for_combine;
{
int number_of_reaching_defs = 0;
struct reg_set *this_reg = *addr_this_reg;
while (this_reg)
{
if (def_reaches_here_p (insn, this_reg->insn))
{
number_of_reaching_defs++;
/* Ignore parallels for now. */
if (GET_CODE (PATTERN (this_reg->insn)) == PARALLEL)
return 0;
if (!for_combine
&& (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER
|| ! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
SET_SRC (PATTERN (insn)))))
{
/* A setting of the reg to a different value reaches INSN. */
return 0;
}
if (number_of_reaching_defs > 1)
{
/* If in this setting the value the register is being
set to is equal to the previous value the register
was set to and this setting reaches the insn we are
trying to do the substitution on then we are ok. */
if (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER)
return 0;
if (! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
SET_SRC (PATTERN (insn))))
return 0;
}
*addr_this_reg = this_reg;
}
/* prev_this_reg = this_reg; */
this_reg = this_reg->next;
}
return number_of_reaching_defs;
}
/* Expression computed by insn is available and the substitution is legal,
so try to perform the substitution.
The result is non-zero if any changes were made. */
static int
handle_avail_expr (insn, expr)
rtx insn;
struct expr *expr;
{
rtx pat, insn_computes_expr;
rtx to;
struct reg_set *this_reg;
int found_setting, use_src;
int changed = 0;
/* We only handle the case where one computation of the expression
reaches this instruction. */
insn_computes_expr = computing_insn (expr, insn);
if (insn_computes_expr == NULL)
return 0;
found_setting = 0;
use_src = 0;
/* At this point we know only one computation of EXPR outside of this
block reaches this insn. Now try to find a register that the
expression is computed into. */
if (GET_CODE (SET_SRC (PATTERN (insn_computes_expr))) == REG)
{
/* This is the case when the available expression that reaches
here has already been handled as an available expression. */
int regnum_for_replacing = REGNO (SET_SRC (PATTERN (insn_computes_expr)));
/* If the register was created by GCSE we can't use `reg_set_table',
however we know it's set only once. */
if (regnum_for_replacing >= max_gcse_regno
/* If the register the expression is computed into is set only once,
or only one set reaches this insn, we can use it. */
|| (((this_reg = reg_set_table[regnum_for_replacing]),
this_reg->next == NULL)
|| can_disregard_other_sets (&this_reg, insn, 0)))
{
use_src = 1;
found_setting = 1;
}
}
if (!found_setting)
{
int regnum_for_replacing = REGNO (SET_DEST (PATTERN (insn_computes_expr)));
/* This shouldn't happen. */
if (regnum_for_replacing >= max_gcse_regno)
abort ();
this_reg = reg_set_table[regnum_for_replacing];
/* If the register the expression is computed into is set only once,
or only one set reaches this insn, use it. */
if (this_reg->next == NULL
|| can_disregard_other_sets (&this_reg, insn, 0))
found_setting = 1;
}
if (found_setting)
{
pat = PATTERN (insn);
if (use_src)
to = SET_SRC (PATTERN (insn_computes_expr));
else
to = SET_DEST (PATTERN (insn_computes_expr));
changed = validate_change (insn, &SET_SRC (pat), to, 0);
/* We should be able to ignore the return code from validate_change but
to play it safe we check. */
if (changed)
{
gcse_subst_count++;
if (gcse_file != NULL)
{
fprintf (gcse_file, "GCSE: Replacing the source in insn %d with reg %d %s insn %d\n",
INSN_UID (insn), REGNO (to),
use_src ? "from" : "set in",
INSN_UID (insn_computes_expr));
}
}
}
/* The register that the expr is computed into is set more than once. */
else if (1 /*expensive_op(this_pattrn->op) && do_expensive_gcse)*/)
{
/* Insert an insn after insnx that copies the reg set in insnx
into a new pseudo register call this new register REGN.
From insnb until end of basic block or until REGB is set
replace all uses of REGB with REGN. */
rtx new_insn;
to = gen_reg_rtx (GET_MODE (SET_DEST (PATTERN (insn_computes_expr))));
/* Generate the new insn. */
/* ??? If the change fails, we return 0, even though we created
an insn. I think this is ok. */
new_insn = emit_insn_after (gen_rtx (SET, VOIDmode, to,
SET_DEST (PATTERN (insn_computes_expr))),
insn_computes_expr);
/* Keep block number table up to date. */
set_block_num (new_insn, BLOCK_NUM (insn_computes_expr));
/* Keep register set table up to date. */
record_one_set (REGNO (to), new_insn);
gcse_create_count++;
if (gcse_file != NULL)
{
fprintf (gcse_file, "GCSE: Creating insn %d to copy value of reg %d, computed in insn %d,\n",
INSN_UID (NEXT_INSN (insn_computes_expr)),
REGNO (SET_SRC (PATTERN (NEXT_INSN (insn_computes_expr)))),
INSN_UID (insn_computes_expr));
fprintf (gcse_file, " into newly allocated reg %d\n", REGNO (to));
}
pat = PATTERN (insn);
/* Do register replacement for INSN. */
changed = validate_change (insn, &SET_SRC (pat),
SET_DEST (PATTERN (NEXT_INSN (insn_computes_expr))),
0);
/* We should be able to ignore the return code from validate_change but
to play it safe we check. */
if (changed)
{
gcse_subst_count++;
if (gcse_file != NULL)
{
fprintf (gcse_file, "GCSE: Replacing the source in insn %d with reg %d set in insn %d\n",
INSN_UID (insn),
REGNO (SET_DEST (PATTERN (NEXT_INSN (insn_computes_expr)))),
INSN_UID (insn_computes_expr));
}
}
}
return changed;
}
/* Perform classic GCSE.
This is called by one_classic_gcse_pass after all the dataflow analysis
has been done.
The result is non-zero if a change was made. */
static int
classic_gcse ()
{
int bb, changed;
rtx insn;
/* Note we start at block 1. */
changed = 0;
for (bb = 1; bb < n_basic_blocks; bb++)
{
/* Reset tables used to keep track of what's still valid [since the
start of the block]. */
reset_opr_set_tables ();
for (insn = BLOCK_HEAD (bb);
insn != NULL && insn != NEXT_INSN (BLOCK_END (bb));
insn = NEXT_INSN (insn))
{
/* Is insn of form (set (pseudo-reg) ...)? */
if (GET_CODE (insn) == INSN
&& GET_CODE (PATTERN (insn)) == SET
&& GET_CODE (SET_DEST (PATTERN (insn))) == REG
&& REGNO (SET_DEST (PATTERN (insn))) >= FIRST_PSEUDO_REGISTER)
{
rtx pat = PATTERN (insn);
rtx src = SET_SRC (pat);
struct expr *expr;
if (want_to_gcse_p (src)
/* Is the expression recorded? */
&& ((expr = lookup_expr (src)) != NULL)
/* Is the expression available [at the start of the
block]? */
&& TEST_BIT (ae_in[bb], expr->bitmap_index)
/* Are the operands unchanged since the start of the
block? */
&& oprs_not_set_p (src, insn))
changed |= handle_avail_expr (insn, expr);
}
/* Keep track of everything modified by this insn. */
/* ??? Need to be careful w.r.t. mods done to INSN. */
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
mark_oprs_set (insn);
}
}
return changed;
}
/* Top level routine to perform one classic GCSE pass.
Return non-zero if a change was made. */
static int
one_classic_gcse_pass (pass)
int pass;
{
int changed = 0;
gcse_subst_count = 0;
gcse_create_count = 0;
alloc_expr_hash_table (max_cuid);
alloc_rd_mem (n_basic_blocks, max_cuid);
compute_expr_hash_table ();
if (gcse_file)
dump_hash_table (gcse_file, "Expression", expr_hash_table,
expr_hash_table_size, n_exprs);
if (n_exprs > 0)
{
compute_kill_rd ();
compute_rd ();
alloc_avail_expr_mem (n_basic_blocks, n_exprs);
compute_ae_gen ();
compute_ae_kill ();
compute_available ();
changed = classic_gcse ();
free_avail_expr_mem ();
}
free_rd_mem ();
free_expr_hash_table ();
if (gcse_file)
{
fprintf (gcse_file, "\n");
fprintf (gcse_file, "GCSE of %s, pass %d: %d bytes needed, %d substs, %d insns created\n",
current_function_name, pass,
bytes_used, gcse_subst_count, gcse_create_count);
}
return changed;
}
/* Compute copy/constant propagation working variables. */
/* Local properties of assignments. */
static sbitmap *cprop_pavloc;
static sbitmap *cprop_absaltered;
/* Global properties of assignments (computed from the local properties). */
static sbitmap *cprop_avin;
static sbitmap *cprop_avout;
/* Allocate vars used for copy/const propagation.
N_BLOCKS is the number of basic blocks.
N_SETS is the number of sets. */
static void
alloc_cprop_mem (n_blocks, n_sets)
int n_blocks, n_sets;
{
cprop_pavloc = sbitmap_vector_alloc (n_blocks, n_sets);
cprop_absaltered = sbitmap_vector_alloc (n_blocks, n_sets);
cprop_avin = sbitmap_vector_alloc (n_blocks, n_sets);
cprop_avout = sbitmap_vector_alloc (n_blocks, n_sets);
}
/* Free vars used by copy/const propagation. */
static void
free_cprop_mem ()
{
free (cprop_pavloc);
free (cprop_absaltered);
free (cprop_avin);
free (cprop_avout);
}
/* For each block, compute whether X is transparent.
X is either an expression or an assignment [though we don't care which,
for this context an assignment is treated as an expression].
For each block where an element of X is modified, set (SET_P == 1) or reset
(SET_P == 0) the INDX bit in BMAP. */
static void
compute_transp (x, indx, bmap, set_p)
rtx x;
int indx;
sbitmap *bmap;
int set_p;
{
int bb,i;
enum rtx_code code;
char *fmt;
/* repeat is used to turn tail-recursion into iteration. */
repeat:
if (x == 0)
return;
code = GET_CODE (x);
switch (code)
{
case REG:
{
reg_set *r;
int regno = REGNO (x);
if (set_p)
{
if (regno < FIRST_PSEUDO_REGISTER)
{
for (bb = 0; bb < n_basic_blocks; bb++)
if (TEST_BIT (reg_set_in_block[bb], regno))
SET_BIT (bmap[bb], indx);
}
else
{
for (r = reg_set_table[regno]; r != NULL; r = r->next)
{
bb = BLOCK_NUM (r->insn);
SET_BIT (bmap[bb], indx);
}
}
}
else
{
if (regno < FIRST_PSEUDO_REGISTER)
{
for (bb = 0; bb < n_basic_blocks; bb++)
if (TEST_BIT (reg_set_in_block[bb], regno))
RESET_BIT (bmap[bb], indx);
}
else
{
for (r = reg_set_table[regno]; r != NULL; r = r->next)
{
bb = BLOCK_NUM (r->insn);
RESET_BIT (bmap[bb], indx);
}
}
}
return;
}
case MEM:
for (bb = 0; bb < n_basic_blocks; bb++)
{
rtx list_entry = modify_mem_list[bb];
while (list_entry)
{
rtx mem;
if (GET_CODE (XEXP (list_entry, 0)) == CALL_INSN)
{
if (set_p)
SET_BIT (bmap[bb], indx);
else
RESET_BIT (bmap[bb], indx);
break;
}
if (GET_CODE (PATTERN (XEXP (list_entry, 0))) == CLOBBER)
mem = PATTERN (XEXP (list_entry, 0));
else
mem = SET_DEST (PATTERN (XEXP (list_entry, 0)));
if (true_dependence (mem, GET_MODE (mem), x, rtx_addr_varies_p))
{
if (set_p)
SET_BIT (bmap[bb], indx);
else
RESET_BIT (bmap[bb], indx);
break;
}
list_entry = XEXP (list_entry, 1);
}
}
x = XEXP (x, 0);
goto repeat;
case PC:
case CC0: /*FIXME*/
case CONST:
case CONST_INT:
case CONST_DOUBLE:
case SYMBOL_REF:
case LABEL_REF:
case ADDR_VEC:
case ADDR_DIFF_VEC:
return;
default:
break;
}
i = GET_RTX_LENGTH (code) - 1;
fmt = GET_RTX_FORMAT (code);
for (; i >= 0; i--)
{
if (fmt[i] == 'e')
{
rtx tem = XEXP (x, i);
/* If we are about to do the last recursive call
needed at this level, change it into iteration.
This function is called enough to be worth it. */
if (i == 0)
{
x = tem;
goto repeat;
}
compute_transp (tem, indx, bmap, set_p);
}
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
compute_transp (XVECEXP (x, i, j), indx, bmap, set_p);
}
}
}
/* Compute the available expressions at the start and end of each
basic block for cprop. This particular dataflow equation is
used often enough that we might want to generalize it and make
as a subroutine for other global optimizations that need available
in/out information. */
static void
compute_cprop_avinout ()
{
int bb, changed, passes;
sbitmap_zero (cprop_avin[0]);
sbitmap_vector_ones (cprop_avout, n_basic_blocks);
passes = 0;
changed = 1;
while (changed)
{
changed = 0;
for (bb = 0; bb < n_basic_blocks; bb++)
{
if (bb != 0)
sbitmap_intersect_of_predecessors (cprop_avin[bb],
cprop_avout, bb, s_preds);
changed |= sbitmap_union_of_diff (cprop_avout[bb],
cprop_pavloc[bb],
cprop_avin[bb],
cprop_absaltered[bb]);
}
passes++;
}
if (gcse_file)
fprintf (gcse_file, "cprop avail expr computation: %d passes\n", passes);
}
/* Top level routine to do the dataflow analysis needed by copy/const
propagation. */
static void
compute_cprop_data ()
{
compute_local_properties (cprop_absaltered, cprop_pavloc, NULL, 1);
compute_cprop_avinout ();
}
/* Copy/constant propagation. */
struct reg_use {
rtx reg_rtx;
};
/* Maximum number of register uses in an insn that we handle. */
#define MAX_USES 8
/* Table of uses found in an insn.
Allocated statically to avoid alloc/free complexity and overhead. */
static struct reg_use reg_use_table[MAX_USES];
/* Index into `reg_use_table' while building it. */
static int reg_use_count;
/* Set up a list of register numbers used in INSN.
The found uses are stored in `reg_use_table'.
`reg_use_count' is initialized to zero before entry, and
contains the number of uses in the table upon exit.
??? If a register appears multiple times we will record it multiple
times. This doesn't hurt anything but it will slow things down. */
static void
find_used_regs (x)
rtx x;
{
int i;
enum rtx_code code;
char *fmt;
/* repeat is used to turn tail-recursion into iteration. */
repeat:
if (x == 0)
return;
code = GET_CODE (x);
switch (code)
{
case REG:
if (reg_use_count == MAX_USES)
return;
reg_use_table[reg_use_count].reg_rtx = x;
reg_use_count++;
return;
case MEM:
x = XEXP (x, 0);
goto repeat;
case PC:
case CC0:
case CONST:
case CONST_INT:
case CONST_DOUBLE:
case SYMBOL_REF:
case LABEL_REF:
case CLOBBER:
case ADDR_VEC:
case ADDR_DIFF_VEC:
case ASM_INPUT: /*FIXME*/
return;
case SET:
if (GET_CODE (SET_DEST (x)) == MEM)
find_used_regs (SET_DEST (x));
x = SET_SRC (x);
goto repeat;
default:
break;
}
/* Recursively scan the operands of this expression. */
fmt = GET_RTX_FORMAT (code);
for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
{
if (fmt[i] == 'e')
{
/* If we are about to do the last recursive call
needed at this level, change it into iteration.
This function is called enough to be worth it. */
if (i == 0)
{
x = XEXP (x, 0);
goto repeat;
}
find_used_regs (XEXP (x, i));
}
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
find_used_regs (XVECEXP (x, i, j));
}
}
}
/* Try to replace all non-SET_DEST occurrences of FROM in INSN with TO.
Returns non-zero is successful. */
static int
try_replace_reg (from, to, insn)
rtx from, to, insn;
{
/* If this fails we could try to simplify the result of the
replacement and attempt to recognize the simplified insn.
But we need a general simplify_rtx that doesn't have pass
specific state variables. I'm not aware of one at the moment. */
return validate_replace_src (from, to, insn);
}
/* Find a set of REGNO that is available on entry to INSN's block.
Returns NULL if not found. */
static struct expr *
find_avail_set (regno, insn)
int regno;
rtx insn;
{
struct expr *set = lookup_set (regno, NULL_RTX);
while (set)
{
if (TEST_BIT (cprop_avin[BLOCK_NUM (insn)], set->bitmap_index))
break;
set = next_set (regno, set);
}
return set;
}
/* Perform constant and copy propagation on INSN.
The result is non-zero if a change was made. */
static int
cprop_insn (insn, alter_jumps)
rtx insn;
int alter_jumps;
{
struct reg_use *reg_used;
int changed = 0;
/* Only propagate into SETs. Note that a conditional jump is a
SET with pc_rtx as the destination. */
if ((GET_CODE (insn) != INSN
&& GET_CODE (insn) != JUMP_INSN)
|| GET_CODE (PATTERN (insn)) != SET)
return 0;
reg_use_count = 0;
find_used_regs (PATTERN (insn));
reg_used = &reg_use_table[0];
for ( ; reg_use_count > 0; reg_used++, reg_use_count--)
{
rtx pat, src;
struct expr *set;
int regno = REGNO (reg_used->reg_rtx);
/* Ignore registers created by GCSE.
We do this because ... */
if (regno >= max_gcse_regno)
continue;
/* If the register has already been set in this block, there's
nothing we can do. */
if (! oprs_not_set_p (reg_used->reg_rtx, insn))
continue;
/* Find an assignment that sets reg_used and is available
at the start of the block. */
set = find_avail_set (regno, insn);
if (! set)
continue;
pat = set->expr;
/* ??? We might be able to handle PARALLELs. Later. */
if (GET_CODE (pat) != SET)
abort ();
src = SET_SRC (pat);
/* Constant propagation. */
if (GET_CODE (src) == CONST_INT)
{
/* Handle normal insns first. */
if (GET_CODE (insn) == INSN
&& try_replace_reg (reg_used->reg_rtx, src, insn))
{
changed = 1;
const_prop_count++;
if (gcse_file != NULL)
{
fprintf (gcse_file, "CONST-PROP: Replacing reg %d in insn %d with constant ",
regno, INSN_UID (insn));
fprintf (gcse_file, HOST_WIDE_INT_PRINT_DEC, INTVAL (src));
fprintf (gcse_file, "\n");
}
/* The original insn setting reg_used may or may not now be
deletable. We leave the deletion to flow. */
}
/* CYGNUS LOCAL gcse/law */
/* Try to propagate a CONST_INT into a conditional jump.
We're pretty specific about what we will handle in this
code, we can extend this as necessary over time.
Right now the insn in question must look like
(set (pc) (if_then_else ...))
Note this does not currently handle machines which use cc0. */
else if (alter_jumps
&& GET_CODE (insn) == JUMP_INSN && condjump_p (insn))
{
/* We want a copy of the JUMP_INSN so we can modify it
in-place as needed without effecting the original. */
rtx copy = copy_rtx (insn);
rtx set = PATTERN (copy);
rtx temp;
/* Replace the register with the appropriate constant. */
replace_rtx (SET_SRC (set), reg_used->reg_rtx, src);
temp = simplify_ternary_operation (GET_CODE (SET_SRC (set)),
GET_MODE (SET_SRC (set)),
GET_MODE (XEXP (SET_SRC (set), 0)),
XEXP (SET_SRC (set), 0),
XEXP (SET_SRC (set), 1),
XEXP (SET_SRC (set), 2));
/* If no simplification can be made, then try the next
register. */
if (temp)
SET_SRC (set) = temp;
else
continue;
/* That may have changed the structure of TEMP, so
force it to be rerecognized if it has not turned
into a nop or unconditional jump. */
INSN_CODE (copy) = -1;
if ((SET_DEST (set) == pc_rtx
&& (SET_SRC (set) == pc_rtx
|| GET_CODE (SET_SRC (set)) == LABEL_REF))
|| recog (PATTERN (copy), copy, NULL) >= 0)
{
/* This has either become an unconditional jump
or a nop-jump. We'd like to delete nop jumps
here, but doing so confuses gcse. So we just
make the replacement and let later passes
sort things out. */
PATTERN (insn) = set;
INSN_CODE (insn) = -1;
/* One less use of the label this insn used to jump to
if we turned this into a NOP jump. */
if (SET_SRC (set) == pc_rtx && JUMP_LABEL (insn) != 0)
--LABEL_NUSES (JUMP_LABEL (insn));
/* If this has turned into an unconditional jump,
then put a barrier after it so that the unreachable
code will be deleted. */
if (GET_CODE (SET_SRC (set)) == LABEL_REF)
emit_barrier_after (insn);
run_jump_opt_after_gcse = 1;
changed = 1;
const_prop_count++;
if (gcse_file != NULL)
{
fprintf (gcse_file, "CONST-PROP: Replacing reg %d in insn %d with constant ",
regno, INSN_UID (insn));
fprintf (gcse_file, HOST_WIDE_INT_PRINT_DEC,
INTVAL (src));
fprintf (gcse_file, "\n");
}
}
}
/* END CYGNUS LOCAL */
}
else if (GET_CODE (src) == REG
&& REGNO (src) >= FIRST_PSEUDO_REGISTER
&& REGNO (src) != regno)
{
/* We know the set is available.
Now check that SET_SRC is ANTLOC (i.e. none of the source operands
have changed since the start of the block). */
if (oprs_not_set_p (src, insn))
{
if (try_replace_reg (reg_used->reg_rtx, src, insn))
{
changed = 1;
copy_prop_count++;
if (gcse_file != NULL)
{
fprintf (gcse_file, "COPY-PROP: Replacing reg %d in insn %d with reg %d\n",
regno, INSN_UID (insn), REGNO (src));
}
/* The original insn setting reg_used may or may not now be
deletable. We leave the deletion to flow. */
/* FIXME: If it turns out that the insn isn't deletable,
then we may have unnecessarily extended register lifetimes
and made things worse. */
}
}
}
}
return changed;
}
/* Forward propagate copies.
This includes copies and constants.
Return non-zero if a change was made. */
static int
cprop (alter_jumps)
int alter_jumps;
{
int bb, changed;
rtx insn;
/* Note we start at block 1. */
changed = 0;
for (bb = 1; bb < n_basic_blocks; bb++)
{
/* Reset tables used to keep track of what's still valid [since the
start of the block]. */
reset_opr_set_tables ();
for (insn = BLOCK_HEAD (bb);
insn != NULL && insn != NEXT_INSN (BLOCK_END (bb));
insn = NEXT_INSN (insn))
{
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
{
changed |= cprop_insn (insn, alter_jumps);
/* Keep track of everything modified by this insn. */
/* ??? Need to be careful w.r.t. mods done to INSN. */
mark_oprs_set (insn);
}
}
}
if (gcse_file != NULL)
fprintf (gcse_file, "\n");
return changed;
}
/* Perform one copy/constant propagation pass.
F is the first insn in the function.
PASS is the pass count. */
static int
one_cprop_pass (pass, alter_jumps)
int pass;
int alter_jumps;
{
int changed = 0;
const_prop_count = 0;
copy_prop_count = 0;
alloc_set_hash_table (max_cuid);
compute_set_hash_table ();
if (gcse_file)
dump_hash_table (gcse_file, "SET", set_hash_table, set_hash_table_size,
n_sets);
if (n_sets > 0)
{
alloc_cprop_mem (n_basic_blocks, n_sets);
compute_cprop_data ();
changed = cprop (alter_jumps);
free_cprop_mem ();
}
free_set_hash_table ();
if (gcse_file)
{
fprintf (gcse_file, "CPROP of %s, pass %d: %d bytes needed, %d const props, %d copy props\n",
current_function_name, pass,
bytes_used, const_prop_count, copy_prop_count);
fprintf (gcse_file, "\n");
}
return changed;
}
/* Compute PRE+LCM working variables. */
/* Local properties of expressions. */
/* Nonzero for expressions that are transparent in the block. */
static sbitmap *transp;
/* Nonzero for expressions that are transparent at the end of the block.
This is only zero for expressions killed by abnormal critical edge
created by a calls. */
static sbitmap *transpout;
/* Nonzero for expressions that are computed (available) in the block. */
static sbitmap *comp;
/* Nonzero for expressions that are locally anticipatable in the block. */
static sbitmap *antloc;
/* Nonzero for expressions where this block is an optimal computation
point. */
static sbitmap *pre_optimal;
/* Nonzero for expressions which are redundant in a particular block. */
static sbitmap *pre_redundant;
static sbitmap *temp_bitmap;
/* Redundant insns. */
static sbitmap pre_redundant_insns;
/* Allocate vars used for PRE analysis. */
static void
alloc_pre_mem (n_blocks, n_exprs)
int n_blocks, n_exprs;
{
transp = sbitmap_vector_alloc (n_blocks, n_exprs);
comp = sbitmap_vector_alloc (n_blocks, n_exprs);
antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
temp_bitmap = sbitmap_vector_alloc (n_blocks, n_exprs);
pre_optimal = sbitmap_vector_alloc (n_blocks, n_exprs);
pre_redundant = sbitmap_vector_alloc (n_blocks, n_exprs);
transpout = sbitmap_vector_alloc (n_blocks, n_exprs);
}
/* Free vars used for PRE analysis. */
static void
free_pre_mem ()
{
free (transp);
free (comp);
free (antloc);
free (pre_optimal);
free (pre_redundant);
free (transpout);
}
/* Top level routine to do the dataflow analysis needed by PRE. */
static void
compute_pre_data ()
{
compute_local_properties (transp, comp, antloc, 0);
compute_transpout ();
pre_lcm (n_basic_blocks, n_exprs, s_preds, s_succs, transp,
antloc, pre_redundant, pre_optimal);
}
/* PRE utilities */
/* Return non-zero if an occurrence of expression EXPR in OCCR_BB would reach
block BB.
VISITED is a pointer to a working buffer for tracking which BB's have
been visited. It is NULL for the top-level call.
CHECK_PRE_COMP controls whether or not we check for a computation of
EXPR in OCCR_BB.
We treat reaching expressions that go through blocks containing the same
reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2 as not reaching. The intent is to improve the probability of finding
only one reaching expression and to reduce register lifetimes by picking
the closest such expression. */
static int
pre_expr_reaches_here_p (occr_bb, expr, bb, check_pre_comp, visited)
int occr_bb;
struct expr *expr;
int bb;
int check_pre_comp;
char *visited;
{
int_list_ptr pred;
if (visited == NULL)
{
visited = (char *) alloca (n_basic_blocks);
zero_memory (visited, n_basic_blocks);
}
for (pred = s_preds[bb]; pred != NULL; pred = pred->next)
{
int pred_bb = INT_LIST_VAL (pred);
if (pred_bb == ENTRY_BLOCK
/* Has predecessor has already been visited? */
|| visited[pred_bb])
{
/* Nothing to do. */
}
/* Does this predecessor generate this expression? */
else if ((!check_pre_comp && occr_bb == pred_bb)
|| TEST_BIT (comp[pred_bb], expr->bitmap_index))
{
/* Is this the occurrence we're looking for?
Note that there's only one generating occurrence per block
so we just need to check the block number. */
if (occr_bb == pred_bb)
return 1;
visited[pred_bb] = 1;
}
/* Ignore this predecessor if it kills the expression. */
else if (! TEST_BIT (transp[pred_bb], expr->bitmap_index))
visited[pred_bb] = 1;
/* Neither gen nor kill. */
else
{
visited[pred_bb] = 1;
if (pre_expr_reaches_here_p (occr_bb, expr, pred_bb,
check_pre_comp, visited))
return 1;
}
}
/* All paths have been checked. */
return 0;
}
/* Add EXPR to the end of basic block BB.
This is used by both the PRE and code hoisting.
For PRE, we want to verify that the expr is either transparent
or locally anticipatable in the target block. This check makes
no sense for code hoisting. */
static void
insert_insn_end_bb (expr, bb, pre)
struct expr *expr;
int bb;
int pre;
{
rtx insn = BLOCK_END (bb);
rtx new_insn;
rtx reg = expr->reaching_reg;
int regno = REGNO (reg);
rtx pat;
pat = gen_rtx (SET, VOIDmode, reg, copy_rtx (expr->expr));
/* If the last insn is a jump, insert EXPR in front [taking care to
handle cc0, etc. properly]. */
if (GET_CODE (insn) == JUMP_INSN)
{
#ifdef HAVE_cc0
rtx note;
#endif
/* If this is a jump table, then we can't insert stuff here. Since
we know the previous real insn must be the tablejump, we insert
the new instruction just before the tablejump. */
if (GET_CODE (PATTERN (insn)) == ADDR_VEC
|| GET_CODE (PATTERN (insn)) == ADDR_DIFF_VEC)
insn = prev_real_insn (insn);
#ifdef HAVE_cc0
/* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
if cc0 isn't set. */
note = find_reg_note (insn, REG_CC_SETTER, NULL_RTX);
if (note)
insn = XEXP (note, 0);
else
{
rtx maybe_cc0_setter = prev_nonnote_insn (insn);
if (maybe_cc0_setter
&& GET_RTX_CLASS (GET_CODE (maybe_cc0_setter)) == 'i'
&& sets_cc0_p (PATTERN (maybe_cc0_setter)))
insn = maybe_cc0_setter;
}
#endif
/* FIXME: What if something in cc0/jump uses value set in new insn? */
new_insn = emit_insn_before (pat, insn);
if (BLOCK_HEAD (bb) == insn)
BLOCK_HEAD (bb) = new_insn;
}
/* Likewise if the last insn is a call, as will happen in the presence
of exception handling. */
else if (GET_CODE (insn) == CALL_INSN)
{
HARD_REG_SET parm_regs;
int nparm_regs;
rtx p;
/* Keeping in mind SMALL_REGISTER_CLASSES and parameters in registers,
we search backward and place the instructions before the first
parameter is loaded. Do this for everyone for consistency and a
presumtion that we'll get better code elsewhere as well. */
/* It should always be the case that we can put these instructions
anywhere in the basic block with performing PRE optimizations.
Check this. */
if (pre
&& !TEST_BIT (antloc[bb], expr->bitmap_index)
&& !TEST_BIT (transp[bb], expr->bitmap_index))
abort ();
/* Since different machines initialize their parameter registers
in different orders, assume nothing. Collect the set of all
parameter registers. */
CLEAR_HARD_REG_SET (parm_regs);
nparm_regs = 0;
for (p = CALL_INSN_FUNCTION_USAGE (insn); p ; p = XEXP (p, 1))
if (GET_CODE (XEXP (p, 0)) == USE
&& GET_CODE (XEXP (XEXP (p, 0), 0)) == REG)
{
int regno = REGNO (XEXP (XEXP (p, 0), 0));
if (regno >= FIRST_PSEUDO_REGISTER)
abort();
SET_HARD_REG_BIT (parm_regs, regno);
nparm_regs++;
}
/* Search backward for the first set of a register in this set. */
while (nparm_regs && BLOCK_HEAD (bb) != insn)
{
insn = PREV_INSN (insn);
p = single_set (insn);
if (p && GET_CODE (SET_DEST (p)) == REG
&& REGNO (SET_DEST (p)) < FIRST_PSEUDO_REGISTER
&& TEST_HARD_REG_BIT (parm_regs, REGNO (SET_DEST (p))))
{
CLEAR_HARD_REG_BIT (parm_regs, REGNO (SET_DEST (p)));
nparm_regs--;
}
}
new_insn = emit_insn_before (pat, insn);
if (BLOCK_HEAD (bb) == insn)
BLOCK_HEAD (bb) = new_insn;
}
else
{
new_insn = emit_insn_after (pat, insn);
BLOCK_END (bb) = new_insn;
}
/* Keep block number table up to date. */
set_block_num (new_insn, bb);
/* Keep register set table up to date. */
record_one_set (regno, new_insn);
gcse_create_count++;
if (gcse_file)
{
fprintf (gcse_file, "PRE/HOIST: end of bb %d, insn %d, copying expression %d to reg %d\n",
bb, INSN_UID (new_insn), expr->bitmap_index, regno);
}
}
/* Insert partially redundant expressions at the ends of appropriate basic
blocks making them fully redundant. */
static void
pre_insert (index_map)
struct expr **index_map;
{
int bb, i, set_size;
sbitmap *inserted;
/* Compute INSERT = PRE_OPTIMAL & ~PRE_REDUNDANT.
Where INSERT is nonzero, we add the expression at the end of the basic
block if it reaches any of the deleted expressions. */
set_size = pre_optimal[0]->size;
inserted = sbitmap_vector_alloc (n_basic_blocks, n_exprs);
sbitmap_vector_zero (inserted, n_basic_blocks);
for (bb = 0; bb < n_basic_blocks; bb++)
{
int indx;
/* This computes the number of potential insertions we need. */
sbitmap_not (temp_bitmap[bb], pre_redundant[bb]);
sbitmap_a_and_b (temp_bitmap[bb], temp_bitmap[bb], pre_optimal[bb]);
/* TEMP_BITMAP[bb] now contains a bitmap of the expressions that we need
to insert at the end of this basic block. */
for (i = indx = 0; i < set_size; i++, indx += SBITMAP_ELT_BITS)
{
SBITMAP_ELT_TYPE insert = temp_bitmap[bb]->elms[i];
int j;
for (j = indx; insert && j < n_exprs; j++, insert >>= 1)
{
if ((insert & 1) != 0 && index_map[j]->reaching_reg != NULL_RTX)
{
struct expr *expr = index_map[j];
struct occr *occr;
/* Now look at each deleted occurence of this expression. */
for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
{
if (! occr->deleted_p)
continue;
/* Insert this expression at the end of BB if it would
reach the deleted occurence. */
if (!TEST_BIT (inserted[bb], j)
&& pre_expr_reaches_here_p (bb, expr,
BLOCK_NUM (occr->insn), 0,
NULL))
{
SET_BIT (inserted[bb], j);
insert_insn_end_bb (index_map[j], bb, 1);
}
}
}
}
}
}
}
/* Copy the result of INSN to REG.
INDX is the expression number. */
static void
pre_insert_copy_insn (expr, insn)
struct expr *expr;
rtx insn;
{
rtx reg = expr->reaching_reg;
int regno = REGNO (reg);
int indx = expr->bitmap_index;
rtx set = single_set (insn);
rtx new_insn;
if (!set)
abort ();
new_insn = emit_insn_after (gen_rtx (SET, VOIDmode, reg, SET_DEST (set)),
insn);
/* Keep block number table up to date. */
set_block_num (new_insn, BLOCK_NUM (insn));
/* Keep register set table up to date. */
record_one_set (regno, new_insn);
gcse_create_count++;
if (gcse_file)
{
fprintf (gcse_file, "PRE: bb %d, insn %d, copying expression %d in insn %d to reg %d\n",
BLOCK_NUM (insn), INSN_UID (new_insn), indx, INSN_UID (insn), regno);
}
}
/* Copy available expressions that reach the redundant expression
to `reaching_reg'. */
static void
pre_insert_copies ()
{
int i, bb;
for (bb = 0; bb < n_basic_blocks; bb++)
{
sbitmap_a_and_b (temp_bitmap[bb], pre_optimal[bb], pre_redundant[bb]);
}
/* For each available expression in the table, copy the result to
`reaching_reg' if the expression reaches a deleted one.
??? The current algorithm is rather brute force.
Need to do some profiling. */
for (i = 0; i < expr_hash_table_size; i++)
{
struct expr *expr;
for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
{
struct occr *occr;
/* If the basic block isn't reachable, PPOUT will be TRUE.
However, we don't want to insert a copy here because the
expression may not really be redundant. So only insert
an insn if the expression was deleted.
This test also avoids further processing if the expression
wasn't deleted anywhere. */
if (expr->reaching_reg == NULL)
continue;
for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
{
struct occr *avail;
if (! occr->deleted_p)
continue;
for (avail = expr->avail_occr; avail != NULL; avail = avail->next)
{
rtx insn = avail->insn;
int bb = BLOCK_NUM (insn);
if (!TEST_BIT (temp_bitmap[bb], expr->bitmap_index))
continue;
/* No need to handle this one if handled already. */
if (avail->copied_p)
continue;
/* Don't handle this one if it's a redundant one. */
if (TEST_BIT (pre_redundant_insns, INSN_CUID (insn)))
continue;
/* Or if the expression doesn't reach the deleted one. */
if (! pre_expr_reaches_here_p (BLOCK_NUM (avail->insn), expr,
BLOCK_NUM (occr->insn),
1, NULL))
continue;
/* Copy the result of avail to reaching_reg. */
pre_insert_copy_insn (expr, insn);
avail->copied_p = 1;
}
}
}
}
}
/* Delete redundant computations.
Deletion is done by changing the insn to copy the `reaching_reg' of
the expression into the result of the SET. It is left to later passes
(cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it.
Returns non-zero if a change is made. */
static int
pre_delete ()
{
int i, bb, changed;
/* Compute the expressions which are redundant and need to be replaced by
copies from the reaching reg to the target reg. */
for (bb = 0; bb < n_basic_blocks; bb++)
{
sbitmap_not (temp_bitmap[bb], pre_optimal[bb]);
sbitmap_a_and_b (temp_bitmap[bb], temp_bitmap[bb], pre_redundant[bb]);
}
changed = 0;
for (i = 0; i < expr_hash_table_size; i++)
{
struct expr *expr;
for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
{
struct occr *occr;
int indx = expr->bitmap_index;
/* We only need to search antic_occr since we require
ANTLOC != 0. */
for (occr = expr->antic_occr; occr != NULL; occr = occr->next)
{
rtx insn = occr->insn;
rtx set;
int bb = BLOCK_NUM (insn);
if (TEST_BIT (temp_bitmap[bb], indx))
{
set = single_set (insn);
if (! set)
abort ();
/* Create a pseudo-reg to store the result of reaching
expressions into. Get the mode for the new pseudo
from the mode of the original destination pseudo. */
if (expr->reaching_reg == NULL)
expr->reaching_reg
= gen_reg_rtx (GET_MODE (SET_DEST (set)));
/* In theory this should never fail since we're creating
a reg->reg copy.
However, on the x86 some of the movXX patterns actually
contain clobbers of scratch regs. This may cause the
insn created by validate_change to not patch any pattern
and thus cause validate_change to fail. */
if (TEST_BIT (temp_bitmap[bb], indx)
&& validate_change (insn, &SET_SRC (set),
expr->reaching_reg, 0))
{
occr->deleted_p = 1;
SET_BIT (pre_redundant_insns, INSN_CUID (insn));
changed = 1;
gcse_subst_count++;
if (gcse_file)
{
fprintf (gcse_file,
"PRE: redundant insn %d (expression %d) in bb %d, reaching reg is %d\n",
INSN_UID (insn), indx, bb, REGNO (expr->reaching_reg));
}
}
}
}
}
}
return changed;
}
/* Perform GCSE optimizations using PRE.
This is called by one_pre_gcse_pass after all the dataflow analysis
has been done.
This is based on the original Morel-Renvoise paper Fred Chow's thesis,
and lazy code motion from Knoop, Ruthing and Steffen as described in
Advanced Compiler Design and Implementation.
??? A new pseudo reg is created to hold the reaching expression.
The nice thing about the classical approach is that it would try to
use an existing reg. If the register can't be adequately optimized
[i.e. we introduce reload problems], one could add a pass here to
propagate the new register through the block.
??? We don't handle single sets in PARALLELs because we're [currently]
not able to copy the rest of the parallel when we insert copies to create
full redundancies from partial redundancies. However, there's no reason
why we can't handle PARALLELs in the cases where there are no partial
redundancies. */
static int
pre_gcse ()
{
int i;
int changed;
struct expr **index_map;
/* Compute a mapping from expression number (`bitmap_index') to
hash table entry. */
index_map = (struct expr **) alloca (n_exprs * sizeof (struct expr *));
zero_memory ((char *) index_map, n_exprs * sizeof (struct expr *));
for (i = 0; i < expr_hash_table_size; i++)
{
struct expr *expr;
for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
index_map[expr->bitmap_index] = expr;
}
pre_redundant_insns = sbitmap_alloc (max_cuid);
sbitmap_zero (pre_redundant_insns);
/* Delete the redundant insns first so that
- we know what register to use for the new insns and for the other
ones with reaching expressions
- we know which insns are redundant when we go to create copies */
changed = pre_delete ();
/* Insert insns in places that make partially redundant expressions
fully redundant. */
pre_insert (index_map);
/* In other places with reaching expressions, copy the expression to the
specially allocated pseudo-reg that reaches the redundant expression. */
pre_insert_copies ();
free (pre_redundant_insns);
return changed;
}
/* Top level routine to perform one PRE GCSE pass.
Return non-zero if a change was made. */
static int
one_pre_gcse_pass (pass)
int pass;
{
int changed = 0;
gcse_subst_count = 0;
gcse_create_count = 0;
alloc_expr_hash_table (max_cuid);
compute_expr_hash_table ();
if (gcse_file)
dump_hash_table (gcse_file, "Expression", expr_hash_table,
expr_hash_table_size, n_exprs);
if (n_exprs > 0)
{
alloc_pre_mem (n_basic_blocks, n_exprs);
compute_pre_data ();
changed |= pre_gcse ();
free_pre_mem ();
}
free_expr_hash_table ();
if (gcse_file)
{
fprintf (gcse_file, "\n");
fprintf (gcse_file, "PRE GCSE of %s, pass %d: %d bytes needed, %d substs, %d insns created\n",
current_function_name, pass,
bytes_used, gcse_subst_count, gcse_create_count);
}
return changed;
}
/* Compute transparent outgoing information for each block.
An expression is transparent to an edge unless it is killed by
the edge itself. This can only happen with abnormal control flow,
when the edge is traversed through a call. This happens with
non-local labels and exceptions.
This would not be necessary if we split the edge. While this is
normally impossible for abnormal critical edges, with some effort
it should be possible with exception handling, since we still have
control over which handler should be invoked. But due to increased
EH table sizes, this may not be worthwhile. */
static void
compute_transpout ()
{
int bb;
sbitmap_vector_ones (transpout, n_basic_blocks);
for (bb = 0; bb < n_basic_blocks; ++bb)
{
int i;
/* Note that flow inserted a nop a the end of basic blocks that
end in call instructions for reasons other than abnormal
control flow. */
if (GET_CODE (BLOCK_END (bb)) != CALL_INSN)
continue;
for (i = 0; i < expr_hash_table_size; i++)
{
struct expr *expr;
for (expr = expr_hash_table[i]; expr ; expr = expr->next_same_hash)
if (GET_CODE (expr->expr) == MEM)
{
rtx addr = XEXP (expr->expr, 0);
if (GET_CODE (addr) == SYMBOL_REF
&& CONSTANT_POOL_ADDRESS_P (addr))
continue;
/* ??? Optimally, we would use interprocedural alias
analysis to determine if this mem is actually killed
by this call. */
RESET_BIT (transpout[bb], expr->bitmap_index);
}
}
}
}
/* CYGNUS LOCAL code hoisting/law */
/* Code Hoisting variables and subroutines. */
/* Very busy expressions. */
static sbitmap *hoist_vbein;
static sbitmap *hoist_vbeout;
/* Hoistable expressions. */
static sbitmap *hoist_exprs;
/* Dominator bitmaps. */
static sbitmap *dominators;
static sbitmap *post_dominators;
/* ??? We could compute post dominators and run this algorithm in
reverse to to perform tail merging, doing so would probably be
more effective than the tail merging code in jump.c.
It's unclear if tail merging could be run in parallel with
code hoisting. It would be nice. */
/* Allocate vars used for code hoisting analysis. */
static void
alloc_code_hoist_mem (n_blocks, n_exprs)
int n_blocks, n_exprs;
{
antloc = sbitmap_vector_alloc (n_blocks, n_exprs);
transp = sbitmap_vector_alloc (n_blocks, n_exprs);
comp = sbitmap_vector_alloc (n_blocks, n_exprs);
hoist_vbein = sbitmap_vector_alloc (n_blocks, n_exprs);
hoist_vbeout = sbitmap_vector_alloc (n_blocks, n_exprs);
hoist_exprs = sbitmap_vector_alloc (n_blocks, n_exprs);
transpout = sbitmap_vector_alloc (n_blocks, n_exprs);
dominators = sbitmap_vector_alloc (n_blocks, n_blocks);
post_dominators = sbitmap_vector_alloc (n_blocks, n_blocks);
}
/* Free vars used for code hoisting analysis. */
static void
free_code_hoist_mem ()
{
free (antloc);
free (transp);
free (comp);
free (hoist_vbein);
free (hoist_vbeout);
free (hoist_exprs);
free (transpout);
free (dominators);
free (post_dominators);
}
/* Compute the very busy expressions at entry/exit from each block.
An expression is very busy if all paths from a given point
compute the expression. */
static void
compute_code_hoist_vbeinout ()
{
int bb, changed, passes;
sbitmap_vector_zero (hoist_vbeout, n_basic_blocks);
sbitmap_vector_zero (hoist_vbein, n_basic_blocks);
passes = 0;
changed = 1;
while (changed)
{
changed = 0;
/* We scan the blocks in the reverse order to speed up
the convergence. */
for (bb = n_basic_blocks - 1; bb >= 0; bb--)
{
changed |= sbitmap_a_or_b_and_c (hoist_vbein[bb], antloc[bb],
hoist_vbeout[bb], transp[bb]);
if (bb != n_basic_blocks - 1)
sbitmap_intersect_of_successors (hoist_vbeout[bb], hoist_vbein,
bb, s_succs);
}
passes++;
}
if (gcse_file)
fprintf (gcse_file, "hoisting vbeinout computation: %d passes\n", passes);
}
/* Top level routine to do the dataflow analysis needed by code hoisting. */
static void
compute_code_hoist_data ()
{
compute_local_properties (transp, comp, antloc, 0);
compute_transpout ();
compute_code_hoist_vbeinout ();
compute_dominators (dominators, post_dominators, s_preds, s_succs);
if (gcse_file)
fprintf (gcse_file, "\n");
}
/* Determine if the expression identified by EXPR_INDEX would
reach BB unimpared if it was placed at the end of EXPR_BB.
It's unclear exactly what Muchnick meant by "unimpared". It seems
to me that the expression must either be computed or transparent in
*every* block in the path(s) from EXPR_BB to BB. Any other definition
would allow the expression to be hoisted out of loops, even if
the expression wasn't a loop invariant.
Contrast this to reachability for PRE where an expression is
considered reachable if *any* path reaches instead of *all*
paths. */
static int
hoist_expr_reaches_here_p (expr_bb, expr_index, bb, visited)
int expr_bb;
int expr_index;
int bb;
char *visited;
{
int_list_ptr pred;
if (visited == NULL)
{
visited = (char *) alloca (n_basic_blocks);
zero_memory (visited, n_basic_blocks);
}
visited[expr_bb] = 1;
for (pred = s_preds[bb]; pred != NULL; pred = pred->next)
{
int pred_bb = INT_LIST_VAL (pred);
if (pred_bb == ENTRY_BLOCK)
break;
else if (visited[pred_bb])
continue;
/* Does this predecessor generate this expression? */
else if (TEST_BIT (comp[pred_bb], expr_index))
break;
else if (! TEST_BIT (transp[pred_bb], expr_index))
break;
/* Not killed. */
else
{
visited[pred_bb] = 1;
if (! hoist_expr_reaches_here_p (expr_bb, expr_index,
pred_bb, visited))
break;
}
}
return (pred == NULL);
}
/* Actually perform code hoisting. */
static void
hoist_code ()
{
int bb, dominated, i;
struct expr **index_map;
sbitmap_vector_zero (hoist_exprs, n_basic_blocks);
/* Compute a mapping from expression number (`bitmap_index') to
hash table entry. */
index_map = (struct expr **) alloca (n_exprs * sizeof (struct expr *));
zero_memory ((char *) index_map, n_exprs * sizeof (struct expr *));
for (i = 0; i < expr_hash_table_size; i++)
{
struct expr *expr;
for (expr = expr_hash_table[i]; expr != NULL; expr = expr->next_same_hash)
index_map[expr->bitmap_index] = expr;
}
/* Walk over each basic block looking for potentially hoistable
expressions, nothing gets hoisted from the entry block. */
for (bb = 0; bb < n_basic_blocks; bb++)
{
int found = 0;
int insn_inserted_p;
/* Examine each expression that is very busy at the exit of this
block. These are the potentially hoistable expressions. */
for (i = 0; i < hoist_vbeout[bb]->n_bits; i++)
{
int hoistable = 0;
if (TEST_BIT (hoist_vbeout[bb], i)
&& TEST_BIT (transpout[bb], i))
{
/* We've found a potentially hoistable expression, now
we look at every block BB dominates to see if it
computes the expression. */
for (dominated = 0; dominated < n_basic_blocks; dominated++)
{
/* Ignore self dominance. */
if (bb == dominated
|| ! TEST_BIT (dominators[dominated], bb))
continue;
/* We've found a dominated block, now see if it computes
the busy expression and whether or not moving that
expression to the "beginning" of that block is safe. */
if (!TEST_BIT (antloc[dominated], i))
continue;
/* Note if the expression would reach the dominated block
unimpared if it was placed at the end of BB.
Keep track of how many times this expression is hoistable
from a dominated block into BB. */
if (hoist_expr_reaches_here_p (bb, i, dominated, NULL))
hoistable++;
}
/* If we found more than one hoistable occurence of this
expression, then note it in the bitmap of expressions to
hoist. It makes no sense to hoist things which are computed
in only one BB, and doing so tends to pessimize register
allocation. One could increase this value to try harder
to avoid any possible code expansion due to register
allocation issues; however experiments have shown that
the vast majority of hoistable expressions are only movable
from two successors, so raising this threshhold is likely
to nullify any benefit we get from code hoisting. */
if (hoistable > 1)
{
SET_BIT (hoist_exprs[bb], i);
found = 1;
}
}
}
/* If we found nothing to hoist, then quit now. */
if (! found)
continue;
/* Loop over all the hoistable expressions. */
for (i = 0; i < hoist_exprs[bb]->n_bits; i++)
{
/* We want to insert the expression into BB only once, so
note when we've inserted it. */
insn_inserted_p = 0;
/* These tests should be the same as the tests above. */
if (TEST_BIT (hoist_vbeout[bb], i))
{
/* We've found a potentially hoistable expression, now
we look at every block BB dominates to see if it
computes the expression. */
for (dominated = 0; dominated < n_basic_blocks; dominated++)
{
/* Ignore self dominance. */
if (bb == dominated
|| ! TEST_BIT (dominators[dominated], bb))
continue;
/* We've found a dominated block, now see if it computes
the busy expression and whether or not moving that
expression to the "beginning" of that block is safe. */
if (!TEST_BIT (antloc[dominated], i))
continue;
/* The expression is computed in the dominated block and
it would be safe to compute it at the start of the
dominated block. Now we have to determine if the
expresion would reach the dominated block if it was
placed at the end of BB. */
if (hoist_expr_reaches_here_p (bb, i, dominated, NULL))
{
struct expr *expr = index_map[i];
struct occr *occr = expr->antic_occr;
rtx insn;
rtx set;
/* Find the right occurence of this expression. */
while (BLOCK_NUM (occr->insn) != dominated && occr)
occr = occr->next;
/* Should never happen. */
if (!occr)
abort ();
insn = occr->insn;
set = single_set (insn);
if (! set)
abort ();
/* Create a pseudo-reg to store the result of reaching
expressions into. Get the mode for the new pseudo
from the mode of the original destination pseudo. */
if (expr->reaching_reg == NULL)
expr->reaching_reg
= gen_reg_rtx (GET_MODE (SET_DEST (set)));
/* In theory this should never fail since we're creating
a reg->reg copy.
However, on the x86 some of the movXX patterns actually
contain clobbers of scratch regs. This may cause the
insn created by validate_change to not patch any
pattern and thus cause validate_change to fail. */
if (validate_change (insn, &SET_SRC (set),
expr->reaching_reg, 0))
{
occr->deleted_p = 1;
if (!insn_inserted_p)
{
insert_insn_end_bb (index_map[i], bb, 0);
insn_inserted_p = 1;
}
}
}
}
}
}
}
}
/* Top level routine to perform one code hoisting (aka unification) pass
Return non-zero if a change was made. */
static int
one_code_hoisting_pass ()
{
int changed = 0;
alloc_expr_hash_table (max_cuid);
compute_expr_hash_table ();
if (gcse_file)
dump_hash_table (gcse_file, "Code Hosting Expressions", expr_hash_table,
expr_hash_table_size, n_exprs);
if (n_exprs > 0)
{
alloc_code_hoist_mem (n_basic_blocks, n_exprs);
compute_code_hoist_data ();
hoist_code ();
free_code_hoist_mem ();
}
free_expr_hash_table ();
return changed;
}
/* These need to be file static for communication between
invalidate_nonnull_info and delete_null_pointer_checks. */
static int current_block;
static sbitmap *nonnull_local;
static sbitmap *nonnull_killed;
/* Called via note_stores. X is set by SETTER. If X is a register we must
invalidate nonnull_local and set nonnull_killed.
We ignore hard registers. */
void
invalidate_nonnull_info (x, setter)
rtx x, setter;
{
int offset, regno;
offset = 0;
while (GET_CODE (x) == SUBREG)
x = SUBREG_REG (x);
/* Ignore anything that is not a register or is a hard register. */
if (GET_CODE (x) != REG
|| REGNO (x) < FIRST_PSEUDO_REGISTER)
return;
regno = REGNO (x);
RESET_BIT (nonnull_local[current_block], regno);
SET_BIT (nonnull_killed[current_block], regno);
}
/* Find EQ/NE comparisons against zero which can be (indirectly) evaluated
at compile time.
This is conceptually similar to global constant/copy propagation and
classic global CSE (it even uses the same dataflow equations as cprop).
If a register is used as memory address with the form (mem (reg)), then we
know that REG can not be zero at that point in the program. Any instruction
which sets REG "kills" this property.
So, if every path leading to a conditional branch has an available memory
reference of that form, then we know the register can not have the value
zero at the conditional branch.
So we merely need to compute the local properies and propagate that data
around the cfg, then optimize where possible.
We run this pass two times. Once before CSE, then again after CSE. This
has proven to be the most profitable approach. It is rare for new
optimization opportunities of this nature to appear after the first CSE
pass.
This could probably be integrated with global cprop with a little work. */
void
delete_null_pointer_checks (f)
rtx f;
{
int_list_ptr *s_preds, *s_succs;
int *num_preds, *num_succs;
int changed, bb;
sbitmap *nonnull_avin, *nonnull_avout;
/* First break the program into basic blocks. */
find_basic_blocks (f, max_reg_num (), NULL);
/* If we have only a single block, then there's nothing to do. */
if (n_basic_blocks <= 1)
{
/* Free storage allocated by find_basic_blocks. */
free_basic_block_vars (0);
return;
}
/* We need predecessor/successor lists as well as pred/succ counts for
each basic block. */
s_preds = (int_list_ptr *) alloca (n_basic_blocks * sizeof (int_list_ptr));
s_succs = (int_list_ptr *) alloca (n_basic_blocks * sizeof (int_list_ptr));
num_preds = (int *) alloca (n_basic_blocks * sizeof (int));
num_succs = (int *) alloca (n_basic_blocks * sizeof (int));
compute_preds_succs (s_preds, s_succs, num_preds, num_succs, 0);
/* Allocate bitmaps to hold local and global properties. */
nonnull_local = sbitmap_vector_alloc (n_basic_blocks, max_reg_num ());
nonnull_killed = sbitmap_vector_alloc (n_basic_blocks, max_reg_num ());
nonnull_avin = sbitmap_vector_alloc (n_basic_blocks, max_reg_num ());
nonnull_avout = sbitmap_vector_alloc (n_basic_blocks, max_reg_num ());
/* Compute local properties, nonnull and killed. A register will have
the nonnull property if at the end of the current block its value is
known to be nonnull. The killed property indicates that somewhere in
the block any information we had about the register is killed.
Note that a register can have both properties in a single block. That
indicates that it's killed, then later in the block a new value is
computed. */
sbitmap_vector_zero (nonnull_local, n_basic_blocks);
sbitmap_vector_zero (nonnull_killed, n_basic_blocks);
for (current_block = 0; current_block < n_basic_blocks; current_block++)
{
rtx insn, stop_insn;
/* Scan each insn in the basic block looking for memory references and
register sets. */
stop_insn = NEXT_INSN (BLOCK_END (current_block));
for (insn = BLOCK_HEAD (current_block);
insn != stop_insn;
insn = NEXT_INSN (insn))
{
rtx set;
/* Ignore anything that is not a normal insn. */
if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
continue;
/* Basically ignore anything that is not a simple SET. We do have
to make sure to invalidate nonnull_local and set nonnull_killed
for such insns though. */
set = single_set (insn);
if (!set)
{
note_stores (PATTERN (insn), invalidate_nonnull_info);
continue;
}
/* See if we've got a useable memory load. We handle it first
in case it uses its address register as a dest (which kills
the nonnull property). */
if (GET_CODE (SET_SRC (set)) == MEM
&& GET_CODE (XEXP (SET_SRC (set), 0)) == REG
&& REGNO (XEXP (SET_SRC (set), 0)) >= FIRST_PSEUDO_REGISTER)
SET_BIT (nonnull_local[current_block],
REGNO (XEXP (SET_SRC (set), 0)));
/* Now invalidate stuff clobbered by this insn. */
note_stores (PATTERN (insn), invalidate_nonnull_info);
/* And handle stores, we do these last since any sets in INSN can
not kill the nonnull property if it is derived from a MEM
appearing in a SET_DEST. */
if (GET_CODE (SET_DEST (set)) == MEM
&& GET_CODE (XEXP (SET_DEST (set), 0)) == REG)
SET_BIT (nonnull_local[current_block],
REGNO (XEXP (SET_DEST (set), 0)));
}
}
/* Now compute global properties based on the local properties. This
is a classic global availablity algorithm. */
sbitmap_zero (nonnull_avin[0]);
sbitmap_vector_ones (nonnull_avout, n_basic_blocks);
changed = 1;
while (changed)
{
changed = 0;
for (bb = 0; bb < n_basic_blocks; bb++)
{
if (bb != 0)
sbitmap_intersect_of_predecessors (nonnull_avin[bb],
nonnull_avout, bb, s_preds);
changed |= sbitmap_union_of_diff (nonnull_avout[bb],
nonnull_local[bb],
nonnull_avin[bb],
nonnull_killed[bb]);
}
}
/* Now look at each bb and see if it ends with a compare of a value
against zero. */
for (bb = 0; bb < n_basic_blocks; bb++)
{
rtx last_insn = BLOCK_END (bb);
rtx condition, earliest, reg;
int compare_and_branch;
/* We only want conditional branches. */
if (GET_CODE (last_insn) != JUMP_INSN
|| !condjump_p (last_insn)
|| simplejump_p (last_insn))
continue;
/* LAST_INSN is a conditional jump. Get its condition. */
condition = get_condition (last_insn, &earliest);
/* If we were unable to get the condition, or it is not a equality
comparison against zero then there's nothing we can do. */
if (!condition
|| (GET_CODE (condition) != NE && GET_CODE (condition) != EQ)
|| GET_CODE (XEXP (condition, 1)) != CONST_INT
|| XEXP (condition, 1) != CONST0_RTX (GET_MODE (XEXP (condition, 0))))
continue;
/* We must be checking a register against zero. */
reg = XEXP (condition, 0);
if (GET_CODE (reg) != REG)
continue;
/* Is the register known to have a nonzero value? */
if (!TEST_BIT (nonnull_avout[bb], REGNO (reg)))
continue;
/* Try to compute whether the compare/branch at the loop end is one or
two instructions. */
if (earliest == last_insn)
compare_and_branch = 1;
else if (earliest == prev_nonnote_insn (last_insn))
compare_and_branch = 2;
else
continue;
/* We know the register in this comparison is nonnull at exit from
this block. We can optimize this comparison. */
if (GET_CODE (condition) == NE)
{
rtx new_jump;
new_jump = emit_jump_insn_before (gen_jump (JUMP_LABEL (last_insn)),
last_insn);
JUMP_LABEL (new_jump) = JUMP_LABEL (last_insn);
LABEL_NUSES (JUMP_LABEL (new_jump))++;
emit_barrier_after (new_jump);
}
delete_insn (last_insn);
if (compare_and_branch == 2)
delete_insn (earliest);
}
/* Free storage allocated by find_basic_blocks. */
free_basic_block_vars (0);
/* Free bitmaps. */
free (nonnull_local);
free (nonnull_killed);
free (nonnull_avin);
free (nonnull_avout);
}
/* END CYGNUS LOCAL */
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