From 4030f32ead5ed02fd43cafa98d13c79a5511b814 Mon Sep 17 00:00:00 2001
From: Torsten Ruger <torsten@villataika.fi>
Date: Fri, 16 May 2014 12:55:51 +0300
Subject: [PATCH] finally coded the logic Shifting (what a beast)

---
 lib/arm/arm_machine.rb       |  2 +-
 lib/arm/logic_instruction.rb | 81 ++++++++++++++++--------------------
 2 files changed, 37 insertions(+), 46 deletions(-)

diff --git a/lib/arm/arm_machine.rb b/lib/arm/arm_machine.rb
index 948562f1..57ad6606 100644
--- a/lib/arm/arm_machine.rb
+++ b/lib/arm/arm_machine.rb
@@ -112,7 +112,7 @@ module Arm
       #          SUB    r2, r1, #10                       # keep (x-10) for later
       block.add_code sub( remainder , left: number , right: 10 )
       #          SUB    r1, r1, r1, lsr #2
-      block.add_code add( number , left: number , right: number ,  shift_right: 4)
+      block.add_code add( number , left: number , right: number ,  shift_lsr: 4)
       #          ADD    r1, r1, r1, lsr #4
       #          ADD    r1, r1, r1, lsr #8
       #          ADD    r1, r1, r1, lsr #16
diff --git a/lib/arm/logic_instruction.rb b/lib/arm/logic_instruction.rb
index fa5219d6..8cbf3d70 100644
--- a/lib/arm/logic_instruction.rb
+++ b/lib/arm/logic_instruction.rb
@@ -13,7 +13,7 @@ module Arm
 
       @left = @attributes[:left]
       raise "Left arg must be given #{inspect}" unless @left
-      @i = 0      
+      @immediate = 0      
     end
     
     # arm intrucioons are pretty sensible, and always 4 bytes (thumb not supported)
@@ -23,71 +23,62 @@ module Arm
 
     # Build representation for source value 
     def build      
-      arg = @attributes[:right]
+      right = @attributes[:right]
       if @left.is_a?(Vm::StringConstant)
         # do pc relative addressing with the difference to the instuction
-        # 8 is for the funny pipeline adjustment (ie oc pointing to fetch and not execute)
-        arg = Vm::IntegerConstant.new( @left.position - self.position - 8 )
+        # 8 is for the funny pipeline adjustment (ie pointing to fetch and not execute)
+        right = @left.position - self.position - 8 
         @left = :pc
       end
-      if( arg.is_a? Fixnum ) #HACK to not have to change the code just now
-        arg = Vm::IntegerConstant.new( arg )
+      # automatic wrapping, for machine internal code and testing
+      if( right.is_a? Fixnum )
+        right = Vm::IntegerConstant.new( right )
       end
-      if (arg.is_a?(Vm::IntegerConstant))
-        if (arg.integer.fits_u8?)
+      if (right.is_a?(Vm::IntegerConstant))
+        if (right.integer.fits_u8?)
           # no shifting needed
-          @operand = arg.integer
-          @i = 1
-        elsif (op_with_rot = calculate_u8_with_rr(arg))
+          @operand = right.integer
+          @immediate = 1
+        elsif (op_with_rot = calculate_u8_with_rr(right))
           @operand = op_with_rot
-          @i = 1
+          @immediate = 1
           raise "hmm"
         else
-          raise "cannot fit numeric literal argument in operand #{arg.inspect}"
+          raise "cannot fit numeric literal argument in operand #{right.inspect}"
         end
-      elsif (arg.is_a?(Symbol) or arg.is_a?(Vm::Integer))
-        @operand = arg
-        @i = 0
-      elsif (arg.is_a?(Arm::Shift))
-        rm_ref = arg.argument
-        @i = 0
-        shift_op = {'lsl' => 0b000, 'lsr' => 0b010, 'asr' => 0b100,
-                    'ror' => 0b110, 'rrx' => 0b110}[arg.type]
-        if (arg.type == 'ror' and arg.value.nil?)
-          # ror #0 == rrx
-          raise "cannot rotate by zero #{arg} #{inspect}"
-        end
-  
-        arg1 = arg.value
-        if (arg1.is_a?(Vm::IntegerConstant))
-          if (arg1.value >= 32)
-            raise "cannot shift by more than 31 #{arg1} #{inspect}"
-          end
-          shift_imm = arg1.value
-        elsif (arg1.is_a?(Arm::Register))
-          shift_op val |= 0x1;
-          shift_imm = arg1.number << 1
-        elsif (arg.type == 'rrx')
-          shift_imm = 0
-        end
-        @operand = rm_ref | (shift_op << 4) | (shift_imm << 4+3)
+      elsif (right.is_a?(Symbol) or right.is_a?(Vm::Integer))
+        @operand = reg_code(right)    #integer means the register the integer is in (otherwise constant)
+        @immediate = 0                # ie not immediate is register
       else
-        raise "invalid operand argument #{arg.inspect} , #{inspect}"
+        raise "invalid operand argument #{right.inspect} , #{inspect}"
+      end
+      #codes that one can shift, first two probably most common.
+      # l (in lsr) means logical, ie unsigned, a (in asl) is arithmetic, ie signed
+      {'lsl' => 0b000, 'lsr' => 0b010, 'asr' => 0b100, 'ror' => 0b110, 'rrx' => 0b110}.each do |short, bin|
+        long = "shift_#{short}".to_sym
+        if shif = @attributes[long]
+          shif = shif.integer if (shif.is_a?(Vm::IntegerConstant))
+          if (shif.is_a?(Vm::Integer))
+            bin |= 0x1;
+            shift = shif.register << 1
+          end
+          raise "0 < shift <= 32  #{shif} #{inspect}"  if (shif >= 32) or( shif < 0)
+          @operand |=   shift(bin  , 4 )
+          @operand |=   shift(shif , 4+3)
+          break
+        end
       end
     end
 
     def assemble(io)
       build
       instuction_class = 0b00 # OPC_DATA_PROCESSING
-      val = (@operand.is_a?(Symbol) or @operand.is_a?(Vm::Integer)) ? reg_code(@operand) : @operand 
-      val = 0 if val == nil
-      val = shift(val , 0)
-      raise inspect unless reg_code(@first)
+      val = shift(@operand , 0)
       val |= shift(reg_code(@first) ,            12)     
       val |= shift(reg_code(@left) ,            12+4)   
       val |= shift(@attributes[:update_status_flag] , 12+4+4)#20 
       val |= shift(op_bit_code ,        12+4+4  +1)
-      val |= shift(@i ,                  12+4+4  +1+4) 
+      val |= shift(@immediate ,                  12+4+4  +1+4) 
       val |= shift(instuction_class ,   12+4+4  +1+4+1) 
       val |= shift(cond_bit_code ,      12+4+4  +1+4+1+2)
       io.write_uint32 val