43 lines
1.3 KiB
Ruby
43 lines
1.3 KiB
Ruby
module Vm
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module WhileStatement
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def on_WhileStatement statement
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#branch_type , condition , statements = *statement
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condition_label = compile_while_preamble( statement ) #jump there
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start = compile_while_body( statement )
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# This is where the loop starts, though in subsequent iterations it's in the middle
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add_code condition_label
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compile_while_condition( statement )
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branch_class = Object.const_get "Risc::Is#{statement.branch_type.capitalize}"
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# this is where the while ends and both branches meet
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add_code branch_class.new( statement.condition , start )
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nil # statements don't return anything
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end
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private
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def compile_while_preamble( statement )
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condition_label = Risc.label(statement.condition , "condition_label")
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# unconditionally branch to the condition upon entering the loop
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add_code Risc::Branch.new(statement.condition , condition_label)
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condition_label
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end
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def compile_while_body( statement )
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start = Risc.label(statement , "while_start" )
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add_code start
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reset_regs
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process(statement.statements)
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start
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end
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def compile_while_condition( statement )
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reset_regs
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process(statement.condition)
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end
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end
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end
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