Optimize consecutive mov/add/sub instructions to single instruction
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Bananymous
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1e8bdf6cd2
commit
db4f37709f
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@ -335,6 +335,7 @@ class CompileData:
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i = 0
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i = 0
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# Remove redundant movq instructions
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# Remove redundant movq instructions
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# movq %rax, %rax
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while i < len(instructions):
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while i < len(instructions):
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if instructions[i].opcode != 'movq' or instructions[i].operands[0] != instructions[i].operands[1]:
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if instructions[i].opcode != 'movq' or instructions[i].operands[0] != instructions[i].operands[1]:
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i += 1
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i += 1
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@ -345,7 +346,11 @@ class CompileData:
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i = 0
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i = 0
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# Optimize movq to register followed by pushq register
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# Optimize movq to register followed by pushq register
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while i < len(instructions):
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# movq $1, %rax
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# pushq %rax
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# becomes
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# pushq $1
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while i < len(instructions) - 1:
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if instructions[i].opcode != 'movq' or instructions[i + 1].opcode != 'pushq':
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if instructions[i].opcode != 'movq' or instructions[i + 1].opcode != 'pushq':
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i += 1
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i += 1
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continue
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continue
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@ -360,7 +365,11 @@ class CompileData:
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i = 0
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i = 0
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# Optimize movq to rax followed by movq from rax
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# Optimize movq to rax followed by movq from rax
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while i < len(instructions):
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# movq $1, %rax
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# movq %rax, %rcx
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# becomes
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# movq $1, %rcx
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while i < len(instructions) - 1:
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if instructions[i].opcode != 'movq' or instructions[i + 1].opcode != 'movq':
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if instructions[i].opcode != 'movq' or instructions[i + 1].opcode != 'movq':
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i += 1
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i += 1
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continue
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continue
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@ -379,8 +388,84 @@ class CompileData:
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changed = True
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changed = True
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if changed: continue
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if changed: continue
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i = 0
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# Replace negative immediate in addq/subq with positive immediate
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# This is not a real optimization, but it makes the code easier to optimize
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# subq $-1, %rax
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# becomes
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# addq $1, %rax
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while i < len(instructions):
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if instructions[i].opcode not in ['addq', 'subq']:
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i += 1
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continue
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if instructions[i].operands[1][0] != '$':
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i += 1
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continue
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value = int(instructions[i].operands[1][1:])
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if value >= 0:
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i += 1
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continue
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new_opcode = 'subq' if instructions[i].opcode == 'addq' else 'addq'
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instructions[i] = Instruction(new_opcode, [instructions[i].operands[0], f'${-value}'])
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changed = True
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if changed: continue
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i = 0
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# Optimize repeated addq/subq instructions
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# addq $1, %rax
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# addq $2, %rax
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# becomes
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# addq $3, %rax
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while i < len(instructions) - 1:
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if instructions[i].opcode not in ['addq', 'subq']:
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i += 1
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continue
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if instructions[i].operands[1] != instructions[i + 1].operands[1]:
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i += 1
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continue
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lhs = int(instructions[i].operands[0][1:])
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if instructions[i].opcode == 'subq': lhs = -lhs
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rhs = int(instructions[i + 1].operands[0][1:])
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if instructions[i + 1].opcode == 'subq': rhs = -rhs
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new_value = lhs + rhs
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new_opcode = 'addq' if new_value >= 0 else 'subq'
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instructions[i] = Instruction(new_opcode, [f'${abs(new_value)}', instructions[i].operands[1]])
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instructions.pop(i + 1)
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i -= 1
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changed = True
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if changed: continue
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i = 0
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# Optimize movq immediate to register followed addq/subq with immediate
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# movq $1, %rax
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# addq $2, %rax
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# becomes
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# movq $3, %rax
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while i < len(instructions) - 1:
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if instructions[i].opcode != 'movq' or instructions[i + 1].opcode not in ['addq', 'subq']:
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i += 1
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continue
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if instructions[i].operands[1] != instructions[i + 1].operands[1]:
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i += 1
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continue
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if instructions[i].operands[0][0] != '$' or instructions[i + 1].operands[0][0] != '$':
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i += 1
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continue
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lhs = int(instructions[i].operands[0][1:])
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rhs = int(instructions[i + 1].operands[0][1:])
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if instructions[i + 1].opcode == 'subq': rhs = -rhs
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new_value = lhs + rhs
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instructions[i] = Instruction('movq', [f'${new_value}', instructions[i].operands[1]])
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instructions.pop(i + 1)
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i -= 1
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changed = True
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if changed: continue
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i = 0
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i = 0
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# Optimize addq/subq for immediate 1
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# Optimize addq/subq for immediate 1
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# addq $1, %rax
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# becomes
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# incq %rax
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while i < len(instructions):
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while i < len(instructions):
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if instructions[i].opcode not in ['addq', 'subq']:
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if instructions[i].opcode not in ['addq', 'subq']:
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i += 1
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i += 1
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@ -395,6 +480,9 @@ class CompileData:
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i = 0
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i = 0
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# Optimize zeroing of register
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# Optimize zeroing of register
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# movq $0, %rax
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# becomes
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# xorq %rax, %rax
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while i < len(instructions):
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while i < len(instructions):
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if instructions[i].opcode != 'movq':
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if instructions[i].opcode != 'movq':
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i += 1
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i += 1
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