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constant_propagation_pass: Add 64-bit variants of shifts to the pass

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These optimizations can also apply to the 64-bit variants of the shift
opcodes; we just need to check if the instruction has an associated
pseudo-op before performing the 32-bit variant's specifics.

While we're at it, we can also relocate the code to its own function
like the rest of the cases to keep organization consistent.
This commit is contained in:
Lioncash 2018-10-12 05:21:51 -04:00
parent fc051d2c5c
commit 2c8c83c2f1
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GPG Key ID: 4E3C3CC1031BA9C7
1 changed files with 26 additions and 14 deletions
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40
src/ir_opt/constant_propagation_pass.cpp
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@ -154,6 +154,26 @@ void FoldOR(IR::Inst& inst, bool is_32_bit) {
}
}
void FoldShifts(IR::Inst& inst) {
IR::Inst* carry_inst = inst.GetAssociatedPseudoOperation(IR::Opcode::GetCarryFromOp);
// The 32-bit variants can contain 3 arguments, while the
// 64-bit variants only contain 2.
if (inst.NumArgs() == 3 && !carry_inst) {
inst.SetArg(2, IR::Value(false));
}
const auto shift_amount = inst.GetArg(1);
if (!shift_amount.IsZero()) {
return;
}
if (carry_inst) {
carry_inst->ReplaceUsesWith(inst.GetArg(2));
}
inst.ReplaceUsesWith(inst.GetArg(0));
}
void FoldSignExtendXToWord(IR::Inst& inst) {
if (!inst.AreAllArgsImmediates()) {
return;
@ -197,23 +217,15 @@ void ConstantPropagation(IR::Block& block) {
switch (opcode) {
case IR::Opcode::LogicalShiftLeft32:
case IR::Opcode::LogicalShiftLeft64:
case IR::Opcode::LogicalShiftRight32:
case IR::Opcode::LogicalShiftRight64:
case IR::Opcode::ArithmeticShiftRight32:
case IR::Opcode::RotateRight32: {
if (!inst.GetAssociatedPseudoOperation(IR::Opcode::GetCarryFromOp)) {
inst.SetArg(2, IR::Value(false));
}
auto shift_amount = inst.GetArg(1);
if (shift_amount.IsImmediate() && shift_amount.GetU8() == 0) {
IR::Inst* carry_inst = inst.GetAssociatedPseudoOperation(IR::Opcode::GetCarryFromOp);
if (carry_inst) {
carry_inst->ReplaceUsesWith(inst.GetArg(2));
}
inst.ReplaceUsesWith(inst.GetArg(0));
}
case IR::Opcode::ArithmeticShiftRight64:
case IR::Opcode::RotateRight32:
case IR::Opcode::RotateRight64:
FoldShifts(inst);
break;
}
case IR::Opcode::Mul32:
case IR::Opcode::Mul64:
FoldMultiply(inst, opcode == IR::Opcode::Mul32);