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Merge pull request #407 from lioncash/div

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constant_propagation_pass: Fold division operations where applicable
This commit is contained in:
Merry 2018-10-11 15:50:47 +01:00 committed by MerryMage
commit 8bfaa9aac0
1 changed files with 36 additions and 0 deletions
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36
src/ir_opt/constant_propagation_pass.cpp
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@ -50,6 +50,34 @@ void FoldAND(IR::Inst& inst, bool is_32_bit) {
}
}
// Folds division operations based on the following:
//
// 1. x / 0 -> 0 (NOTE: This is an ARM-specific behavior defined in the architecture reference manual)
// 2. imm_x / imm_y -> result
// 3. x / 1 -> x
//
void FoldDivide(IR::Inst& inst, bool is_32_bit, bool is_signed) {
const auto rhs = inst.GetArg(1);
if (rhs.IsZero()) {
ReplaceUsesWith(inst, is_32_bit, 0);
return;
}
const auto lhs = inst.GetArg(0);
if (lhs.IsImmediate() && rhs.IsImmediate()) {
if (is_signed) {
const s64 result = lhs.GetImmediateAsS64() / rhs.GetImmediateAsS64();
ReplaceUsesWith(inst, is_32_bit, static_cast<u64>(result));
} else {
const u64 result = lhs.GetImmediateAsU64() / rhs.GetImmediateAsU64();
ReplaceUsesWith(inst, is_32_bit, result);
}
} else if (rhs.IsUnsignedImmediate(1)) {
inst.ReplaceUsesWith(IR::Value{lhs});
}
}
// Folds EOR operations based on the following:
//
// 1. imm_x ^ imm_y -> result
@ -190,6 +218,14 @@ void ConstantPropagation(IR::Block& block) {
case IR::Opcode::Mul64:
FoldMultiply(inst, opcode == IR::Opcode::Mul32);
break;
case IR::Opcode::SignedDiv32:
case IR::Opcode::SignedDiv64:
FoldDivide(inst, opcode == IR::Opcode::SignedDiv32, true);
break;
case IR::Opcode::UnsignedDiv32:
case IR::Opcode::UnsignedDiv64:
FoldDivide(inst, opcode == IR::Opcode::UnsignedDiv32, false);
break;
case IR::Opcode::And32:
case IR::Opcode::And64:
FoldAND(inst, opcode == IR::Opcode::And32);