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ConstProp: negate adds -> subs

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the arm ops are equiv, even though the x86 isn't (due to inverted carry).

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
This commit is contained in:
Alyssa Rosenzweig committed 2024-04-02 13:53:21 -04:00
1 parent 37f2b417e4
commit fa76961873
1 file changed
+4 -3
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FEXCore/Source/Interface/IR/Passes/ConstProp.cpp
+4 -3
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@@ -681,14 +681,15 @@ bool ConstProp::ConstantPropagation(IREmitter *IREmit, const IRListView& Current
break;
}
case OP_ADD: {
case OP_ADD:
case OP_ADDWITHFLAGS: {
auto Op = IROp->C<IR::IROp_Add>();
uint64_t Constant1{};
uint64_t Constant2{};
bool IsConstant1 = IREmit->IsValueConstant(Op->Header.Args[0], &Constant1);
bool IsConstant2 = IREmit->IsValueConstant(Op->Header.Args[1], &Constant2);
if (IsConstant1 && IsConstant2) {
if (IsConstant1 && IsConstant2 && IROp->Op == OP_ADD) {
uint64_t NewConstant = (Constant1 + Constant2) & getMask(Op) ;
IREmit->ReplaceWithConstant(CodeNode, NewConstant);
Changed = true;
@@ -697,7 +698,7 @@ bool ConstProp::ConstantPropagation(IREmitter *IREmit, const IRListView& Current
// If the second argument is constant, the immediate is not ImmAddSub, but when negated is.
// This means we can convert the operation in to a subtract.
// Change the IR operation itself.
IROp->Op = OP_SUB;
IROp->Op = IROp->Op == OP_ADD ? OP_SUB : OP_SUBWITHFLAGS;
// Set the write cursor to just before this operation.
auto CodeIter = CurrentIR.at(CodeNode);
--CodeIter;