[llvm] [GlobalIsel] Combine cast of const integer II (PR #100835)
Thorsten Schütt via llvm-commits
llvm-commits at lists.llvm.org
Sun Jul 28 08:31:52 PDT 2024
================
@@ -209,3 +209,48 @@ bool CombinerHelper::matchCastOfSelect(const MachineInstr &CastMI,
return true;
}
+
+bool CombinerHelper::matchCastOfInteger(const MachineInstr &CastMI,
+ APInt &MatchInfo) {
+ const GExtOrTruncOp *Cast = cast<GExtOrTruncOp>(&CastMI);
+
+ std::optional<APInt> Input = getIConstantVRegVal(Cast->getSrcReg(), MRI);
+ if (!Input)
+ return false;
+
+ LLT DstTy = MRI.getType(Cast->getReg(0));
+ LLT SrcTy = MRI.getType(Cast->getSrcReg());
+
+ if (!isConstantLegalOrBeforeLegalizer(DstTy))
+ return false;
+
+ switch (Cast->getOpcode()) {
+ case TargetOpcode::G_ZEXT: {
+ MatchInfo = Input->zext(DstTy.getScalarSizeInBits());
+ return true;
+ }
+ case TargetOpcode::G_SEXT: {
+ MatchInfo = Input->sext(DstTy.getScalarSizeInBits());
+ return true;
+ }
+ case TargetOpcode::G_TRUNC: {
+ MatchInfo = Input->trunc(DstTy.getScalarSizeInBits());
+ return true;
+ }
+ case TargetOpcode::G_ANYEXT: {
+ const auto &TLI = getTargetLowering();
+ LLVMContext &Ctx = getContext();
+ const DataLayout &DL = getDataLayout();
+
+ // Some targets like RISC-V prefer to sign extend some types.
+ if (TLI.isSExtCheaperThanZExt(SrcTy, DstTy, DL, Ctx))
+ MatchInfo = Input->sext(DstTy.getScalarSizeInBits());
+ else
+ MatchInfo = Input->zext(DstTy.getScalarSizeInBits());
+
+ return true;
+ }
+ default:
+ return false;
----------------
tschuett wrote:
```
llvm_unreachable();
return false;
```
It is unreachable because of the pattern and return false to make the compiler happy.
https://github.com/llvm/llvm-project/pull/100835
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