================
@@ -229,6 +229,41 @@ static Value *createWhileLO(IRBuilder<> &Builder, unsigned
ElementSizeInBits,
WhileLO, {Start, End, Builder.getInt32(VectorScale)}, "pac.mask");
}
+/// If \p UserI is an extractelement use of the original loop mask, attempt to
+/// rewrite it to `extractelement(pext(count, 0), idx)` if the extract index is
+/// known to be within the first mask section (which means pext index = 0). If
+/// the user of the extract is a branch and the source of the mask is a
whilelo,
+/// this form can be optimized into checking the status flags.
+static bool tryRewriteExtractElement(Instruction &UserI,
+ const MaskRewriteCandidate &C,
+ Value *Count) {
+ auto *EEI = dyn_cast<ExtractElementInst>(&UserI);
+ if (!EEI)
+ return false;
+
+ ElementCount LegalEC = getSVEElementCount(C.ElementSizeInBits);
+ auto *Idx = dyn_cast<ConstantInt>(EEI->getIndexOperand());
+ if (!Idx || Idx->getValue().uge(LegalEC.getKnownMinValue()))
+ return false;
+
+ IRBuilder<> Builder(EEI);
+ Builder.SetCurrentDebugLocation(EEI->getDebugLoc());
+
+ Module *M = EEI->getModule();
+ FunctionCallee PExt = Intrinsic::getOrInsertDeclaration(
+ M, Intrinsic::aarch64_sve_pext,
+ {VectorType::get(Builder.getInt1Ty(), LegalEC)});
+ auto *ExtractMask =
+ Builder.CreateCall(PExt, {Count, Builder.getInt32(0)}, "pac.pext");
+
+ Value *Extracted = Builder.CreateExtractElement(
+ ExtractMask, EEI->getIndexOperand(), EEI->getName() + ".pac");
----------------
sdesmalen-arm wrote:
```suggestion
ExtractMask, EEI->getIndexOperand(), EEI->getName() + ".pn");
```
https://github.com/llvm/llvm-project/pull/220961
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