================
@@ -2660,6 +2660,64 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst
&CI) {
return &CI;
break;
}
+ case Intrinsic::pdep:
+ if (auto *MaskC = dyn_cast<ConstantInt>(II->getArgOperand(1))) {
+ if (MaskC->isNullValue())
+ return replaceInstUsesWith(*II, ConstantInt::get(II->getType(), 0));
+
+ if (MaskC->isAllOnesValue())
+ return replaceInstUsesWith(*II, II->getArgOperand(0));
+
+ unsigned MaskIdx, MaskLen;
+ if (MaskC->getValue().isShiftedMask(MaskIdx, MaskLen)) {
+ // any single contingous sequence of 1s anywhere in the mask simply
+ // describes a subset of the input bits shifted to the appropriate
+ // position. Replace with the straight forward IR.
+ Value *Input = II->getArgOperand(0);
+ Value *ShiftAmt = ConstantInt::get(II->getType(), MaskIdx);
+ Value *Shifted = Builder.CreateShl(Input, ShiftAmt);
+ Value *Masked = Builder.CreateAnd(Shifted, II->getArgOperand(1));
+ return replaceInstUsesWith(*II, Masked);
+ }
+
+ if (auto *SrcC = dyn_cast<ConstantInt>(II->getArgOperand(0))) {
+ // constant folding.
+ APInt Result =
+ llvm::APIntOps::expandBits(SrcC->getValue(), MaskC->getValue());
+ return replaceInstUsesWith(*II,
+ ConstantInt::get(II->getType(), Result));
----------------
nikic wrote:
Should go in ConstantFolding
https://github.com/llvm/llvm-project/pull/204144
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