[llvm] [InstCombine] Match intrinsic recurrences when known to be hoisted (PR #149858)

[Nikita Popov via llvm-commits]

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@@ -1532,6 +1532,46 @@ static Instruction *foldBitOrderCrossLogicOp(Value *V,
   return nullptr;
 }
 
+static bool foldBinaryIntrinsicRecurrence(InstCombinerImpl &IC,
+                                          IntrinsicInst *II) {
+  PHINode *PN;
+  Value *Init, *OtherOp;
+
+  // A binary intrinsic recurrence with loop-invariant operands is equivalent to
+  // `call @llvm.binary.intrinsic(Init, OtherOp)`.
+  if (!matchSimpleBinaryIntrinsicRecurrence(II, PN, Init, OtherOp) ||
+      isa<Constant>(OtherOp) || !PN->hasOneUse() ||
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nikic wrote:

Similarly, I don't think excluding multi-use phi is necessary. In that case the phi would stay, but we'd still make the intrinsic loop-invariant. Or do you think that's not profitable?

https://github.com/llvm/llvm-project/pull/149858