[llvm] [VPlan] Optimize FindLast of (binop %IV, live-in) by sinking. (PR #183911)

[Mel Chen via llvm-commits]

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@@ -5650,6 +5650,40 @@ void VPlanTransforms::addExitUsersForFirstOrderRecurrences(VPlan &Plan,
   }
 }
 
+/// Check if \p V is a binary expression of a widened IV and a loop-invariant
+/// value. Returns the widened IV if found, nullptr otherwise.
+static VPWidenIntOrFpInductionRecipe *getExpressionIV(VPValue *V) {
+  auto *BinOp = dyn_cast<VPWidenRecipe>(V);
+  if (!BinOp || !Instruction::isBinaryOp(BinOp->getOpcode()))
+    return nullptr;
+
+  VPValue *Op0 = BinOp->getOperand(0);
+  VPValue *Op1 = BinOp->getOperand(1);
+  if (!isa<VPWidenIntOrFpInductionRecipe>(Op0))
+    std::swap(Op0, Op1);
+
+  if (!Op1->isDefinedOutsideLoopRegions())
+    return nullptr;
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Mel-Chen wrote:

This makes me wonder if running this optimization after LICM might work better.

https://github.com/llvm/llvm-project/pull/183911