[llvm] [InstCombine] Iterative replacement in PtrReplacer (PR #137215)

[Anshil Gandhi via llvm-commits]

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@@ -365,12 +414,20 @@ void PointerReplacer::replace(Instruction *I) {
     // replacement (new value).
     WorkMap[NewI] = NewI;
   } else if (auto *PHI = dyn_cast<PHINode>(I)) {
-    Type *NewTy = getReplacement(PHI->getIncomingValue(0))->getType();
-    auto *NewPHI = PHINode::Create(NewTy, PHI->getNumIncomingValues(),
-                                   PHI->getName(), PHI->getIterator());
+    // Create a new PHI by replacing any incoming value that is a user of the
+    // root pointer and has a replacement.
+    SmallVector<Value *, 4> IncomingValues;
+    for (unsigned int I = 0; I < PHI->getNumIncomingValues(); ++I) {
+      Value *V = getReplacement(PHI->getIncomingValue(I));
+      if (!V)
+        V = PHI->getIncomingValue(I);
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gandhi56 wrote:

`@func_phi_loop` in Transforms/InstCombine/AMDGPU/ptr-replace-alloca.ll

https://github.com/llvm/llvm-project/pull/137215