[llvm] [CodeGen] Fix partial phi input removal in TailDuplicator. (PR #158265)

[Afanasyev Ivan via llvm-commits]

https://github.com/ivafanas updated https://github.com/llvm/llvm-project/pull/158265

>From 79dd1ed8b72ebafcf59de375d7a7519c72b5544c Mon Sep 17 00:00:00 2001
From: Ivan Afanasyev <ivafanas at gmail.com>
Date: Fri, 12 Sep 2025 17:24:49 +0700
Subject: [PATCH] [TailDup] Fix partial phi input removal in TailDuplicator.

---
 llvm/lib/CodeGen/TailDuplicator.cpp | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/CodeGen/TailDuplicator.cpp b/llvm/lib/CodeGen/TailDuplicator.cpp
index 5d720fbbf1c61..9b1420a94142d 100644
--- a/llvm/lib/CodeGen/TailDuplicator.cpp
+++ b/llvm/lib/CodeGen/TailDuplicator.cpp
@@ -375,9 +375,14 @@ void TailDuplicator::processPHI(
   if (!Remove)
     return;
 
-  // Remove PredBB from the PHI node.
-  MI->removeOperand(SrcOpIdx + 1);
-  MI->removeOperand(SrcOpIdx);
+  // MI might have multiple entries for PredBB. Need to remove them all.
+  for (unsigned N = MI->getNumOperands(); N > 2; N -= 2) {
+    if (MI->getOperand(N - 1).getMBB() == PredBB) {
+      MI->removeOperand(N - 1);
+      MI->removeOperand(N - 2);
+    }
+  }
+
   if (MI->getNumOperands() == 1 && !TailBB->hasAddressTaken())
     MI->eraseFromParent();
   else if (MI->getNumOperands() == 1)