[TypePromotion] Replace Zext to Truncate for the case src bitwidth is larger

Fix: https://github.com/llvm/llvm-project/issues/58843

Reviewed By: samtebbs

Differential Revision: https://reviews.llvm.org/D137613

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/TypePromotion.cpp b/llvm/lib/CodeGen/TypePromotion.cpp
index 6a747a31eabd..6903e9f645c7 100644
--- a/llvm/lib/CodeGen/TypePromotion.cpp
+++ b/llvm/lib/CodeGen/TypePromotion.cpp
@@ -578,7 +578,8 @@ void IRPromoter::TruncateSinks() {
 void IRPromoter::Cleanup() {
   LLVM_DEBUG(dbgs() << "IR Promotion: Cleanup..\n");
   // Some zexts will now have become redundant, along with their trunc
-  // operands, so remove them
+  // operands, so remove them.
+  // Some zexts need to be replaced with truncate if src bitwidth is larger.
   for (auto *V : Visited) {
     if (!isa<ZExtInst>(V))
       continue;
@@ -593,6 +594,11 @@ void IRPromoter::Cleanup() {
                         << "\n");
       ReplaceAllUsersOfWith(ZExt, Src);
       continue;
+    } else if (ZExt->getSrcTy()->getScalarSizeInBits() > PromotedWidth) {
+      IRBuilder<> Builder{ZExt};
+      Value *Trunc = Builder.CreateTrunc(Src, ZExt->getDestTy());
+      ReplaceAllUsersOfWith(ZExt, Trunc);
+      continue;
     }
 
     // We've inserted a trunc for a zext sink, but we already know that the