[llvm-branch-commits] [llvm] InstCombine: Set unknown profile metadata in memchr-to-select folding (PR #179758)

[Snehasish Kumar via llvm-branch-commits]

https://github.com/snehasish updated https://github.com/llvm/llvm-project/pull/179758

>From 950190ddcc169c3b1c829f1f6e237dace9eaf894 Mon Sep 17 00:00:00 2001
From: Snehasish Kumar <snehasishk at google.com>
Date: Tue, 3 Feb 2026 04:37:37 +0000
Subject: [PATCH] InstCombine: Set unknown profile metadata in memchr-to-select
 folding

---
 llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp | 11 ++++++++++-
 llvm/utils/profcheck-xfail.txt                 |  1 -
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 5de9230cdc485..80dde3db360c8 100644
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -485,10 +485,19 @@ static Value* memChrToCharCompare(CallInst *CI, Value *NBytes,
     Value *Zero = ConstantInt::get(NBytes->getType(), 0);
     Value *And = B.CreateICmpNE(NBytes, Zero);
     Cmp = B.CreateLogicalAnd(And, Cmp);
+    if (!ProfcheckDisableMetadataFixes)
+      if (auto *I = dyn_cast<Instruction>(Cmp))
+        setExplicitlyUnknownBranchWeightsIfProfiled(*I, DEBUG_TYPE,
+                                                    CI->getFunction());
   }
 
   Value *NullPtr = Constant::getNullValue(CI->getType());
-  return B.CreateSelect(Cmp, Src, NullPtr);
+  Value *Res = B.CreateSelect(Cmp, Src, NullPtr);
+  if (!ProfcheckDisableMetadataFixes)
+    if (auto *I = dyn_cast<Instruction>(Res))
+      setExplicitlyUnknownBranchWeightsIfProfiled(*I, DEBUG_TYPE,
+                                                  CI->getFunction());
+  return Res;
 }
 
 Value *LibCallSimplifier::optimizeStrChr(CallInst *CI, IRBuilderBase &B) {
diff --git a/llvm/utils/profcheck-xfail.txt b/llvm/utils/profcheck-xfail.txt
index 94d718eb6b1fb..1758afc920258 100644
--- a/llvm/utils/profcheck-xfail.txt
+++ b/llvm/utils/profcheck-xfail.txt
@@ -225,7 +225,6 @@ Transforms/InstCombine/load.ll
 Transforms/InstCombine/load-select.ll
 Transforms/InstCombine/loadstore-metadata.ll
 Transforms/InstCombine/logical-select.ll
-Transforms/InstCombine/memchr-11.ll
 Transforms/InstCombine/memchr-2.ll
 Transforms/InstCombine/memchr-3.ll
 Transforms/InstCombine/memchr-6.ll