[llvm] [profcheck] Add unknown branch weights for inlined strcmp/strncmp (PR #160455)

[Jin Huang via llvm-commits]

https://github.com/jinhuang1102 created https://github.com/llvm/llvm-project/pull/160455

The strcmp/strncmp inliner creates new conditional branches but was failing to add profile metadata. This caused the ProfileVerifierPass to fail when profcheck is enabled.

This patch fixes the issue by explicitly adding unknown branch weights to these branches.

>From ad625aff9f91f507e86509fbc8a6ad66810d54a0 Mon Sep 17 00:00:00 2001
From: Jin Huang <jingold at google.com>
Date: Wed, 24 Sep 2025 07:25:22 +0000
Subject: [PATCH] [profcheck]Add the missing profile handling in for
 strcmp/strncmp.

---
 .../AggressiveInstCombine/AggressiveInstCombine.cpp  | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp b/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
index 40de36d81ddd2..d00a3bc86d6b8 100644
--- a/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
+++ b/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
@@ -29,6 +29,7 @@
 #include "llvm/IR/Function.h"
 #include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/PatternMatch.h"
+#include "llvm/IR/ProfDataUtils.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/BuildLibCalls.h"
 #include "llvm/Transforms/Utils/Local.h"
@@ -1283,11 +1284,14 @@ void StrNCmpInliner::inlineCompare(Value *LHS, StringRef RHS, uint64_t N,
     Value *VR =
         ConstantInt::get(CI->getType(), static_cast<unsigned char>(RHS[i]));
     Value *Sub = Swapped ? B.CreateSub(VR, VL) : B.CreateSub(VL, VR);
-    if (i < N - 1)
-      B.CreateCondBr(B.CreateICmpNE(Sub, ConstantInt::get(CI->getType(), 0)),
-                     BBNE, BBSubs[i + 1]);
-    else
+    if (i < N - 1) {
+      BranchInst *CondBrInst = B.CreateCondBr(
+          B.CreateICmpNE(Sub, ConstantInt::get(CI->getType(), 0)), BBNE,
+          BBSubs[i + 1]);
+      setExplicitlyUnknownBranchWeights(*CondBrInst, DEBUG_TYPE);
+    } else {
       B.CreateBr(BBNE);
+    }
 
     Phi->addIncoming(Sub, BBSubs[i]);
   }