[llvm] c4a134f - [profcheck] Add unknown branch weights for inlined strcmp/strncmp (#160455)

[via llvm-commits]

Author: Jin Huang
Date: 2025-09-25T20:11:30-07:00
New Revision: c4a134f59108c8a5e41d9f2539b0ee96f5cbccec

URL: https://github.com/llvm/llvm-project/commit/c4a134f59108c8a5e41d9f2539b0ee96f5cbccec
DIFF: https://github.com/llvm/llvm-project/commit/c4a134f59108c8a5e41d9f2539b0ee96f5cbccec.diff

LOG: [profcheck] Add unknown branch weights for inlined strcmp/strncmp (#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.

Issue #147390

Added: 
    

Modified: 
    llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
    llvm/test/Transforms/AggressiveInstCombine/inline-strcmp-debugloc.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp b/llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
index 40de36d81ddd2..ee1fec0da3d73 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 +1284,19 @@ 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]);
+
+      Function *F = CI->getFunction();
+      assert(F && "Instruction does not belong to a function!");
+      std::optional<Function::ProfileCount> EC = F->getEntryCount();
+      if (EC && EC->getCount() > 0)
+        setExplicitlyUnknownBranchWeights(*CondBrInst, DEBUG_TYPE);
+    } else {
       B.CreateBr(BBNE);
+    }
 
     Phi->addIncoming(Sub, BBSubs[i]);
   }

diff  --git a/llvm/test/Transforms/AggressiveInstCombine/inline-strcmp-debugloc.ll b/llvm/test/Transforms/AggressiveInstCombine/inline-strcmp-debugloc.ll
index 94c912876d7b9..6015607c05df4 100644
--- a/llvm/test/Transforms/AggressiveInstCombine/inline-strcmp-debugloc.ll
+++ b/llvm/test/Transforms/AggressiveInstCombine/inline-strcmp-debugloc.ll
@@ -5,8 +5,9 @@
 
 @.str = constant [3 x i8] c"-h\00"
 
-define i32 @main() {
-; CHECK-LABEL: define i32 @main() {
+define i32 @main() !prof !8 {
+; CHECK-LABEL: define i32 @main()
+; CHECK: !prof [[PROF_0:![0-9]+]]
 ; CHECK-NEXT:  [[ENTRY:.*:]]
 ; CHECK-NEXT:    br label %[[SUB_0:.*]], !dbg [[DBG4:![0-9]+]]
 ; CHECK:       [[SUB_0]]:
@@ -14,13 +15,13 @@ define i32 @main() {
 ; CHECK-NEXT:    [[TMP1:%.*]] = zext i8 [[TMP0]] to i32, !dbg [[DBG4]]
 ; CHECK-NEXT:    [[TMP2:%.*]] = sub i32 [[TMP1]], 45, !dbg [[DBG4]]
 ; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne i32 [[TMP2]], 0, !dbg [[DBG4]]
-; CHECK-NEXT:    br i1 [[TMP3]], label %[[NE:.*]], label %[[SUB_1:.*]], !dbg [[DBG4]]
+; CHECK-NEXT:    br i1 [[TMP3]], label %[[NE:.*]], label %[[SUB_1:.*]], !dbg [[DBG4]], !prof [[PROF_1:![0-9]+]]
 ; CHECK:       [[SUB_1]]:
 ; CHECK-NEXT:    [[TMP4:%.*]] = load i8, ptr getelementptr inbounds (i8, ptr null, i64 1), align 1, !dbg [[DBG4]]
 ; CHECK-NEXT:    [[TMP5:%.*]] = zext i8 [[TMP4]] to i32, !dbg [[DBG4]]
 ; CHECK-NEXT:    [[TMP6:%.*]] = sub i32 [[TMP5]], 104, !dbg [[DBG4]]
 ; CHECK-NEXT:    [[TMP7:%.*]] = icmp ne i32 [[TMP6]], 0, !dbg [[DBG4]]
-; CHECK-NEXT:    br i1 [[TMP7]], label %[[NE]], label %[[SUB_2:.*]], !dbg [[DBG4]]
+; CHECK-NEXT:    br i1 [[TMP7]], label %[[NE]], label %[[SUB_2:.*]], !dbg [[DBG4]], !prof [[PROF_1]]
 ; CHECK:       [[SUB_2]]:
 ; CHECK-NEXT:    br label %[[NE]], !dbg [[DBG4]]
 ; CHECK:       [[NE]]:
@@ -46,11 +47,14 @@ declare i32 @strcmp(ptr, ptr)
 !4 = !DILocation(line: 258, column: 10, scope: !5)
 !5 = distinct !DISubprogram(name: "streq", scope: !1, file: !1, line: 257, type: !7, scopeLine: 257, unit: !0, retainedNodes: !2)
 !7 = !DISubroutineType(types: !2)
+!8 = !{!"function_entry_count", i64 1000}
 ;.
 ; CHECK: [[META0:![0-9]+]] = distinct !DICompileUnit(language: DW_LANG_C11, file: [[META1:![0-9]+]], producer: "{{.*}}clang version {{.*}}", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: [[META2:![0-9]+]], retainedTypes: [[META2]], globals: [[META2]])
 ; CHECK: [[META1]] = !DIFile(filename: "test.c", directory: {{.*}})
 ; CHECK: [[META2]] = !{}
+; CHECK: [[PROF_0]] = !{!"function_entry_count", i64 1000}
 ; CHECK: [[DBG4]] = !DILocation(line: 258, column: 10, scope: [[META5:![0-9]+]])
 ; CHECK: [[META5]] = distinct !DISubprogram(name: "streq", scope: [[META1]], file: [[META1]], line: 257, type: [[META6:![0-9]+]], scopeLine: 257, spFlags: DISPFlagDefinition, unit: [[META0]], retainedNodes: [[META2]])
 ; CHECK: [[META6]] = !DISubroutineType(types: [[META2]])
+; CHECK: [[PROF_1]] = !{!"unknown", !"aggressive-instcombine"}
 ;.