[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

Author: jinhuang1102

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]);
   }

llvm/test/Transforms/AggressiveInstCombine/inline-strcmp-debugloc.ll

@@ -5,22 +5,23 @@
 
 @.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]]:
 ; CHECK-NEXT:    [[TMP0:%.*]] = load i8, ptr null, align 1, !dbg [[DBG4]]
 ; 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"}
 ;.