Revert "clang-misexpect: Profile Guided Validation of Performance Annotations in LLVM"

See discussion in https://bugs.llvm.org/show_bug.cgi?id=45073 / https://reviews.llvm.org/D66324#2334485
the implementation is known-broken for certain inputs,
the bugreport was up for a significant amount of timer,
and there has been no activity to address it.
Therefore, just completely rip out all of misexpect handling.

I suspect, fixing it requires redesigning the internals of MD_misexpect.
Should anyone commit to fixing the implementation problem,
starting from clean slate may be better anyways.

This reverts commit 7bdad08,
and some of it's follow-ups, that don't stand on their own.

Author: LebedevRI

clang/docs/DiagnosticsReference.rst

@@ -7977,15 +7977,6 @@ This diagnostic is enabled by default.
 +------------------------------------------------------------------------------------------------+
 
 
--Wmisexpect
------------
-**Diagnostic text:**
-
-+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
-|:warning:`warning:` |nbsp| :diagtext:`Potential performance regression from use of \_\_builtin\_expect(): Annotation was correct on` |nbsp| :placeholder:`A` |nbsp| :diagtext:`of profiled executions.`|
-+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
-
-
 -Wmisleading-indentation
 ------------------------
 **Diagnostic text:**

clang/include/clang/Basic/DiagnosticFrontendKinds.td

@@ -299,12 +299,6 @@ def warn_profile_data_missing : Warning<
 def warn_profile_data_unprofiled : Warning<
   "no profile data available for file \"%0\"">,
   InGroup<ProfileInstrUnprofiled>;
-def warn_profile_data_misexpect : Warning<
-  "Potential performance regression from use of __builtin_expect(): "
-  "Annotation was correct on %0 of profiled executions.">,
-  BackendInfo,
-  InGroup<MisExpect>,
-  DefaultIgnore;
 } // end of instrumentation issue category
 
 }

clang/include/clang/Basic/DiagnosticGroups.td

@@ -1156,7 +1156,6 @@ def BackendOptimizationFailure : DiagGroup<"pass-failed">;
 def ProfileInstrMissing : DiagGroup<"profile-instr-missing">;
 def ProfileInstrOutOfDate : DiagGroup<"profile-instr-out-of-date">;
 def ProfileInstrUnprofiled : DiagGroup<"profile-instr-unprofiled">;
-def MisExpect : DiagGroup<"misexpect">;
 
 // AddressSanitizer frontend instrumentation remarks.
 def SanitizeAddressRemarks : DiagGroup<"sanitize-address">;

clang/lib/CodeGen/CodeGenAction.cpp

@@ -404,9 +404,6 @@ namespace clang {
     bool StackSizeDiagHandler(const llvm::DiagnosticInfoStackSize &D);
     /// Specialized handler for unsupported backend feature diagnostic.
     void UnsupportedDiagHandler(const llvm::DiagnosticInfoUnsupported &D);
-    /// Specialized handler for misexpect warnings.
-    /// Note that misexpect remarks are emitted through ORE
-    void MisExpectDiagHandler(const llvm::DiagnosticInfoMisExpect &D);
     /// Specialized handlers for optimization remarks.
     /// Note that these handlers only accept remarks and they always handle
     /// them.
@@ -674,36 +671,6 @@ void BackendConsumer::UnsupportedDiagHandler(
         << Filename << Line << Column;
 }
 
-void BackendConsumer::MisExpectDiagHandler(
-    const llvm::DiagnosticInfoMisExpect &D) {
-  StringRef Filename;
-  unsigned Line, Column;
-  bool BadDebugInfo = false;
-  FullSourceLoc Loc;
-  std::string Msg;
-  raw_string_ostream MsgStream(Msg);
-  DiagnosticPrinterRawOStream DP(MsgStream);
-
-  // Context will be nullptr for IR input files, we will construct the diag
-  // message from llvm::DiagnosticInfoMisExpect.
-  if (Context != nullptr) {
-    Loc = getBestLocationFromDebugLoc(D, BadDebugInfo, Filename, Line, Column);
-    MsgStream << D.getMsg();
-  } else {
-    DiagnosticPrinterRawOStream DP(MsgStream);
-    D.print(DP);
-  }
-  Diags.Report(Loc, diag::warn_profile_data_misexpect) << MsgStream.str();
-
-  if (BadDebugInfo)
-    // If we were not able to translate the file:line:col information
-    // back to a SourceLocation, at least emit a note stating that
-    // we could not translate this location. This can happen in the
-    // case of #line directives.
-    Diags.Report(Loc, diag::note_fe_backend_invalid_loc)
-        << Filename << Line << Column;
-}
-
 void BackendConsumer::EmitOptimizationMessage(
     const llvm::DiagnosticInfoOptimizationBase &D, unsigned DiagID) {
   // We only support warnings and remarks.
@@ -881,9 +848,6 @@ void BackendConsumer::DiagnosticHandlerImpl(const DiagnosticInfo &DI) {
   case llvm::DK_Unsupported:
     UnsupportedDiagHandler(cast<DiagnosticInfoUnsupported>(DI));
     return;
-  case llvm::DK_MisExpect:
-    MisExpectDiagHandler(cast<DiagnosticInfoMisExpect>(DI));
-    return;
   default:
     // Plugin IDs are not bound to any value as they are set dynamically.
     ComputeDiagRemarkID(Severity, backend_plugin, DiagID);

clang/lib/Frontend/CompilerInvocation.cpp

@@ -3833,9 +3833,6 @@ bool CompilerInvocation::CreateFromArgs(CompilerInvocation &Res,
     }
   }
 
-  if (Diags.isIgnored(diag::warn_profile_data_misexpect, SourceLocation()))
-    Res.FrontendOpts.LLVMArgs.push_back("-pgo-warn-misexpect");
-
   LangOpts.FunctionAlignment =
       getLastArgIntValue(Args, OPT_function_alignment, 0, Diags);
 

clang/test/CodeGen/thinlto-clang-diagnostic-handler-in-be.c

@@ -7,7 +7,6 @@
 // RUN: llvm-lto -thinlto -o %t %t1.bo
 // RUN: %clang -cc1 -O2 -fexperimental-new-pass-manager -x ir %t1.bo -fthinlto-index=%t.thinlto.bc -emit-obj -Rpass-analysis=info 2>&1 | FileCheck %s -check-prefix=CHECK-REMARK
 // RUN: llvm-profdata merge -o %t2.profdata %S/Inputs/thinlto_expect2.proftext
-// RUN: %clang -cc1 -O2 -fexperimental-new-pass-manager -x ir %t1.bo -fthinlto-index=%t.thinlto.bc -fprofile-instrument-use-path=%t2.profdata -emit-obj -Wmisexpect 2>&1 | FileCheck %s -check-prefix=CHECK-WARNING
 // RUN: %clang -cc1 -O2 -fexperimental-new-pass-manager -x ir %t1.bo -fthinlto-index=%t.thinlto.bc -fprofile-instrument-use-path=%t2.profdata -emit-obj 2>&1 | FileCheck %s -allow-empty -check-prefix=CHECK-NOWARNING
 
 int sum;
@@ -20,5 +19,4 @@ __attribute__((noinline)) void foo(int m) {
     bar();
 }
 // CHECK-REMARK: remark: {{.*}}.c:
-// CHECK-WARNING: warning: Potential performance regression from use of __builtin_expect(): Annotation was correct on {{.*}}.c:{{[0-9]*}}:{{[0-9]*}}: 50.00% (12 / 24) of profiled executions.
 // CHECK-NOWARNING-NOT: warning: {{.*}}.c:{{[0-9]*}}:26: 50.00% (12 / 24)

clang/test/CodeGenCXX/attr-likelihood-if-vs-builtin-expect.cpp

@@ -36,7 +36,7 @@ void ab0(int &i) {
   // CHECK: br {{.*}}end{{$}}
   // CHECK: br {{.*}}end{{$}}
   // CHECK: br {{.*}}end{{$}}
-  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !9
   if (__builtin_expect(a() && b() && c(), 0)) {
     ++i;
   } else {
@@ -48,7 +48,7 @@ void au(int &i) {
   // CHECK-LABEL: define{{.*}}au
   // CHECK: br {{.*}}else{{$}}
   // CHECK: br {{.*}}else{{$}}
-  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !9
   if (a() && b() && c()) [[unlikely]] {
     ++i;
   } else {
@@ -83,9 +83,9 @@ void ol(int &i) {
 
 void ob0(int &i) {
   // CHECK-LABEL: define{{.*}}ob0
-  // CHECK: br {{.*}} !prof !10
-  // CHECK: br {{.*}} !prof !10
-  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !9
+  // CHECK: br {{.*}} !prof !9
+  // CHECK: br {{.*}} !prof !9
   if (__builtin_expect(a() || b() || c(), 0)) {
     i = 0;
   } else {
@@ -95,9 +95,9 @@ void ob0(int &i) {
 
 void ou(int &i) {
   // CHECK-LABEL: define{{.*}}ou
-  // CHECK: br {{.*}} !prof !10
-  // CHECK: br {{.*}} !prof !10
-  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !9
+  // CHECK: br {{.*}} !prof !9
+  // CHECK: br {{.*}} !prof !9
   if (a() || b() || c()) [[unlikely]] {
     i = 0;
   } else {
@@ -127,7 +127,7 @@ void nl(int &i) {
 
 void nb0(int &i) {
   // CHECK-LABEL: define{{.*}}nb0
-  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !9
   if (__builtin_expect(!a(), 0)) {
     ++i;
   } else {
@@ -137,7 +137,7 @@ void nb0(int &i) {
 
 void nu(int &i) {
   // CHECK-LABEL: define{{.*}}nu
-  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !9
   if (bool d = !a()) [[unlikely]] {
     ++i;
   } else {
@@ -188,7 +188,7 @@ void tb0(int &i) {
   // CHECK: br {{.*}}false{{$}}
   // CHECK: br {{.*}}end{{$}}
   // CHECK: br {{.*}}end{{$}}
-  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !9
   if (__builtin_expect(a() ? b() : c(), 0)) {
     ++i;
   } else {
@@ -201,7 +201,7 @@ void tu(int &i) {
   // CHECK: br {{.*}}false{{$}}
   // CHECK: br {{.*}}end{{$}}
   // CHECK: br {{.*}}end{{$}}
-  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !9
   if (bool d = a() ? b() : c()) [[unlikely]] {
     ++i;
   } else {
@@ -212,8 +212,8 @@ void tu(int &i) {
 void tu2(int &i) {
   // CHECK-LABEL: define{{.*}}tu
   // CHECK: br {{.*}}false{{$}}
-  // CHECK: br {{.*}} !prof !10
-  // CHECK: br {{.*}} !prof !10
+  // CHECK: br {{.*}} !prof !9
+  // CHECK: br {{.*}} !prof !9
   if (a() ? b() : c()) [[unlikely]] {
     ++i;
   } else {
@@ -222,4 +222,4 @@ void tu2(int &i) {
 }
 
 // CHECK: !6 = !{!"branch_weights", i32 2000, i32 1}
-// CHECK: !10 = !{!"branch_weights", i32 1, i32 2000}
+// CHECK: !9 = !{!"branch_weights", i32 1, i32 2000}