[clang] Add flag fallow-runtime-check-skip-hot-cutoff (#145999)

Co-authored-by: Kazu Hirata <kazu@google.com>

clang/include/clang/Basic/CodeGenOptions.h

@@ -399,6 +399,8 @@ public:
   /// with extra debug info.
   SanitizerSet SanitizeAnnotateDebugInfo;
 
+  std::optional<double> AllowRuntimeCheckSkipHotCutoff;
+
   /// List of backend command-line options for -fembed-bitcode.
   std::vector<uint8_t> CmdArgs;
 

clang/include/clang/Driver/Options.td

@@ -2668,6 +2668,15 @@ def fsanitize_skip_hot_cutoff_EQ
 
 } // end -f[no-]sanitize* flags
 
+def fallow_runtime_check_skip_hot_cutoff_EQ
+    : Joined<["-"], "fallow-runtime-check-skip-hot-cutoff=">,
+      Group<f_clang_Group>,
+      Visibility<[ClangOption, CC1Option]>,
+      HelpText<"Exclude __builtin_allow_runtime_check for the top hottest "
+               "code responsible for the given fraction of PGO counters "
+               "(0.0 [default] = skip none; 1.0 = skip all). "
+               "Argument format: <value>">;
+
 def funsafe_math_optimizations : Flag<["-"], "funsafe-math-optimizations">,
   Group<f_Group>, Visibility<[ClangOption, CC1Option]>,
   HelpText<"Allow unsafe floating-point math optimizations which may decrease precision">,

clang/lib/CodeGen/BackendUtil.cpp

@@ -805,17 +805,21 @@ static void addSanitizers(const Triple &TargetTriple,
   // SanitizeSkipHotCutoffs: doubles with range [0, 1]
   // Opts.cutoffs: unsigned ints with range [0, 1000000]
   auto ScaledCutoffs = CodeGenOpts.SanitizeSkipHotCutoffs.getAllScaled(1000000);
-
+  uint64_t AllowRuntimeCheckSkipHotCutoff =
+      CodeGenOpts.AllowRuntimeCheckSkipHotCutoff.value_or(0.0) * 1000000;
   // TODO: remove IsRequested()
-  if (LowerAllowCheckPass::IsRequested() || ScaledCutoffs.has_value()) {
+  if (LowerAllowCheckPass::IsRequested() || ScaledCutoffs.has_value() ||
+      CodeGenOpts.AllowRuntimeCheckSkipHotCutoff.has_value()) {
     // We want to call it after inline, which is about OptimizerEarlyEPCallback.
     PB.registerOptimizerEarlyEPCallback(
-        [ScaledCutoffs](ModulePassManager &MPM, OptimizationLevel Level,
-                        ThinOrFullLTOPhase Phase) {
+        [ScaledCutoffs, AllowRuntimeCheckSkipHotCutoff](
+            ModulePassManager &MPM, OptimizationLevel Level,
+            ThinOrFullLTOPhase Phase) {
           LowerAllowCheckPass::Options Opts;
           // TODO: after removing IsRequested(), make this unconditional
           if (ScaledCutoffs.has_value())
             Opts.cutoffs = ScaledCutoffs.value();
+          Opts.runtime_check = AllowRuntimeCheckSkipHotCutoff;
           MPM.addPass(
               createModuleToFunctionPassAdaptor(LowerAllowCheckPass(Opts)));
         });

clang/lib/Driver/ToolChains/Clang.cpp

@@ -6028,7 +6028,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   // -fasynchronous-unwind-tables and -fnon-call-exceptions interact in more
   // complicated ways.
   auto SanitizeArgs = TC.getSanitizerArgs(Args);
-
+  Args.AddLastArg(CmdArgs,
+                  options::OPT_fallow_runtime_check_skip_hot_cutoff_EQ);
   bool IsAsyncUnwindTablesDefault =
       TC.getDefaultUnwindTableLevel(Args) == ToolChain::UnwindTableLevel::Asynchronous;
   bool IsSyncUnwindTablesDefault =

clang/lib/Frontend/CompilerInvocation.cpp

@@ -1820,6 +1820,11 @@ void CompilerInvocationBase::GenerateCodeGenArgs(const CodeGenOptions &Opts,
   for (std::string Sanitizer : Values)
     GenerateArg(Consumer, OPT_fsanitize_skip_hot_cutoff_EQ, Sanitizer);
 
+  if (Opts.AllowRuntimeCheckSkipHotCutoff) {
+    GenerateArg(Consumer, OPT_fallow_runtime_check_skip_hot_cutoff_EQ,
+                std::to_string(*Opts.AllowRuntimeCheckSkipHotCutoff));
+  }
+
   for (StringRef Sanitizer :
        serializeSanitizerKinds(Opts.SanitizeAnnotateDebugInfo))
     GenerateArg(Consumer, OPT_fsanitize_annotate_debug_info_EQ, Sanitizer);
@@ -2322,6 +2327,18 @@ bool CompilerInvocation::ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args,
       Args.getAllArgValues(OPT_fsanitize_annotate_debug_info_EQ), Diags,
       Opts.SanitizeAnnotateDebugInfo);
 
+  if (StringRef V =
+          Args.getLastArgValue(OPT_fallow_runtime_check_skip_hot_cutoff_EQ);
+      !V.empty()) {
+    double A;
+    if (V.getAsDouble(A) || A < 0.0 || A > 1.0) {
+      Diags.Report(diag::err_drv_invalid_value)
+          << "-fallow-runtime-check-skip-hot-cutoff=" << V;
+    } else {
+      Opts.AllowRuntimeCheckSkipHotCutoff = A;
+    }
+  }
+
   Opts.EmitVersionIdentMetadata = Args.hasFlag(OPT_Qy, OPT_Qn, true);
 
   if (!LangOpts->CUDAIsDevice)

clang/test/CodeGen/fallow-runtime-check-skip-hot-cutoff.c

@@ -0,0 +1,15 @@
+// RUN: %clang -fallow-runtime-check-skip-hot-cutoff=1.0 -S -emit-llvm %s -o - -O2 | FileCheck --check-prefix=ONE %s
+// RUN: %clang -fallow-runtime-check-skip-hot-cutoff=0.0 -S -emit-llvm %s -o - -O2 | FileCheck --check-prefix=ZERO %s
+// RUN: not %clang -fallow-runtime-check-skip-hot-cutoff=6.0 -S -emit-llvm %s -o - -O2 2>&1 | FileCheck --check-prefix=SIX %s
+// RUN: not %clang -fallow-runtime-check-skip-hot-cutoff=-1.0 -S -emit-llvm %s -o - -O2 2>&1 | FileCheck --check-prefix=MINUSONE %s
+// RUN: not %clang -fallow-runtime-check-skip-hot-cutoff=string -S -emit-llvm %s -o - -O2 2>&1 | FileCheck --check-prefix=STRING %s
+
+// ONE: ret i32 0
+// ZERO: ret i32 1
+// SIX: invalid value '6.0' in '-fallow-runtime-check-skip-hot-cutoff='
+// MINUSONE: invalid value '-1.0' in '-fallow-runtime-check-skip-hot-cutoff='
+// STRING: invalid value 'string' in '-fallow-runtime-check-skip-hot-cutoff='
+
+int main(int argc, char** argv) {
+    return __builtin_allow_runtime_check("foo");
+}

clang/test/Driver/fallow-runtime-check-skip-hot-cutoff.c

@@ -0,0 +1,6 @@
+// RUN: %clang -### -fallow-runtime-check-skip-hot-cutoff=1.0 %s 2>&1 | FileCheck %s
+// CHECK: -fallow-runtime-check-skip-hot-cutoff=1.0
+
+int main(int argc, char** argv) {
+    return __builtin_allow_runtime_check("foo");
+}