[ubsan] Connect -fsanitize-skip-hot-cutoff to LowerAllowCheckPass<cutoffs> (#124857)

This adds the plumbing between -fsanitize-skip-hot-cutoff (introduced in
https://github.com/llvm/llvm-project/pull/121619) and
LowerAllowCheckPass<cutoffs> (introduced in
https://github.com/llvm/llvm-project/pull/124211).
    
The net effect is that -fsanitize-skip-hot-cutoff now combines the
functionality of -ubsan-guard-checks and
-lower-allow-check-percentile-cutoff (though this patch does not remove
those yet), and generalizes the latter to allow per-sanitizer cutoffs.
    
Note: this patch replaces Intrinsic::allow_ubsan_check's
SanitizerHandler parameter with SanitizerOrdinal; this is necessary
because the hot cutoffs are specified in terms of SanitizerOrdinal
(e.g., null, alignment), not SanitizerHandler (e.g., TypeMismatch).
Likewise, CodeGenFunction::EmitCheck is changed to emit
allow_ubsan_check() for each individual check.

---------

Co-authored-by: Vitaly Buka <vitalybuka@gmail.com>
Co-authored-by: Vitaly Buka <vitalybuka@google.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 3e65eeb..bc32878 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -795,12 +795,20 @@ static void addSanitizers(const Triple &TargetTriple,
     PB.registerOptimizerLastEPCallback(SanitizersCallback);
   }
 
-  if (LowerAllowCheckPass::IsRequested()) {
+  // SanitizeSkipHotCutoffs: doubles with range [0, 1]
+  // Opts.cutoffs: unsigned ints with range [0, 1000000]
+  auto ScaledCutoffs = CodeGenOpts.SanitizeSkipHotCutoffs.getAllScaled(1000000);
+
+  // TODO: remove IsRequested()
+  if (LowerAllowCheckPass::IsRequested() || ScaledCutoffs.has_value()) {
     // We want to call it after inline, which is about OptimizerEarlyEPCallback.
     PB.registerOptimizerEarlyEPCallback([&](ModulePassManager &MPM,
                                             OptimizationLevel Level,
                                             ThinOrFullLTOPhase Phase) {
       LowerAllowCheckPass::Options Opts;
+      // TODO: after removing IsRequested(), make this unconditional
+      if (ScaledCutoffs.has_value())
+        Opts.cutoffs = ScaledCutoffs.value();
       MPM.addPass(createModuleToFunctionPassAdaptor(LowerAllowCheckPass(Opts)));
     });
   }