Reapply "[ubsan] Connect -fsanitize-skip-hot-cutoff to LowerAllowCheckPass<cutoffs>" (#125032) (#125037)

This reverts commit 928cad49beec0120686478f502899222e836b545 i.e.,
relands dccd27112722109d2e2f03e8da9ce8690f06e11b, with a fix to avoid
use-after-scope by changing the lambda to capture by value.

2 files changed, 32 insertions, 19 deletions

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 3e65eeb..97e9bbc 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -795,14 +795,23 @@ 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;
-      MPM.addPass(createModuleToFunctionPassAdaptor(LowerAllowCheckPass(Opts)));
-    });
+    PB.registerOptimizerEarlyEPCallback(
+        [ScaledCutoffs](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)));
+        });
   }
 }
 
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 9676e61..bf8df27 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -3614,29 +3614,33 @@ void CodeGenFunction::EmitCheck(
   llvm::Value *RecoverableCond = nullptr;
   llvm::Value *TrapCond = nullptr;
   bool NoMerge = false;
+  // Expand checks into:
+  //   (Check1 || !allow_ubsan_check) && (Check2 || !allow_ubsan_check) ...
+  // We need separate allow_ubsan_check intrinsics because they have separately
+  // specified cutoffs.
+  // This expression looks expensive but will be simplified after
+  // LowerAllowCheckPass.
   for (auto &[Check, Ord] : Checked) {
+    llvm::Value *GuardedCheck = Check;
+    if (ClSanitizeGuardChecks ||
+        (CGM.getCodeGenOpts().SanitizeSkipHotCutoffs[Ord] > 0)) {
+      llvm::Value *Allow = Builder.CreateCall(
+          CGM.getIntrinsic(llvm::Intrinsic::allow_ubsan_check),
+          llvm::ConstantInt::get(CGM.Int8Ty, Ord));
+      GuardedCheck = Builder.CreateOr(Check, Builder.CreateNot(Allow));
+    }
+
     // -fsanitize-trap= overrides -fsanitize-recover=.
     llvm::Value *&Cond = CGM.getCodeGenOpts().SanitizeTrap.has(Ord) ? TrapCond
                          : CGM.getCodeGenOpts().SanitizeRecover.has(Ord)
                              ? RecoverableCond
                              : FatalCond;
-    Cond = Cond ? Builder.CreateAnd(Cond, Check) : Check;
+    Cond = Cond ? Builder.CreateAnd(Cond, GuardedCheck) : GuardedCheck;
 
     if (!CGM.getCodeGenOpts().SanitizeMergeHandlers.has(Ord))
       NoMerge = true;
   }
 
-  if (ClSanitizeGuardChecks) {
-    llvm::Value *Allow =
-        Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::allow_ubsan_check),
-                           llvm::ConstantInt::get(CGM.Int8Ty, CheckHandler));
-
-    for (llvm::Value **Cond : {&FatalCond, &RecoverableCond, &TrapCond}) {
-      if (*Cond)
-        *Cond = Builder.CreateOr(*Cond, Builder.CreateNot(Allow));
-    }
-  }
-
   if (TrapCond)
     EmitTrapCheck(TrapCond, CheckHandler, NoMerge);
   if (!FatalCond && !RecoverableCond)