Remove -bounds-checking-unique-traps (replace with -fno-sanitize-merge=local-bounds) (#120682)

#120613 removed -ubsan-unique-traps and replaced it with
-fno-sanitize-merge (introduced in #120511), which allows fine-grained
control of which UBSan checks to prevent merging. This analogous patch
removes -bound-checking-unique-traps, and allows it to be controlled via
-fno-sanitize-merge=local-bounds.

Most of this patch is simply plumbing through the compiler flags into
the bounds checking pass.

Note: this patch subtly changes -fsanitize-merge (the default) to also
include -fsanitize-merge=local-bounds. This is different from the
previous behavior, where -fsanitize-merge (or the old
-ubsan-unique-traps) did not affect local-bounds (requiring the separate
-bounds-checking-unique-traps). However, we argue that the new behavior
is more intuitive.

Removing -bounds-checking-unique-traps and merging its functionality
into -fsanitize-merge breaks backwards compatibility; we hope that this
is acceptable since '-mllvm -bounds-checking-unique-traps' was an
experimental flag.

1 files changed, 5 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index e6c9d77..04358cd 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -1030,6 +1030,9 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
       PB.registerScalarOptimizerLateEPCallback(
           [this](FunctionPassManager &FPM, OptimizationLevel Level) {
             BoundsCheckingPass::ReportingMode Mode;
+            bool Merge = CodeGenOpts.SanitizeMergeHandlers.has(
+                SanitizerKind::LocalBounds);
+
             if (CodeGenOpts.SanitizeTrap.has(SanitizerKind::LocalBounds)) {
               Mode = BoundsCheckingPass::ReportingMode::Trap;
             } else if (CodeGenOpts.SanitizeMinimalRuntime) {
@@ -1041,7 +1044,8 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
                          ? BoundsCheckingPass::ReportingMode::FullRuntime
                          : BoundsCheckingPass::ReportingMode::FullRuntimeAbort;
             }
-            FPM.addPass(BoundsCheckingPass(Mode));
+            BoundsCheckingPass::BoundsCheckingOptions Options(Mode, Merge);
+            FPM.addPass(BoundsCheckingPass(Options));
           });
 
     // Don't add sanitizers if we are here from ThinLTO PostLink. That already