Reapply "[ubsan] Add -fsanitize-merge (and -fno-sanitize-merge) (#120…464)" (#120511)

This reverts commit 2691b964150c77a9e6967423383ad14a7693095e. This
reapply fixes the buildbot breakage of the original patch, by updating
clang/test/CodeGen/ubsan-trap-debugloc.c to specify -fsanitize-merge
(the default, which is merge, is applied by the driver but not
clang_cc1).

This reapply also expands clang/test/CodeGen/ubsan-trap-merge.c.

----

Original commit message:
'-mllvm -ubsan-unique-traps'
(https://github.com/llvm/llvm-project/pull/65972) applies to all UBSan
checks. This patch introduces -fsanitize-merge (defaults to on,
maintaining the status quo behavior) and -fno-sanitize-merge (equivalent
to '-mllvm -ubsan-unique-traps'), with the option to selectively
applying non-merged handlers to a subset of UBSan checks (e.g.,
-fno-sanitize-merge=bool,enum).

N.B. we do not use "trap" in the argument name since
https://github.com/llvm/llvm-project/pull/119302 has generalized
-ubsan-unique-traps to work for non-trap modes (min-rt and regular rt).

This patch does not remove the -ubsan-unique-traps flag; that will
override -f(no-)sanitize-merge.

1 files changed, 2 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 847999c..4d41391 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -5171,7 +5171,8 @@ public:
 
   /// Create a basic block that will call the trap intrinsic, and emit a
   /// conditional branch to it, for the -ftrapv checks.
-  void EmitTrapCheck(llvm::Value *Checked, SanitizerHandler CheckHandlerID);
+  void EmitTrapCheck(llvm::Value *Checked, SanitizerHandler CheckHandlerID,
+                     bool NoMerge = false);
 
   /// Emit a call to trap or debugtrap and attach function attribute
   /// "trap-func-name" if specified.