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.
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