Have the front-end use the `nounwind` attribute on atomic libcalls.
This prevents us from seeing `invoke __atomic_load` in MSAN, which
is problematic as it has no successor for instrumentation to be added.
Problems with instrumenting atomic_load when the call has no successor,
blocking compiler roll
This reverts commit 33d239513c881d8c11c60d5710c55cf56cc309a5.
Otherwise we end up compiling in C++ mode and on FreeBSD
/usr/include/stdatomic.h is not compatible with C++ since it uses _Bool.
Reviewed By: guiand, eugenis, vitalybuka, emaste
Differential Revision: https://reviews.llvm.org/D84510
These calls are neither intercepted by compiler-rt nor is libatomic.a
naturally instrumented.
This patch uses the existing libcall mechanism to detect a call
to atomic_load or atomic_store, and instruments them much like
the preexisting instrumentation for atomics.
Calls to _load are modified to have at least Acquire ordering, and
calls to _store at least Release ordering. Because this needs to be
converted at runtime, msan injects a LUT (implemented as a vector
with extractelement).
Differential Revision: https://reviews.llvm.org/D83337
