FreeBSD does not install a number of Clang-provided headers for the
compiler in the base system due to incompatibilities between FreeBSD's
and Clang's versions. As a workaround do not use --sysroot=. on FreeBSD
until this is addressed.
llvm.org/pr26651
Differential Revision: http://reviews.llvm.org/D17383
llvm-svn: 261229
FreeBSD also needs to have sanitizer_linux_libcdep.cc included,
otherwise linking will fail with "undefined reference to
`__sanitizer::GetRSS()'".
While here, tabify the FreeBSD part, similar to the other parts.
llvm-svn: 260839
r260695 caused extra push/pop instruction pair in __tsan_read1
implementation. Still, that change in InstCombine is believed to
be good, as it reduces the number of instructions performed.
Adjust the expectations to match the newly generated code.
llvm-svn: 260775
Summary:
This is a workaround to a problem in the 3.8 release that affects MIPS and
possibly other targets where the default is not supported but a sibling is
supported.
When TSAN_SUPPORTED_ARCH is not empty, cmake currently attempts to build a
tsan'd libcxx as well as test tsan for the default target regardless of whether
the default target is supported or not. This causes problems on MIPS32 since
tsan is supported for MIPS64 but not MIPS32.
This patch causes cmake to only build the libcxx and run the lit test-suite for
archictures in ${TSAN_SUPPORTED_ARCH}
This re-commit fixes an issue where 'check-tsan' continued to look for the
tsan'd libc++ in the directory it used to be built in.
Reviewers: hans, samsonov
Subscribers: tberghammer, llvm-commits, danalbert, srhines, dvyukov
Differential Revision: http://reviews.llvm.org/D16685
llvm-svn: 259542
check-tsan does not pick up the correct libc++.so. It succeeded on my machine
by picking up the libc++.so that was built before making this change.
llvm-svn: 259519
Summary:
This is a workaround to a problem in the 3.8 release that affects MIPS and
possibly other targets where the default is not supported but a sibling is
supported.
When TSAN_SUPPORTED_ARCH is not empty, cmake currently attempts to build a
tsan'd libcxx as well as test tsan for the default target regardless of whether
the default target is supported or not. This causes problems on MIPS32 since
tsan is supported for MIPS64 but not MIPS32.
This patch causes cmake to only build the libcxx and run the lit test-suite for
archictures in ${TSAN_SUPPORTED_ARCH}
Reviewers: hans, samsonov
Subscribers: tberghammer, llvm-commits, danalbert, srhines, dvyukov
Differential Revision: http://reviews.llvm.org/D16685
llvm-svn: 259512
Summary:
1. Android doesn't support __thread keyword. So allocate ThreadState
dynamically and store its pointer in one TLS slot provided by Android.
2. On Android, intercepted functions can be called before ThreadState
is initialized. So add test of thr_->is_inited in some places.
3. On Android, intercepted functions can be called after ThreadState
is destroyed. So add a fake dead_thread_state to represent all
destroyed ThreadStates. And that is also why we don't store the pointer
to ThreadState in shadow memory of pthread_self().
Reviewers: kcc, eugenis, dvyukov
Subscribers: kubabrecka, llvm-commits, tberghammer, danalbert, srhines
Differential Revision: http://reviews.llvm.org/D15301
llvm-svn: 257866
Summary:
Android doesn't intercept sigfillset, so REAL(sigfillset) is null.
And we can use internal_sigfillset() for all cases.
Reviewers: kcc, eugenis, kubabrecka, dvyukov
Subscribers: llvm-commits, tberghammer, danalbert
Differential Revision: http://reviews.llvm.org/D15296
llvm-svn: 257862
With COMPILER_RT_INCLUDE_TESTS turned ON and in a cross compiling
environment, the unit tests fail to link. This patch does the following changes
>Rename COMPILER_RT_TEST_CFLAGS to COMPILER_RT_UNITTEST_CFLAGS to reflect the
way it's used.
>Add COMPILER_RT_TEST_COMPILER_CFLAGS to COMPILER_RT_UNITTEST_CFLAGS so
that cross-compiler would be able to build/compile the unit tests
>Add COMPILER_RT_UNITTEST_LINKFLAGS to COMPILER_RT_UNITTEST_CFLAGS so
that cross-compiler would be able to link the unit tests (if needed)
Differential Revision: http://reviews.llvm.org/D16165
llvm-svn: 257783
On OS X, TSan already passes all unit and lit tests, but for real-world applications (even very simple ones), we currently produce a lot of false positive reports about data races. This makes TSan useless at this point, because the noise dominates real bugs. This introduces a runtime flag, "ignore_interceptors_accesses", off by default, which makes TSan ignore all memory accesses that happen from interceptors. This will significantly lower the coverage and miss a lot of bugs, but it eliminates most of the current false positives on OS X.
Differential Revision: http://reviews.llvm.org/D15189
llvm-svn: 257760
The value of the constant PTHREAD_MUTEX_RECURSIVE is not "1" on FreeBSD and OS X.
Differential Revision: http://reviews.llvm.org/D16075
llvm-svn: 257758
This broke the build. For example, from
http://lab.llvm.org:8011/builders/clang-cmake-aarch64-full/builds/1191/steps/cmake%20stage%201/logs/stdio:
-- Compiler-RT supported architectures: aarch64
CMake Error at projects/compiler-rt/cmake/Modules/AddCompilerRT.cmake:170 (string):
string sub-command REPLACE requires at least four arguments.
Call Stack (most recent call first):
projects/compiler-rt/lib/CMakeLists.txt:4 (include)
llvm-svn: 257694
environment, the unit tests fail to link. This patch does the following changes
>Rename COMPILER_RT_TEST_CFLAGS to COMPILER_RT_UNITTEST_CFLAGS to reflect the
way it's used.
>Add COMPILER_RT_TEST_COMPILER_CFLAGS to COMPILER_RT_UNITTEST_CFLAGS so that
cross-compiler would be able to build/compile the unit tests
>Add COMPILER_RT_UNITTEST_LINKFLAGS to COMPILER_RT_UNITTEST_CFLAGS so that
cross-compiler would be able to link the unit tests (if needed)
Differential Revision:http://reviews.llvm.org/D15082
llvm-svn: 257686
This patch adds PIE executable support for aarch64-linux. It adds
two more segments:
- 0x05500000000-0x05600000000: 39-bits PIE program segments
- 0x2aa00000000-0x2ab00000000: 42-bits PIE program segments
Fortunately it is possible to use the same transformation formula for
the new segments range with some adjustments in shadow to memory
formula (it adds a constant offset based on the VMA size).
A simple testcase is also added, however it is disabled on x86 due the
fact it might fail on newer kernels [1].
[1] https://git.kernel.org/linus/d1fd836dcf00d2028c700c7e44d2c23404062c90
llvm-svn: 256184
Interceptors using ScopedInteceptor should never call into user's code before the ScopedInterceptor is out of scope (and its destructor is called). Let's add a DCHECK to enforce that.
Differential Revision: http://reviews.llvm.org/D15381
llvm-svn: 255996
Some interceptors in tsan_libdispatch_mac.cc currently wrongly use TSAN_SCOPED_INTERCEPTOR/ScopedInterceptor. Its constructor can start ignoring memory accesses, and the destructor the stops this -- however, e.g. dispatch_sync can call user's code, so the ignoring will extend to user's code as well. This is not expected and we should only limit the scope of ScopedInterceptor to TSan code. This patch introduces annotations that mark the beginning and ending of a callback into user's code.
Differential Revision: http://reviews.llvm.org/D15419
llvm-svn: 255995
We're using the dispatch group itself to synchronize (to call Release() and Acquire() on it), but in dispatch group notifications, the group can already be disposed/deallocated. This causes a later assertion failure at `DCHECK_EQ(*meta, 0);` in `MetaMap::AllocBlock` when the same memory is reused (note that the failure only happens in debug builds).
Fixing this by retaining the group and releasing it in the notification. Adding a stress test case that reproduces this.
Differential Revision: http://reviews.llvm.org/D15380
llvm-svn: 255494
check_memcpy test added in r254959 fails on some configurations due to
memcpy() calls inserted by Clang. Try harder to avoid them by using
internal_memcpy() where applicable.
llvm-svn: 255287
Summary:
Rather than having to add new "experimental" options each time someone wants to work on bringing a sanitizer to a new platform, this patch makes options for all of them.
The default values for the options are set by the platform checks that would have enabled them, but they can be overridden on or off.
Reviewers: kubabrecka, samsonov
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D14846
llvm-svn: 255170
Summary:
Android doesn't have __libc_malloc and related allocation
functions. As its dynamic linker doesn't use malloc, so
we can use REAL(malloc) to replace __libc_malloc safely.
Reviewers: kcc, eugenis, dvyukov
Subscribers: llvm-commits, tberghammer, danalbert, srhines
Differential Revision: http://reviews.llvm.org/D15297
llvm-svn: 255167
check_memcpy test added in r254959 fails on some configurations due to
memset() calls inserted by Clang. Try harder to avoid them:
* Explicitly use internal_memset() instead of empty braced-initializer.
* Replace "new T()" with "new T", as the former generates zero-initialization
for structs in C++11.
llvm-svn: 255136
This patch provides the assembly support for setjmp/longjmp for use
with the thread sanitizer. This is a big more complicated than for
aarch64, because sibcalls are only legal under our ABIs if the TOC
pointer is unchanged. Since the true setjmp function trashes the TOC
pointer, and we have to leave the stack in a correct state, we emulate
the setjmp function rather than branching to it.
We also need to materialize the TOC for cases where the _setjmp code
is called from libc. This is done differently under the ELFv1 and
ELFv2 ABIs.
llvm-svn: 255059
This patch is by Simone Atzeni with portions by Adhemerval Zanella.
This contains the LLVM patches to enable the thread sanitizer for
PPC64, both big- and little-endian. Two different virtual memory
sizes are supported: Old kernels use a 44-bit address space, while
newer kernels require a 46-bit address space.
There are two companion patches that will be added shortly. There is
a Clang patch to actually turn on the use of the thread sanitizer for
PPC64. There is also a patch that I wrote to provide interceptor
support for setjmp/longjmp on PPC64.
Patch discussion at reviews.llvm.org/D12841.
llvm-svn: 255057
Summary:
It was barely supported for a several years for now, somewhat
rotten and doesn't correspond to the way we build/test TSan runtime
in Clang anymore.
CMake build has proper compile flags, library layout, build
dependencies etc.
Shell scripts that depended on the output of Makefile.old are
either obsolete now (check_cmake.sh), or moved to lit tests
(check_memcpy.sh), or kept as a standalone scripts not suitable
for generic test suite, but invoked on bots (check_analyze.sh).
It is not used on bots anymore: all "interesting" configurations
(gcc/clang as a host compiler; debug/release build types) are now
tested via CMake.
Reviewers: dvyukov, kcc
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15316
llvm-svn: 255032
Another attempt at fixing tsan_invisible_barrier.
Current implementation causes:
https://llvm.org/bugs/show_bug.cgi?id=25643
There were several unsuccessful iterations for this functionality:
Initially it was implemented in user code using REAL(pthread_barrier_wait). But pthread_barrier_wait is not supported on MacOS. Futexes are linux-specific for this matter.
Then we switched to atomics+usleep(10). But usleep produced parasitic "as-if synchronized via sleep" messages in reports which failed some output tests.
Then we switched to atomics+sched_yield. But this produced tons of tsan- visible events, which lead to "failed to restore stack trace" failures.
Move implementation into runtime and use internal_sched_yield in the wait loop.
This way tsan should see no events from the barrier, so not trace overflows and
no "as-if synchronized via sleep" messages.
llvm-svn: 255030
This patch adds release and acquire semantics for dispatch groups, plus a test case.
Differential Revision: http://reviews.llvm.org/D15048
llvm-svn: 255020
Check that TSan runtime doesn't contain compiler-inserted calls
to memset/memmove functions.
In future, we may consider moving this test to test/sanitizer_common,
as we don't want to have compiler-inserted memcpy/memmove calls in
any sanitizer runtime.
llvm-svn: 254955
De-hardcode path to TSan-ified executable: pass it as an input to
the scripts. Fix them so that they don't write to the current
directory. Remove their invocation from Makefile.old: they are
broken there anyway, as check_analyze.sh now matches trunk Clang.
llvm-svn: 254936
This script is superseded by lit test suite integrated into CMake
for quite a while now. It doesn't support many tests, and require
custom hacks for a few other.
llvm-svn: 254932
This option builds TSan runtime with extra debug printfs
and stats collection. This build configuration is developer-only
and should rarely be used, but we need to keep it to make sure
it doesn't bitrot.
llvm-svn: 254818
mac_ignore_invalid_free was helpful when ASan runtime used to intercept
CFAllocator and sometimes corrupted its memory. This behavior had been long
gone, and the flag was unused.
This patch also deletes ReportMacCfReallocUnknown(), which was used by the
CFAllocator realloc() wrapper.
llvm-svn: 254722
On OS X, there are other-than-pthread locking APIs that are used quite extensively - OSSpinLock and os_lock_lock. Let's add interceptors for those.
Differential Revision: http://reviews.llvm.org/D14987
llvm-svn: 254611
In AddressSanitizer, we have the MaybeReexec method to detect when we're running without DYLD_INSERT_LIBRARIES (in which case interceptors don't work) and re-execute with the environment variable set. On OS X 10.11+, this is no longer necessary, but to have ThreadSanitizer supported on older versions of OS X, let's use the same method as well. This patch moves the implementation from `asan/` into `sanitizer_common/`.
Differential Revision: http://reviews.llvm.org/D15123
llvm-svn: 254600
This patch adds release and acquire semantics for libdispatch semaphores and a test case.
Differential Revision: http://reviews.llvm.org/D14992
llvm-svn: 254412
1) There's a few wrongly defined things in tsan_interceptors.cc,
2) a typo in tsan_rtl_amd64.S which calls setjmp instead of sigsetjmp in the interceptor, and
3) on OS X, accessing an mprotected page results in a SIGBUS (and not SIGSEGV).
Differential Revision: http://reviews.llvm.org/D15052
llvm-svn: 254299
On OS X, for weak function (that user can override by providing their own implementation in the main binary), we need extern `"C" SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE NOINLINE`.
Fixes a broken test case on OS X, java_symbolization.cc, which uses a weak function __tsan_symbolize_external.
Differential Revision: http://reviews.llvm.org/D14907
llvm-svn: 254298
Serial queues need extra happens-before between individual tasks executed in the same queue. This patch adds `Acquire(queue)` before the executed task and `Release(queue)` just after it (for serial queues only). Added a test case.
Differential Revision: http://reviews.llvm.org/D15011
llvm-svn: 254229
This patch ports the assembly file tsan_rtl_amd64.S to OS X, where we need several changes:
* Some assembler directives are not available on OS X (.hidden, .type, .size)
* Symbol names need to start with an underscore (added a ASM_TSAN_SYMBOL macro for that).
* To make the interceptors work, we ween to name the function "_wrap_setjmp" (added ASM_TSAN_SYMBOL_INTERCEPTOR for that).
* Calling the original setjmp is done with a simple "jmp _setjmp".
* __sigsetjmp doesn't exist on OS X.
Differential Revision: http://reviews.llvm.org/D14947
llvm-svn: 254228
When a race on file descriptors is detected, `FindThreadByUidLocked()` is called to retrieve ThreadContext with a specific unique_id. However, this ThreadContext might not exist in the thread registry anymore (it may have been recycled), in which case `FindThreadByUidLocked` will cause an assertion failure in `GetThreadLocked`. Adding a test case that reproduces this, producing:
FATAL: ThreadSanitizer CHECK failed: sanitizer_common/sanitizer_thread_registry.h:92 "((tid)) < ((n_contexts_))" (0x34, 0x34)
This patch fixes this by replacing the loop with `FindThreadContextLocked`.
Differential Revision: http://reviews.llvm.org/D14984
llvm-svn: 254223
This patch unify the 39 and 42-bit support for AArch64 by using an external
memory read to check the runtime detected VMA and select the better mapping
and transformation. Although slower, this leads to same instrumented binary
to be independent of the kernel.
Along with this change this patch also fix some 42-bit failures with
ALSR disable by increasing the upper high app memory threshold and also
the 42-bit madvise value for non large page set.
llvm-svn: 254151
We need to intercept libdispatch APIs (dispatch_sync, dispatch_async, etc.) to add synchronization between the code that submits the task and the code that gets executed (possibly on a different thread). This patch adds release+acquire semantics for dispatch_sync, and dispatch_async (plus their "_f" and barrier variants). The synchronization is done on malloc'd contexts (separate for each submitted block/callback). Added tests to show usage of dispatch_sync and dispatch_async, for cases where we expect no warnings and for cases where TSan finds races.
Differential Revision: http://reviews.llvm.org/D14745
llvm-svn: 253982
On OS X, interceptors don't work in unit tests, so calloc() calls the system allocator. We need to use user_calloc() instead.
Differential Revision: http://reviews.llvm.org/D14918
llvm-svn: 253979
This patch fixes the __cxa_guard_acquire, __cxa_guard_release and __cxa_guard_abort interceptors on OS X. They apparently work on Linux just by having the same name, but on OS X, we actually need to use TSAN_INTERCEPTOR.
Differential Revision: http://reviews.llvm.org/D14868
llvm-svn: 253776
We need to call the intercepted version of pthread_detach. Secondly, PTHREAD_CREATE_JOINABLE and PTHREAD_CREATE_DETACHED are not 0 and 1 on OS X, so we need to properly pass these constants and not just a bool.
Differential Revision: http://reviews.llvm.org/D14837
llvm-svn: 253775
The tsan_test_util_posix.cc implementation of mutexes call pthread APIs directly, which on OS X don't end up calling the intercepted versions and we miss the synchronization. This patch changes the unit tests to directly call the intercepted versions. This fixes several test failures on OS X.
Differential Revision: http://reviews.llvm.org/D14835
llvm-svn: 253774
When ASan currently detects a bug, by default it will only print out the text
of the report to stderr. This patch changes this behavior and writes the full
text of the report to syslog before we terminate the process. It also calls
os_trace (Activity Tracing available on OS X and iOS) with a message saying
that the report is available in syslog. This is useful, because this message
will be shown in the crash log.
For this to work, the patch makes sure we store the full report into
error_message_buffer unconditionally, and it also strips out ANSI escape
sequences from the report (they are used when producing colored reports).
I've initially tried to log to syslog during printing, which is done on Android
right now. The advantage is that if we crash during error reporting or the
produced error does not go through ScopedInErrorReport, we would still get a
(partial) message in the syslog. However, that solution is very problematic on
OS X. One issue is that the logging routine uses GCD, which may spawn a new
thread on its behalf. In many cases, the reporting logic locks threadRegistry,
which leads to deadlocks.
Reviewed at http://reviews.llvm.org/D13452
(In addition, add sanitizer_common_libcdep.cc to buildgo.sh to avoid
build failures on Linux.)
llvm-svn: 253688
On OS X, this unit test (ThreadSpecificDtors) fails, because the new and delete operators actually call the overridden operators, which end up using TLVs and crash. Since C++'s new and delete is not important in this test, let's just replace them with a local variable. This fixes the test on OS X.
Differential Revision: http://reviews.llvm.org/D14826
llvm-svn: 253583
On OS X, the thread finalization is fragile due to thread-local variables destruction order. I've seen cases where the we destroy the ThreadState too early and subsequent thread-local values' destructors call interceptors again. Let's replace the TLV-based thread finalization method with libpthread hooks. The notification PTHREAD_INTROSPECTION_THREAD_TERMINATE is called *after* all TLVs have been destroyed.
Differential Revision: http://reviews.llvm.org/D14777
llvm-svn: 253560
On OS X, we build a dylib of the TSan runtime, which doesn't necessarily need to contain debugging symbols (and file and line information), so llvm-symbolizer might not be able to find file names for TSan internal frames. FrameIsInternal currently only considers filenames, but we should simply treat all frames within `libclang_rt.tsan_osx_dynamic.dylib` as internal. This patch treats all modules starting with `libclang_rt.tsan_` as internal, because there may be more runtimes for other platforms in the future.
Differential Revision: http://reviews.llvm.org/D14813
llvm-svn: 253559
Reimplement dispatch_once in an interceptor to solve these issues that may produce false positives with TSan on OS X:
1) there is a racy load inside an inlined part of dispatch_once,
2) the fast path in dispatch_once doesn't perform an acquire load, so we don't properly synchronize the initialization and subsequent uses of whatever is initialized,
3) dispatch_once is already used in a lot of already-compiled code, so TSan doesn't see the inlined fast-path.
This patch uses a trick to avoid ever taking the fast path (by never storing ~0 into the predicate), which means the interceptor will always be called even from already-compiled code. Within the interceptor, our own atomic reads and writes are not written into shadow cells, so the race in the inlined part is not reported (because the accesses are only loads).
Differential Revision: http://reviews.llvm.org/D14811
llvm-svn: 253552
Symbolizers can call malloc/realloc/free/..., which we don't want to intercept. This is already implemented on Linux, let's do it for OS X as well.
Differential Revision: http://reviews.llvm.org/D14710
llvm-svn: 253460
This patch adds assembly routines to enable setjmp/longjmp for aarch64
on linux. It fixes:
* test/tsan/longjmp2.cc
* test/tsan/longjmp3.cc
* test/tsan/longjmp4.cc
* test/tsan/signal_longjmp.cc
I also checked with perlbench from specpu2006 (it fails to run
with missing setjmp/longjmp intrumentation).
llvm-svn: 253205
Currently, we crash on finalization of detached threads, because we'll try to clear the ThreadState twice.
Differential Revision: http://reviews.llvm.org/D14644
llvm-svn: 253079
The default symbolizer, `llvm-symbolizer` provides sizes for global symbols. On OS X, we want to also allow using `atos` (because it's available everywhere and users don't need to copy/install it) and `dladdr` (it's the only available option when running in a sandbox). However, these symbolizers do not supply the symbol sizes, only names and starting addresses. This patch changes the reporting functions to hide the size of the symbol when this value is unavailable, and modifies tests to make this part of the report "optional".
Differential Revision: http://reviews.llvm.org/D14608
llvm-svn: 252896
The TSan unit test build currently fails if we're also building the iOS parts of compiler-rt, because `TSAN_SUPPORTED_ARCH` contains ARM64. For unit tests, we need to filter this only to host architecture(s).
Differential Revision: http://reviews.llvm.org/D14604
llvm-svn: 252873
Summary:
On Darwin, interposed functions are prefixed with "wrap_". On Linux,
they are prefixed with "__interceptor_".
Reviewers: dvyukov, samsonov, glider, kcc, kubabrecka
Subscribers: zaks.anna, llvm-commits
Differential Revision: http://reviews.llvm.org/D14512
llvm-svn: 252695
Fixing `tsan_interceptors.cc`, which on OS X produces a bunch of warnings about unused constants and functions.
Differential Revision: http://reviews.llvm.org/D14381
llvm-svn: 252165
On OS X, memcpy and memmove are actually aliases of the same implementation, which means the interceptor of memcpy is also invoked when memmove is called. The current implementation of the interceptor uses `internal_memcpy` to perform the actual memory operation, which can produce an incorrect result when memmove semantics are expected. Let's call `internal_memmove` instead.
Differential Revision: http://reviews.llvm.org/D14336
llvm-svn: 252162
A call to memmove is used early during new thread initialization on OS X. This patch uses the `COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED` check, similarly to how we deal with other early-used interceptors.
Differential Revision: http://reviews.llvm.org/D14377
llvm-svn: 252161
TSan has a re-implementation of `pthread_once` in its interceptor, which assumes that the `pthread_once_t *once_control` pointer is actually pointing to a "storage" which is zero-initialized and used for the atomic operations. However, that's not true on OS X, where pthread_once_t is a structure, that contains a header (with a magic value) and the actual storage follows after that. This patch skips the header to make the interceptor work on OS X.
Differential Revision: http://reviews.llvm.org/D14379
llvm-svn: 252160
This implements a "poor man's TLV" to be used for TSan's ThreadState on OS X. Based on the fact that `pthread_self()` is always available and reliable and returns a valid pointer to memory, we'll use the shadow memory of this pointer as a thread-local storage. No user code should ever read/write to this internal libpthread structure, so it's safe to use it for this purpose. We lazily allocate the ThreadState object and store the pointer here.
Differential Revision: http://reviews.llvm.org/D14288
llvm-svn: 252159
TSan needs to use a custom malloc zone on OS X, which is already implemented in ASan. This patch uses the sanitizer_common implementation in `sanitizer_malloc_mac.inc` for TSan as well.
Reviewed at http://reviews.llvm.org/D14330
llvm-svn: 252155
Ed Maste