This change introduces GOMP doacross compatibility. There are 12 new interface
functions 6 for long type and 6 for unsigned long long type:
GOMP_doacross_post, GOMP_doacross_wait, GOMP_loop_doacross_[schedule]_start
where schedule can be static, dynamic, guided, or runtime.
These functions just translate the parameters if necessary and send them
to the corresponding kmp function.
E.g., GOMP_doacross_post() -> __kmpc_doacross_post()
For the GOMP_doacross_post function, there is template specialization to
account for when long is a four byte vs an eight byte type. If it is a
four byte type, then a temporary array has to be created to convert the
four byte integers into eight byte integers and then sending that into
__kmpc_doacross_post(). Because GOMP_doacross_wait uses varargs, it
always needs a temporary array and does not need template specialization.
Differential Revision: https://reviews.llvm.org/D49857
llvm-svn: 338280
This change fixes build errors when building a runtime with adaptive lock stats
enabled. Most of the errors were due to the recent changes in the runtime, but
it seems that we have not tried to build this debug runtime on Windows for a
long time.
Patch by Hansang Bae
Differential Revision: https://reviews.llvm.org/D49823
llvm-svn: 338277
1) Remove unnecessary data from list node structure
2) Remove timerPair in favor of pushing/popping explicitTimers.
This way, nested timers will work properly.
3) Fix #pragma omp critical timers
4) Add histogram capability
5) Add KMP_STATS_FILE formatting capability
6) Have time partitioned into serial & parallel by introducing
partitionedTimers::exchange(). This also counts the number of serial regions
in the executable.
7) Fix up the timers around OMP loops so that scheduling overhead and work are
both counted correctly.
8) Fix up the iterations statistics so they count the number of iterations the
thread receives at each loop scheduling event
9) Change timers so there is only one RDTSC read per event change
10) Fix up the outdated comments for the timers
Differential Revision: https://reviews.llvm.org/D49699
llvm-svn: 338276
Fix the order of callbacks related to the taskloop construct.
Add the iteration_count to work callbacks (according to the spec).
Use kmpc_omp_task() instead of kmp_omp_task() to include OMPT callbacks.
Add a testcase.
Patch by Simon Convent
Reviewed by: protze.joachim, hbae
Subscribers: openmp-commits
Differential Revision: https://reviews.llvm.org/D47709
llvm-svn: 338146
The ompt/tasks/task_types.c testcase did not test untied tasks properly. Now,
frame addresses are tested and two scheduling points are added at which the
task can switch to another thread. Due to scheduling effects, the frame address
could be NULL.
This needed a restructure of the way OMPT callbacks are called.
__ompt_task_finish() now as an extra parameter, whether a task is completed.
Its invocation has been moved into __kmp_task_finish(). Thus, the order of the
writes to the frame addresses is not subject to scheduling effects anymore.
Patch by Simon Convent
Reviewed by: protze.joachim, hbae
Subscribers: openmp-commits
Differential Revision: https://reviews.llvm.org/D49181
llvm-svn: 338145
This function was not enabled by default and not exported when manually
tweaking the build flags. Additionally it was hard to use since there
is no corresponding __kmp_ft_page_free().
The code itself is questionable because the returned memory address
is padded by an extra pointer which stores the unpadded start of the
allocated region (this would need to be freed).
Differential Revision: https://reviews.llvm.org/D49802
llvm-svn: 338052
This change fixes possibly invalid access to the internal data structure during
library shutdown. In a heavily oversubscribed situation, the library shutdown
sequence can reach the point where resources are deallocated while there still
exist threads in their final spinning loop. The added loop in
__kmp_internal_end() checks if there are such busy-waiting threads and blocks
the shutdown sequence if that is the case. Two versions of kmp_wait_template()
are now used to minimize performance impact.
Patch by Hansang Bae
Differential Revision: https://reviews.llvm.org/D49452
llvm-svn: 337486
This patch introduces the logic implementing hierarchical scheduling.
First and foremost, hierarchical scheduling is off by default
To enable, use -DLIBOMP_USE_HIER_SCHED=On during CMake's configure stage.
This work is based off if the IWOMP paper:
"Workstealing and Nested Parallelism in SMP Systems"
Hierarchical scheduling is the layering of OpenMP schedules for different layers
of the memory hierarchy. One can have multiple layers between the threads and
the global iterations space. The threads will go up the hierarchy to grab
iterations, using possibly a different schedule & chunk for each layer.
[ Global iteration space (0-999) ]
(use static)
[ L1 | L1 | L1 | L1 ]
(use dynamic,1)
[ T0 T1 | T2 T3 | T4 T5 | T6 T7 ]
In the example shown above, there are 8 threads and 4 L1 caches begin targeted.
If the topology indicates that there are two threads per core, then two
consecutive threads will share the data of one L1 cache unit. This example
would have the iteration space (0-999) split statically across the four L1
caches (so the first L1 would get (0-249), the second would get (250-499), etc).
Then the threads will use a dynamic,1 schedule to grab iterations from the L1
cache units. There are currently four supported layers: L1, L2, L3, NUMA
OMP_SCHEDULE can now read a hierarchical schedule with this syntax:
OMP_SCHEDULE='EXPERIMENTAL LAYER,SCHED[,CHUNK][:LAYER,SCHED[,CHUNK]...]:SCHED,CHUNK
And OMP_SCHEDULE can still read the normal SCHED,CHUNK syntax from before
I've kept most of the hierarchical scheduling logic inside kmp_dispatch_hier.h
to try to keep it separate from the rest of the code.
Differential Revision: https://reviews.llvm.org/D47962
llvm-svn: 336571
This patch reorganizes the loop scheduling code in order to allow hierarchical
scheduling to use it more effectively. In particular, the goal of this patch
is to separate the algorithmic parts of the scheduling from the thread
logistics code.
Moves declarations & structures to kmp_dispatch.h for easier access in
other files. Extracts the algorithmic part of __kmp_dispatch_init() and
__kmp_dispatch_next() into __kmp_dispatch_init_algorithm() and
__kmp_dispatch_next_algorithm(). The thread bookkeeping logic is still kept in
__kmp_dispatch_init() and __kmp_dispatch_next(). This is done because the
hierarchical scheduler needs to access the scheduling logic without the
bookkeeping logic. To prepare for new pointer in dispatch_private_info_t, a
new flags variable is created which stores the ordered and nomerge flags instead
of them being in two separate variables. This will keep the
dispatch_private_info_t structure the same size.
Differential Revision: https://reviews.llvm.org/D47961
llvm-svn: 336568
These are preliminary changes that attempt to use C++11 Atomics in the runtime.
We are expecting better portability with this change across architectures/OSes.
Here is the summary of the changes.
Most variables that need synchronization operation were converted to generic
atomic variables (std::atomic<T>). Variables that are updated with combined CAS
are packed into a single atomic variable, and partial read/write is done
through unpacking/packing
Patch by Hansang Bae
Differential Revision: https://reviews.llvm.org/D47903
llvm-svn: 336563
The current implementation always provides the thread-num for the current
parallel region. This patch fixes the behavior for ancestor levels >0.
Differential Revision: https://reviews.llvm.org/D46533
llvm-svn: 336085
Introduce OPENMP_INSTALL_LIBDIR and use in all install() commands.
This also fixes installation of libomptarget-nvptx that previously
didn't honor {OPENMP,LLVM}_LIBDIR_SUFFIX.
Differential Revision: https://reviews.llvm.org/D47130
llvm-svn: 333284
implicit_task_end callbacks in nested parallel regions did not always give the
correct thread_num, since the inner parallel region may have already been
finalized.
Now, the thread_num is stored at the beginning of the implicit task and
retrieved at the end, whenever necessary.
A testcase was added as well.
Differential Revision: https://reviews.llvm.org/D46260
llvm-svn: 331632
Currently, the affinity API reports garbage for the initial place list and any
thread's place lists when using KMP_AFFINITY=none|compact|scatter.
This patch does two things:
for KMP_AFFINITY=none, Creates a one entry table for the places, this way, the
initial place list is just a single place with all the proc ids in it. We also
set the initial place of any thread to 0 instead of KMP_PLACE_ALL so that the
thread reports that single place (place 0) instead of garbage (-1) when using
the affinity API.
When non-OMP_PROC_BIND affinity is used
(including KMP_AFFINITY=compact|scatter), a thread's place list is populated
correctly. We assume that each thread is assigned to a single place. This is
implemented in two of the affinity API functions
Differential Revision: https://reviews.llvm.org/D45527
llvm-svn: 330283
This patch introduces GOMP_taskloop to our API. It adds GOMP_4.5 to our
version symbols. Being a wrapper around __kmpc_taskloop, the function
creates a task with the loop bounds properly nested in the shareds so that
the GOMP task thunk will work properly. Also, the firstprivate copy constructors
are properly handled using the __kmp_gomp_task_dup() auxiliary function.
Currently, only linear spawning of tasks is supported
for the GOMP_taskloop interface.
Differential Revision: https://reviews.llvm.org/D45327
llvm-svn: 330282
This change removes the unnecessary lock operation on __kmp_initz_lock inside
the __kmp_atfork_child() function for Linux; the lock variable is initialized
in the same function later.
Patch by Hansang Bae
Differential Revision: https://reviews.llvm.org/D44949
llvm-svn: 328900
Added settings code to read OMP_TARGET_OFFLOAD environment variable. Added
target-offload-var ICV as __kmp_target_offload, set via OMP_TARGET_OFFLOAD,
if available, otherwise defaulting to DEFAULT. Valid values for the ICV are
specified as enum values {0,1,2} for disabled, default, and mandatory. An
internal API access function __kmpc_get_target_offload is provided.
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D44577
llvm-svn: 328046
The thread_num parameter of ompt_get_task_info() was not being used previously,
but need to be set.
The print_task_type() function (form the task-types.c testcase) was merged into
the print_ids() function (in callback.h). Testing of ompt_get_task_info() was
added to the task-types.c testcase. It was not tested extensively previously.
Differential Revision: https://reviews.llvm.org/D42472
llvm-svn: 326338
This is required to be NULL for implicit barriers at the end of a
parallel region. Noticed in review of D43191.
Differential Revision: https://reviews.llvm.org/D43308
llvm-svn: 325922
Only use ompt_ functions when testing OMPT in api_calls testcase.
Add size parameter to print_list.
Fix small bug in implementation of ompt_get_partition_place_nums(): return correct length.
Differential Revision: https://reviews.llvm.org/D42162
llvm-svn: 325422
If tool initialization returns 0, OMPT should not be active. The current
implementation provided some callback invocations in this case.
Differential Revision: https://reviews.llvm.org/D42709
llvm-svn: 324320
The defintion is not part of the spec and thus should not have the prefix
"ompt_" but rather a prefix that indicates that this is implementation
specific.
Differential Revision: https://reviews.llvm.org/D41166
llvm-svn: 322621
When the current thread is not an (initialized) OpenMP thread, the runtime
entry points return values that correspond to "not available" or similar
Differential Revision: https://reviews.llvm.org/D41167
llvm-svn: 322620
If user requested affinity with granularity=tile we need to either use HWLOC
or ignore the request. The change allows user to not specify
KMP_TOPOLOGY_METHOD=hwloc and choose it automatically instead.
Patch by Andrey Churbanov
Differential Revision: https://reviews.llvm.org/D40905
llvm-svn: 322205
This change simplifies __kmp_expand_threads to take a single argument.
Previously, it allowed two arguments and had logic to decide on different
potential expansion sizes. However, no calls to __kmp_expand_threads in the
runtime make use of this extra logic. Thus the extra argument and logic is
removed here.
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D41836
llvm-svn: 322204
This change improves stability of the runtime when the application forks child
processes. Acquiring/releasing __kmp_initz_lock and __kmp_forkjoin_lock in the
atfork handlers insures that the actual fork does not occur while those two
locks are held, and __kmp_itt_reset() reverts the itt's global state to the
initial state which also initializes the mutex stored in the global state.
Some missing initialization code was also inserted in the child's atfork handler.
Patch by Hansang Bae
Differential Revision: https://reviews.llvm.org/D41462
llvm-svn: 322202
This field is defined as kmp_int32, so we should use neither
pointers to kmp_int64 nor 64 bit atomic instructions.
(Found while testing on a Raspberry Pi, 32 bit ARM)
Differential Revision: https://reviews.llvm.org/D41656
llvm-svn: 321964
As for normal task creation, the task frame addresses need to be stored
for the encountering task.
Differential Revision: https://reviews.llvm.org/D41165
llvm-svn: 321421
The format string for hints only prints the second argument (string) and drops
the first argument (hint id). Depending on how you read the POSIX text for
printf, this could be valid. But for practical reason, i.e., unpacking the
va_list passed to printf based on the formating information, it makes sense
to fix the implementation and not pass the id for hint.
Failing testcases were:
misc_bugs/teams-reduction.c
ompt/parallel/not_enough_threads.c
Differential Revision: https://reviews.llvm.org/D41504
llvm-svn: 321361
This function is defined in OpenMP-TR6 section 4.1.5.1.6
The functions was not implemented yet.
Since ompt-functions can only be called after the runtime was initialized and
has loaded a tool, it can assume the runtime to be initialized. In contrast
to omp_get_num_procs which needs to check whether the runtime is initialized.
Differential Revision: https://reviews.llvm.org/D40949
llvm-svn: 321269
This revision fixes failing testcases with parallel for loops and the gomp
interface. The return address needs to be stored at entry to runtime.
The storage is cleared on usage, so we need to update the storage before
calling again internal functions, that will trigger event callbacks.
Differential Revision: https://reviews.llvm.org/D41181
llvm-svn: 321265
We use the bitmap ompt_enabled thoughout the runtime, to avoid loading the
vector of callback functions when testing if specific code should be executed.
Before invoking an event callback function, the pointer is tested for NULL.
This revision resets the corresponding bit in ompt_enabled to 0 if
NULL is passed in set_callback.
Differential Revision: https://reviews.llvm.org/D41171
llvm-svn: 321264
There are two /proc/cpuinfo layots in use for AArch64: old and new.
The old one has all 'processor : n' lines in one section, hence
checking for duplications does not make sense.
Differential Revision: https://reviews.llvm.org/D41000
llvm-svn: 320593
All architectures except x86_64 used the linear barrier implementation
by default which doesn't give good performance for a larger number
of threads.
Improvements for PARALLEL overhead (EPCC) with this patch on a Power8
system (2 sockets x 10 cores x 8 threads, OMP_PLACES=cores)
20 threads: 4.55us -> 3.49us
40 threads: 8.84us -> 4.06us
80 threads: 19.18us -> 4.74us
160 threads: 54.22us -> 6.73us
Differential Revision: https://reviews.llvm.org/D40358
llvm-svn: 320152
To make thread affinity work according to the OpenMP spec, the
runtime needs information about the hardware topology. On Linux
the default way is to parse /proc/cpuinfo which contains this
information for x86 machines but (at least) not for AArch64 and
Power architectures.
Fortunately, there is a different code path which is able to get
that data from sysfs. The needed patch has landed in 2006 for
Linux 2.6.16 which is safe to assume nowadays (even RHEL 5 had
a kernel version derived from 2.6.18, and we are now at RHEL 7!).
Differential Revision: https://reviews.llvm.org/D40357
llvm-svn: 320151
Otherwise I see hangs in the omp_single_copyprivate test when
compiling in release mode. With the debug assertions, I get a
failure `head > 0 && tail > 0`.
Differential Revision: https://reviews.llvm.org/D40722
llvm-svn: 320150
Redundant extra verbose output of binding to full mask in case
affinity=balanced or OMP_PLACES=<any> or OMP_PROC_BIND=<any>
Differential Revision: https://reviews.llvm.org/D40624
llvm-svn: 319960
This change is a trivial fix for enums that removes specification of "last" or
"upper" values, or other boundary values. This simplifies the code in places,
and results in never needing to update the "upper" values again.
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D40804
llvm-svn: 319957
__kmpc_reduce_nowait() correctly swapped the teams for reductions
in a teams construct. Apply the same logic to __kmpc_reduce() and
__kmpc_reduce_end().
Differential Revision: https://reviews.llvm.org/D40753
llvm-svn: 319788
This change makes kmp_r_sched_t type into a union for simpler
comparisons and assignments
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D40374
llvm-svn: 319379
kmp_aligned_malloc() always returned NULL on Windows (stub library only)
that may cause Fortran application crash. With this change all memory
allocation functions were fixed to use aligned{m,re,rec}alloc() to
allocate/reallocate memory. To deallocate that memory _aligned_free() is
used in kmp_free().
Patch by Olga Malysheva
Differential Revision: https://reviews.llvm.org/D40296
llvm-svn: 319375
Added two warnings:
1) Before building the topology map check if tiles are requested but the
topo method is not hwloc;
2) After building the topology map check if tiles are requested but not
detected by the library.
Patch by Olga Malysheva
Differential Revision: https://reviews.llvm.org/D40340
llvm-svn: 319374
Fortran array elements made default integer in OMP_GET_PLACE_PROC_IDS and
OMP_GET_PARTITION_PLACE_NUMS subroutines, otherwise call to them produces
incorrect result.
Patch by Olga Malysheva
Differential Revision: https://reviews.llvm.org/D40356
llvm-svn: 319372
These are needed by both libraries, so we can do that in a
common namespace and unify configuration parameters.
Also make sure that the user isn't requesting libomptarget
if the library cannot be built on the system. Issue an error
in that case.
Differential Revision: https://reviews.llvm.org/D40081
llvm-svn: 319342
As a first step, this allows us to generalize the detection of
standalone builds and make it fully compatible when building in
llvm/runtimes/ which automatically sets OPENMP_STANDLONE_BUILD.
Differential Revision: https://reviews.llvm.org/D40080
llvm-svn: 319341
Power has a weak consistency model so we need memory barriers to
make writes (both from runtime and from user code) available for
all threads.
Differential Revision: https://reviews.llvm.org/D40175
llvm-svn: 318848
Traditionally, the library had a weak symbol for ompt_start_tool()
that served as fallback and disabled OMPT if called. Tools could
provide their own version and replace the default implementation
to register callbacks and lookup functions. This mechanism has
worked reasonably well on Linux systems where this interface was
initially developed.
On Darwin / Mac OS X the situation is a bit more complicated and
the weak symbol doesn't work out-of-the-box. In my tests, the
library with the tool needed to link against the OpenMP runtime
to make the process work. This would effectively mean that a tool
needed to choose a runtime library whereas one design goal of the
interface was to allow tools that are agnostic of the runtime.
The solution is to use dlsym() with the argument RTLD_DEFAULT so
that static implementations of ompt_start_tool() are found in the
main executable. This works because the linker on Mac OS X includes
all symbols of an executable in the global symbol table by default.
To use the same code path on Linux, the application would need to
be built with -Wl,--export-dynamic. To avoid this restriction, we
continue to use weak symbols on Linux systems as before.
Finally this patch extends the existing test to cover all possible
ways of initializing the tool as described by the standard. It
also fixes ompt_finalize() to not call omp_get_thread_num() when
the library is shut down which resulted in hangs on Darwin.
The changes have been tested on Linux to make sure that it passes
the current tests as well as the newly extended one.
Differential Revision: https://reviews.llvm.org/D39801
llvm-svn: 317980
For up-to-date compilers, this assertion is reasonable, but it breaks
compatibility with the typical compiler installed on most systems.
This patch changes the default value to what we had when there was no
compiler support. A warning about the outdated compiler is printed during
runtime, when this point is reached.
Differential Revision: https://reviews.llvm.org/D39890
llvm-svn: 317928
In these places the const attribute seems correct and doesn't
need any other change, so let's do it.
Differential Revision: https://reviews.llvm.org/D39756
llvm-svn: 317798
Allocated memory is typically not 'const' if it needs to be freed.
This patch removes around 50 wrong const attributes, modifies the
corresponding functions and finally gets rid of some const_casts.
These have especially been strange for __kmp_str_fname_free() that
added a 'const' to call __kmp_str_free() which removed it again.
Two minor cleanups that I performed in this process:
* __kmp_tool_libraries now lives in kmp_settings.cpp as it is
used nowhere else.
* __kmp_msg_empty was removed as it was never used and Clang
now complained that it was assigned a string literal that
is 'const char *'.
Differential Revision: https://reviews.llvm.org/D39755
llvm-svn: 317797
1) Get rid of xaliasify, xexpand and xversionify for KMP_EXPAND_NAME and
KMP_VERSION_SYMBOL. KMP_VERSION_SYMBOL is a combination of xaliasify and
xversionify.
2) Put all attribute and __declspec definitions in kmp_os.h
Differential Revision: https://reviews.llvm.org/D39516
llvm-svn: 317636
The TR6 document is expected to be publically released around November 15.
This patch does not implement OMPT for libomptarget.
Patch by Simon Convent and Joachim Protze
Differential Revision: https://reviews.llvm.org/D39182
llvm-svn: 317436
This is part of the renaming of data types from OpenMP TR4 to TR6
Patch by Simon Convent
Differential Revision: https://reviews.llvm.org/D39326
llvm-svn: 317435
The TR6 document is expected to be publically released around November 15.
This patch does not implement OMPT for libomptarget.
Patch by Simon Convent and Joachim Protze
Differential Revision: https://reviews.llvm.org/D39182
llvm-svn: 317339
This is part of the renaming of data types from OpenMP TR4 to TR6
Patch by Simon Convent
Differential Revision: https://reviews.llvm.org/D39326
llvm-svn: 317338
This is a partial fix for bug 34050.
This prevents callers of omp_set_lock (which does not hold __kmp_global_lock)
from ever seeing an uninitialized version of __kmp_i_lock_table.table.
It does not solve a use-after-free race condition if omp_set_lock obtains a
pointer to __kmp_i_lock_table.table before it is updated and then attempts to
dereference afterwards. That race is far less likely and can be handled in a
separate patch.
The unit test usually segfaults on the current trunk revision. It passes with
the patch.
Patch by Adam Azarchs
Differential Revision: https://reviews.llvm.org/D39439
llvm-svn: 317115
The code is tested to work with latest clang, GNU and Intel compiler. The implementation
is optimized for low overhead when no tool is attached shifting the cost to execution with
tool attached.
This patch does not implement OMPT for libomptarget.
Patch by Simon Convent and Joachim Protze
Differential Revision: https://reviews.llvm.org/D38185
llvm-svn: 317085
Replacing call to __kmp_msg(kmp_ms_fatal,...) with __kmp_fatal(...) caused an
issue when incomplete message is displayed in case an error message is followed
by another message (e.g. by a hint messa)ge. This is because __kmp_fatal()
passes incomplete list of arguments to __kmp_msg().
Patch by Olga Malysheva
Differential Revision: https://reviews.llvm.org/D39248
llvm-svn: 316623
The problem is due to the runtime's threadprivate cleanup code which tries to
access data that was already destroyed by one of the root threads.
__kmp_init_gtid is used as a checker here since it is set to false before actual
resource cleanup is done in __kmp_cleanup().
Patch by Hansang Bae
llvm-svn: 316452
If both KMP_HW_SUBSET and KMP_PLACE_THREADS are set and KMP_PLACE_THREADS gets
parsed first, then the current environment variable parser rejects both and
neither get used. This patch uses the rivals mechanism that is used for other
environment variable groups (e.g., KMP_STACKSIZE, GOMP_STACKSIZE, OMP_STACKSIZE).
If both are set, then it tells the user that it is ignoring KMP_PLACE_THREADS in
favor of KMP_HW_SUBSET. The message about deprecating KMP_PLACE_THREADS when it
is set is still printed regardless.
Differential Revision: https://reviews.llvm.org/D38292
llvm-svn: 315091
Removes semicolons after if {} blocks, function definitions, etc.
I was able to apply the large OMPT patch cleanly on top of this one
with no conflicts.
llvm-svn: 314340
Minor code cleanup of Klocwork issues. Fatal messages are given no return
attribute. Define and use KMP_NORETURN to work for multiple C++ versions.
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D37275
llvm-svn: 312538
Cleanup code to remove BUILD_TV and unused code bracketed by it.
Patch by Terry Wilmarth
Differential Revision: https://reviews.llvm.org/D36011
llvm-svn: 311114
This change improves the way threads are spread across cores
when OMP_PROC_BIND=spread is set and no unusual affinity masks are in use.
Differential Revision: https://reviews.llvm.org/D36510
llvm-svn: 310670
The original locations can be reached without initializing the lock variable
(td_deque_lock), so it is potentially unsafe. It is guaranteed that the lock
is initialized if the deque (td_deque) is not NULL, and lock functions can be
safely called.
Patch by Hansang Bae
Differential Revision: https://reviews.llvm.org/D36017
llvm-svn: 309875
Jonathan Peyton