Commit Graph

261 Commits

Author SHA1 Message Date
Matt Morehouse bb3a3da38d [DFSan] Don't unmap during dfsan_flush().
Unmapping and remapping is dangerous since another thread could touch
the shadow memory while it is unmapped.  But there is really no need to
unmap anyway, since mmap(MAP_FIXED) will happily clobber the existing
mapping with zeroes.  This is thread-safe since the mmap() is done under
the same kernel lock as page faults are done.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D85947
2020-08-14 11:43:49 -07:00
Pierre Gousseau 14948a08f3 [compiler-rt] Normalize some in/out doxygen parameter in interface
headers. NFC.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D84945
2020-08-05 10:17:25 +01:00
Hiroshi Yamauchi f78f509c75 [PGO] Extend the value profile buckets for mem op sizes.
Extend the memop value profile buckets to be more flexible (could accommodate a
mix of individual values and ranges) and to cover more value ranges (from 11 to
22 buckets).

Disabled behind a flag (to be enabled separately) and the existing code to be
removed later.

Differential Revision: https://reviews.llvm.org/D81682
2020-08-03 11:04:32 -07:00
Fangrui Song 27650ec554 Revert D81682 "[PGO] Extend the value profile buckets for mem op sizes."
This reverts commit 4a539faf74.

There is a __llvm_profile_instrument_range related crash in PGO-instrumented clang:

```
(gdb) bt
llvm::ConstantRange const&, llvm::APInt const&, unsigned int, bool) ()
llvm::ScalarEvolution::getRangeForAffineAR(llvm::SCEV const*, llvm::SCEV
const*, llvm::SCEV const*, unsigned int) ()
```

(The body of __llvm_profile_instrument_range is inlined, so we can only find__llvm_profile_instrument_target in the trace)

```
 23│    0x000055555dba0961 <+65>:    nopw   %cs:0x0(%rax,%rax,1)
 24│    0x000055555dba096b <+75>:    nopl   0x0(%rax,%rax,1)
 25│    0x000055555dba0970 <+80>:    mov    %rsi,%rbx
 26│    0x000055555dba0973 <+83>:    mov    0x8(%rsi),%rsi  # %rsi=-1 -> SIGSEGV
 27│    0x000055555dba0977 <+87>:    cmp    %r15,(%rbx)
 28│    0x000055555dba097a <+90>:    je     0x55555dba0a76 <__llvm_profile_instrument_target+342>
```
2020-07-22 16:08:25 -07:00
Hiroshi Yamauchi 4a539faf74 [PGO] Extend the value profile buckets for mem op sizes.
Extend the memop value profile buckets to be more flexible (could accommodate a
mix of individual values and ranges) and to cover more value ranges (from 11 to
22 buckets).

Disabled behind a flag (to be enabled separately) and the existing code to be
removed later.
2020-07-15 10:26:15 -07:00
Hiroshi Yamauchi 9878996c70 Revert "[PGO] Extend the value profile buckets for mem op sizes."
This reverts commit 63a89693f0.

Due to a build failure like http://lab.llvm.org:8011/builders/sanitizer-windows/builds/65386/steps/annotate/logs/stdio
2020-06-25 11:13:49 -07:00
Hiroshi Yamauchi 63a89693f0 [PGO] Extend the value profile buckets for mem op sizes.
Extend the memop value profile buckets to be more flexible (could accommodate a
mix of individual values and ranges) and to cover more value ranges (from 11 to
22 buckets).

Disabled behind a flag (to be enabled separately) and the existing code to be
removed later.

Differential Revision: https://reviews.llvm.org/D81682
2020-06-25 10:22:56 -07:00
Hiroshi Yamauchi 14bb6770f2 [profile] Sync InstrProfData.inc with llvm.
Reviewers: davidxl

Subscribers: #sanitizers, llvm-commits

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D81038
2020-06-03 10:00:11 -07:00
Max Moroz 6d0488f75b [compiler-rt] Mark FDP non-template methods inline to avoid ODR violations. 2020-03-25 13:43:54 -07:00
Max Moroz 1e65209e04 [compiler-rt] FuzzedDataProvider: make linter happy. 2020-03-25 00:39:17 -07:00
Max Moroz 1262db1b6a [compiler-rt] Refactor FuzzedDataProvider for better readability.
Summary: Separate class definition and actual methods implementation. The main
goal is to keep the list of available methods in a concise readable form inside
the class definition.

Reviewers: hctim, metzman

Subscribers: dberris, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D76651
2020-03-24 23:51:49 -07:00
Max Moroz 2136d17d8d [compiler-rt] Add ConsumeRandomLengthString() version without arguments.
Reviewers: hctim, metzman

Subscribers: dberris, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D76448
2020-03-23 16:32:37 -07:00
Dmitry Vyukov a72dc86cdd tsan: tsan_interface.h: make constants static
Note that in C++ the static keyword is implicit for const objects.
In C however it is not, and we get clashes at link time after
including the header from more than one C file:

lib.a(bar.o):(.rodata+0x0): multiple definition of `__tsan_mutex_linker_init'
lib.a(foo.o):(.rodata+0x0): first defined here
lib.a(bar.o):(.rodata+0xc): multiple definition of `__tsan_mutex_not_static'
lib.a(foo.o):(.rodata+0xc): first defined here
<snip>
Indeed both foo.o and bar.o define the clashing symbols:

$ nm foo.o
<snip>
0000000000000000 R __tsan_mutex_linker_init
000000000000000c R __tsan_mutex_not_static
<snip>
Fix it by explicitly making the constants static.

Reviewed-in: https://reviews.llvm.org/D75820
Author: cota (Emilio G. Cota)
2020-03-10 09:13:41 +01:00
Vedant Kumar dd1ea9de2e Reland: [Coverage] Revise format to reduce binary size
Try again with an up-to-date version of D69471 (99317124 was a stale
revision).

---

Revise the coverage mapping format to reduce binary size by:

1. Naming function records and marking them `linkonce_odr`, and
2. Compressing filenames.

This shrinks the size of llc's coverage segment by 82% (334MB -> 62MB)
and speeds up end-to-end single-threaded report generation by 10%. For
reference the compressed name data in llc is 81MB (__llvm_prf_names).

Rationale for changes to the format:

- With the current format, most coverage function records are discarded.
  E.g., more than 97% of the records in llc are *duplicate* placeholders
  for functions visible-but-not-used in TUs. Placeholders *are* used to
  show under-covered functions, but duplicate placeholders waste space.

- We reached general consensus about giving (1) a try at the 2017 code
  coverage BoF [1]. The thinking was that using `linkonce_odr` to merge
  duplicates is simpler than alternatives like teaching build systems
  about a coverage-aware database/module/etc on the side.

- Revising the format is expensive due to the backwards compatibility
  requirement, so we might as well compress filenames while we're at it.
  This shrinks the encoded filenames in llc by 86% (12MB -> 1.6MB).

See CoverageMappingFormat.rst for the details on what exactly has
changed.

Fixes PR34533 [2], hopefully.

[1] http://lists.llvm.org/pipermail/llvm-dev/2017-October/118428.html
[2] https://bugs.llvm.org/show_bug.cgi?id=34533

Differential Revision: https://reviews.llvm.org/D69471
2020-02-28 18:12:04 -08:00
Vedant Kumar 3388871714 Revert "[Coverage] Revise format to reduce binary size"
This reverts commit 99317124e1. This is
still busted on Windows:

http://lab.llvm.org:8011/builders/lld-x86_64-win7/builds/40873

The llvm-cov tests report 'error: Could not load coverage information'.
2020-02-28 18:03:15 -08:00
Vedant Kumar 99317124e1 [Coverage] Revise format to reduce binary size
Revise the coverage mapping format to reduce binary size by:

1. Naming function records and marking them `linkonce_odr`, and
2. Compressing filenames.

This shrinks the size of llc's coverage segment by 82% (334MB -> 62MB)
and speeds up end-to-end single-threaded report generation by 10%. For
reference the compressed name data in llc is 81MB (__llvm_prf_names).

Rationale for changes to the format:

- With the current format, most coverage function records are discarded.
  E.g., more than 97% of the records in llc are *duplicate* placeholders
  for functions visible-but-not-used in TUs. Placeholders *are* used to
  show under-covered functions, but duplicate placeholders waste space.

- We reached general consensus about giving (1) a try at the 2017 code
  coverage BoF [1]. The thinking was that using `linkonce_odr` to merge
  duplicates is simpler than alternatives like teaching build systems
  about a coverage-aware database/module/etc on the side.

- Revising the format is expensive due to the backwards compatibility
  requirement, so we might as well compress filenames while we're at it.
  This shrinks the encoded filenames in llc by 86% (12MB -> 1.6MB).

See CoverageMappingFormat.rst for the details on what exactly has
changed.

Fixes PR34533 [2], hopefully.

[1] http://lists.llvm.org/pipermail/llvm-dev/2017-October/118428.html
[2] https://bugs.llvm.org/show_bug.cgi?id=34533

Differential Revision: https://reviews.llvm.org/D69471
2020-02-28 17:33:25 -08:00
Max Moroz 5517d3b80b [compiler-rt] Fix a typo in a comment in FuzzedDataProvider.h. 2020-02-25 17:10:16 -08:00
Max Moroz 20a604d3f5 [compiler-rt] FuzzedDataProvider: add ConsumeData and method.
Reviewers: metzman

Subscribers: dberris, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D74359
2020-02-11 13:46:24 -08:00
Evgenii Stepanov dd921cb89b [sanitizer] Add missing declarations for sigaltstack syscall wrappers.
Subscribers: #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D73987
2020-02-04 13:10:43 -08:00
Evgenii Stepanov 28c91219c7 [compiler-rt] implement sigaltstack interception
Summary:
An implementation for `sigaltstack` to make its side effect be visible to MSAN.

```
ninja check-msan
```

Reviewers: vitalybuka, eugenis

Reviewed By: eugenis

Subscribers: dberris, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D73816

Patch by Igor Sugak.
2020-02-03 16:28:47 -08:00
Kamil Rytarowski 4b8232d4f0 [compiler-rt] Adapt for ptrace(2) changes in NetBSD-9.99.30
Enable compat support for now legacy PT_LWPINFO.
Support PT_LWPSTATUS and PT_LWPNEXT.
2019-12-24 20:34:58 +01:00
Max Moroz a44ef027eb [compiler-rt] FuzzedDataProvider: do not call memcpy on empty vector.
Summary:
Some versions of memcpy mark pointer arguments as __nonnull, that triggers UBSan
errors even when the length passed is 0.

Reviewers: manojgupta, metzman

Subscribers: dberris, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D71031

[compiler-rt] FDP: assert that num_bytes_to_consume == 0 when size == 0.
2019-12-04 14:18:52 -08:00
Vedant Kumar f208b70fbc Revert "[Coverage] Revise format to reduce binary size"
This reverts commit e18531595b.

On Windows, there is an error:

http://lab.llvm.org:8011/builders/sanitizer-windows/builds/54963/steps/stage%201%20check/logs/stdio

error: C:\b\slave\sanitizer-windows\build\stage1\projects\compiler-rt\test\profile\Profile-x86_64\Output\instrprof-merging.cpp.tmp.v1.o: Failed to load coverage: Malformed coverage data
2019-12-04 10:35:14 -08:00
Vedant Kumar e18531595b [Coverage] Revise format to reduce binary size
Revise the coverage mapping format to reduce binary size by:

1. Naming function records and marking them `linkonce_odr`, and
2. Compressing filenames.

This shrinks the size of llc's coverage segment by 82% (334MB -> 62MB)
and speeds up end-to-end single-threaded report generation by 10%. For
reference the compressed name data in llc is 81MB (__llvm_prf_names).

Rationale for changes to the format:

- With the current format, most coverage function records are discarded.
  E.g., more than 97% of the records in llc are *duplicate* placeholders
  for functions visible-but-not-used in TUs. Placeholders *are* used to
  show under-covered functions, but duplicate placeholders waste space.

- We reached general consensus about giving (1) a try at the 2017 code
  coverage BoF [1]. The thinking was that using `linkonce_odr` to merge
  duplicates is simpler than alternatives like teaching build systems
  about a coverage-aware database/module/etc on the side.

- Revising the format is expensive due to the backwards compatibility
  requirement, so we might as well compress filenames while we're at it.
  This shrinks the encoded filenames in llc by 86% (12MB -> 1.6MB).

See CoverageMappingFormat.rst for the details on what exactly has
changed.

Fixes PR34533 [2], hopefully.

[1] http://lists.llvm.org/pipermail/llvm-dev/2017-October/118428.html
[2] https://bugs.llvm.org/show_bug.cgi?id=34533

Differential Revision: https://reviews.llvm.org/D69471
2019-12-04 10:10:55 -08:00
Petr Hosek f35032e03d Reland "[CMake] Support installation of InstrProfData.inc"
This header fragment is useful on its own for any consumer that wants
to use custom instruction profile runtime with the LLVM instrumentation.
The concrete use case is in Fuchsia's kernel where we want to use
instruction profile instrumentation, but we cannot use the compiler-rt
runtime because it's not designed for use in the kernel environment.
This change allows installing this header as part of compiler-rt.

Differential Revision: https://reviews.llvm.org/D64532
2019-11-22 14:09:46 -08:00
Petr Hosek 262b10ba1f Revert "[CMake] Support installation of InstrProfData.inc"
This reverts commit f11bc1776f since it's
failing to build on some bots.
2019-11-22 12:00:23 -08:00
Petr Hosek f11bc1776f [CMake] Support installation of InstrProfData.inc
This header fragment is useful on its own for any consumer that wants
to use custom instruction profile runtime with the LLVM instrumentation.
The concrete use case is in Fuchsia's kernel where we want to use
instruction profile instrumentation, but we cannot use the compiler-rt
runtime because it's not designed for use in the kernel environment.
This change allows installing this header as part of compiler-rt.

Differential Revision: https://reviews.llvm.org/D64532
2019-11-22 11:52:50 -08:00
Kamil Rytarowski 01f91c3526 [compiler-rt] Sync NetBSD syscall hooks with 9.99.17
Document the minimal version supported as 9.0 and add compat code for
renamed syscalls after 9.0.
2019-11-03 16:22:02 +01:00
Evgenii Stepanov 13e04607f7 [asan] Provide an interface to update an allocation stack trace.
Summary:
Sometimes an allocation stack trace is not very informative. Provide a
way to replace it with a stack trace of the user's choice.

Reviewers: pcc, kcc

Subscribers: #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D69208
2019-10-31 13:54:46 -07:00
Pierre Gousseau 1ae9e6918d [compiler-rt] Add ubsan interface header.
This is to document __ubsan_default_options().

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D67503

llvm-svn: 371822
2019-09-13 08:22:58 +00:00
Vitaly Buka d2af368aee [compiler-rt] Remove some cpplint filters
llvm-svn: 371704
2019-09-12 02:20:36 +00:00
Vitaly Buka 33f01663f7 [dfsan] Revert dfsan_set_label removal
It's part of interface, maybe it is used in external code.

llvm-svn: 371691
2019-09-11 23:43:23 +00:00
Vitaly Buka c0fa632236 Remove NOLINTs from compiler-rt
llvm-svn: 371687
2019-09-11 23:19:48 +00:00
Vitaly Buka 48eb4a27d1 Update compiler-rt cpplint.py
adb3500107

llvm-svn: 371675
2019-09-11 21:33:06 +00:00
Max Moroz f8744ab57a [compiler-rt] FuzzedDataProvider: use C++ headers only instead of a C/C++ mix.
Reviewers: Dor1s

Reviewed By: Dor1s

Subscribers: dberris, delcypher, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D66017

llvm-svn: 368448
2019-08-09 16:00:53 +00:00
Max Moroz df3b465c9c [compiler-rt] Add ConsumeProbability and ConsumeFloatingPoint methods to FDP.
Summary:
Also slightly cleaned up the comments and changed the header's extension
back to `.h` as per comments on https://reviews.llvm.org/D65812.

New methods added:

* `ConsumeProbability` returns [0.0, 1.0] by consuming an unsigned integer value
   from the input data and dividing that value by the integer's max value.
* `ConsumeFloatingPointInRange` returns a floating point value in the given
   range. Relies on `ConsumeProbability` method. This method does not have the
   limitation of `std::uniform_real_distribution` that requires the given range
   to be <= the floating point type's max. If the range is too large, this
   implementation will additionally call `ConsumeBool` to decide whether the
   result will be in the first or the second half of the range.
* `ConsumeFloatingPoint` returns a floating point value in the range
  `[std::numeric_limits<T>::lowest(), std::numeric_limits<T>::min()]`.

Tested on Linux, Mac, Windows.


Reviewers: morehouse

Reviewed By: morehouse

Subscribers: kubamracek, mgorny, dberris, delcypher, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D65905

llvm-svn: 368331
2019-08-08 19:49:37 +00:00
Max Moroz 6c619aadc4 [compiler-rt] Rename FuzzedDataProvider.h to .hpp and other minor changes.
Summary:
.hpp makes more sense for this header as it's C++ only, plus it
contains the actual implementation.

Reviewers: Dor1s

Reviewed By: Dor1s

Subscribers: kubamracek, dberris, mgorny, delcypher, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D65812

llvm-svn: 368054
2019-08-06 16:02:39 +00:00
Max Moroz f1b0a93e3a [compiler-rt] Move FDP to include/fuzzer/FuzzedDataProvider.h for easier use.
Summary:
FuzzedDataProvider is a helper class for writing fuzz targets that fuzz
multple inputs simultaneously. The header is supposed to be used for fuzzing
engine agnostic fuzz targets (i.e. the same target can be used with libFuzzer,
AFL, honggfuzz, and other engines). The common thing though is that fuzz targets
are typically compiled with clang, as it provides all sanitizers as well as
different coverage instrumentation modes. Therefore, making this FDP class a
part of the compiler-rt installation package would make it easier to develop
and distribute fuzz targets across different projects, build systems, etc.
Some context also available in https://github.com/google/oss-fuzz/pull/2547.

This CL does not delete the header from `lib/fuzzer/utils` directory in order to
provide the downstream users some time for a smooth migration to the new
header location.

Reviewers: kcc, morehouse

Reviewed By: morehouse

Subscribers: lebedev.ri, kubamracek, dberris, mgorny, delcypher, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D65661

llvm-svn: 367917
2019-08-05 19:55:52 +00:00
Kostya Serebryany 6b936d88a4 [dfsan] Introduce dfsan_flush().
Summary:
dfsan_flush() allows to restart tain tracking from scratch in the same process.
The primary purpose right now is to allow more efficient data flow tracing
for DFT fuzzing: https://github.com/google/oss-fuzz/issues/1632

Reviewers: pcc

Reviewed By: pcc

Subscribers: delcypher, #sanitizers, llvm-commits

Tags: #llvm, #sanitizers

Differential Revision: https://reviews.llvm.org/D63037

llvm-svn: 363321
2019-06-13 20:11:06 +00:00
Pierre Gousseau 012ae4cc40 [compiler-rt] Update comments in asan header to doxygen format; NFC.
Add description to undocumented functions.
Improve spelling, grammar and formatting.

Patch by: Craig Flores, Filipe Cabecinhas, Pierre Gousseau

Reviewed By: Johannes Doerfert

Differential Revision: https://reviews.llvm.org/D62245

llvm-svn: 363038
2019-06-11 08:59:46 +00:00
Matt Morehouse a612b5adb7 [MSan] Introduce __msan_unpoison_param().
Summary:
This allows libFuzzer to unpoison parameter shadow before calling
LLVMFuzzerTestOneInput to eliminate the false positives described
in https://github.com/google/oss-fuzz/issues/2369.

Reviewers: eugenis

Reviewed By: eugenis

Subscribers: llvm-commits, metzman, kcc

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61751

llvm-svn: 360379
2019-05-09 21:50:57 +00:00
Evgeniy Stepanov d1a710047b [sanitizer] Implement reallocarray.
Summary:
It's a cross of calloc and realloc. Sanitizers implement calloc-like check for size
overflow.

Reviewers: vitalybuka, kcc

Subscribers: kubamracek, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D61108

llvm-svn: 359708
2019-05-01 17:33:01 +00:00
Nico Weber 885b790f89 Remove esan.
It hasn't seen active development in years, and it hasn't reached a
state where it was useful.

Remove the code until someone is interested in working on it again.

Differential Revision: https://reviews.llvm.org/D59133

llvm-svn: 355862
2019-03-11 20:23:40 +00:00
Evgeniy Stepanov f46a52b536 [hwasan, asan] Intercept vfork.
Summary:
Intercept vfork on arm, aarch64, i386 and x86_64.

Reviewers: pcc, vitalybuka

Subscribers: kubamracek, mgorny, javed.absar, krytarowski, kristof.beyls, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D58533

llvm-svn: 355030
2019-02-27 21:11:50 +00:00
Evgeniy Stepanov 45eea20d2a Revert "[asan] Fix vfork handling.", +1
Revert r354625, r354627 - multiple build failures.

llvm-svn: 354629
2019-02-21 22:02:24 +00:00
Evgeniy Stepanov df91386806 [hwasan,asan] Intercept vfork.
Summary: AArch64 only for now.

Reviewers: vitalybuka, pcc

Subscribers: srhines, kubamracek, mgorny, javed.absar, krytarowski, kristof.beyls, jdoerfert, #sanitizers, llvm-commits, kcc

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D58313

llvm-svn: 354625
2019-02-21 21:32:24 +00:00
Dmitry Vyukov 76e961207b tsan: add fiber support
This patch adds functions for managing fibers:

__tsan_get_current_fiber()
__tsan_create_fiber()
__tsan_destroy_fiber()
__tsan_switch_to_fiber()
__tsan_set_fiber_name()

See the added tests for use examples.

Author: yuri (Yuri Per)
Reviewed in: https://reviews.llvm.org/D54889

[The previous commit of this change was reverted,
this is a resubmit with a squashed fix for check_analyze.sh
and COMMON_INTERCEPTOR_NOTHING_IS_INITIALIZED]

llvm-svn: 353947
2019-02-13 13:21:24 +00:00
Diana Picus 4152a09e55 Revert "tsan: add fiber support"
This reverts commit r353817 because we think it broke AARch64 and
PowerPC buildbots.

llvm-svn: 353939
2019-02-13 11:32:56 +00:00
Dmitry Vyukov 6e7089ad40 tsan: add fiber support
This patch adds functions for managing fibers:

__tsan_get_current_fiber()
__tsan_create_fiber()
__tsan_destroy_fiber()
__tsan_switch_to_fiber()
__tsan_set_fiber_name()

See the added tests for use examples.

Author: yuri (Yuri Per)
Reviewed in: https://reviews.llvm.org/D54889

llvm-svn: 353817
2019-02-12 10:11:58 +00:00
Peter Collingbourne 886b7cc107 hwasan: Add __hwasan_init_static() function.
This function initializes enough of the runtime to be able to run
instrumented code in a statically linked executable. It replaces
__hwasan_shadow_init() which wasn't doing enough initialization for
instrumented code that uses either TLS or IFUNC to work.

Differential Revision: https://reviews.llvm.org/D57490

llvm-svn: 352816
2019-01-31 23:37:12 +00:00