462 Commits

Author SHA1 Message Date
Anna Zaks
92d577bd41 Revert "[asan] LLVM: Switch to using dynamic shadow offset on iOS"
This reverts commit abe77a118615cd90b0d7f127e4797096afa2b394.

Revert as these changes broke a Chromium buildbot.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283348 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-05 17:42:02 +00:00
Anna Zaks
a8e8b59519 [asan] LLVM: Switch to using dynamic shadow offset on iOS
The VM layout is not stable between iOS version releases, so switch to dynamic shadow offset.

This is the LLVM counterpart of https://reviews.llvm.org/D25218

Differential Revision: https://reviews.llvm.org/D25219

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283239 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-04 19:02:29 +00:00
Mehdi Amini
67f335d992 Use StringRef in Pass/PassManager APIs (NFC)
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283004 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-01 02:56:57 +00:00
Mehdi Amini
090f75dc83 [ASAN] Add the binder globals on Darwin to llvm.compiler.used to avoid LTO dead-stripping
The binder is in a specific section that "reverse" the edges in a
regular dead-stripping: the binder is live as long as a global it
references is live.

This is a big hammer that prevents LLVM from dead-stripping these,
while still allowing linker dead-stripping (with special knowledge
of the section).

Differential Revision: https://reviews.llvm.org/D24673

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282988 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-01 00:05:34 +00:00
Etienne Bergeron
937044fdd2 [asan] Support dynamic shadow address instrumentation
Summary:
This patch is adding the support for a shadow memory with
dynamically allocated address range.

The compiler-rt needs to export a symbol containing the shadow
memory range.

This is required to support ASAN on windows 64-bits.

Reviewers: kcc, rnk, vitalybuka

Subscribers: zaks.anna, kubabrecka, dberris, llvm-commits, chrisha

Differential Revision: https://reviews.llvm.org/D23354

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282881 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-30 17:46:32 +00:00
Etienne Bergeron
3abbc4d854 [compiler-rt] fix typo in option description [NFC]
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282163 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-22 14:57:24 +00:00
Nico Weber
5f630a9121 revert 281908 because 281909 got reverted
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282097 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-21 18:25:43 +00:00
Adrian Prantl
3051c6d512 ASAN: Don't drop debug info attachements for global variables.
This is a follow-up to r281284. Global Variables now can have
!dbg attachements, so ASAN should clone these when generating a
sanitized copy of a global variable.

<rdar://problem/24899262>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281994 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-20 18:28:42 +00:00
Etienne Bergeron
b87b0d3795 [asan] Support dynamic shadow address instrumentation
Summary:
This patch is adding the support for a shadow memory with
dynamically allocated address range.

The compiler-rt needs to export a symbol containing the shadow
memory range.

This is required to support ASAN on windows 64-bits.

Reviewers: kcc, rnk, vitalybuka

Subscribers: kubabrecka, dberris, llvm-commits, chrisha

Differential Revision: https://reviews.llvm.org/D23354

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281908 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-19 15:58:38 +00:00
Vitaly Buka
d26bf22afc Revert "[asan] Avoid lifetime analysis for allocas with can be in ambiguous state"
This approach is not good enough. Working on the new solution.

This reverts commit r280907.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281689 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-16 01:38:46 +00:00
Vitaly Buka
1354d58f56 Revert "[asan] Add flag to allow lifetime analysis of problematic allocas"
This approach is not good enough. Working on the new solution.

This reverts commit r281126.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281688 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-16 01:38:43 +00:00
Etienne Bergeron
d40500c24d [compiler-rt] Changing function prototype returning unused value
Summary: The return value of `maybeInsertAsanInitAtFunctionEntry` is ignored.

Reviewers: rnk

Subscribers: llvm-commits, chrisha, dberris

Differential Revision: https://reviews.llvm.org/D24568

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281620 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-15 15:45:05 +00:00
Etienne Bergeron
51832f72bd Fix silly mistake introduced here : https://reviews.llvm.org/D24566
Asan bots are currently broken without this patch.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281618 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-15 15:35:59 +00:00
Etienne Bergeron
28f64ff6ba address comments from: https://reviews.llvm.org/D24566
using startswith instead of find.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281617 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-15 15:19:19 +00:00
Etienne Bergeron
24624732a0 [compiler-rt] Avoid instrumenting sanitizer functions
Summary:
Function __asan_default_options is called by __asan_init before the
shadow memory got initialized. Instrumenting that function may lead
to flaky execution.

As the __asan_default_options is provided by users, we cannot expect
them to add the appropriate function atttributes to avoid
instrumentation.

Reviewers: kcc, rnk

Subscribers: dberris, chrisha, llvm-commits

Differential Revision: https://reviews.llvm.org/D24566

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281503 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-14 17:18:37 +00:00
Etienne Bergeron
e9c64c5da5 Fix typo in comment [NFC]
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281492 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-14 15:59:32 +00:00
Kuba Brecka
62660f0e5a [asan] Enable -asan-use-private-alias on Darwin/Mach-O, add test for ODR false positive with LTO (llvm part)
The '-asan-use-private-alias’ option (disabled by default) option is currently only enabled for Linux and ELF, but it also works on Darwin and Mach-O. This option also fixes a known problem with LTO on Darwin (https://github.com/google/sanitizers/issues/647). This patch enables the support for Darwin (but still keeps it off by default) and adds the LTO test case.

Differential Revision: https://reviews.llvm.org/D24292



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281470 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-14 14:06:33 +00:00
Vitaly Buka
c4644d2241 [asan] Add flag to allow lifetime analysis of problematic allocas
Summary:
Could be useful for comparison when we suspect that alloca was skipped
because of this.

Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D24437

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@281126 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-10 01:06:11 +00:00
Vitaly Buka
52bc7ab5ec [asan] Avoid lifetime analysis for allocas with can be in ambiguous state
Summary:
C allows to jump over variables declaration so lifetime.start can be
avoid before variable usage. To avoid false-positives on such rare cases
we detect them and remove from lifetime analysis.

PR27453
PR28267

Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D24321

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280907 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-08 06:27:58 +00:00
Vitaly Buka
f555e2686a Revert "[asan] Avoid lifetime analysis for allocas with can be in ambiguous state"
Fails on Windows.

This reverts commit r280880.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280883 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-07 23:37:15 +00:00
Vitaly Buka
f8002f1611 [asan] Avoid lifetime analysis for allocas with can be in ambiguous state
Summary:
C allows to jump over variables declaration so lifetime.start can be
avoid before variable usage. To avoid false-positives on such rare cases
we detect them and remove from lifetime analysis.

PR27453
PR28267

Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D24321

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@280880 91177308-0d34-0410-b5e6-96231b3b80d8
2016-09-07 23:18:23 +00:00
Vitaly Buka
6e3f5dd44f [asan] Enable new stack poisoning with store instruction by default
Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23968

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279993 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-29 19:28:34 +00:00
Vitaly Buka
b8ae70f140 Use store operation to poison allocas for lifetime analysis.
Summary:
Calling __asan_poison_stack_memory and __asan_unpoison_stack_memory for small
variables is too expensive.

Code is disabled by default and can be enabled by -asan-experimental-poisoning.

PR27453

Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23947

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279984 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-29 18:17:21 +00:00
Vitaly Buka
997a485279 [asan] Separate calculation of ShadowBytes from calculating ASanStackFrameLayout
Summary: No functional changes, just refactoring to make D23947 simpler.

Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23954

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279982 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-29 17:41:29 +00:00
Vitaly Buka
663b75a377 [asan] Use 1 byte aligned stores to poison shadow memory
Summary: r279379 introduced crash on arm 32bit bot. I suspect this is alignment issue.

Reviewers: eugenis

Subscribers: llvm-commits, aemerson

Differential Revision: https://reviews.llvm.org/D23762

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279413 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-22 04:16:14 +00:00
Vitaly Buka
49a5f5ed32 [asan] Minimize code size by using __asan_set_shadow_* for large blocks
Summary:
We can insert function call instead of multiple store operation.
Current default is blocks larger than 64 bytes.
Changes are hidden behind -asan-experimental-poisoning flag.

PR27453

Differential Revision: https://reviews.llvm.org/D23711

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279383 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-20 20:23:50 +00:00
Vitaly Buka
d66cc578a7 [asan] Initialize __asan_set_shadow_* callbacks
Summary:
Callbacks are not being used yet.

PR27453

Reviewers: kcc, eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23634

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279380 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-20 18:34:39 +00:00
Vitaly Buka
7b2eb8e4d0 [asan] Optimize store size in FunctionStackPoisoner::poisonRedZones
Summary: Reduce store size to avoid leading and trailing zeros.

Reviewers: kcc, eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23648

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279379 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-20 18:34:36 +00:00
Vitaly Buka
c662b7eae3 [asan] Cleanup instrumentation of dynamic allocas
Summary:
Extract instrumenting dynamic allocas into separate method.
Rename asan-instrument-allocas -> asan-instrument-dynamic-allocas

Differential Revision: https://reviews.llvm.org/D23707

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279376 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-20 17:22:27 +00:00
Vitaly Buka
939300ca39 [asan] Add support of lifetime poisoning into ComputeASanStackFrameLayout
Summary:
We are going to combine poisoning of red zones and scope poisoning.

PR27453

Reviewers: kcc, eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23623

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279373 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-20 16:48:24 +00:00
Vitaly Buka
b2ae2edf5a Revert "[asan] Add support of lifetime poisoning into ComputeASanStackFrameLayout"
This reverts commit r279020.

Speculative revert in hope to fix asan test on arm.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279332 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-19 22:12:58 +00:00
Vitaly Buka
31c625e355 Revert "[asan] Optimize store size in FunctionStackPoisoner::poisonRedZones"
This reverts commit r279178.

Speculative revert in hope to fix asan crash on arm.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279277 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-19 17:15:38 +00:00
Vitaly Buka
588e241acb Revert "[asan] Fix size of shadow incorrectly calculated in r279178"
This reverts commit r279222.

Speculative revert in hope to fix asan crash on arm.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279276 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-19 17:15:33 +00:00
Vitaly Buka
bc8fdf73ab [asan] Fix size of shadow incorrectly calculated in r279178
Summary: r279178 generates 8 times more stores than necessary.

Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23708

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279222 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-19 08:33:53 +00:00
Vitaly Buka
0c6c3b22db [asan] Optimize store size in FunctionStackPoisoner::poisonRedZones
Summary: Reduce store size to avoid leading and trailing zeros.

Reviewers: kcc, eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23648

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279178 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-18 23:51:15 +00:00
Vitaly Buka
76e81b28c6 [asan] Add support of lifetime poisoning into ComputeASanStackFrameLayout
Summary:
We are going to combine poisoning of red zones and scope poisoning.

PR27453

Reviewers: kcc, eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23623

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@279020 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-18 00:56:58 +00:00
Vitaly Buka
fc819213c1 [Asan] Unpoison red zones even if use-after-scope was disabled with runtime flag
Summary: PR27453

Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D23481

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@278818 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-16 16:24:10 +00:00
Vitaly Buka
34ad8f0f0b [asan] Add const into few methods
Summary: No functional changes

Reviewers: eugenis

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D22899

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277069 91177308-0d34-0410-b5e6-96231b3b80d8
2016-07-28 22:50:50 +00:00
Vitaly Buka
ecefac9053 Unpoison stack before resume instruction
Summary:
Clang inserts cleanup code before resume similar way as before return instruction.
This makes asan poison local variables causing false use-after-scope reports.

__asan_handle_no_return does not help here as it was executed before
llvm.lifetime.end inserted into resume block.

To avoid false report we need to unpoison stack for resume same way as for return.

PR27453

Reviewers: kcc, eugenis

Differential Revision: https://reviews.llvm.org/D22661

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@276480 91177308-0d34-0410-b5e6-96231b3b80d8
2016-07-22 22:04:38 +00:00
Vitaly Buka
cb5c574105 Fix detection of stack-use-after scope for char arrays.
Summary:
Clang inserts GetElementPtrInst so findAllocaForValue was not
able to find allocas.

PR27453

Reviewers: kcc, eugenis

Differential Revision: https://reviews.llvm.org/D22657

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@276374 91177308-0d34-0410-b5e6-96231b3b80d8
2016-07-22 00:56:17 +00:00
Ryan Govostes
4205e17d8c [asan] Add a hidden option for Mach-O global metadata liveness tracking
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274578 91177308-0d34-0410-b5e6-96231b3b80d8
2016-07-05 21:53:08 +00:00
Kuba Brecka
b41eaf7778 [asan] fix false dynamic-stack-buffer-overflow report with constantly-sized dynamic allocas, LLVM part
See the bug report at https://github.com/google/sanitizers/issues/691. When a dynamic alloca has a constant size, ASan instrumentation will treat it as a regular dynamic alloca (insert calls to poison and unpoison), but the backend will turn it into a regular stack variable. The poisoning/unpoisoning is then broken. This patch will treat such allocas as static.

Differential Revision: http://reviews.llvm.org/D21509



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273888 91177308-0d34-0410-b5e6-96231b3b80d8
2016-06-27 15:57:08 +00:00
Benjamin Kramer
5288df58b7 Apply clang-tidy's modernize-loop-convert to most of lib/Transforms.
Only minor manual fixes. No functionality change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273808 91177308-0d34-0410-b5e6-96231b3b80d8
2016-06-26 12:28:59 +00:00
Vedant Kumar
f317b6e2b1 [asan] Do not instrument accesses to profiling globals
It's only useful to asan-itize profiling globals while debugging llvm's
profiling instrumentation passes. Enabling asan along with instrprof or
gcov instrumentation shouldn't incur extra overhead.

This patch is in the same spirit as r264805 and r273202, which disabled
tsan instrumentation of instrprof/gcov globals.

Differential Revision: http://reviews.llvm.org/D21541

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273444 91177308-0d34-0410-b5e6-96231b3b80d8
2016-06-22 17:30:58 +00:00
Anna Zaks
b523d2b232 [asan] Do not instrument pointers with address space attributes
Do not instrument pointers with address space attributes since we cannot track
them anyway. Instrumenting them results in false positives in ASan and a
compiler crash in TSan. (The compiler should not crash in any case, but that's
a different problem.)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273339 91177308-0d34-0410-b5e6-96231b3b80d8
2016-06-22 00:15:52 +00:00
Etienne Bergeron
b4f51c3ea5 This is part of the effort for asan to support Windows 64 bit.
The large offset is being tested on Windows 10 (which has larger usable
virtual address space than Windows 8 or earlier)

Patch by:  Wei Wang
Differential Revision: http://reviews.llvm.org/D21523



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273269 91177308-0d34-0410-b5e6-96231b3b80d8
2016-06-21 15:07:29 +00:00
Marcin Koscielnicki
ccb3bb979e [sanitizers] Disable target-specific lowering of string functions.
CodeGen has hooks that allow targets to emit specialized code instead
of calls to memcmp, memchr, strcpy, stpcpy, strcmp, strlen, strnlen.
When ASan/MSan/TSan/ESan is in use, this sidesteps its interceptors, resulting
in uninstrumented memory accesses.  To avoid that, make these sanitizers
mark the calls as nobuiltin.

Differential Revision: http://reviews.llvm.org/D19781

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273083 91177308-0d34-0410-b5e6-96231b3b80d8
2016-06-18 10:10:37 +00:00
Peter Collingbourne
63b34cdf34 IR: Introduce local_unnamed_addr attribute.
If a local_unnamed_addr attribute is attached to a global, the address
is known to be insignificant within the module. It is distinct from the
existing unnamed_addr attribute in that it only describes a local property
of the module rather than a global property of the symbol.

This attribute is intended to be used by the code generator and LTO to allow
the linker to decide whether the global needs to be in the symbol table. It is
possible to exclude a global from the symbol table if three things are true:
- This attribute is present on every instance of the global (which means that
  the normal rule that the global must have a unique address can be broken without
  being observable by the program by performing comparisons against the global's
  address)
- The global has linkonce_odr linkage (which means that each linkage unit must have
  its own copy of the global if it requires one, and the copy in each linkage unit
  must be the same)
- It is a constant or a function (which means that the program cannot observe that
  the unique-address rule has been broken by writing to the global)

Although this attribute could in principle be computed from the module
contents, LTO clients (i.e. linkers) will normally need to be able to compute
this property as part of symbol resolution, and it would be inefficient to
materialize every module just to compute it.

See:
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160509/356401.html
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160516/356738.html
for earlier discussion.

Part of the fix for PR27553.

Differential Revision: http://reviews.llvm.org/D20348

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272709 91177308-0d34-0410-b5e6-96231b3b80d8
2016-06-14 21:01:22 +00:00
Vitaly Buka
e330b7d89a Make sure that not interesting allocas are not instrumented.
Summary:
We failed to unpoison uninteresting allocas on return as unpoisoning is part of
main instrumentation which skips such allocas.

Added check -asan-instrument-allocas for dynamic allocas. If instrumentation of
dynamic allocas is disabled it will not will not be unpoisoned.

PR27453

Reviewers: kcc, eugenis

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D21207

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272341 91177308-0d34-0410-b5e6-96231b3b80d8
2016-06-09 23:31:59 +00:00
Vitaly Buka
af4c28d141 Unpoison stack memory in use-after-return + use-after-scope mode
Summary:
We still want to unpoison full stack even in use-after-return as it can be disabled at runtime.

PR27453

Reviewers: eugenis, kcc

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D21202

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@272334 91177308-0d34-0410-b5e6-96231b3b80d8
2016-06-09 23:05:35 +00:00