Commit Graph

34632 Commits

Author SHA1 Message Date
Sam McCall e6057bc689 [Support] Harded JSON against invalid UTF-8.
Parsing invalid UTF-8 input is now a parse error.
Creating JSON values from invalid UTF-8 now triggers an assertion, and
(in no-assert builds) substitutes the unicode replacement character.
Strings retrieved from json::Value are always valid UTF-8.

llvm-svn: 336657
2018-07-10 11:51:26 +00:00
Simon Pilgrim c048599f22 Fix MSVC "signed/unsigned mismatch" warning. NFCI.
llvm-svn: 336649
2018-07-10 09:46:57 +00:00
Craig Topper 3e7406b45b [X86] Add back GCCBuiltin on mask_div_ss/sd_round.
We no longer need custom handling in clang.

llvm-svn: 336627
2018-07-10 00:49:50 +00:00
Manoj Gupta 77eeac3d9e llvm: Add support for "-fno-delete-null-pointer-checks"
Summary:
Support for this option is needed for building Linux kernel.
This is a very frequently requested feature by kernel developers.

More details : https://lkml.org/lkml/2018/4/4/601

GCC option description for -fdelete-null-pointer-checks:
This Assume that programs cannot safely dereference null pointers,
and that no code or data element resides at address zero.

-fno-delete-null-pointer-checks is the inverse of this implying that
null pointer dereferencing is not undefined.

This feature is implemented in LLVM IR in this CL as the function attribute
"null-pointer-is-valid"="true" in IR (Under review at D47894).
The CL updates several passes that assumed null pointer dereferencing is
undefined to not optimize when the "null-pointer-is-valid"="true"
attribute is present.

Reviewers: t.p.northover, efriedma, jyknight, chandlerc, rnk, srhines, void, george.burgess.iv

Reviewed By: efriedma, george.burgess.iv

Subscribers: eraman, haicheng, george.burgess.iv, drinkcat, theraven, reames, sanjoy, xbolva00, llvm-commits

Differential Revision: https://reviews.llvm.org/D47895

llvm-svn: 336613
2018-07-09 22:27:23 +00:00
Rui Ueyama 0230f7c763 Use StringRef instead of `const char *`.
I don't think there's a need to use `const char *`. In most (probably all?)
cases, we need a length of a name later, so discarding a length will
lead to a wasted effort.

Differential Revision: https://reviews.llvm.org/D49046

llvm-svn: 336612
2018-07-09 22:26:49 +00:00
Lang Hames f07dad3d8f [ORC] Rename MaterializationResponsibility::delegate to replace and add a new
delegate method (and unit test).

The name 'replace' better captures what the old delegate method did: it
returned materialization responsibility for a set of symbols to the VSO.

The new delegate method delegates responsibility for a set of symbols to a new
MaterializationResponsibility instance. This can be used to split responsibility
between multiple threads, or multiple materialization methods.

llvm-svn: 336603
2018-07-09 20:54:36 +00:00
Stefan Pintilie 58e3e0a827 [Power9] [LLVM] Add __float128 support for trunc to double round to odd
Add support for this builtin:
double builtin_truncf128_round_to_odd(float128)

Differential Revision: https://reviews.llvm.org/D48483

llvm-svn: 336595
2018-07-09 20:09:22 +00:00
Daniel Sanders 9481399c0f [globalisel][irtranslator] Add support for atomicrmw and (strong) cmpxchg
Summary:
This patch adds support for the atomicrmw instructions and the strong
cmpxchg instruction to the IRTranslator.

I've left out weak cmpxchg because LangRef.rst isn't entirely clear on what
difference it makes to the backend. As far as I can tell from the code, it
only matters to AtomicExpandPass which is run at the LLVM-IR level.

Reviewers: ab, t.p.northover, qcolombet, rovka, aditya_nandakumar, volkan, javed.absar

Reviewed By: qcolombet

Subscribers: kristof.beyls, javed.absar, igorb, llvm-commits

Differential Revision: https://reviews.llvm.org/D40092

llvm-svn: 336589
2018-07-09 19:33:40 +00:00
Roman Lebedev 5ccae1750b [X86][TLI] DAGCombine: Unfold variable bit-clearing mask to two shifts.
Summary:
This adds a reverse transform for the instcombine canonicalizations
that were added in D47980, D47981.

As discussed later, that was worse at least for the code size,
and potentially for the performance, too.

https://rise4fun.com/Alive/Zmpl

Reviewers: craig.topper, RKSimon, spatel

Reviewed By: spatel

Subscribers: reames, llvm-commits

Differential Revision: https://reviews.llvm.org/D48768

llvm-svn: 336585
2018-07-09 19:06:42 +00:00
Stefan Pintilie 83a5fe146e [Power9] Add __float128 builtins for Round To Odd
GCC has builtins for these round to odd instructions:

__float128 __builtin_sqrtf128_round_to_odd (__float128)
__float128 __builtin_{add,sub,mul,div}f128_round_to_odd (__float128, __float128)
__float128 __builtin_fmaf128_round_to_odd (__float128, __float128, __float128)

Differential Revision: https://reviews.llvm.org/D47550

llvm-svn: 336578
2018-07-09 18:50:06 +00:00
Diego Caballero 29a07b37bf [LoopInfo] Port loop exit interfaces from Loop to LoopBase
This patch ports hasDedicatedExits, getUniqueExitBlocks and
getUniqueExitBlock in Loop to LoopBase so that they can be used
from other LoopBase sub-classes.

Reviewers: chandlerc, sanjoy, hfinkel, fhahn

Reviewed By: chandlerc

Differential Revision: https://reviews.llvm.org/D48817

llvm-svn: 336572
2018-07-09 17:52:49 +00:00
Sam McCall 7e4234fc97 [Support] Allow JSON serialization of Optional<T> for supported T.
This is ported from r333881 to JSON's new home.

llvm-svn: 336542
2018-07-09 12:26:09 +00:00
Sam McCall d93eaeb7c3 [Support] Make JSON handle doubles and int64s losslessly
Summary:
This patch adds a new "integer" ValueType, and renames Number -> Double.
This allows us to preserve the full precision of int64_t when parsing integers
from the wire, or constructing from an integer.
The API is unchanged, other than giving asInteger() a clearer contract.

In addition, always output doubles with enough precision that parsing will
reconstruct the same double.

Reviewers: simon_tatham

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D46209

llvm-svn: 336541
2018-07-09 12:16:40 +00:00
Sam McCall fd75fc50b6 [Support] Fix GCC compile after r336534
llvm-svn: 336537
2018-07-09 10:43:32 +00:00
Sam McCall 6be3824721 Lift JSON library from clang-tools-extra/clangd to llvm/Support.
Summary:
This consists of four main parts:
 - an type json::Expr representing JSON values of dynamic kind, which can be
   composed, inspected, and modified
 - a JSON parser from string -> json::Expr
 - a JSON printer from json::Expr -> string, with optional pretty-printing
 - a convention for mapping json::Expr <=> native types (fromJSON/toJSON)
   Mapping functions are provided for primitives (e.g. int, vector) and the
   ObjectMapper helper helps implement fromJSON for struct/object types.

Based on clangd's usage, a couple of places I'd appreciate review attention:
 - fromJSON returns only bool. A richer error-signaling mechanism may be useful
   to provide useful messages, or let recursive fromJSONs (containers/structs)
   do careful error recovery.
 - should json::obj be always explicitly written (like json::ary)
 - there's no streaming parse API. I suspect there are some simple wins like
   a callback API where the document is a long array, and each element is small.
   But this can probably be bolted on easily when we see the need.

Reviewers: bkramer, labath

Subscribers: mgorny, ilya-biryukov, ioeric, MaskRay, llvm-commits

Differential Revision: https://reviews.llvm.org/D45753

llvm-svn: 336534
2018-07-09 10:05:41 +00:00
Jonas Devlieghere 5e810a878d [AccelTable] Provide abstraction for emitting DWARF5 accelerator tables.
When emitting the DWARF accelerator tables from dsymutil, we don't have
a DwarfDebug instance and we use a custom class to represent Dwarf
compile units. This patch adds an interface AccelTableWriterInfo to
abstract these from the Dwarf5AccelTableWriter, so we can have a custom
implementation for this in dsymutil.

Differential revision: https://reviews.llvm.org/D49031

llvm-svn: 336529
2018-07-09 09:08:44 +00:00
Craig Topper fdf3f1ff82 [X86] Add new scalar fma intrinsics with rounding mode that use f32/f64 types.
This allows us to handle masking in a very similar way to the default rounding version that uses llvm.fma.

I had to add new rounding mode CodeGenOnly instructions to support isel when we can't find a movss to grab the upper bits from to use the b_Int instruction.

Fast-isel tests have been updated to match new clang codegen.

We are currently having trouble folding fneg into the new intrinsic. I'm going to correct that in a follow up patch to keep the size of this one down.

A future patch will also remove the old intrinsics.

llvm-svn: 336506
2018-07-08 01:10:43 +00:00
Simon Pilgrim 23f9eddabe [SelectionDAG] Split float and integer isKnownNeverZero tests
Splits off isKnownNeverZeroFloat to handle +/- 0 float cases.

This will make it easier to be more aggressive with the integer isKnownNeverZero tests (similar to ValueTracking), use computeKnownBits etc.

Differential Revision: https://reviews.llvm.org/D48969

llvm-svn: 336492
2018-07-07 18:17:14 +00:00
Yvan Roux a96a04558d [MachineOutliner] Assert that Liveness tracking is accurate (NFC)
The checking is done deeper inside MachineBasicBlock, but this will
hopefully help to find issues when porting the machine outliner to a
target where Liveness tracking is broken (like ARM).

Differential Revision: https://reviews.llvm.org/D49023

llvm-svn: 336481
2018-07-07 08:02:19 +00:00
Chandler Carruth 9659a127a3 [Support] Clear errno before calling the function in RetryAfterSignal.
For certain APIs, the return value of the function does not distinguish
between failure (which populates errno) and other non-error conditions
(which do not set errno).

For example, `fgets` returns `NULL` both when an error has occurred, or
upon EOF. If `errno` is already `EINTR` for whatever reason, then
```
RetryAfterSignal(nullptr, fgets, ...);
```
on a stream that has reached EOF would infinite loop.

Fix this by setting `errno` to `0` before each attempt in
`RetryAfterSignal`.

Patch by Ricky Zhou!

Differential Revision: https://reviews.llvm.org/D48755

llvm-svn: 336479
2018-07-07 02:46:12 +00:00
Vedant Kumar 71c7c43695 Fix DIExpression::ExprOperand::appendToVector
appendToVector used the wrong overload of SmallVector::append, resulting
in it appending the same element to a vector `getSize()` times. This did
not cause a problem when initially committed because appendToVector was
only used to append 1-element operands.

This changes appendToVector to use the correct overload of append().

Testing: ./unittests/IR/IRTests --gtest_filter='*DIExpressionTest*'
llvm-svn: 336466
2018-07-06 21:06:21 +00:00
Fangrui Song 3c1b5dbbf1 [IR] Fix inconsistent declaration parameter name
llvm-svn: 336459
2018-07-06 19:26:00 +00:00
Vedant Kumar 6379a62250 [Local] replaceAllDbgUsesWith: Update debug values before RAUW
The replaceAllDbgUsesWith utility helps passes preserve debug info when
replacing one value with another.

This improves upon the existing insertReplacementDbgValues API by:

- Updating debug intrinsics in-place, while preventing use-before-def of
  the replacement value.
- Falling back to salvageDebugInfo when a replacement can't be made.
- Moving the responsibiliy for rewriting llvm.dbg.* DIExpressions into
  common utility code.

Along with the API change, this teaches replaceAllDbgUsesWith how to
create DIExpressions for three basic integer and pointer conversions:

- The no-op conversion. Applies when the values have the same width, or
  have bit-for-bit compatible pointer representations.
- Truncation. Applies when the new value is wider than the old one.
- Zero/sign extension. Applies when the new value is narrower than the
  old one.

Testing:

- check-llvm, check-clang, a stage2 `-g -O3` build of clang,
  regression/unit testing.
- This resolves a number of mis-sized dbg.value diagnostics from
  Debugify.

Differential Revision: https://reviews.llvm.org/D48676

llvm-svn: 336451
2018-07-06 17:32:39 +00:00
Sanjay Patel e85a300a77 [Constants] extend getBinOpIdentity(); NFC
The enhanced version will be used in D48893 and related patches
and an almost identical (fadd is different) version is proposed 
in D28907, so adding this as a preliminary step.

llvm-svn: 336444
2018-07-06 15:18:58 +00:00
Sanjay Patel e6dda2fee7 [Constant] add undef element query for vector constants; NFC
This is likely to be used in D48987 and similar patches, 
so adding it as an NFC preliminary step.

llvm-svn: 336442
2018-07-06 14:52:36 +00:00
Tim Northover 7ee46ed992 CallGraphSCCPass: iterate over all functions.
Previously we only iterated over functions reachable from the set of
external functions in the module. But since some of the passes under
this (notably the always-inliner and coroutine lowerer) are required for
correctness, they need to run over everything.

This just adds an extra layer of iteration over the CallGraph to keep
track of which functions we've already visited and get the next batch of
SCCs.

Should fix PR38029.

llvm-svn: 336419
2018-07-06 08:04:47 +00:00
Craig Topper c60e1807b3 [X86] Remove FMA4 scalar intrinsics. Use llvm.fma intrinsic instead.
The intrinsics can be implemented with a f32/f64 llvm.fma intrinsic and an insert into a zero vector.

There are a couple regressions here due to SelectionDAG not being able to pull an fneg through an extract_vector_elt. I'm not super worried about this though as InstCombine should be able to do it before we get to SelectionDAG.

llvm-svn: 336416
2018-07-06 07:14:41 +00:00
Sam McCall 8ca99100ba [Support] Make support types more easily printable.
Summary:
Error's new operator<< is the first way to print an error without consuming it.

formatv() can now print objects with an operator<< that works with raw_ostream.

Reviewers: bkramer

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D48966

llvm-svn: 336412
2018-07-06 05:45:45 +00:00
Craig Topper 7b35585ff1 [X86] Remove all of the avx512 masked packed fma intrinsics. Use llvm.fma or unmasked 512-bit intrinsics with rounding mode.
This upgrades all of the intrinsics to use fneg instructions to convert fma into fmsub/fnmsub/fnmadd/fmsubadd. And uses a select instruction for masking.

This matches how clang uses the intrinsics these days.

llvm-svn: 336409
2018-07-06 03:42:09 +00:00
Mandeep Singh Grang 083f4d7da4 [OpenEmbedded] Add OpenEmbedded vendor
Summary: The lib paths are not correctly picked up for OpenEmbedded sysroots
(like arm-oe-linux-gnueabi). I fix this in a follow-up clang patch. But in
order to add the correct libs I need to detect if the vendor is oe. For this
reason, it is first necessary to teach llvm to detect oe vendor, which is what
this patch does.

Reviewers: chandlerc, compnerd, rengolin, javed.absar

Reviewed By: compnerd

Subscribers: kristof.beyls, dexonsmith, llvm-commits

Differential Revision: https://reviews.llvm.org/D48861

llvm-svn: 336401
2018-07-05 23:41:17 +00:00
Lang Hames 7bd8970743 [ORC] In CompileOnDemandLayer2, clone modules on to different contexts by
writing them to a buffer and re-loading them.

Also introduces a multithreaded variant of SimpleCompiler
(MultiThreadedSimpleCompiler) for compiling IR concurrently on multiple
threads.

These changes are required to JIT IR on multiple threads correctly.

No test case yet. I will be looking at how to modify LLI / LLJIT to test
multithreaded JIT support soon.

llvm-svn: 336385
2018-07-05 19:01:27 +00:00
Craig Topper 88d361e976 [X86] Remove the last of the 'x86.fma.' intrinsics and autoupgrade them to 'llvm.fma'. Add upgrade tests for all.
Still need to remove the AVX512 masked versions.

llvm-svn: 336383
2018-07-05 18:43:58 +00:00
Simon Pilgrim 9e987e0917 Fix comment typo. NFCI.
llvm-svn: 336351
2018-07-05 13:51:35 +00:00
Chandler Carruth f26e7d1fe9 [ADT] Switch to indirect even the trivial case through an object pointer
that has required alignment. This avoids issues that keep coming up with
function pointers being less aligned.

I'm pretty annoyed that we can't take advantage of function alignment
even on platforms where they *are* aligned, but build modes and other
things make taking advantage of it somewhere between hard and
impossible. The best case scenario would still embed various build modes
into the ABI causing really hard to debug issues if you compiled one
object file differently from another. =/

This should at least bring the bots back that were having trouble with
this.

llvm-svn: 336337
2018-07-05 11:56:34 +00:00
Craig Topper 350c5f1881 [X86] Remove X86 specific scalar FMA intrinsics and upgrade to tart independent FMA and extractelement/insertelement.
llvm-svn: 336315
2018-07-05 06:52:55 +00:00
Craig Topper e4b9257b69 [X86] Remove some of the packed FMA3 intrinsics since we no longer use them in clang.
There's a regression in here due to inability to combine fneg inputs of X86ISD::FMSUB/FNMSUB/FNMADD nodes.

More removals to come, but I wanted to stop and fix the regression that showed up in this first.

llvm-svn: 336303
2018-07-05 02:52:54 +00:00
Jakub Kuderski bea19a9493 [Dominators] Add DomTreeUpdater constructor from DT* and PDT*
Summary:
Previously, if a function accepts an optional DT pointer,
```
void Foo (.., DominatorTree * DT = nullptr) {
  ...
  if(DT)
    DomTreeUpdater(*DT, ...).insertEdge(A, B);
  if(DT){
    DomTreeUpdater DTU(*DT, ...);
    ... // Construct the update vector and applyUpdates
  }
  ...
  if(DT){
    DomTreeUpdater DTU(*DT, ...);
    ... // Construct the update vector and applyUpdates
  }
}
```
After this patch, it can be simplified as
```
void Foo (.., DominatorTree * DT = nullptr) {
  DomTreeUpdater DTU(DT, ...);
  ...
  DTU.insertEdge(A, B);
  if(DT){
    ... // Construct the update vector and applyUpdates
  }
  ...
  if(DT){
    ... // Construct the update vector and applyUpdates
  }
}
```
Patch by Chijun Sima <simachijun@gmail.com>.

Reviewers: kuhar, brzycki, dmgreen

Reviewed By: kuhar

Author: NutshellySima

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D48923

llvm-svn: 336294
2018-07-04 18:37:15 +00:00
Yvan Roux eaececf5e0 [MachineOutliner] Fix typo in getOutliningCandidateInfo function name
getOutlininingCandidateInfo -> getOutliningCandidateInfo

Differential Revision: https://reviews.llvm.org/D48867

llvm-svn: 336285
2018-07-04 15:37:08 +00:00
Paul Semel d2af4d6f1b [llvm-objdump] Add --file-headers (-f) option
llvm-svn: 336284
2018-07-04 15:25:03 +00:00
Andrew Ng 089303d8ff [ThinLTO] Update ThinLTO cache file atimes when on Windows
ThinLTO cache file access times are used for expiration based pruning
and since Vista, file access times are not updated by Windows by
default:

https://blogs.technet.microsoft.com/filecab/2006/11/07/disabling-last-access-time-in-windows-vista-to-improve-ntfs-performance

This means on Windows, cache files are currently being pruned from
creation time. This change manually updates cache files that are
accessed by ThinLTO, when on Windows.

Patch by Owen Reynolds.

Differential Revision: https://reviews.llvm.org/D47266

llvm-svn: 336276
2018-07-04 14:17:10 +00:00
Fangrui Song 5e4ca9fc9f [Support] Remove SaveOr which is no longer used
llvm-svn: 336237
2018-07-03 23:31:19 +00:00
Chandler Carruth 7f3feec6bb [ADT] Disable the single callback optimization on Windows.
It appears that the function pointer we use there isn't reliably 4-byte
aligned. I have no idea why or how we could correct this, so for now we
just regress the Windows performance some.

Someone with access to Windows could try working on a fix. At the very
least we could use a double indirection rather than a table, but maybe
there is some way to fully restore this optimization. I don't want to
play too much with this when I don't have access to the platform and
this at least should restore the last bots.

llvm-svn: 336178
2018-07-03 08:19:10 +00:00
Chandler Carruth 83e5f81d26 [ADT] Try to work around a crash in MSVC.
Putting `sizeof(T) <= 16` into the parameter of a `std::conditional`
causes every version of MSVC I've tried to crash:

  https://godbolt.org/g/eqVULL

Really frustrating, but an extra layer of indirection through an
instantiated type gives a working way to access this computed constant.

llvm-svn: 336170
2018-07-03 05:46:20 +00:00
Chandler Carruth dc62c17dd6 [ADT] Switch another place to `llvm::is_trivially_move_constructible`.
I missed this the first time around, sorry.

llvm-svn: 336166
2018-07-03 04:07:26 +00:00
Jakub Kuderski 5e3ab7a940 Reappl "[Dominators] Add the DomTreeUpdater class"
Summary:
This patch is the first in a series of patches related to the [[ http://lists.llvm.org/pipermail/llvm-dev/2018-June/123883.html | RFC - A new dominator tree updater for LLVM ]].

This patch introduces the DomTreeUpdater class, which provides a cleaner API to perform updates on available dominator trees (none, only DomTree, only PostDomTree, both) using different update strategies (eagerly or lazily) to simplify the updating process.

—Prior to the patch—

   - Directly calling update functions of DominatorTree updates the data structure eagerly while DeferredDominance does updates lazily.
   - DeferredDominance class cannot be used when a PostDominatorTree also needs to be updated.
   - Functions receiving DT/DDT need to branch a lot which is currently necessary.
   - Functions using both DomTree and PostDomTree need to call the update function separately on both trees.
   - People need to construct an additional DeferredDominance class to use functions only receiving DDT.

—After the patch—

Patch by Chijun Sima <simachijun@gmail.com>.

Reviewers: kuhar, brzycki, dmgreen, grosser, davide

Reviewed By: kuhar, brzycki

Author: NutshellySima

Subscribers: vsk, mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D48383

llvm-svn: 336163
2018-07-03 02:06:23 +00:00
Chandler Carruth f814ad8932 [Support] Fix llvm::unique_function when building with GCC 4.9 by
introducing llvm::trivially_{copy,move}_constructible type traits.

This uses a completely portable implementation of these traits provided
by Richard Smith. You can see it on compiler explorer in all its glory:

  https://godbolt.org/g/QEDZjW

I have transcribed it, clang-formatted it, added some comments, and made
the tests fit into a unittest file.

I have also switched llvm::unique_function over to use these new, much
more portable traits. =D

Hopefully this will fix the build bot breakage from my prior commit.

llvm-svn: 336161
2018-07-03 01:18:21 +00:00
Chandler Carruth aa60b3fd87 [ADT] Add llvm::unique_function which is like std::function but
supporting move-only closures.

Most of the core optimizations for std::function are here plus
a potentially novel one that detects trivially movable and destroyable
functors and implements those with fewer indirections.

This is especially useful as we start trying to add concurrency
primitives as those often end up with move-only types (futures,
promises, etc) and wanting them to work through lambdas.

As further work, we could add better support for things like const-qualified
operator()s to support more algorithms, and r-value ref qualified operator()s
to model call-once. None of that is here though.

We can also provide our own llvm::function that has some of the optimizations
used in this class, but with copy semantics instead of move semantics.

This is motivated by increasing usage of things like executors and the task
queue where it is useful to embed move-only types like a std::promise within
a type erased function. That isn't possible without this version of a type
erased function.

Differential Revision: https://reviews.llvm.org/D48349

llvm-svn: 336156
2018-07-02 23:57:29 +00:00
Francis Visoiu Mistrih 4d5b1073ba [MC] Error on a .zerofill directive in a non-virtual section
On darwin, all virtual sections have zerofill type, and having a
.zerofill directive in a non-virtual section is not allowed. Instead of
asserting, show a nicer error.

In order to use the equivalent of .zerofill in a non-virtual section,
the usage of .zero of .space is required.

This patch replaces the assert with an error.

Differential Revision: https://reviews.llvm.org/D48517

llvm-svn: 336127
2018-07-02 17:29:43 +00:00
Jakub Kuderski 198f3b16dc Revert "[Dominators] Add the DomTreeUpdater class"
Temporary revert because of a failing test on some buildbots.

This reverts commit r336114.

llvm-svn: 336117
2018-07-02 16:10:49 +00:00
Sjoerd Meijer b0004b834b Follow up of r335953 - [ARM][AArch64] Armv8.4-A Enablement
Imply dotprod for armv8.4-a, because it is mandatory from v8.4.

llvm-svn: 336115
2018-07-02 15:38:37 +00:00