Commit Graph

42 Commits

Author SHA1 Message Date
Thomas Lively ca9ba76481 [WebAssembly] Replace all calls with generalized multivalue calls
Summary:
Extends the multivalue call infrastructure to tail calls, removes all
legacy calls specialized for particular result types, and removes the
CallIndirectFixup pass, since all indirect call arguments are now
fixed up directly in the post-insertion hook.

In order to keep supporting pretty-printed defs and uses in test
expectations, MCInstLower now inserts an immediate containing the
number of defs for each call and call_indirect. The InstPrinter is
updated to query this immediate if it is present and determine which
MCOperands are defs and uses accordingly.

Depends on D72902.

Reviewers: aheejin

Subscribers: dschuff, mgorny, sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74192
2020-02-18 15:55:20 -08:00
Thomas Lively d51910967f Reland "[WebAssembly] Split and recombine multivalue calls for ISel"
This reverts commit 8acedb595d and
relands a prerequisite for the patch series culminating in
https://reviews.llvm.org/D74192.
2020-02-18 13:49:46 -08:00
Thomas Lively 7b64a59060 Reland "[WebAssembly][InstrEmitter] Foundation for multivalue call lowering"
This reverts commit 649aba93a2, now that
the approach started there has been shown to be workable in the patch
series culminating in https://reviews.llvm.org/D74192.
2020-02-18 13:49:46 -08:00
Thomas Lively 649aba93a2 Revert "[WebAssembly][InstrEmitter] Foundation for multivalue call lowering"
Summary:
This reverts commit 3ef169e586. The
purpose of this commit was to allow stack machines to perform
instruction selection for instructions with variadic defs. However,
MachineInstrs fundamentally cannot support variadic defs right now, so
this change does not turn out to be useful.

Depends on D73927.

Reviewers: aheejin

Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73928
2020-02-04 20:04:59 -08:00
Thomas Lively 8acedb595d Revert "[WebAssembly] Split and recombine multivalue calls for ISel"
Summary:
This reverts commit 28857d14a8. This
commit worked toward a solution that did not turn out to be feasible
because MachineInstrs cannot contain an arbitrary number of defs.

Reviewers: aheejin

Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73927
2020-02-04 18:46:43 -08:00
Thomas Lively 28857d14a8 [WebAssembly] Split and recombine multivalue calls for ISel
Summary:
Multivalue calls both take and return an arbitrary number of
arguments, but ISel only supports one or the other in a single
instruction. To get around this, calls are modeled as two pseudo
instructions during ISel. These pseudo instructions, CALL_PARAMS and
CALL_RESULTS, are recombined into a single CALL MachineInstr in a
custom emit hook.

RegStackification and the MC layer will additionally need to be made
aware of multivalue calls before the tests will produce correct
output.

Reviewers: aheejin, dschuff

Subscribers: sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71496
2020-01-21 11:31:33 -08:00
Thomas Lively 3ef169e586 [WebAssembly][InstrEmitter] Foundation for multivalue call lowering
Summary:
WebAssembly is unique among upstream targets in that it does not at
any point use physical registers to store values. Instead, it uses
virtual registers to model positions in its value stack. This means
that some target-independent lowering activities that would use
physical registers need to use virtual registers instead for
WebAssembly and similar downstream targets. This CL generalizes the
existing `usesPhysRegsForPEI` lowering hook to
`usesPhysRegsForValues` in preparation for using it in more places.

One such place is in InstrEmitter for instructions that have variadic
defs. On register machines, it only makes sense for these defs to be
physical registers, but for WebAssembly they must be virtual registers
like any other values. This CL changes InstrEmitter to check the new
target lowering hook to determine whether variadic defs should be
physical or virtual registers.

These changes are necessary to support a generalized CALL instruction
for WebAssembly that is capable of returning an arbitrary number of
arguments. Fully implementing that instruction will require additional
changes that are described in comments here but left for a follow up
commit.

Reviewers: aheejin, dschuff, qcolombet

Subscribers: sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71484
2020-01-21 11:13:46 -08:00
Fangrui Song 5edb40c022 [SelectionDAG] Disallow indirect "i" constraint
This allows us to delete InlineAsm::Constraint_i workarounds in
SelectionDAGISel::SelectInlineAsmMemoryOperand overrides and
TargetLowering::getInlineAsmMemConstraint overrides.

They were introduced to X86 in r237517 to prevent crashes for
constraints like "=*imr". They were later copied to other targets.
2019-12-29 16:50:42 -08:00
Reid Kleckner 5d986953c8 [IR] Split out target specific intrinsic enums into separate headers
This has two main effects:
- Optimizes debug info size by saving 221.86 MB of obj file size in a
  Windows optimized+debug build of 'all'. This is 3.03% of 7,332.7MB of
  object file size.
- Incremental step towards decoupling target intrinsics.

The enums are still compact, so adding and removing a single
target-specific intrinsic will trigger a rebuild of all of LLVM.
Assigning distinct target id spaces is potential future work.

Part of PR34259

Reviewers: efriedma, echristo, MaskRay

Reviewed By: echristo, MaskRay

Differential Revision: https://reviews.llvm.org/D71320
2019-12-11 18:02:14 -08:00
Hiroshi Yamauchi 70a3c9f55f [WebAssembly][SelectionDAG] Remove unused WebAssemblyDAGToDAGISel::ForCodeSize.
Summary:
This follows from the discussion at D70095.

D70095 moves hasOptSize calls into SelectionDAG::shouldOptForSize to allow
querying size optimization conditions together with profile guided size
optimization.

Since it appears that size optimizations for WebAssembly SelectionDAG haven't
been implemented yet and thus ForCodeSize is unused, and it would not make a lot
of sense to call shouldOptForSize here as the necessary profile data like
PSI/BFI aren't available at this point, it seems good and less confusing to
remove this for now and use shouldOptForSize when they are implemented in the
future.

Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, aheejin, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70567
2019-11-22 09:00:23 -08:00
Thomas Lively 5b74c39d72 [WebAssembly] Error when using wasm64 for ISel
Summary:
64-bit WebAssembly (wasm64) is not specified and not supported in the
WebAssembly backend. We do have support for it in clang, however, and
we would like to keep that support because we expect wasm64 to be
specified and supported in the future. For now add an error when
trying to use wasm64 from the backend to minimize user confusion from
unexplained crashes.

Reviewers: aheejin, dschuff, sunfish

Subscribers: sbc100, jgravelle-google, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68254

llvm-svn: 373493
2019-10-02 17:34:44 +00:00
Heejin Ahn d85fd5a3f4 [WebAssembly] Add atomic.fence instruction
Summary:
This adds `atomic.fence` instruction:
https://github.com/WebAssembly/threads/blob/master/proposals/threads/Overview.md#fence-operator

And we now emit the new `atomic.fence` instruction for multithread
fences, rather than the prevous `atomic.rmw` hack.

Reviewers: dschuff

Subscribers: sbc100, jgravelle-google, hiraditya, sunfish, jfb, tlively, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66794

llvm-svn: 370272
2019-08-28 23:13:43 +00:00
Guanzhong Chen 5204f7611f [WebAssembly] Compute and export TLS block alignment
Summary:
Add immutable WASM global `__tls_align` which stores the alignment
requirements of the TLS segment.

Add `__builtin_wasm_tls_align()` intrinsic to get this alignment in Clang.

The expected usage has now changed to:

    __wasm_init_tls(memalign(__builtin_wasm_tls_align(),
                             __builtin_wasm_tls_size()));

Reviewers: tlively, aheejin, sbc100, sunfish, alexcrichton

Reviewed By: tlively

Subscribers: dschuff, jgravelle-google, hiraditya, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D65028

llvm-svn: 366624
2019-07-19 23:34:16 +00:00
Guanzhong Chen df4479200b [WebAssembly] Fix __builtin_wasm_tls_base intrinsic
Summary:
Properly generate the outchain for the `__builtin_wasm_tls_base` intrinsic.

Also marked the intrinsic pure, per @sunfish's suggestion.

Reviewers: tlively, aheejin, sbc100, sunfish

Reviewed By: tlively

Subscribers: dschuff, jgravelle-google, hiraditya, cfe-commits, llvm-commits, sunfish

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D64949

llvm-svn: 366499
2019-07-18 21:17:52 +00:00
Guanzhong Chen 801fa8e6b9 [WebAssembly] Implement __builtin_wasm_tls_base intrinsic
Summary:
Add `__builtin_wasm_tls_base` so that LeakSanitizer can find the thread-local
block and scan through it for memory leaks.

Reviewers: tlively, aheejin, sbc100

Subscribers: dschuff, jgravelle-google, hiraditya, sunfish, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D64900

llvm-svn: 366475
2019-07-18 17:53:22 +00:00
Guanzhong Chen 0a8d4df799 [WebAssembly] Compile all TLS on Emscripten as local-exec
Summary:
Currently, on Emscripten, dynamic linking is not supported with threads.
This means that if thread-local storage is used, it must be used in a
statically-linked executable. Hence, local-exec is the only possible model.

This diff compiles all TLS variables to use local-exec on Emscripten as a
temporary measure until dynamic linking is supported with threads.

The goal for this is to allow C++ types with constructors to be thread-local.

Currently, when `clang` compiles a `thread_local` variable with a constructor,
it generates `__tls_guard` variable:

    @__tls_guard = internal thread_local global i8 0, align 1

As no TLS model is specified, this is treated as general-dynamic, which we do
not support (and cannot support without implementing dynamic linking support
with threads in Emscripten). As a result, any C++ constructor in `thread_local`
variables would not compile.

By compiling all `thread_local` as local-exec, `__tls_guard` will compile and
we can support C++ constructors with TLS without implementing dynamic linking
with threads.

Depends on D64537

Reviewers: tlively, aheejin, sbc100

Reviewed By: aheejin

Subscribers: dschuff, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64776

llvm-svn: 366275
2019-07-16 22:22:08 +00:00
Guanzhong Chen 42bba4b852 [WebAssembly] Implement thread-local storage (local-exec model)
Summary:
Thread local variables are placed inside a `.tdata` segment. Their symbols are
offsets from the start of the segment. The address of a thread local variable
is computed as `__tls_base` + the offset from the start of the segment.

`.tdata` segment is a passive segment and `memory.init` is used once per thread
to initialize the thread local storage.

`__tls_base` is a wasm global. Since each thread has its own wasm instance,
it is effectively thread local. Currently, `__tls_base` must be initialized
at thread startup, and so cannot be used with dynamic libraries.

`__tls_base` is to be initialized with a new linker-synthesized function,
`__wasm_init_tls`, which takes as an argument a block of memory to use as the
storage for thread locals. It then initializes the block of memory and sets
`__tls_base`. As `__wasm_init_tls` will handle the memory initialization,
the memory does not have to be zeroed.

To help allocating memory for thread-local storage, a new compiler intrinsic
is introduced: `__builtin_wasm_tls_size()`. This instrinsic function returns
the size of the thread-local storage for the current function.

The expected usage is to run something like the following upon thread startup:

    __wasm_init_tls(malloc(__builtin_wasm_tls_size()));

Reviewers: tlively, aheejin, kripken, sbc100

Subscribers: dschuff, jgravelle-google, hiraditya, sunfish, jfb, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D64537

llvm-svn: 366272
2019-07-16 22:00:45 +00:00
Heejin Ahn 5514658591 [WebAssembly] Support for atomic fences
Summary:
This adds support for translation of LLVM IR fence instruction. We
convert a singlethread fence to a pseudo compiler barrier which becomes
0 instructions in final binary, and a thread fence to an idempotent
atomicrmw instruction to a memory address.

Reviewers: dschuff, jfb, sunfish, tlively

Subscribers: sbc100, jgravelle-google, llvm-commits

Differential Revision: https://reviews.llvm.org/D50277

llvm-svn: 361884
2019-05-28 22:09:12 +00:00
Heejin Ahn 5f3a04510a [WebAssembly] Use Function::hasOptSize() (NFC)
Summary: Use member function.

Reviewers: aheejin

Subscribers: sunfish, hiraditya, sbc100, jgravelle-google, dschuff, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60651

Patch by Hideto Ueno (uenoku)

llvm-svn: 358336
2019-04-13 16:54:39 +00:00
Heejin Ahn 18c56a0762 [WebAssembly] clang-tidy (NFC)
Summary:
This patch fixes clang-tidy warnings on wasm-only files.
The list of checks used is:
`-*,clang-diagnostic-*,llvm-*,misc-*,-misc-unused-parameters,readability-identifier-naming,modernize-*`
(LLVM's default .clang-tidy list is the same except it does not have
`modernize-*`. But I've seen in multiple CLs in LLVM the modernize style
was recommended and code was fixed based on the style, so I added it as
well.)

The common fixes are:
- Variable names start with an uppercase letter
- Function names start with a lowercase letter
- Use `auto` when you use casts so the type is evident
- Use inline initialization for class member variables
- Use `= default` for empty constructors / destructors
- Use `using` in place of `typedef`

Reviewers: sbc100, tlively, aardappel

Subscribers: dschuff, sunfish, jgravelle-google, yurydelendik, kripken, MatzeB, mgorny, rupprecht, llvm-commits

Differential Revision: https://reviews.llvm.org/D57500

llvm-svn: 353075
2019-02-04 19:13:39 +00:00
Chandler Carruth 2946cd7010 Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636
2019-01-19 08:50:56 +00:00
Thomas Lively 64a39a1c4e [WebAssembly] Add unimplemented-simd128 subtarget feature
Summary:
This is a third attempt, but this time we have vetted it on Windows
first. The previous errors were due to an uninitialized class member.

Reviewers: aheejin

Subscribers: dschuff, sbc100, jgravelle-google, sunfish, jfb, llvm-commits

Differential Revision: https://reviews.llvm.org/D56560

llvm-svn: 350901
2019-01-10 22:32:11 +00:00
Thomas Lively fdd4999b86 Revert "[WebAssembly] Add simd128-unimplemented subtarget feature"
This reverts rL350791.

llvm-svn: 350795
2019-01-10 04:09:25 +00:00
Thomas Lively eb6f9abd41 [WebAssembly] Add simd128-unimplemented subtarget feature
This is a second attempt at r350778, which was reverted in
r350789. The only change is that the unimplemented-simd128 feature has
been renamed simd128-unimplemented, since naming it
unimplemented-simd128 somehow made the simd128 feature flag enable the
unimplemented-simd128 feature on Windows.

llvm-svn: 350791
2019-01-10 02:55:52 +00:00
Thomas Lively fdca5fab60 Revert "[WebAssembly] Add unimplemented-simd128 subtarget feature"
This reverts L350778.

llvm-svn: 350789
2019-01-10 01:37:44 +00:00
Thomas Lively 2eeade1814 [WebAssembly] Add unimplemented-simd128 subtarget feature
Summary:
This replaces the old ad-hoc -wasm-enable-unimplemented-simd
flag. Also makes the new unimplemented-simd128 feature imply the
simd128 feature.

Reviewers: aheejin, dschuff

Subscribers: sbc100, jgravelle-google, sunfish, llvm-commits, alexcrichton

Differential Revision: https://reviews.llvm.org/D56501

llvm-svn: 350778
2019-01-09 23:59:37 +00:00
Heejin Ahn 569f090922 [WebAssembly] Print a debug message at the start of each pass
Summary:
Looks like many passes print its pass description as a debug message at
the start of each pass, so added that to (mostly newly added) other
passes as well.

Reviewers: dschuff

Subscribers: jgravelle-google, sbc100, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D56142

llvm-svn: 350771
2019-01-09 23:05:21 +00:00
Thomas Lively 8dbf29af95 [WebAssembly] Gate unimplemented SIMD ops on flag
Summary:
Gates v128.const, f32x4.sqrt, f32x4.div, i8x16.extract_lane_u, and
i16x8.extract_lane_u on the --wasm-enable-unimplemented-simd flag,
since these ops are not implemented yet in V8.

Reviewers: aheejin, dschuff

Subscribers: sbc100, jgravelle-google, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D55904

llvm-svn: 349720
2018-12-20 02:10:22 +00:00
Heejin Ahn a86152d0a7 [WebAssembly] Comment out a switch block in ISelDAGToDAG
Summary: Fixes PR37977.

Reviewers: RKSimon

Subscribers: dschuff, sbc100, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D48737

llvm-svn: 336017
2018-06-29 21:19:22 +00:00
Nicola Zaghen d34e60ca85 Rename DEBUG macro to LLVM_DEBUG.
The DEBUG() macro is very generic so it might clash with other projects.
The renaming was done as follows:
- git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g'
- git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM
- Manual change to APInt
- Manually chage DOCS as regex doesn't match it.

In the transition period the DEBUG() macro is still present and aliased
to the LLVM_DEBUG() one.

Differential Revision: https://reviews.llvm.org/D43624

llvm-svn: 332240
2018-05-14 12:53:11 +00:00
Adrian Prantl 5f8f34e459 Remove \brief commands from doxygen comments.
We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they are a visual distraction and we don't want to
encourage more \brief markers in new code either, this patch removes
them all.

Patch produced by

  for i in $(git grep -l '\\brief'); do perl -pi -e 's/\\brief //g' $i & done

Differential Revision: https://reviews.llvm.org/D46290

llvm-svn: 331272
2018-05-01 15:54:18 +00:00
Craig Topper 8f324bb1a4 [SelectionDAGISel] Add a debug print before call to Select. Adjust where blank lines are printed during isel process to make things more sensibly grouped.
Previously some targets printed their own message at the start of Select to indicate what they were selecting. For the targets that didn't, it means there was no print of the root node before any custom handling in the target executed. So if the target did something custom and never called SelectNodeCommon, no print would be made. For the targets that did print a message in Select, if they didn't custom handle a node SelectNodeCommon would reprint the root node before walking the isel table.

It seems better to just print the message before the call to Select so all targets behave the same. And then remove the root node printing from SelectNodeCommon and just leave a message that says we're starting the table search.

There were also some oddities in blank line behavior. Usually due to a \n after a call to SelectionDAGNode::dump which already inserted a new line.

llvm-svn: 323551
2018-01-26 19:34:20 +00:00
David Blaikie 2110924909 Fix WebAssembly backend for some LLVM API changes
llvm-svn: 320893
2017-12-15 23:52:06 +00:00
Chandler Carruth 6bda14b313 Sort the remaining #include lines in include/... and lib/....
I did this a long time ago with a janky python script, but now
clang-format has built-in support for this. I fed clang-format every
line with a #include and let it re-sort things according to the precise
LLVM rules for include ordering baked into clang-format these days.

I've reverted a number of files where the results of sorting includes
isn't healthy. Either places where we have legacy code relying on
particular include ordering (where possible, I'll fix these separately)
or where we have particular formatting around #include lines that
I didn't want to disturb in this patch.

This patch is *entirely* mechanical. If you get merge conflicts or
anything, just ignore the changes in this patch and run clang-format
over your #include lines in the files.

Sorry for any noise here, but it is important to keep these things
stable. I was seeing an increasing number of patches with irrelevant
re-ordering of #include lines because clang-format was used. This patch
at least isolates that churn, makes it easy to skip when resolving
conflicts, and gets us to a clean baseline (again).

llvm-svn: 304787
2017-06-06 11:49:48 +00:00
Craig Topper 053cf4da9d [WebAssembly] Update calls to computeKnownBits after the changes from r301620.
I didn't realize WebAssembly wasn't a default build target so I missed that changes were needed.

llvm-svn: 301629
2017-04-28 08:15:33 +00:00
Mehdi Amini 117296c0a0 Use StringRef in Pass/PassManager APIs (NFC)
llvm-svn: 283004
2016-10-01 02:56:57 +00:00
Justin Bogner c6afd4bb36 SDAG: Implement Select instead of SelectImpl in WebAssemblyDAGToDAGISel
This backend doesn't do anything custom here yet, so we just modernize
the boilerplate.

Part of llvm.org/pr26808.

llvm-svn: 269506
2016-05-13 22:44:57 +00:00
Justin Bogner b012699741 SDAG: Rename Select->SelectImpl and repurpose Select as returning void
This is a step towards removing the rampant undefined behaviour in
SelectionDAG, which is a part of llvm.org/PR26808.

We rename SelectionDAGISel::Select to SelectImpl and update targets to
match, and then change Select to return void and consolidate the
sketchy behaviour we're trying to get away from there.

Next, we'll update backends to implement `void Select(...)` instead of
SelectImpl and eventually drop the base Select implementation.

llvm-svn: 268693
2016-05-05 23:19:08 +00:00
Dan Gohman 9c54d3b4c6 [WebAssembly] Clean up several FIXME comments.
llvm-svn: 254079
2015-11-25 18:13:18 +00:00
Dan Gohman f19ed56288 [WebAssembly] Inline asm support.
llvm-svn: 252997
2015-11-13 01:42:29 +00:00
JF Bastien b9073fb20a WebAssembly: basic bitcode → assembly CodeGen test
Summary:
Add a basic CodeGen bitcode test which (for now) only prints out the function name and nothing else. The current code merely implements the basic needed for the test run to not crash / assert. Getting to that point required:

 - Basic InstPrinter.
 - Basic AsmPrinter.
 - DiagnosticInfoUnsupported (not strictly required, but nice to have, duplicated from AMDGPU/BPF's ISelLowering).
 - Some SP and register setup in WebAssemblyTargetLowering.
 - Basic LowerFormalArguments.
 - GenInstrInfo.
 - Placeholder LowerFormalArguments.
 - Placeholder CanLowerReturn and LowerReturn.
 - Basic DAGToDAGISel::Select, which requiresGenDAGISel.inc as well as GET_INSTRINFO_ENUM with GenInstrInfo.inc.
 - Remove WebAssemblyFrameLowering::determineCalleeSaves and rely on default.
 - Implement WebAssemblyFrameLowering::hasFP, same as AArch64's implementation.

Follow-up patches will implement a real AsmPrinter, which will require adding MI opcodes specific to WebAssembly.

Reviewers: sunfish

Subscribers: aemerson, jfb, llvm-commits

Differential Revision: http://reviews.llvm.org/D11369

llvm-svn: 242939
2015-07-22 21:28:15 +00:00
Dan Gohman 10e730a263 [WebAssembly] Initial WebAssembly backend
This WebAssembly backend is just a skeleton at this time and is not yet
functional.

llvm-svn: 241022
2015-06-29 23:51:55 +00:00