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30028 Commits

Author SHA1 Message Date
Matt Arsenault
1ad1497bb5 DAG: Handle dbg_value for arguments split into multiple subregs
This was handled previously for arguments split due to not fitting in
an MVT. This was dropping the register for argument registers split
due to TLI::getRegisterTypeForCallingConv.

llvm-svn: 366574
2019-07-19 13:36:46 +00:00
Kai Luo
aa4508e98a [MachineCSE][MachinePRE] Avoid hoisting code from code regions into hot BBs.
Summary:
Current PRE hoists common computations into
CMBB = DT->findNearestCommonDominator(MBB, MBB1).
However, if CMBB is in a hot loop body, we might get performance
degradation.

Differential Revision: https://reviews.llvm.org/D64394

llvm-svn: 366570
2019-07-19 12:58:16 +00:00
Than McIntosh
fb3f89d50d [X86] for split stack, not save/restore nested arg if unused
Summary:
For split-stack, if the nested argument (i.e. R10) is not used, no need to save/restore it in the prologue.

Reviewers: thanm

Reviewed By: thanm

Subscribers: mstorsjo, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64673

llvm-svn: 366569
2019-07-19 12:54:44 +00:00
Oliver Stannard
5b6f9348e5 Don't update NoTrappingFPMath and FPDenormalMode in resetTargetOptions
We'd like to remove this whole function, because these are properties of
functions, not the target as a whole. These two are easy to remove
because they are only used for emitting ARM build attributes, which
expects them to represent the defaults for the whole module, not just
the last function generated.

This is needed to get correct build attributes when using IPRA on ARM,
because IPRA causes resetTargetOptions to get called before
ARMAsmPrinter::emitAttributes.

Differential revision: https://reviews.llvm.org/D64929

llvm-svn: 366562
2019-07-19 10:37:37 +00:00
Oliver Stannard
1900a7e6ef [IPRA] Don't rely on non-exact function definitions
If a function definition is not exact, then the linker could select a
differently-compiled version of it, which could use different registers.

https://reviews.llvm.org/D64909

llvm-svn: 366557
2019-07-19 09:59:26 +00:00
Jay Foad
70edc47b65 [AMDGPU] Simplify the exclusive scan used for optimized atomics
Summary:
Change the scan algorithm to use only power-of-two shifts (1, 2, 4, 8,
16, 32) instead of starting off shifting by 1, 2 and 3 and then doing
a 3-way ADD, because:

1. It simplifies the compiler a little.
2. It minimizes vgpr pressure because each instruction is now of the
   form vn = vn + vn << c.
3. It is more friendly to the DPP combiner, which currently can't
   combine into an ADD3 instruction.

Because of #2 and #3 the end result is improved from this:

  v_add_u32_dpp v4, v3, v3  row_shr:1 row_mask:0xf bank_mask:0xf bound_ctrl:0
  v_mov_b32_dpp v5, v3  row_shr:2 row_mask:0xf bank_mask:0xf
  v_mov_b32_dpp v1, v3  row_shr:3 row_mask:0xf bank_mask:0xf
  v_add3_u32 v1, v4, v5, v1
  s_nop 1
  v_add_u32_dpp v1, v1, v1  row_shr:4 row_mask:0xf bank_mask:0xe
  s_nop 1
  v_add_u32_dpp v1, v1, v1  row_shr:8 row_mask:0xf bank_mask:0xc
  s_nop 1
  v_add_u32_dpp v1, v1, v1  row_bcast:15 row_mask:0xa bank_mask:0xf
  s_nop 1
  v_add_u32_dpp v1, v1, v1  row_bcast:31 row_mask:0xc bank_mask:0xf

To this:

  v_add_u32_dpp v1, v1, v1  row_shr:1 row_mask:0xf bank_mask:0xf bound_ctrl:0
  s_nop 1
  v_add_u32_dpp v1, v1, v1  row_shr:2 row_mask:0xf bank_mask:0xf bound_ctrl:0
  s_nop 1
  v_add_u32_dpp v1, v1, v1  row_shr:4 row_mask:0xf bank_mask:0xe
  s_nop 1
  v_add_u32_dpp v1, v1, v1  row_shr:8 row_mask:0xf bank_mask:0xc
  s_nop 1
  v_add_u32_dpp v1, v1, v1  row_bcast:15 row_mask:0xa bank_mask:0xf
  s_nop 1
  v_add_u32_dpp v1, v1, v1  row_bcast:31 row_mask:0xc bank_mask:0xf

I.e. two fewer computational instructions, one extra nop where we could
schedule something else.

Reviewers: arsenm, sheredom, critson, rampitec, vpykhtin

Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64411

llvm-svn: 366543
2019-07-19 08:40:37 +00:00
Kang Zhang
cba82396ee [NFC][PowerPC] Modify the test case add_cmp.ll
llvm-svn: 366526
2019-07-19 02:23:26 +00:00
Hsiangkai Wang
fc3df54f27 [DebugInfo] Generate fixups as emitting DWARF .debug_frame/.eh_frame.
It is necessary to generate fixups in .debug_frame or .eh_frame as
relaxation is enabled due to the address delta may be changed after
relaxation.

There is an opcode with 6-bits data in debug frame encoding. So, we
also need 6-bits fixup types.

Differential Revision: https://reviews.llvm.org/D58335

llvm-svn: 366524
2019-07-19 02:03:34 +00:00
Bill Wendling
249f10d605 Use the MachineBasicBlock symbol for a callbr target
Summary:
Inline asm doesn't use labels when compiled as an object file. Therefore, we
shouldn't create one for the (potential) callbr destination. Instead, use the
symbol for the MachineBasicBlock.

Reviewers: nickdesaulniers, craig.topper

Reviewed By: nickdesaulniers

Subscribers: xbolva00, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64888

llvm-svn: 366523
2019-07-19 01:10:28 +00:00
Amara Emerson
00955b788c [GlobalISel] Translate calls to memcpy et al to G_INTRINSIC_W_SIDE_EFFECTs and legalize later.
I plan on adding memcpy optimizations in the GlobalISel pipeline, but we can't
do that unless we delay lowering to actual function calls. This patch changes
the translator to generate G_INTRINSIC_W_SIDE_EFFECTS for these functions, and
then have each target specify that using the new custom legalizer for intrinsics
hook that they want it expanded it a libcall.

Differential Revision: https://reviews.llvm.org/D64895

llvm-svn: 366516
2019-07-19 00:24:45 +00:00
Jessica Paquette
1ca6c316ea [GlobalISel][AArch64] Add support for base register + offset register loads
Add support for folding G_GEPs into loads of the form

```
ldr reg, [base, off]
```

when possible. This can save an add before the load. Currently, this is only
supported for loads of 64 bits into 64 bit registers.

Add a new addressing mode function, `selectAddrModeRegisterOffset` which
performs this folding when it is profitable.

Also add a test for addressing modes for G_LOAD.

Differential Revision: https://reviews.llvm.org/D64944

llvm-svn: 366503
2019-07-18 21:50:11 +00:00
Peter Collingbourne
658ff0579c CodeGen: Allow !associated metadata to point to aliases.
This is a small extension of !associated, mostly useful for the implementation
convenience of instrumentation passes that RAUW globals with aliases, such
as LowerTypeTests.

Differential Revision: https://reviews.llvm.org/D64951

llvm-svn: 366502
2019-07-18 21:37:16 +00:00
Reid Kleckner
8fbcf61f43 Revert [X86] EltsFromConsecutiveLoads - support common source loads
This reverts r366441 (git commit 48104ef7c9c653bbb732b66d7254957389fea337)

This causes clang to fail to compile some file in Skia. Reduction soon.

llvm-svn: 366501
2019-07-18 21:26:41 +00:00
Guanzhong Chen
23d1b51c00 [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
Peter Collingbourne
f86f6b7dee IR: Teach Constant::needsRelocation() that relative pointers don't need to be relocated.
This causes sections with relative pointers to be marked as read only,
which means that they won't end up sharing pages with writable data.

Differential Revision: https://reviews.llvm.org/D64948

llvm-svn: 366494
2019-07-18 20:56:21 +00:00
Guanzhong Chen
06b4c69d40 [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
Hsiangkai Wang
8690bbfb57 Revert "[DebugInfo] Generate fixups as emitting DWARF .debug_frame/.eh_frame."
This reverts commit 17e3cbf5fe656483d9016d0ba9e1d0cd8629379e.

llvm-svn: 366444
2019-07-18 15:06:50 +00:00
Hsiangkai Wang
945bcd9b26 [DebugInfo] Generate fixups as emitting DWARF .debug_frame/.eh_frame.
It is necessary to generate fixups in .debug_frame or .eh_frame as
relaxation is enabled due to the address delta may be changed after
relaxation.

There is an opcode with 6-bits data in debug frame encoding. So, we
also need 6-bits fixup types.

Differential Revision: https://reviews.llvm.org/D58335

llvm-svn: 366442
2019-07-18 14:47:34 +00:00
Simon Pilgrim
d2a4d69930 [X86] EltsFromConsecutiveLoads - support common source loads
This patch enables us to find the source loads for each element, splitting them into a Load and ByteOffset, and attempts to recognise consecutive loads that are in fact from the same source load.

A helper function, findEltLoadSrc, recurses to find a LoadSDNode and determines the element's byte offset within it. When attempting to match consecutive loads, byte offsetted loads then attempt to matched against a previous load that has already been confirmed to be a consecutive match.

Next step towards PR16739 - after this we just need to account for shuffling/repeated elements to create a vector load + shuffle.

Differential Revision: https://reviews.llvm.org/D64551

llvm-svn: 366441
2019-07-18 14:33:25 +00:00
Sanjay Patel
f84fc5ad12 [x86] try harder to form LEA from ADD to avoid flag conflicts (PR40483)
LEA doesn't affect flags, so use it more liberally to replace an ADD when
we know that the ADD operands affect flags.

In the motivating example from PR40483:
https://bugs.llvm.org/show_bug.cgi?id=40483
...this lets us avoid duplicating a math op just to avoid flag conflict.

As mentioned in the TODO comments, this heuristic can be extended to
fire more often if that leads to more improvements.

Differential Revision: https://reviews.llvm.org/D64707

llvm-svn: 366431
2019-07-18 12:48:01 +00:00
Diogo N. Sampaio
a08d5736a7 [ARM][DAGCOMBINE][FIX] PerformVMOVRRDCombine
Summary:
PerformVMOVRRDCombine ommits adding a offset
of 4 to the PointerInfo, when converting a
f64 = load[M]
to
{i32, i32} = {load[M], load[M + 4]}

Which would allow the machine scheduller
to break dependencies with the second load.

 - pr42638

Reviewers: eli.friedman, dmgreen, ostannard

Reviewed By: ostannard

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64870

llvm-svn: 366423
2019-07-18 10:05:56 +00:00
Kang Zhang
bc9f6c869b [NFC][PowerPC] Add the test to test the pass block-placement
llvm-svn: 366407
2019-07-18 06:56:49 +00:00
Craig Topper
48fa2fec03 [X86] Disable combineConcatVectors for vXi1 vectors.
I'm not convinced the code this calls is properly vetted for
vXi1 vectors. Experimental vector widening legalization testing
for D55251 is now hitting an assertion failure inside
EltsFromConsecutiveLoads. This is occurring from a v2i1 load
having a store size different than its VT size. Hopefully
this commit will keep such issues from happening.

llvm-svn: 366405
2019-07-18 06:18:06 +00:00
Philip Reames
6489953965 [Tests] Add a test showing how we handle overaligned allocas w/ no-realign-stack
(At the moment, we ignore the alignment requirement.)

llvm-svn: 366393
2019-07-18 00:26:03 +00:00
Craig Topper
40dd1346f3 [X86] Make sure we mark 128/256 MLOAD as Legal with VLX when min-legal-vector-width=256 is in effect.
This started triggering an assertion after r364718 when we made
these Custom under AVX2.

llvm-svn: 366382
2019-07-17 22:26:00 +00:00
Francis Visoiu Mistrih
4591f8af22 [PEI] Don't re-allocate a pre-allocated stack protector slot
The LocalStackSlotPass pre-allocates a stack protector and makes sure
that it comes before the local variables on the stack.

We need to make sure that later during PEI we don't re-allocate a new
stack protector slot. If that happens, the new stack protector slot will
end up being **after** the local variables that it should be protecting.

Therefore, we would have two slots assigned for two different stack
protectors, one at the top of the stack, and one at the bottom. Since
PEI will overwrite the assigned slot for the stack protector, the load
that is used to compare the value of the stack protector will use the
slot assigned by PEI, which is wrong.

For this, we need to check if the object is pre-allocated, and re-use
that pre-allocated slot.

Differential Revision: https://reviews.llvm.org/D64757

llvm-svn: 366371
2019-07-17 20:46:19 +00:00
Francis Visoiu Mistrih
652b9873ed [CodeGen] Add stack protector tests where the guard gets re-assigned
In preparation of a fix, add tests for multiple backends.

llvm-svn: 366370
2019-07-17 20:46:16 +00:00
Matt Arsenault
0c0bddc3d0 GlobalISel: Handle widenScalar of arbitrary G_MERGE_VALUES sources
Extract the sources to the GCD of the original size and target size,
padding with implicit_def as necessary.

Also fix the case where the requested source type is wider than the
original result type. This was ignoring the type, and just using the
destination. Do the operation in the requested type and truncate back.

llvm-svn: 366367
2019-07-17 20:22:44 +00:00
Matt Arsenault
5d75c7a2b6 GlobalISel: Handle more cases for widenScalar of G_MERGE_VALUES
Use an anyext to the requested type for the leftover operand to
produce a slightly wider type, and then truncate the final merge.

I have another implementation almost ready which handles arbitrary
widens, but I think it produces worse code in this example (which I
think is 90% due to not folding redundant copies or folding out
implicit_def users), so I wanted to add this as a baseline first.

llvm-svn: 366366
2019-07-17 20:22:38 +00:00
Evgeniy Stepanov
26f466be75 Basic MTE stack tagging instrumentation.
Summary:
Use MTE intrinsics to tag stack variables in functions with
sanitize_memtag attribute.

Reviewers: pcc, vitalybuka, hctim, ostannard

Subscribers: srhines, mgorny, javed.absar, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64173

llvm-svn: 366361
2019-07-17 19:24:12 +00:00
Evgeniy Stepanov
e010508942 Basic codegen for MTE stack tagging.
Implement IR intrinsics for stack tagging. Generated code is very
unoptimized for now.

Two special intrinsics, llvm.aarch64.irg.sp and llvm.aarch64.tagp are
used to implement a tagged stack frame pointer in a virtual register.

Differential Revision: https://reviews.llvm.org/D64172

llvm-svn: 366360
2019-07-17 19:24:02 +00:00
Momchil Velikov
d9da0d9f91 Revert [AArch64] Add support for Transactional Memory Extension (TME)
This reverts r366322 (git commit 4b8da3a503e434ddbc08ecf66582475765f449bc)

llvm-svn: 366355
2019-07-17 17:43:32 +00:00
Daniil Fukalov
63e1e9076b [AMDGPU] Tune inlining parameters for AMDGPU target
Summary:
Since the target has no significant advantage of vectorization,
vector instructions bous threshold bonus should be optional.

amdgpu-inline-arg-alloca-cost parameter default value and the target
InliningThresholdMultiplier value tuned then respectively.

Reviewers: arsenm, rampitec

Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, eraman, hiraditya, haicheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64642

llvm-svn: 366348
2019-07-17 16:51:29 +00:00
Matt Arsenault
26b8c36c13 AMDGPU: Use getTargetConstant
Avoids creating an extra intermediate mov.

llvm-svn: 366340
2019-07-17 15:35:36 +00:00
Alex Bradbury
40360466ab [RISCV][NFC] Remove outdated TODO from test/CodeGen/RISCV/dwarf-eh.ll
llvm-svn: 366330
2019-07-17 14:04:48 +00:00
Alex Bradbury
ee64434d8e [AsmPrinter] Make the encoding of call sites in .gcc_except_table configurable and use for RISC-V
The original behavior was to always emit the offsets to each call site in the
call site table as uleb128 values, however on some architectures (eg RISCV)
these uleb128 offsets into the code cannot always be resolved until link time
(because relaxation will invalidate any calculated offsets), and there are no
appropriate relocations for uleb128 values. As a consequence it needs to be
possible to specify an alternative.

This also switches RISCV to use DW_EH_PE_udata4 for call side encodings in
.gcc_except_table

Differential Revision: https://reviews.llvm.org/D63415
Patch by Edward Jones.

llvm-svn: 366329
2019-07-17 14:00:35 +00:00
Alex Bradbury
b167839943 [RISCV] Set correct encodings for DWARF exception handling
This patch sets correct encodings for DWARF exception handling for RISC-V
(other than call site encoding, which must be udata4 rather than uleb128 and
is handled by D63415).

This has the same intend as D63409, except this version matches GCC/binutils
behaviour which uses the same encodings regardless of PIC/non-PIC and
medlow/medany code model.

llvm-svn: 366327
2019-07-17 13:54:38 +00:00
Alex Bradbury
68d3ce72d2 [RISCV][NFC] Add tests that capture current encodings for DWARF EH
Items which are known to be wrong/different vs GCC are marked as TODO and will
be address in follow-up patches.

llvm-svn: 366326
2019-07-17 13:48:49 +00:00
Jay Foad
b05f60662f [AMDGPU] Optimize atomic AND/OR/XOR
Summary: Extend the atomic optimizer to handle AND, OR and XOR.

Reviewers: arsenm, sheredom

Subscribers: kzhuravl, jvesely, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, hiraditya, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64809

llvm-svn: 366323
2019-07-17 13:40:03 +00:00
Momchil Velikov
cdfc2797e3 [AArch64] Add support for Transactional Memory Extension (TME)
TME is a future architecture technology, documented in

https://developer.arm.com/architectures/cpu-architecture/a-profile/exploration-tools
https://developer.arm.com/docs/ddi0601/a

More about the future architectures:

https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/new-technologies-for-the-arm-a-profile-architecture

This patch adds support for the TME instructions TSTART, TTEST, TCOMMIT, and
TCANCEL and the target feature/arch extension "tme".

It also implements TME builtin functions, defined in ACLE Q2 2019
(https://developer.arm.com/docs/101028/latest)

Patch by Javed Absar and Momchil Velikov

Differential Revision: https://reviews.llvm.org/D64416

llvm-svn: 366322
2019-07-17 13:23:27 +00:00
Justin Hibbits
43d936c30c PowerPC/SPE: Fix load/store handling for SPE
Summary:
Pointed out in a comment for D49754, register spilling will currently
spill SPE registers at almost any offset.  However, the instructions
`evstdd` and `evldd` require a) 8-byte alignment, and b) a limit of 256
(unsigned) bytes from the base register, as the offset must fix into a
5-bit offset, which ranges from 0-31 (indexed in double-words).

The update to the register spill test is taken partially from the test
case shown in D49754.

Additionally, pointed out by Kei Thomsen, globals will currently use
evldd/evstdd, though the offset isn't known at compile time, so may
exceed the 8-bit (unsigned) offset permitted.  This fixes that as well,
by forcing it to always use evlddx/evstddx when accessing globals.

Part of the patch contributed by Kei Thomsen.

Reviewers: nemanjai, hfinkel, joerg

Subscribers: kbarton, jsji, llvm-commits

Differential Revision: https://reviews.llvm.org/D54409

llvm-svn: 366318
2019-07-17 12:30:04 +00:00
Petar Avramovic
5cb6bebcf0 [MIPS GlobalISel] ClampScalar and select pointer G_ICMP
Add narrowScalar to half of original size for G_ICMP.
ClampScalar G_ICMP's operands 2 and 3 to to s32.
Select G_ICMP for pointers for MIPS32. Pointer compare is same
as for integers, it is enough to declare them as legal type.

Differential Revision: https://reviews.llvm.org/D64856

llvm-svn: 366317
2019-07-17 12:08:01 +00:00
Nicolai Haehnle
a2d9ffdbee AMDGPU/GFX10: Apply the VMEM-to-scalar-write hazard also to writes to EXEC
Summary: Change-Id: I854fbf7d48e937bef9f8f3f5d0c8aeb970652630

Reviewers: rampitec, mareko

Subscribers: arsenm, kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64807

Change-Id: I4405b3a7f84186acea5a78d291bff71056e745fc
llvm-svn: 366314
2019-07-17 11:22:57 +00:00
Nicolai Haehnle
b38a60e03a AMDGPU: Improve alias analysis for GDS
Summary: GDS cannot alias anything else.

Original patch by: Marek Olšák

Reviewers: arsenm, mareko

Subscribers: kzhuravl, jvesely, wdng, yaxunl, dstuttard, tpr, t-tye, Petar.Avramovic, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64114

Change-Id: I07bfbd96f5d5c37a6dfba7997df12f291dd794b0
llvm-svn: 366313
2019-07-17 11:22:19 +00:00
Simon Atanasyan
8ed9748256 [mips] Remove redundant test case. NFC
The `inlineasm-constraint-reg64.ll` test checks the same functionality.

llvm-svn: 366303
2019-07-17 08:12:03 +00:00
Simon Atanasyan
24287b9edb [mips] Name inline asm constraint test cases in a uniform manner. NFC
llvm-svn: 366302
2019-07-17 08:11:57 +00:00
Simon Atanasyan
3c5d3ebc26 [mips] Use mult/mflo pattern on 64-bit targets prior to MIPS64
The `MUL` instruction is available starting from the MIPS32/MIPS64 targets.

llvm-svn: 366301
2019-07-17 08:11:40 +00:00
Simon Atanasyan
94c2670118 [mips] Support the "o" inline asm constraint
As well as other LLVM targets we do not handle "offsettable"
memory addresses in any special way. In other words, the "o" constraint
is an exact equivalent of the "m" one. But some existing code require
the "o" constraint support.

This fixes PR42589.

Differential Revision: https://reviews.llvm.org/D64792

llvm-svn: 366299
2019-07-17 08:11:15 +00:00
Guanzhong Chen
bd82c7f4d1 [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
0c5cac5f91 [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