93 Commits

Author SHA1 Message Date
Sergei Barannikov
0c73009236
[WebAssembly] TableGen-erate SDNode descriptions (#166259)
This allows SDNodes to be validated against their expected type profiles
and reduces the number of changes required to add a new node.

CALL and RET_CALL do not have a description in td files, and it is not
currently possible to add one as these nodes have both variable operands
and variable results.

This also fixes a subtle bug detected by the enabled verification
functionality. `LOCAL_GET` is declared with `SDNPHasChain` property, and
thus should have both a chain operand and a chain result. The original
code created a node without a chain result, which caused a check in
`SDNodeInfo::verifyNode()` to fail.

Part of #119709.

Pull Request: https://github.com/llvm/llvm-project/pull/166259
2025-11-05 06:24:53 +03:00
Sam Parker
1820102167
Wasm fmuladd relaxed (#163177)
Reland #161355, after fixing up the cross-projects-tests for the wasm
simd intrinsics.

Original commit message:
Lower v4f32 and v2f64 fmuladd calls to relaxed_madd instructions.
If we have FP16, then lower v8f16 fmuladds to FMA.

I've introduced an ISD node for fmuladd to maintain the rounding
ambiguity through legalization / combine / isel.
2025-10-13 16:50:53 +01:00
Sam Parker
30d3441cf0
Revert "[WebAssembly] Lower fmuladd to madd and nmadd" (#163171)
Reverts llvm/llvm-project#161355

Looks like I've broken some intrinsic code generation.
2025-10-13 11:53:40 +01:00
Sam Parker
a4eb7ea225
[WebAssembly] Lower fmuladd to madd and nmadd (#161355)
Lower v4f32 and v2f64 fmuladd calls to relaxed_madd instructions.
If we have FP16, then lower v8f16 fmuladds to FMA.

I've introduced an ISD node for fmuladd to maintain the rounding
ambiguity through legalization / combine / isel.
2025-10-13 10:36:08 +01:00
Sam Parker
156e9b4b69
[WebAssembly] Use partial_reduce_mla ISD nodes (#161184)
Addresssing issue #160847.
 
Move away from combining the intrinsic call and instead lower the ISD
nodes, using tablegen for pattern matching.
2025-09-30 08:28:56 +01:00
Alex Crichton
a415b7f86e
[WebAssembly] Add more lowerings for wide-arithmetic (#132430)
This commit is the result of investigation and discussion on
WebAssembly/wide-arithmetic#6 where alternatives to the `i64.add128`
instruction were discussed but ultimately deferred to a future proposal.
In spite of this though I wanted to apply a few changes to the LLVM
backend here with `wide-arithmetic` enabled for a few minor changes:

* A lowering for the `ISD::UADDO` node is added which uses `add128`
where the upper bits of the two operands are constant zeros and the
result of the 128-bit addition is the result of the overflowing
addition.
* The high bits of a `I64_ADD128` node are now flagged as "known zero"
if the upper bits of the inputs are also zero, assisting this `UADDO`
lowering to ensure the backend knows that the carry result is a 1-bit
result.

A few tests were then added to showcase various lowerings for various
operations that can be done with wide-arithmetic. They don't all
optimize super well at this time but I wanted to add them as a reference
here regardless to have them on-hand for future evaluations if
necessary.
2025-03-31 11:36:32 -07:00
Sam Parker
df2de13695
[WebAssembly] Autovec support for dot (#123207)
Enable the use of partial.reduce.add that we can lower to dot or a tree
of (add (extmul_low_u, extmul_high_u)) for the unsigned case. We support
both v8i16 and v16i8 inputs.
2025-02-03 08:58:43 +00:00
yingopq
754ed95b66
[Mips] Fix compiler crash when returning fp128 after calling a functi… (#117525)
…on returning { i8, i128 }

Fixes https://github.com/llvm/llvm-project/issues/96432.
2025-01-20 16:47:40 +08:00
Sergei Barannikov
9ae92d7056
[SelectionDAG] Virtualize isTargetStrictFPOpcode / isTargetMemoryOpcode (#119969)
With this change, targets are no longer required to put memory / strict-fp opcodes after special
`ISD::FIRST_TARGET_MEMORY_OPCODE`/`ISD::FIRST_TARGET_STRICTFP_OPCODE` markers.
This will also allow autogenerating `isTargetMemoryOpcode`/`isTargetStrictFPOpcode (#119709).

Pull Request: https://github.com/llvm/llvm-project/pull/119969
2024-12-21 05:29:51 +03:00
Alex Crichton
c2293b33dd
[WebAssembly] Implement the wide-arithmetic proposal (#111598)
This commit implements the [wide-arithmetic] proposal which has recently
reached phase 2 in the WebAssembly proposals process. The goal here is
to implement support in LLVM for emitting these instructions which are
gated behind a new feature flag by default. A new `wide-arithmetic`
feature flag is introduced which gates these four new instructions from
being emitted.

Emission of each instruction itself is relatively simple given LLVM's
preexisting lowering rules and infrastructure. The main gotcha is that
due to the multi-result nature of all of these instructions it needed
the lowerings to be implemented in C++ rather than in TableGen.

[wide-arithmetic]: https://github.com/WebAssembly/wide-arithmetic
2024-10-23 11:39:58 -07:00
Jeffrey Byrnes
853c43d04a
[TTI] NFC: Port TLI.shouldSinkOperands to TTI (#110564)
Porting to TTI provides direct access to the instruction cost model,
which can enable instruction cost based sinking without introducing code
duplication.
2024-10-09 14:30:09 -07:00
Roger Ferrer Ibáñez
05e6bb40eb
[SelectionDAG] Add an ISD::CLEAR_CACHE node to lower llvm.clear_cache (#93795)
The current way of lowering `llvm.clear_cache` is a bit unusual. As
suggested by Matt Arsenault we are better off using an ISD node.

This change introduces a new `ISD::CLEAR_CACHE`, registers a new libcall
by default named `__clear_cache` and the default legalisation is a
libcall.

This is preparatory work for a custom lowering of `ISD::CLEAR_CACHE`
needed by RISC-V on some platforms.
2024-05-30 14:55:32 +02:00
Yolanda Chen
291101aa8e [WebAssembly] Optimize vector shift using a splat value from outside block
The vector shift operation in WebAssembly uses an i32 shift amount type, while
the LLVM IR requires binary operator uses the same type of operands. When the
shift amount operand is splated from a different block, the splat source will
not be exported and the vector shift will be unrolled to scalar shifts. This
patch enables the vector shift to identify the splat source value from the other
block, and generate expected WebAssembly bytecode when lowering.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D158399
2023-08-25 08:13:27 -07:00
Caleb Zulawski
18077e9fd6 [WebAssembly] Re-land 8392bf6000ad
Correctly handle single-element vectors to fix an assertion failure. Add tests
that were missing from the original commit.

Differential Revision: D151782
2023-06-09 08:42:27 -07:00
Thomas Lively
100c756d96 Revert "Improve WebAssembly vector bitmask, mask reduction, and extending"
This reverts commit 8392bf6000ad039bd0e55383d40a05ddf7b4af13.

The commit missed some edge cases that led to crashes. Reverting to resolve
downstream breakage while a fix is pending.
2023-06-08 14:36:29 -07:00
Caleb Zulawski
8392bf6000 Improve WebAssembly vector bitmask, mask reduction, and extending
This is inspired by a recently filed Rust issue noting poor codegen for vector masks (https://github.com/rust-lang/portable-simd/issues/351).

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D151782
2023-06-07 10:20:22 -07:00
Kazu Hirata
d594e0dcb8 [WebAssembly] Remove dead declaration MatchTableForLowering
The corresponding function definition was removed on Sep 27, 2022 in
commit 1bd1a4407058c4a159eee6f6956f3bcabeb0d7f8.
2023-05-06 11:26:30 -07:00
Stanislav Mekhanoshin
bcaf31ec3f [AMDGPU] Allow finer grain control of an unaligned access speed
A target can return if a misaligned access is 'fast' as defined
by the target or not. In reality there can be different levels
of 'fast' and 'slow'. This patch changes the boolean 'Fast'
argument of the allowsMisalignedMemoryAccesses family of functions
to an unsigned representing its speed.

A target can still define it as it wants and the direct translation
of the current code uses 0 and 1 for current false and true. This
makes the change an NFC.

Subsequent patch will start using an actual value of speed in
the load/store vectorizer to compare if a vectorized access going
to be not just fast, but not slower than before.

Differential Revision: https://reviews.llvm.org/D124217
2022-11-17 09:23:53 -08:00
Simon Pilgrim
f9de13232f [X86] Promote i8/i16 CTTZ (BSF) instructions and remove speculation branch
This patch adds a Type operand to the TLI isCheapToSpeculateCttz/isCheapToSpeculateCtlz callbacks, allowing targets to decide whether branches should occur on a type-by-type/legality basis.

For X86, this patch proposes to allow CTTZ speculation for i8/i16 types that will lower to promoted i32 BSF instructions by masking the operand above the msb (we already do something similar for i8/i16 TZCNT). This required a minor tweak to CTTZ lowering - if the src operand is known never zero (i.e. due to the promotion masking) we can remove the CMOV zero src handling.

Although BSF isn't very fast, most CPUs from the last 20 years don't do that bad a job with it, although there are some annoying passthrough EFLAGS dependencies. Additionally, now that we emit 'REP BSF' in most cases, we are tending towards assuming this will most likely be executed as a TZCNT instruction on any semi-modern CPU.

Differential Revision: https://reviews.llvm.org/D132520
2022-08-24 17:28:18 +01:00
Heejin Ahn
b8038a916d [WebAssembly] Disable SimplifyDemandedVectorElts after legalization
This fixes a reported bug that caused an infinite loop during the
SelectionDAG optimization phase in ISel, by creating an overridable hook
in `TargetLowering` that allows us to bail out from running
`SimplifyDemandedVectorElts`.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D121869
2022-03-16 20:52:43 -07:00
Paulo Matos
6d0c7bc17d [WebAssembly] Implementation of table.get/set for reftypes in LLVM IR
This change implements new DAG nodes TABLE_GET/TABLE_SET, and lowering
methods for load and stores of reference types from IR arrays. These
global LLVM IR arrays represent tables at the Wasm level.

Differential Revision: https://reviews.llvm.org/D111154
2021-10-20 10:31:31 +02:00
Paulo Matos
91fe069c35 [WebAssembly] De-duplicate WasmAddressSpace and refactor reftype predicates
This is a non-functional change to remove the duplicate
WasmAddressSpace enum and refactor reftype predicates by moving them
to the Utilities source file.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D111144
2021-10-06 09:56:23 +02:00
Thomas Lively
b69374ca58 [WebAssembly] Legalize vector types by widening
The default legalization of unsupported vector types is to promote the integers
in each lane, which leads to extra sign or zero extending and masking when
moving data into and out of vectors. Switch our preferred type legalization from
the default to vector widening, which keeps the data in the low lanes of the
vector rather than in the low bits of each lane. The unused high lanes can be
ignored.

Half-wide vectors are now loaded from memory into the low 64 bits of the v128
rather than spread out among the lanes. As a result, v128.load64_splat is a much
more common operation, so add new patterns to support it.

Differential Revision: https://reviews.llvm.org/D107502
2021-08-19 12:07:33 -07:00
Heejin Ahn
78e87970af [WebAssembly] Disable offset folding for function addresses
Wasm does not support function addresses with offsets, but isel can
generate folded SDValues in the form of (@func + offset) without this
patch.

Fixes https://bugs.llvm.org/show_bug.cgi?id=43133.

Reviewed By: dschuff, sbc100

Differential Revision: https://reviews.llvm.org/D107940
2021-08-12 13:40:41 -07:00
Thomas Lively
417e500668 [WebAssembly] Compute known bits for SIMD bitmask intrinsics
This optimizes out the mask when the result of a bitmask is interpreted as an i8
or i16 value. Resolves PR50507.

Differential Revision: https://reviews.llvm.org/D107103
2021-08-02 09:52:34 -07:00
Paulo Matos
46667a1003 [WebAssembly] Implementation of global.get/set for reftypes in LLVM IR
Reland of 31859f896.

This change implements new DAG notes GLOBAL_GET/GLOBAL_SET, and
lowering methods for load and stores of reference types from IR
globals. Once the lowering creates the new nodes, tablegen pattern
matches those and converts them to Wasm global.get/set.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D104797
2021-07-22 22:07:24 +02:00
Thomas Lively
3dd75f5371 [WebAssembly] Scalarize extract_vector_elt of binops
Override the `shouldScalarizeBinop` target lowering hook using the same
implementation used in the x86 backend. This causes `extract_vector_elt`s of
vector binary ops to be scalarized if the scalarized version would be supported.

Differential Revision: https://reviews.llvm.org/D105646
2021-07-08 14:31:53 -07:00
Roman Lebedev
c2c0d3ea89
Revert "[WebAssembly] Implementation of global.get/set for reftypes in LLVM IR"
This reverts commit 4facbf213c51e4add2e8c19b08d5e58ad71c72de.

```
********************
FAIL: LLVM :: CodeGen/WebAssembly/funcref-call.ll (44466 of 44468)
******************** TEST 'LLVM :: CodeGen/WebAssembly/funcref-call.ll' FAILED ********************
Script:
--
: 'RUN: at line 1';   /builddirs/llvm-project/build-Clang12/bin/llc < /repositories/llvm-project/llvm/test/CodeGen/WebAssembly/funcref-call.ll --mtriple=wasm32-unknown-unknown -asm-verbose=false -mattr=+reference-types | /builddirs/llvm-project/build-Clang12/bin/FileCheck /repositories/llvm-project/llvm/test/CodeGen/WebAssembly/funcref-call.ll
--
Exit Code: 2

Command Output (stderr):
--
llc: /repositories/llvm-project/llvm/include/llvm/Support/LowLevelTypeImpl.h:44: static llvm::LLT llvm::LLT::scalar(unsigned int): Assertion `SizeInBits > 0 && "invalid scalar size"' failed.

```
2021-07-02 11:49:51 +03:00
Paulo Matos
4facbf213c [WebAssembly] Implementation of global.get/set for reftypes in LLVM IR
Reland of 31859f896.

This change implements new DAG notes GLOBAL_GET/GLOBAL_SET, and
lowering methods for load and stores of reference types from IR
globals. Once the lowering creates the new nodes, tablegen pattern
matches those and converts them to Wasm global.get/set.

Differential Revision: https://reviews.llvm.org/D104797
2021-07-02 09:46:28 +02:00
David Spickett
64de8763aa Revert "Implementation of global.get/set for reftypes in LLVM IR"
This reverts commit 31859f896cf90d64904134ce7b31230f374c3fcc.

Causing SVE and RISCV-V test failures on bots.
2021-06-10 10:11:17 +00:00
Paulo Matos
31859f896c Implementation of global.get/set for reftypes in LLVM IR
This change implements new DAG notes GLOBAL_GET/GLOBAL_SET, and
lowering methods for load and stores of reference types from IR
globals. Once the lowering creates the new nodes, tablegen pattern
matches those and converts them to Wasm global.get/set.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D95425
2021-06-10 10:07:45 +02:00
Paulo Matos
d7086af214 [WebAssembly] Support for WebAssembly globals in LLVM IR
This patch adds support for WebAssembly globals in LLVM IR, representing
them as pointers to global values, in a non-default, non-integral
address space.  Instruction selection legalizes loads and stores to
these pointers to new WebAssemblyISD nodes GLOBAL_GET and GLOBAL_SET.
Once the lowering creates the new nodes, tablegen pattern matches those
and converts them to Wasm global.get/set of the appropriate type.

Based on work by Paulo Matos in https://reviews.llvm.org/D95425.

Reviewed By: pmatos

Differential Revision: https://reviews.llvm.org/D101608
2021-05-11 11:19:29 +02:00
Thomas Lively
5c729750a6 [WebAssembly] Remove saturating fp-to-int target intrinsics
Use the target-independent @llvm.fptosi and @llvm.fptoui intrinsics instead.
This includes removing the instrinsics for i32x4.trunc_sat_zero_f64x2_{s,u},
which are now represented in IR as a saturating truncation to a v2i32 followed by
a concatenation with a zero vector.

Differential Revision: https://reviews.llvm.org/D100596
2021-04-16 12:11:20 -07:00
Craig Topper
11ef356d9e [TargetLowering] Use Align in allowsMisalignedMemoryAccesses.
Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D96097
2021-02-04 19:22:06 -08:00
Sam Clegg
a28a466210 [WebAssembly] Add new relocation type for TLS data symbols
These relocations represent offsets from the __tls_base symbol.

Previously we were just using normal MEMORY_ADDR relocations and relying
on the linker to select a segment-offset rather and absolute value in
Symbol::getVirtualAddress().  Using an explicit relocation type allows
allow us to clearly distinguish absolute from relative relocations based
on the relocation information alone.

One place this is useful is being able to reject absolute relocation in
the PIC case, but still accept TLS relocations.

Differential Revision: https://reviews.llvm.org/D91276
2020-11-13 07:59:29 -08:00
Thomas Lively
40af48101b [WebAssembly] Optimize splats of bitcasted vectors
Summary:
This new custom DAG combine fixes a codegen issue with the
wasm_simd128.h intrinsics. Clang lowers the

  return (v128_t)(__f32x4){__a, __a, __a, __a};

body of f32x4_splat to a splat shuffle of a bitcasted vector, as seen
in the new simd-shuffle-bitcast.ll test. The bitcast interfered with
the target-independent DAG combine that combines splat shuffles into
BUILD_VECTOR nodes, so this patch introduces a new custom DAG combine
to hoist the bitcast out of the shuffle, allowing the
target-independent combine to work as intended.

Reviewers: aheejin, dschuff

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80021
2020-05-15 12:12:20 -07:00
Simon Pilgrim
5387899bb4 [WebAssembly] Remove unused forward declarations. NFC. 2020-04-23 16:30:45 +01:00
Thomas Lively
ecb7daf68f Reland "[WebAssembly] Expand setcc of v2i64"
This reverts commit e5cae5692b5899631b5bfe5c23234deb5efda10c, which
reverted 11850a6305c5778b180243eb06aefe86762dd4ce. The original revert
was done because of breakage that was actually in a separate commit,
2ab1b8c1ec452fb743f6cc5051e75a01039cabfe, which was also reverted and
has since been fixed and relanded.
2019-11-01 10:34:01 -07:00
Thomas Lively
3479fd25b9 Reland "[WebAssembly] Handle multiple loads of splatted loads"
This reverts commit 92a25fbf11da51c8e3573b81a877d3b226990c07 and fixes
the ambiguous method call that was causing build failures.
2019-10-31 20:02:24 -07:00
Vlad Tsyrklevich
92a25fbf11 Revert "[WebAssembly] Handle multiple loads of splatted loads"
This reverts commit 2ab1b8c1ec452fb743f6cc5051e75a01039cabfe, it is
causing build failures on numerous bots, including
sanitizer-x86_64-linux-bootstrap-ubsan. My previous revert was for the
wrong commit.
2019-10-31 16:52:44 -07:00
Vlad Tsyrklevich
e5cae5692b Revert "[WebAssembly] Expand setcc of v2i64"
This reverts commit 11850a6305c5778b180243eb06aefe86762dd4ce, it was
causing build failures on numerous bots, including
sanitizer-x86_64-linux-bootstrap-ubsan.
2019-10-31 16:44:09 -07:00
Thomas Lively
2ab1b8c1ec [WebAssembly] Handle multiple loads of splatted loads
Summary:
Fixes an ISel failure when a splatted load is used more than once. The
failure was due to the hacks we were doing in ISel lowering to
preserve the original load as the operand of a LOAD_SPLAT node. The
fix is to properly lower the splatted use of the load to a separate
LOAD_SPLAT node.

Reviewers: aheejin

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69640
2019-10-31 14:59:30 -07:00
Thomas Lively
11850a6305 [WebAssembly] Expand setcc of v2i64
Summary:
The SIMD spec does not include i64x2 comparisons, so they need to be
expanded. Using setOperationAction to expand them also causes f64x2
comparisons to be expanded, so setCondCodeAction needs to be used
instead. But since there are no legal condition codes, the legalizer
does not know how to expand the comparisons. We therefore manually
unroll the operation, taking care to fill each lane with -1 or 0
rather than 1 or 0 for consistency with the other vector comparisons.

Reviewers: aheejin

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69604
2019-10-31 14:22:30 -07:00
Thomas Lively
81125f7362 [WebAssembly] SIMD Load and extend operations
Summary:
As specified at
https://github.com/webassembly/simd/blob/master/proposals/simd/SIMD.md#load-and-extend.
These instructions are behind the unimplemented-simd128 target feature
for now because they have not been implemented in V8 yet.

Reviewers: aheejin

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68058

llvm-svn: 373040
2019-09-27 02:06:50 +00:00
Heejin Ahn
54c136bbdf [WebAssembly] Print error message for llvm.clear_cache intrinsic
Summary:
Wasm does not currently support `llvm.clear_cache` intrinsic, and this
prints a proper error message instead of segfault.

Reviewers: dschuff, sbc100, sunfish

Subscribers: jgravelle-google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64322

llvm-svn: 365731
2019-07-11 05:55:47 +00:00
Simon Pilgrim
4e0648a541 [TargetLowering] Add MachineMemOperand::Flags to allowsMemoryAccess tests (PR42123)
As discussed on D62910, we need to check whether particular types of memory access are allowed, not just their alignment/address-space.

This NFC patch adds a MachineMemOperand::Flags argument to allowsMemoryAccess and allowsMisalignedMemoryAccesses, and wires up calls to pass the relevant flags to them.

If people are happy with this approach I can then update X86TargetLowering::allowsMisalignedMemoryAccesses to handle misaligned NT load/stores.

Differential Revision: https://reviews.llvm.org/D63075

llvm-svn: 363179
2019-06-12 17:14:03 +00:00
Thomas Lively
e18b5c6237 [WebAssembly] Implement ReplaceNodeResults to fix a SIMD crash
Reviewers: aheejin

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61037

llvm-svn: 361526
2019-05-23 18:09:26 +00:00
Thomas Lively
1a3cbe720c [WebAssembly] Implement __builtin_return_address for emscripten
Summary:
In this patch, `ISD::RETURNADDR` is lowered on the emscripten target
to the new Emscripten runtime function `emscripten_return_address`, which
implements the functionality.

Patch by Guanzhong Chen

Reviewers: tlively, aheejin

Reviewed By: tlively

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62210

llvm-svn: 361454
2019-05-23 01:24:01 +00:00
Sam Clegg
b7708ec87f [WebAssembly] Don't override default implementation of isOffsetFoldingLegal. NFC.
The default implementation does we want and is going to more compatible
with dynamic linking (-fPIC) support that is planned.

This is NFC because currently we only build wasm with
`-relocation-model=static` which in turn means that the default
`isOffsetFoldingLegal` always returns true today.

Differential Revision: https://reviews.llvm.org/D54661

llvm-svn: 356410
2019-03-18 21:21:12 +00:00
Heejin Ahn
d6f487863d [WebAssembly] Exception handling: Switch to the new proposal
Summary:
This switches the EH implementation to the new proposal:
https://github.com/WebAssembly/exception-handling/blob/master/proposals/Exceptions.md
(The previous proposal was
 https://github.com/WebAssembly/exception-handling/blob/master/proposals/old/Exceptions.md)

- Instruction changes
  - Now we have one single `catch` instruction that returns a except_ref
    value
  - `throw` now can take variable number of operations
  - `rethrow` does not have 'depth' argument anymore
  - `br_on_exn` queries an except_ref to see if it matches the tag and
    branches to the given label if true.
  - `extract_exception` is a pseudo instruction that simulates popping
    values from wasm stack. This is to make `br_on_exn`, a very special
    instruction, work: `br_on_exn` puts values onto the stack only if it
    is taken, and the # of values can vay depending on the tag.

- Now there's only one `catch` per `try`, this patch removes all special
  handling for terminate pad with a call to `__clang_call_terminate`.
  Before it was the only case there are two catch clauses (a normal
  `catch` and `catch_all` per `try`).

- Make `rethrow` act as a terminator like `throw`. This splits BB after
  `rethrow` in WasmEHPrepare, and deletes an unnecessary `unreachable`
  after `rethrow` in LateEHPrepare.

- Now we stop at all catchpads (because we add wasm `catch` instruction
  that catches all exceptions), this creates new
  `findWasmUnwindDestinations` function in SelectionDAGBuilder.

- Now we use `br_on_exn` instrution to figure out if an except_ref
  matches the current tag or not, LateEHPrepare generates this sequence
  for catch pads:
```
  catch
  block i32
  br_on_exn $__cpp_exception
  end_block
  extract_exception
```

- Branch analysis for `br_on_exn` in WebAssemblyInstrInfo

- Other various misc. changes to switch to the new proposal.

Reviewers: dschuff

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

Differential Revision: https://reviews.llvm.org/D57134

llvm-svn: 352598
2019-01-30 03:21:57 +00:00