[WebAssembly] Define call-indirect-overlong and bulk-memory-opt features (#117087)

This defines some new target features. These are subsets of existing
features that reflect implementation concerns

[WebAssembly] Define call-indirect-overlong and bulk-memory-opt features (#117087)

This defines some new target features. These are subsets of existing
features that reflect implementation concerns:

- "call-indirect-overlong" - implied by "reference-types"; just the
overlong encoding for the `call_indirect` immediate, and not the actual
reference types.

- "bulk-memory-opt" - implied by "bulk-memory": just `memory.copy` and
`memory.fill`, and not the other instructions in the bulk-memory
proposal.

This is split out from https://github.com/llvm/llvm-project/pull/112035.

---------

Co-authored-by: Heejin Ahn <aheejin@gmail.com>

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[WebAssembly] Remove unused includes (NFC) (#116318)

Identified with misc-include-cleaner.

[WebAssembly] Add assembly support for final EH proposal (#107917)

This adds the basic assembly generation support for the final EH
proposal, which was newly adopted in Sep 2023 and advanced into P

[WebAssembly] Add assembly support for final EH proposal (#107917)

This adds the basic assembly generation support for the final EH
proposal, which was newly adopted in Sep 2023 and advanced into Phase 4
in Jul 2024:

https://github.com/WebAssembly/exception-handling/blob/main/proposals/exception-handling/Exceptions.md

This adds support for the generation of new `try_table` and `throw_ref`
instruction in .s asesmbly format. This does NOT yet include
- Block annotation comment generation for .s format
- .o object file generation
- .s assembly parsing
- Type checking (AsmTypeCheck)
- Disassembler
- Fixing unwind mismatches in CFGStackify

These will be added as follow-up PRs.

---

The format for `TRY_TABLE`, both for `MachineInstr` and `MCInst`, is as
follows:
```
TRY_TABLE type number_of_catches catch_clauses*
```
where `catch_clause` is
```
catch_opcode tag+ destination
```
`catch_opcode` should be one of 0/1/2/3, which denotes
`CATCH`/`CATCH_REF`/`CATCH_ALL`/`CATCH_ALL_REF` respectively. (See
`BinaryFormat/Wasm.h`) `tag` exists when the catch is one of `CATCH` or
`CATCH_REF`.
The MIR format is printed as just the list of raw operands. The
(stack-based) assembly instruction supports pretty-printing, including
printing `catch` clauses by name, in InstPrinter.

In addition to the new instructions `TRY_TABLE` and `THROW_REF`, this
adds four pseudo instructions: `CATCH`, `CATCH_REF`, `CATCH_ALL`, and
`CATCH_ALL_REF`. These are pseudo instructions to simulate block return
values of `catch`, `catch_ref`, `catch_all`, `catch_all_ref` clauses in
`try_table` respectively, given that we don't support block return
values except for one case (`fixEndsAtEndOfFunction` in CFGStackify).
These will be omitted when we lower the instructions to `MCInst` at the
end.

LateEHPrepare now will have one more stage to covert
`CATCH`/`CATCH_ALL`s to `CATCH_REF`/`CATCH_ALL_REF`s when there is a
`RETHROW` to rethrow its exception. The pass also converts `RETHROW`s
into `THROW_REF`. Note that we still use `RETHROW` as an interim pseudo
instruction until we convert them to `THROW_REF` in LateEHPrepare.

CFGStackify has a new `placeTryTableMarker` function, which places
`try_table`/`end_try_table` markers with a necessary `catch` clause and
also `block`/`end_block` markers for the destination of the `catch`
clause.

In MCInstLower, now we need to support one more case for the multivalue
block signature (`catch_ref`'s destination's `(i32, exnref)` return
type).

InstPrinter has a new routine to print the `catch_list` type, which is
used to print `try_table` instructions.

The new test, `exception.ll`'s source is the same as
`exception-legacy.ll`, with the FileCheck expectations changed. One
difference is the commands in this file have `-wasm-enable-exnref` to
test the new format, and don't have `-wasm-disable-explicit-locals
-wasm-keep-registers`, because the new custom InstPrinter routine to
print `catch_list` only works for the stack-based instructions (`_S`),
and we can't use `-wasm-keep-registers` for them.

As in `exception-legacy.ll`, the FileCheck lines for the new tests do
not contain the whole program; they mostly contain only the control flow
instructions for readability.

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[WebAssembly] Set IS_64 flag correctly on __indirect_function_table in object files (#94487)

Follow up to #92042

[WebAssembly] Add exnref type (#93586)

This adds (back) the exnref type restored in the new EH proposal adopted
in Oct 2023 CG meeting:

https://github.com/WebAssembly/exception-handling/blob/mai

[WebAssembly] Add exnref type (#93586)

This adds (back) the exnref type restored in the new EH proposal adopted
in Oct 2023 CG meeting:

https://github.com/WebAssembly/exception-handling/blob/main/proposals/exception-handling/Exceptions.md:x

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[WebAssembly] Enable multivalue return when multivalue ABI is used (#88492)

Multivalue feature of WebAssembly has been standardized for several
years now. I think it makes sense to be able to enabl

[WebAssembly] Enable multivalue return when multivalue ABI is used (#88492)

Multivalue feature of WebAssembly has been standardized for several
years now. I think it makes sense to be able to enable it in the feature
section by default for our clang/llvm-produced binaries so that the
multivalue feature can be used as necessary when necessary within our
toolchain and also when running other optimizers (e.g. wasm-opt) after
the LLVM code generation.

But some WebAssembly toolchains, such as Emscripten, do not provide both
mulvalue-returning and not-multivalue-returning versions of libraries.
Also allowing the uses of multivalue in the features section does not
necessarily mean we generate them whenever we can to the fullest, which
is a different code generation / optimization option.

So this makes the lowering of multivalue returns conditional on the use
of 'experimental-mv' target ABI. This ABI is turned off by default and
turned on by passing `-Xclang -target-abi -Xclang experimental-mv` to
`clang`, or `-target-abi experimental-mv` to `clang -cc1` or `llc`.

But the purpose of this PR is not tying the multivalue lowering to this
specific 'experimental-mv'. 'experimental-mv' is just one multivalue ABI
we currently have, and it is still experimental, meaning it is not very
well optimized or tuned for performance. (e.g. it does not have the
limitation of the max number of multivalue-lowered values, which can be
detrimental to performance.) We may change the name of this ABI, or
improve it, or add a new multivalue ABI in the future. Also I heard that
WASI is planning to add their multivalue ABI soon. So the plan is,
whenever any one of multivalue ABIs is enabled, we enable the lowering
of multivalue returns in the backend. We currently have only
'experimental-mv' in the repo so we only check for that in this PR.

Related past discussions:
#82714
https://github.com/WebAssembly/tool-conventions/pull/223#issuecomment-2008298652

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[WebAssembly] Use ValType instead of integer types to model wasm tables (#78012)

LLVM models some features found in the binary format with raw integers
and others with nested or enumerated types. T

[WebAssembly] Use ValType instead of integer types to model wasm tables (#78012)

LLVM models some features found in the binary format with raw integers
and others with nested or enumerated types. This PR switches modeling of
tables and segments to use wasm::ValType rather than uint32_t. This NFC
change is in preparation for modeling more reference types, but IMO is
also cleaner and closer to the spec.

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[WebAssembly] Create separation between MC and CodeGen layers

Move WebAssemblyUtilities from Utils to the CodeGen library. It
primarily deals in MIR layer types, so it really lives in the CodeGen
li

[WebAssembly] Create separation between MC and CodeGen layers

Move WebAssemblyUtilities from Utils to the CodeGen library. It
primarily deals in MIR layer types, so it really lives in the CodeGen
library.

Move a variety of other things around to try create better separation.

See issue #64166 for more info on layering.

Move llvm/include/CodeGen/WasmAddressSpaces.h back to
llvm/lib/Target/WebAssembly/Utils.

Differential Revision: https://reviews.llvm.org/D156472

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[WebAssembly] Disable uses of __clang_call_terminate

Background:

Wasm EH, while using Windows EH (catchpad/cleanuppad based) IR, uses
Itanium-based libraries and ABIs with some modifications.

`__c

[WebAssembly] Disable uses of __clang_call_terminate

Background:

Wasm EH, while using Windows EH (catchpad/cleanuppad based) IR, uses
Itanium-based libraries and ABIs with some modifications.

`__clang_call_terminate` is a wrapper generated in Clang's Itanium C++
ABI implementation. It contains this code, in C-style pseudocode:
```
void __clang_call_terminate(void *exn) {
__cxa_begin_catch(exn);
std::terminate();
}
```
So this function is a wrapper to call `__cxa_begin_catch` on the
exception pointer before termination.

In Itanium ABI, this function is called when another exception is thrown
while processing an exception. The pointer for this second, violating
exception is passed as the argument of this `__clang_call_terminate`,
which calls `__cxa_begin_catch` with that pointer and calls
`std::terminate` to terminate the program.

The spec (https://libcxxabi.llvm.org/spec.html) for `__cxa_begin_catch`
says,
```
When the personality routine encounters a termination condition, it
will call __cxa_begin_catch() to mark the exception as handled and then
call terminate(), which shall not return to its caller.
```

In wasm EH's Clang implementation, this function is called from
cleanuppads that terminates the program, which we also call terminate
pads. Cleanuppads normally don't access the thrown exception and the
wasm backend converts them to `catch_all` blocks. But because we need
the exception pointer in this cleanuppad, we generate
`wasm.get.exception` intrinsic (which will eventually be lowered to
`catch` instruction) as we do in the catchpads. But because terminate
pads are cleanup pads and should run even when a foreign exception is
thrown, so what we have been doing is:
1. In `WebAssemblyLateEHPrepare::ensureSingleBBTermPads()`, we make sure
terminate pads are in this simple shape:
```
%exn = catch
call @__clang_call_terminate(%exn)
unreachable
```
2. In `WebAssemblyHandleEHTerminatePads` pass at the end of the
pipeline, we attach a `catch_all` to terminate pads, so they will be in
this form:
```
%exn = catch
call @__clang_call_terminate(%exn)
unreachable
catch_all
call @std::terminate()
unreachable
```
In `catch_all` part, we don't have the exception pointer, so we call
`std::terminate()` directly. The reason we ran HandleEHTerminatePads at
the end of the pipeline, separate from LateEHPrepare, was it was
convenient to assume there was only a single `catch` part per `try`
during CFGSort and CFGStackify.

---

Problem:

While it thinks terminate pads could have been possibly split or calls
to `__clang_call_terminate` could have been duplicated,
`WebAssemblyLateEHPrepare::ensureSingleBBTermPads()` assumes terminate
pads contain no more than calls to `__clang_call_terminate` and
`unreachable` instruction. I assumed that because in LLVM very limited
forms of transformations are done to catchpads and cleanuppads to
maintain the scoping structure. But it turned out to be incorrect;
passes can merge cleanuppads into one, including terminate pads, as long
as the new code has a correct scoping structure. One pass that does this
I observed was `SimplifyCFG`, but there can be more. After this
transformation, a single cleanuppad can contain any number of other
instructions with the call to `__clang_call_terminate` and can span many
BBs. It wouldn't be practical to duplicate all these BBs within the
cleanuppad to generate the equivalent `catch_all` blocks, only with
calls to `__clang_call_terminate` replaced by calls to `std::terminate`.

Unless we do more complicated transformation to split those calls to
`__clang_call_terminate` into a separate cleanuppad, it is tricky to
solve.

---

Solution (?):

This CL just disables the generation and use of `__clang_call_terminate`
and calls `std::terminate()` directly in its place.

The possible downside of this approach can be, because the Itanium ABI
intended to "mark" the violating exception handled, we don't do that
anymore. What `__cxa_begin_catch` actually does is increment the
exception's handler count and decrement the uncaught exception count,
which in my opinion do not matter much given that we are about to
terminate the program anyway. Also it does not affect info like stack
traces that can be possibly shown to developers.

And while we use a variant of Itanium EH ABI, we can make some
deviations if we choose to; we are already different in that in the
current version of the EH spec we don't support two-phase unwinding. We
can possibly consider a more complicated transformation later to
reenable this, but I don't think that has high priority.

Changes in this CL contains:
- In Clang, we don't generate a call to `wasm.get.exception()` intrinsic
and `__clang_call_terminate` function in terminate pads anymore; we
simply generate calls to `std::terminate()`, which is the default
implementation of `CGCXXABI::emitTerminateForUnexpectedException`.
- Remove `WebAssembly::ensureSingleBBTermPads() function and
`WebAssemblyHandleEHTerminatePads` pass, because terminate pads are
already `catch_all` now (because they don't need the exception
pointer) and we don't need these transformations anymore.
- Change tests to use `std::terminate` directly. Also removes tests that
tested `LateEHPrepare::ensureSingleBBTermPads` and
`HandleEHTerminatePads` pass.
- Drive-by fix: Add some function attributes to EH intrinsic
declarations

Fixes https://github.com/emscripten-core/emscripten/issues/13582.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D97834

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[WebAssembly] call_indirect issues table number relocs

If the reference-types feature is enabled, call_indirect will explicitly
reference its corresponding function table via TABLE_NUMBER
relocation

[WebAssembly] call_indirect issues table number relocs

If the reference-types feature is enabled, call_indirect will explicitly
reference its corresponding function table via TABLE_NUMBER
relocations against a table symbol.

Also, as before, address-taken functions can also cause the function
table to be created, only with reference-types they additionally cause a
symbol table entry to be emitted.

Differential Revision: https://reviews.llvm.org/D90948

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Revert "[WebAssembly] call_indirect issues table number relocs"

This reverts commit 861dbe1a021e6439af837b72b219fb9c449a57ae. It broke
emscripten -- see https://reviews.llvm.org/D90948#2578843.

[WebAssembly] call_indirect issues table number relocs

If the reference-types feature is enabled, call_indirect will explicitly
reference its corresponding function table via `TABLE_NUMBER`
relocati

[WebAssembly] call_indirect issues table number relocs

If the reference-types feature is enabled, call_indirect will explicitly
reference its corresponding function table via `TABLE_NUMBER`
relocations against a table symbol.

Also, as before, address-taken functions can also cause the function
table to be created, only with reference-types they additionally cause a
symbol table entry to be emitted.

We abuse the used-in-reloc flag on symbols to indicate which tables
should end up in the symbol table. We do this because unfortunately
older wasm-ld will carp if it see a table symbol.

Differential Revision: https://reviews.llvm.org/D90948

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[WebAssembly] Ensure terminate pads are a single BB

This ensures every single terminate pad is a single BB in the form of:
```
%exn = catch $__cpp_exception
call @__clang_call_terminate(%exn)
unreac

[WebAssembly] Ensure terminate pads are a single BB

This ensures every single terminate pad is a single BB in the form of:
```
%exn = catch $__cpp_exception
call @__clang_call_terminate(%exn)
unreachable
```

This is a preparation for HandleEHTerminatePads pass, which will be
added in a later CL and will run after CFGStackify. That pass duplicates
terminate pads with a `catch_all` instruction, and duplicating it
becomes simpler if we can ensure every terminate pad is a single BB.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D94045

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[WebAssembly] call_indirect causes indirect function table import

For wasm-ld table linking work to proceed, object files should indicate
if they use an indirect function table. In the future this

[WebAssembly] call_indirect causes indirect function table import

For wasm-ld table linking work to proceed, object files should indicate
if they use an indirect function table. In the future this will be done
by the usual symbols and relocations mechanism, but until that support
lands in the linker, the presence of an `__indirect_function_table` in
the object file's import section shows that the object file needs an
indirect function table.

Prior to https://reviews.llvm.org/D91637, this condition was met by all
object files residualizing an `__indirect_function_table` import.

Since https://reviews.llvm.org/D91637, the intention has been that only
those object files needing an indirect function table would have the
`__indirect_function_table` import. However, we missed the case of
object files which use the table via `call_indirect` but which
themselves do not declare any indirect functions.

This changeset makes it so that when we lower a call to `call_indirect`,
that we ensure that a `__indirect_function_table` symbol is present and
that it will be propagated to the linker.

A followup patch will revise this mechanism to make an explicit link
between `call_indirect` and its associated indirect function table; see
https://reviews.llvm.org/D90948.

Differential Revision: https://reviews.llvm.org/D92840

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[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,

[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

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[WebAssembly] Implement multivalue call_indirects

Summary:
Unlike normal calls, call_indirects have immediate arguments that
caused a MachineVerifier failure without a small tweak to loosen the
veri

[WebAssembly] Implement multivalue call_indirects

Summary:
Unlike normal calls, call_indirects have immediate arguments that
caused a MachineVerifier failure without a small tweak to loosen the
verifier's requirements for variadicOpsAreDefs instructions.

One nice thing about the new call_indirects is that they do not need
to participate in the PCALL_INDIRECT mechanism because their post-isel
hook handles moving the function pointer argument and adding the flags
and typeindex arguments itself.

Reviewers: aheejin

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74191

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Reland "[WebAssembly][InstrEmitter] Foundation for multivalue call lowering"

This reverts commit 649aba93a27170cb03a4b17c98a19b9237a880b8, now that
the approach started there has been shown to be wo

Reland "[WebAssembly][InstrEmitter] Foundation for multivalue call lowering"

This reverts commit 649aba93a27170cb03a4b17c98a19b9237a880b8, now that
the approach started there has been shown to be workable in the patch
series culminating in https://reviews.llvm.org/D74192.

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Revert "[WebAssembly][InstrEmitter] Foundation for multivalue call lowering"

Summary:
This reverts commit 3ef169e586f4d14efe690c23c878d5aa92a80eb5. The
purpose of this commit was to allow stack mach

Revert "[WebAssembly][InstrEmitter] Foundation for multivalue call lowering"

Summary:
This reverts commit 3ef169e586f4d14efe690c23c878d5aa92a80eb5. 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

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[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. Ins

[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

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[WebAssembly] Add memory intrinsics handling to mayThrow()

Summary:
Previously, `WebAssembly::mayThrow()` assumed all inputs are global
addresses. But when intrinsics, such as `memcpy`, `memmove`, o

[WebAssembly] Add memory intrinsics handling to mayThrow()

Summary:
Previously, `WebAssembly::mayThrow()` assumed all inputs are global
addresses. But when intrinsics, such as `memcpy`, `memmove`, or `memset`
are lowered to external symbols in instruction selection and later
emitted as library calls. And these functions don't throw.

This patch adds handling to those memory intrinsics to `mayThrow`
function. But while most of libcalls don't throw, we can't guarantee all
of them don't throw, so currently we conservatively return true for all
other external symbols.

I think a better way to solve this problem is to embed 'nounwind' info
in `TargetLowering::CallLoweringInfo`, so that we can access the info
from the backend. This will also enable transferring 'nounwind'
properties of LLVM IR instructions. Currently we don't transfer that
info and we can only access properties of callee functions, if the
callees are within the module. Other targets don't need this info in the
backend because they do all the processing before isel, but it will help
us because that info will reduce code size increase in fixing unwind
destination mismatches in CFGStackify.

But for now we return false for these memory intrinsics and true for all
other libcalls conservatively.

Reviewers: dschuff

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68553

llvm-svn: 373967

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[webassembly] Apply llvm-prefer-register-over-unsigned from clang-tidy to LLVM

Summary:
This clang-tidy check is looking for unsigned integer variables whose initializer
starts with an implicit cast

[webassembly] Apply llvm-prefer-register-over-unsigned from clang-tidy to LLVM

Summary:
This clang-tidy check is looking for unsigned integer variables whose initializer
starts with an implicit cast from llvm::Register and changes the type of the
variable to llvm::Register (dropping the llvm:: where possible).

Reviewers: aheejin

Subscribers: jholewinski, MatzeB, qcolombet, dschuff, jyknight, dylanmckay, sdardis, nemanjai, jvesely, wdng, nhaehnle, sbc100, jgravelle-google, kristof.beyls, hiraditya, aheejin, kbarton, fedor.sergeev, javed.absar, asb, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, jrtc27, MaskRay, zzheng, edward-jones, atanasyan, rogfer01, MartinMosbeck, brucehoult, the_o, tpr, PkmX, jocewei, jsji, Petar.Avramovic, asbirlea, Jim, s.egerton, llvm-commits

Tags: #llvm

Differential Revision for whole review: https://reviews.llvm.org/D65962

llvm-svn: 368627

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Finish moving TargetRegisterInfo::isVirtualRegister() and friends to llvm::Register as started by r367614. NFC

llvm-svn: 367633

[WebAssembly] refactored utilities to not depend on MachineInstr

Summary:
Most of these functions can work for MachineInstr and MCInst
equally now.

Reviewers: dschuff

Subscribers: MatzeB, sbc100,

[WebAssembly] refactored utilities to not depend on MachineInstr

Summary:
Most of these functions can work for MachineInstr and MCInst
equally now.

Reviewers: dschuff

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64643

llvm-svn: 365965

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[WebAssembly] Implement tail calls and unify tablegen call classes

Summary:
Implements direct and indirect tail calls enabled by the 'tail-call'
feature in both DAG ISel and FastISel. Updates existi

[WebAssembly] Implement tail calls and unify tablegen call classes

Summary:
Implements direct and indirect tail calls enabled by the 'tail-call'
feature in both DAG ISel and FastISel. Updates existing call tests and
adds new tests including a binary encoding test.

Reviewers: aheejin

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62877

llvm-svn: 364445

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[WebAssembly] Fix unwind destination mismatches in CFG stackify

Summary:
Linearing the control flow by placing `try`/`end_try` markers can create
mismatches in unwind destinations. This patch resolv

[WebAssembly] Fix unwind destination mismatches in CFG stackify

Summary:
Linearing the control flow by placing `try`/`end_try` markers can create
mismatches in unwind destinations. This patch resolves these mismatches
by wrapping those instructions with an incorrect unwind destination with
a nested `try`/`catch`/`end_try` and branching to the right destination
within the new catch block.

Reviewers: dschuff

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D48345

llvm-svn: 357343

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