[WebAssembly][NFC] Consolidate TargetRegisterClass=>COPY opcode conversion into a single helper

Previously WebAssemblyCFGStackify, WebAssemblyInstrInfo, and
WebAssemblyPeephole all had equivalent lo

[WebAssembly][NFC] Consolidate TargetRegisterClass=>COPY opcode conversion into a single helper

Previously WebAssemblyCFGStackify, WebAssemblyInstrInfo, and
WebAssemblyPeephole all had equivalent logic for this. Move it into a
common helper in WebAssemblyUtilities.

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[WebAssembly] Support clang -fwasm-exceptions for bitcode

This supports bitcode compilation using `clang -fwasm-exceptions`.

---

The current situation:

Currently the backend requires two options

[WebAssembly] Support clang -fwasm-exceptions for bitcode

This supports bitcode compilation using `clang -fwasm-exceptions`.

---

The current situation:

Currently the backend requires two options for Wasm EH:
`-wasm-enable-eh` and `-exception-model=wasm`. Wasm SjLj requires two
options as well: `-wasm-enable-sjlj` and `-exception-model=wasm`. When
using Wasm EH via Emscripten, you only need to pass `-fwasm-exceptions`,
and these options will be added within the clang driver. This
description will focus on the case of Wasm EH going forward, but Wasm
SjLj's case is similar.

When you pass `-fwasm-exceptions` to emcc and clang driver, the clang
driver adds these options to the command line that calls the clang
frontend (`clang -cc1`): `-mllvm -wasm-enable-eh` and
`-exception-model=wasm`. `-wasm-enable-eh` is prefixed with `-mllvm`, so
it is passed as is to the backend. But `-exception-model` is parsed and
processed within the clang frontend and stored in `LangOptions` class.
This info is later transferred to `TargetOptions` class, and then
eventually passed to `MCAsmInfo` class. All LLVM code queries this
`MCAsmInfo` to get the exception model.

---

Problem:

The problem is the whole `LangOptions` processing is bypassed when
compiling bitcode, so the information transfer of `LangOptions` ->
`TargetOptions` -> `MCAsmInfo` does not happen. They are all set to
`ExceptionHandling::None`, which is the default value.

---

What other targets do, and why we can't do the same:

Other targets support bitcode compilation by the clang driver, but they
can do that by using different triples. For example, X86 target supports
multiple triples, each of which has its own subclass of `MCAsmInfo`, so
it can hardcode the appropriate exception model within those subclasses'
constructors. But we don't have separate triples for each exception
mode: none, emscripten, and wasm.

---

What this CL does:

If we can figure out whether `-wasm-enable-eh` is passed to the backend,
we can programatically set the exception model from the backend, rather
than requiring it to be passed.

So we check `WasmEnableEH` and `WasmEnableSjLj` variables, which are
`cl::opt` for `-wasm-enable-eh` and `-wasm-enable-sjlj`, in
`WebAssemblyMCAsmInfo` constructor, and if either of them is set, we set
`MCAsmInfo.ExceptionType` to Wasm. `TargetOptions` cannot be updated
there, so we make sure they are the same later.

Fixes https://github.com/emscripten-core/emscripten/issues/15712.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D115893

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[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 r

[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

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Revert "[WebAssembly] Implementation of global.get/set for reftypes in LLVM IR"

This reverts commit 4facbf213c51e4add2e8c19b08d5e58ad71c72de.

```
********************
FAIL: LLVM :: CodeGen/WebAssem

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.

```

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[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 r

[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

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Revert "Implementation of global.get/set for reftypes in LLVM IR"

This reverts commit 31859f896cf90d64904134ce7b31230f374c3fcc.

Causing SVE and RISCV-V test failures on bots.

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

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

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Revert "[WebAssembly][CodeGen] IR support for WebAssembly local variables"

This reverts commit bf35f4af51cddd743435bb6b94a45592c967891a. There was
an error in a shared-library build.

[WebAssembly][CodeGen] IR support for WebAssembly local variables

This patch adds TargetStackID::WasmLocal. This stack holds locations of
values that are only addressable by name -- not via a point

[WebAssembly][CodeGen] IR support for WebAssembly local variables

This patch adds TargetStackID::WasmLocal. This stack holds locations of
values that are only addressable by name -- not via a pointer to memory.
For the WebAssembly target, these objects are lowered to WebAssembly
local variables, which are managed by the WebAssembly run-time and are
not addressable by linear memory.

For the WebAssembly target IR indicates that an AllocaInst should be put
on TargetStackID::WasmLocal by putting it in the non-integral address
space WASM_ADDRESS_SPACE_WASM_VAR, with value 1. SROA will mostly lift
these allocations to SSA locals, but any alloca that reaches instruction
selection (usually in non-optimized builds) will be assigned the new
TargetStackID there. Loads and stores to those values are transformed
to new WebAssemblyISD::LOCAL_GET / WebAssemblyISD::LOCAL_SET nodes,
which then lower to the type-specific LOCAL_GET_I32 etc instructions via
tablegen patterns.

Differential Revision: https://reviews.llvm.org/D101140

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Revert "[WebAssembly][CodeGen] IR support for WebAssembly local variables"

This reverts commit 00ecf18979e3326b3afee8af3dc701c53ffdc93f, as it
broke the AMDGPU build. Will reland later with a fix.

[WebAssembly][CodeGen] IR support for WebAssembly local variables

This patch adds TargetStackID::WasmLocal. This stack holds locations of
values that are only addressable by name -- not via a point

[WebAssembly][CodeGen] IR support for WebAssembly local variables

This patch adds TargetStackID::WasmLocal. This stack holds locations of
values that are only addressable by name -- not via a pointer to memory.
For the WebAssembly target, these objects are lowered to WebAssembly
local variables, which are managed by the WebAssembly run-time and are
not addressable by linear memory.

For the WebAssembly target IR indicates that an AllocaInst should be put
on TargetStackID::WasmLocal by putting it in the non-integral address
space WASM_ADDRESS_SPACE_WASM_VAR, with value 1. SROA will mostly lift
these allocations to SSA locals, but any alloca that reaches instruction
selection (usually in non-optimized builds) will be assigned the new
TargetStackID there. Loads and stores to those values are transformed
to new WebAssemblyISD::LOCAL_GET / WebAssemblyISD::LOCAL_SET nodes,
which then lower to the type-specific LOCAL_GET_I32 etc instructions via
tablegen patterns.

Differential Revision: https://reviews.llvm.org/D101140

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[WebAssembly] Add TargetInstrInfo::getCalleeOperand

DwarfDebug unconditionally assumes for all call instructions the 0th
operand is the callee operand, which seems to be true for other targets,
but

[WebAssembly] Add TargetInstrInfo::getCalleeOperand

DwarfDebug unconditionally assumes for all call instructions the 0th
operand is the callee operand, which seems to be true for other targets,
but not for WebAssembly. This adds `TargetInstrInfo::getCallOperand`
method whose default implementation returns `getOperand(0)` and makes
WebAssembly overrides it to use its own utility method to get the callee
operand.

This also fixes an existing bug in `WebAssembly::getCalleeOp`, which was
uncovered by this CL.

Reviewed By: dschuff, djtodoro

Differential Revision: https://reviews.llvm.org/D102978

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[WebAssembly] Put utility functions in Utils directory (NFC)

This CL
1. Creates Utils/ directory under lib/Target/WebAssembly
2. Moves existing WebAssemblyUtilities.cpp|h into the Utils/ directory
3

[WebAssembly] Put utility functions in Utils directory (NFC)

This CL
1. Creates Utils/ directory under lib/Target/WebAssembly
2. Moves existing WebAssemblyUtilities.cpp|h into the Utils/ directory
3. Creates Utils/WebAssemblyTypeUtilities.cpp|h and put type
declarataions and type conversion functions scattered in various
places into this single place.

It has been suggested several times that it is not easy to share utility
functions between subdirectories (AsmParser, DIsassembler, MCTargetDesc,
...). Sometimes we ended up [[ https://reviews.llvm.org/D92840#2478863 | duplicating ]] the same function because of
this.

There are already other targets doing this: AArch64, AMDGPU, and ARM
have Utils/ subdirectory under their target directory.

This extracts the utility functions into a single directory Utils/ and
make them sharable among all passes in WebAssembly/ and its
subdirectories. Also I believe gathering all type-related conversion
functionalities into a single place makes it more usable. (Actually I
was working on another CL that uses various type conversion functions
scattered in multiple places, which became the motivation for this CL.)

Reviewed By: dschuff, aardappel

Differential Revision: https://reviews.llvm.org/D100995

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