If the SDNode is used it can pick up the wrong results number, for
example looking at the known bits of the first result where it should be
looking at the second. The SDValue is already present as the
SelectCodeCommon checks move from parent to child, pass the SDValue
through to CheckNodePredicate as Op so that it can use it if necessary.
SDNode *N is still generated, keeping most PatFrags the same.

Fixes #137274

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>

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

This better aligns with how the feature is being referred to and what
runtimes (V8) are calling it.

Even though in `Subtarget` we defined `SIMDLevel` as a number so
`hasRelaxedSIMD` automatically means `hasSIMD128`,
https://github.com/llvm/llvm-project/blob/0caf0c93e759816663af52e8632d1c3953dbc715/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h#L36-L40
https://github.com/llvm/llvm-project/blob/0caf0c93e759816663af52e8632d1c3953dbc715/llvm/lib/Target/WebAssembly/WebAssemblySubtarget.h#L107

specifying only `relaxed-simd` feature on a program that needs `simd128`
instructions to compile fails, because of this query in `AsmPrinter`:
https://github.com/llvm/llvm-project/blob/d0d05aec3b6792136a9f75eb85dd2ea66005ae12/llvm/lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp#L644-L645

This `verifyInstructionPredicates` function (and other functions called
by this function) is generated by

https://github.com/llvm/llvm-project/blob/main/llvm/utils/TableGen/InstrInfoEmitter.cpp,
and looks like this (you can check it in the
`lib/Target/WebAssembly/WebAssemblyGenInstrInfo.inc` in your build
directory):
```cpp
void verifyInstructionPredicates(
    unsigned Opcode, const FeatureBitset &Features) {
  FeatureBitset AvailableFeatures = computeAvailableFeatures(Features);
  FeatureBitset RequiredFeatures = computeRequiredFeatures(Opcode);
  FeatureBitset MissingFeatures =
      (AvailableFeatures & RequiredFeatures) ^
      RequiredFeatures;
  ...
}
```

And `computeAvailableFeatures` is just a set query, like this:
```cpp
inline FeatureBitset computeAvailableFeatures(const FeatureBitset &FB) {
  FeatureBitset Features;
  if (FB[WebAssembly::FeatureAtomics])
    Features.set(Feature_HasAtomicsBit);
  if (FB[WebAssembly::FeatureBulkMemory])
    Features.set(Feature_HasBulkMemoryBit);
  if (FB[WebAssembly::FeatureExceptionHandling])
    Features.set(Feature_HasExceptionHandlingBit);
  ...
```

So this is how currently `HasSIMD128` is defined:

https://github.com/llvm/llvm-project/blob/0caf0c93e759816663af52e8632d1c3953dbc715/llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.td#L79-L81

The things being checked in this `computeAvailableFeatures`, and in turn
in `AsmPrinter`, are `AssemblerPredicate`s. These only check which bits
are set in the features set and are different from `Predicate`s, which
can call `Subtarget` functions like `Subtarget->hasSIMD128()`.

But apparently we can use `all_of` and `any_of` directives in
`AssemblerPredicate`, and we can make `simd128`'s `AssemblerPredicate`
set in `relaxed-simd` is set by the condition as an 'or' of the two.

Fixes #98502.

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

This currently only defines a constant, but in the future will be used
to gate builtins for experimenting and prototyping half-precision
proposal (https://github.com/WebAssembly/half-precision).

Adding to allow users to get this flag into the target features section for
future use cases.

Reviewed By: tlively, aheejin

Differential Revision: https://reviews.llvm.org/D158409