Identified with misc-include-cleaner.

This adds support for binary generation for the new EH proposal.

So far the only case that we emitted variable immediate operands in
binary has been `br_table`'s destinations. (Other `variable_ops` uses in
TableGen files are register operands, such as the operands of `call`, so
they don't get emitted in binary as a part of the same instruction.)

With this PR, variable immediate operands can include `try_table`'s
operands:
- The number of of catch clauses
- catch clauses sub-opcodes
  - `catch`: 0x00
  - `catch_ref`: 0x01
  - `catch_all`: 0x02
  - `catch_all_ref`: 0x03
- catch clauses' destinations

With `try_table`, we now have variable expr operands for `try_table`'s
catch clauses' tags. We treat their fixups in the same way we do for
tags in other instructions such as in `throw`.

Diff without whitespace will be easier to view.

Note that llvm::support::endianness has been renamed to
llvm::endianness while becoming an enum class as opposed to an
enum. This patch replaces support::{big,little,native} with
llvm::endianness::{big,little,native}.

For inline WebAssembly, passing a numeric operand to global.get is
unsupported. This causes encodeInstruction to reach an llvm_unreachable
call, leading to undefined behaviors. This patch fixes the issue for
this invalid instruction encoding, making it report an error by adding
an MCContext field in class WebAssemblyMCCodeEmitter.

Reviewed By: sbc100, bryanpkc

Differential Revision: https://reviews.llvm.org/D154734

Change MCInstrDesc::operands to return an ArrayRef so we can easily use
it everywhere instead of the (IMHO ugly) opInfo_begin and opInfo_end.
A future patch will remove opInfo_begin and opInfo_end.

Also use it instead of raw access to the OpInfo pointer. A future patch
will remove this pointer.

Differential Revision: https://reviews.llvm.org/D142213

This patch implements the intrinsic for ref.null.
In the process of implementing int_wasm_ref_null_func() and
int_wasm_ref_null_extern() intrinsics, it removes the redundant
HeapType.

This also causes the textual assembler syntax for ref.null to
change. Instead of receiving an argument: `func` or `extern`, the
instruction mnemonic is either ref.null_func or ref.null_extern,
without the need for a further operand.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D114979

We recently decided to change 'event' to 'tag', and 'event section' to
'tag section', out of the rationale that the section contains a
generalized tag that references a type, which may be used for something
other than exceptions, and the name 'event' can be confusing in the web
context.

See
- https://github.com/WebAssembly/exception-handling/issues/159#issuecomment-857910130
- https://github.com/WebAssembly/exception-handling/pull/161

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D104423

As mentioned in TODO comment, casting double to float causes NaNs to change bits.
To avoid the change, this patch adds support for single-floating-point immediate value on MachineCode.

Patch by Yuta Saito.

Differential Revision: https://reviews.llvm.org/D77384