[WebAssembly] Added initial type checker to MC Assembler

This to protect against non-sensical instruction sequences being assembled,
which would either cause asserts/crashes further down, or a Wasm

[WebAssembly] Added initial type checker to MC Assembler

This to protect against non-sensical instruction sequences being assembled,
which would either cause asserts/crashes further down, or a Wasm module being output that doesn't validate.

Unlike a validator, this type checker is able to give type-errors as part of the parsing process, which makes the assembler much friendlier to be used by humans writing manual input.

Because the MC system is single pass (instructions aren't even stored in MC format, they are directly output) the type checker has to be single pass as well, which means that from now on .globaltype and .functype decls must come before their use. An extra pass is added to Codegen to collect information for this purpose, since AsmPrinter is normally single pass / streaming as well, and would otherwise generate this information on the fly.

A `-no-type-check` flag was added to llvm-mc (and any other tools that take asm input) that surpresses type errors, as a quick escape hatch for tests that were not intended to be type correct.

This is a first version of the type checker that ignores control flow, i.e. it checks that types are correct along the linear path, but not the branch path. This will still catch most errors. Branch checking could be added in the future.

Differential Revision: https://reviews.llvm.org/D104945

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[WebAssembly] Rename event to tag

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 referenc

[WebAssembly] Rename event to tag

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

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[WebAssembly] Update InstPrinter and AsmParser for new EH instructions

This updates InstPrinter and AsmParser for `delegate` and `catch_all`
instructions. Both will reject programs with multiple `ca

[WebAssembly] Update InstPrinter and AsmParser for new EH instructions

This updates InstPrinter and AsmParser for `delegate` and `catch_all`
instructions. Both will reject programs with multiple `catch_all`s per a
single `try`. And InstPrinter uses `EHInstStack` to figure out whether
to print catch label comments: It does not print catch label comments
for second `catch` or `catch_all` in a `try`.

Reviewed By: aardappel

Differential Revision: https://reviews.llvm.org/D94051

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[WebAssembly] Update InstPrinter support for EH

- Updates InstPrinter to handle `catch_all`.
- Makes `rethrow` condition an early exit from the function to make the
rest simpler.
- Unify label and

[WebAssembly] Update InstPrinter support for EH

- Updates InstPrinter to handle `catch_all`.
- Makes `rethrow` condition an early exit from the function to make the
rest simpler.
- Unify label and catch counters. They don't need to be counted
separately and this will help `delegate` instruction later.
- Removes `LastSeenEHInst` field. This was first introduced to handle
when there are more than one `catch` blocks per `try`, but this was
not implemented correctly and not being used at the moment anyway.
- Reenables all tests in cfg-stackify-eh.ll that don't deal with unwind
destination mismatches, which will be handled in a later CL.

Reviewed By: dschuff, tlively, aardappel

Differential Revision: https://reviews.llvm.org/D94043

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[WebAssembly] Update basic EH instructions for the new spec

This implements basic instructions for the new spec.

- Adds new versions of instructions: `catch`, `catch_all`, and `rethrow`
- Adds supp

[WebAssembly] Update basic EH instructions for the new spec

This implements basic instructions for the new spec.

- Adds new versions of instructions: `catch`, `catch_all`, and `rethrow`
- Adds support for instruction selection for the new instructions
- `catch` needs a custom routine for the same reason `throw` needs one,
to encode `__cpp_exception` tag symbol.
- Updates `WebAssembly::isCatch` utility function to include `catch_all`
and Change code that compares an instruction's opcode with `catch` to
use that function.
- LateEHPrepare
- Previously in LateEHPrepare we added `catch` instruction to both
`catchpad`s (for user catches) and `cleanuppad`s (for destructors).
In the new version `catch` is generated from `llvm.catch` intrinsic
in instruction selection phase, so we only need to add `catch_all`
to the beginning of cleanup pads.
- `catch` is generated from instruction selection, but we need to
hoist the `catch` instruction to the beginning of every EH pad,
because `catch` can be in the middle of the EH pad or even in a
split BB from it after various code transformations.
- Removes `addExceptionExtraction` function, which was used to
generate `br_on_exn` before.
- CFGStackfiy: Deletes `fixUnwindMismatches` function. Running this
function on the new instruction causes crashes, and the new version
will be added in a later CL, whose contents will be completely
different. So deleting the whole function will make the diff easier to
read.
- Reenables all disabled tests in exception.ll and eh-lsda.ll and a
single basic test in cfg-stackify-eh.ll.
- Updates existing tests to use the new assembly format. And deletes
`br_on_exn` instructions from the tests and FileCheck lines.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D94040

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[WebAssembly] Remove unneeded MCSymbolRefExpr variants

We record the type of the symbol (event/function/data/global) in the
MCWasmSymbol and so it should always be clear how to handle a relocation
b

[WebAssembly] Remove unneeded MCSymbolRefExpr variants

We record the type of the symbol (event/function/data/global) in the
MCWasmSymbol and so it should always be clear how to handle a relocation
based on the symbol itself.

The exception is a function which still needs the special @TYPEINDEX
then the relocation contains the signature rather than the address
of the functions.

Differential Revision: https://reviews.llvm.org/D58472

llvm-svn: 354697

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[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

[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

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