[WebAssembly] Always emit functype directives for defined functions

This fixes bug <https://github.com/llvm/llvm-project/issues/54022>. For
now this means that defined functions will have two .funct

[WebAssembly] Always emit functype directives for defined functions

This fixes bug <https://github.com/llvm/llvm-project/issues/54022>. For
now this means that defined functions will have two .functype directives
emitted. Given discussion in that bug has suggested interest in moving
towards using something other than .functype to mark the beginning of a
function (which would, as a side-effect, solve this issue), this patch
doesn't attempt to avoid that duplication.

Some test cases that used CHECK-LABEL: foo rather than CHECK-LABEL: foo:
are broken by this change. This patch updates those test cases to always
have a colon at the end of the CHECK-LABEL string.

Differential Revision: https://reviews.llvm.org/D122134

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[WebAssembly] Tidy up EH/SjLj options

This CL is small, but the description can be a little long because I'm
trying to sum up the status quo for Emscripten/Wasm EH/SjLj options.

First, this CL adds

[WebAssembly] Tidy up EH/SjLj options

This CL is small, but the description can be a little long because I'm
trying to sum up the status quo for Emscripten/Wasm EH/SjLj options.

First, this CL adds an option for Wasm SjLj (`-wasm-enable-sjlj`), which
handles SjLj using Wasm EH. The implementation for this will be added as
a followup CL, but this adds the option first to do error checking.

This also adds an option for Wasm EH (`-wasm-enable-eh`), which has been
already implemented. Before we used `-exception-model=wasm` as the same
meaning as enabling Wasm EH, but after we add Wasm SjLj, it will be
possible to use Wasm EH instructions for Wasm SjLj while not enabling
EH, so going forward, to use Wasm EH, `opt` and `llc` will need this
option. This only affects `opt` and `llc` command lines and does not
affect Emscripten user interface.

Now we have two modes of EH (Emscripten/Wasm) and also two modes of SjLj
(also Emscripten/Wasm). The options corresponding to each of are:
- Emscripten EH: `-enable-emscripten-cxx-exceptions`
- Emscripten SjLj: `-enable-emscripten-sjlj`
- Wasm EH: `-wasm-enable-eh -exception-model=wasm`
`-mattr=+exception-handling`
- Wasm SjLj: `-wasm-enable-sjlj -exception-model=wasm`
`-mattr=+exception-handling`
The reason Wasm EH/SjLj's options are a little complicated are
`-exception-model` and `-mattr` are common LLVM options ane not under
our control. (`-mattr` can be omitted if it is embedded within the
bitcode file.)

And we have the following rules of the option composition:
- Emscripten EH and Wasm EH cannot be turned on at the same itme
- Emscripten SjLj and Wasm SjLj cannot be turned on at the same time
- Wasm SjLj should be used with Wasm EH

Which means we now allow these combinations:
- Emscripten EH + Emscripten SjLj: the current default in `emcc`
- Wasm EH + Emscripten SjLj:
This is allowed, but only as an interim step in which we are testing
Wasm EH but not yet have a working implementation of Wasm SjLj. This
will error out (D107687) in compile time if `setjmp` is called in a
function in which Wasm exception is used.
- Wasm EH + Wasm SjLj:
This will be the default mode later when using Wasm EH. Currently Wasm
SjLj implementation doesn't exist, so it doesn't work.
- Emscripten EH + Wasm SjLj will not work.

This CL moves these error checking routines to
`WebAssemblyPassConfig::addIRPasses`. Not sure if this is an ideal place
to do this, but I couldn't find elsewhere. Currently some checking is
done within LowerEmscriptenEHSjLj, but these checks only run if
LowerEmscriptenEHSjLj runs so it may not run when Wasm EH is used. This
moves that to `addIRPasses` and adds some more checks.

Currently LowerEmscriptenEHSjLj pass is responsible for Emscripten EH
and Emscripten SjLj. Wasm EH transformations are done in multiple
places, including WasmEHPrepare, LateEHPrepare, and CFGStackify. But in
the followup CL, LowerEmscriptenEHSjLj pass will be also responsible for
a part of Wasm SjLj transformation, because WasmSjLj will also be using
several Emscripten library functions, and we will be sharing more than
half of the transformation to do that between Emscripten SjLj and Wasm
SjLj.

Currently we have `-enable-emscripten-cxx-exceptions` and
`-enable-emscripten-sjlj` but these only work for `llc`, because for
`llc` we feed these options to the pass but when we run the pass using
`opt` the pass will be created with no options and the default options
will be used, which turns both Emscripten EH and Emscripten SjLj on.

Now we have one more SjLj option to care for, LowerEmscriptenEHSjLj pass
needs a finer way to control these options. This CL removes those
default parameters and make LowerEmscriptenEHSjLj pass read directly
from command line options specified. So if we only run
`opt -wasm-lower-em-ehsjlj`, currently both Emscripten EH and Emscripten
SjLj will run, but with this CL, none will run unless we additionally
pass `-enable-emscripten-cxx-exceptions` or `-enable-emscripten-sjlj`,
or both. This does not affect users; this only affects our `opt` tests
because `emcc` will not call either `opt` or `llc`. As a result of this,
our existing Emscripten EH/SjLj tests gained one or both of those
options in their `RUN` lines.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D107685

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[WebAssembly] Remove datalayout strings from llc tests

The data layout strings do not have any effect on llc tests and will become
misleadingly out of date as we continue to update the canonical dat

[WebAssembly] Remove datalayout strings from llc tests

The data layout strings do not have any effect on llc tests and will become
misleadingly out of date as we continue to update the canonical data layout, so
remove them from the tests.

Differential Revision: https://reviews.llvm.org/D105842

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[WebAssembly] Fix ExceptionInfo grouping again

This is a case D97677 missed. When taking out remaining BBs that are
reachable from already-taken-out exceptions (because they are not
subexcptions but

[WebAssembly] Fix ExceptionInfo grouping again

This is a case D97677 missed. When taking out remaining BBs that are
reachable from already-taken-out exceptions (because they are not
subexcptions but unwind destinations), I assumed the remaining BBs are
not EH pads, but they can be. For example,
```
try {
try {
throw 0;
} catch (int) { // (a)
}
} catch (int) { // (b)
}
try {
foo();
} catch (int) { // (c)
}
```
In this code, (b) is the unwind destination of (a) so its exception is
taken out of (a)'s exception, But even though the next try-catch is not
inside the first two-level try-catches, because the first try always
throws, its continuation BB is unreachable and the whole rest of the
function is dominated by EH pad (a), including EH pad (c). So after we
take out of (b)'s exception out of (a)'s, we also need to take out (c)'s
exception out of (a)'s, because (c) is reachable from (b).

This adds one more step before what we did for remaining BBs in D97677;
it traverses EH pads first to take subexceptions out of their incorrect
parent exception. It's the same thing as D97677, but because we can do
this before we add BBs to exceptions' sets, we don't need to fix sets
and only need to fix parent exception pointers.

Other changes are variable name changes (I changed `WE` -> `SrcWE`,
`UnwindWE` -> `DstWE` for clarity), some comment changes, and a drive-by
fix in a bug in a `LLVM_DEBUG` print statement.

Fixes https://github.com/emscripten-core/emscripten/issues/13588.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D97929

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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] Fix more ExceptionInfo grouping bugs

This fixes two bugs in `WebAssemblyExceptionInfo` grouping, created by
D97247. These two bugs are not easy to split into two different CLs,
because

[WebAssembly] Fix more ExceptionInfo grouping bugs

This fixes two bugs in `WebAssemblyExceptionInfo` grouping, created by
D97247. These two bugs are not easy to split into two different CLs,
because tests that fail for one also tend to fail for the other.

- In D97247, when fixing `ExceptionInfo` grouping by taking out
the unwind destination' exception from the unwind src's exception, we
just iterated the BBs in the function order, but this was incorrect;
this changes it to dominator tree preorder. Please refer to the
comments in the code for the reason and an example.

- After this subexception-taking-out fix, there still can be remaining
BBs we have to take out. When Exception B is taken out of Exception A
(because EHPad B is the unwind destination of EHPad A), there can
still be BBs within Exception A that are reachable from Exception B,
which also should be taken out. Please refer to the comments in the
code for more detailed explanation on why this can happen. To make
this possible, this splits `WebAssemblyException::addBlock` into two
parts: adding to a set and adding to a vector. We need to iterate on
BBs within a `WebAssemblyException` to fix this, so we add BBs to sets
first. But we add BBs to vectors later after we fix all incorrectness
because deleting BBs from vectors is expensive. I considered removing
the vector from `WebAssemblyException`, but it was not easy because
this class has to maintain a similar interface with `MachineLoop` to
be wrapped into a single interface `SortRegion`, which is used in
CFGSort.

Other misc. drive-by fixes:
- Make `WebAssemblyExceptionInfo` do not even run when wasm EH is not
used or the function doesn't have any EH pads, not to waste time
- Add `LLVM_DEBUG` lines for easy debugging
- Fix `preds` comments in cfg-stackify-eh.ll
- Fix `__cxa_throw`'s signature in cfg-stackify-eh.ll

Fixes https://github.com/emscripten-core/emscripten/issues/13554.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D97677

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[WebAssembly] Fix reverse mapping in WasmEHFuncInfo

D97247 added the reverse mapping from unwind destination to their
source, but it had a critical bug; sources can be multiple, because
multiple BBs

[WebAssembly] Fix reverse mapping in WasmEHFuncInfo

D97247 added the reverse mapping from unwind destination to their
source, but it had a critical bug; sources can be multiple, because
multiple BBs can have a single BB as their unwind destination.

This changes `WasmEHFuncInfo::getUnwindSrc` to `getUnwindSrcs` and makes
it return a vector rather than a single BB. It does not return the const
reference to the existing vector but creates a new vector because
`WasmEHFuncInfo` stores not `BasicBlock*` or `MachineBasicBlock*` but
`PointerUnion` of them. Also I hoped to unify those methods for
`BasicBlock` and `MachineBasicBlock` into one using templates to reduce
duplication, but failed because various usages require `BasicBlock*` to
be `const` but it's hard to make it `const` for `MachineBasicBlock`
usages.

Fixes https://github.com/emscripten-core/emscripten/issues/13514.
(More precisely, fixes
https://github.com/emscripten-core/emscripten/issues/13514#issuecomment-784708744)

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D97583

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[WebAssembly] Fix remapping branch dests in fixCatchUnwindMismatches

This is a case D97178 tried to solve but missed. D97178 could not handle
the case when
multiple consecutive delegates are generat

[WebAssembly] Fix remapping branch dests in fixCatchUnwindMismatches

This is a case D97178 tried to solve but missed. D97178 could not handle
the case when
multiple consecutive delegates are generated:
- Before:
```
block
br (a)
try
catch
end_try
end_block
<- (a)
```

- After
```
block
br (a)
try
...
try
try
catch
end_try
<- (a)
delegate
delegate
end_block
<- (b)
```
(The `br` should point to (b) now)

D97178 assumed `end_block` exists two BBs later than `end_try`, because
it assumed the order as `end_try` BB -> `delegate` BB -> `end_block` BB.
But it turned out there can be multiple `delegate`s in between. This
patch changes the logic so we just search from `end_try` BB until we
find `end_block`.

Fixes https://github.com/emscripten-core/emscripten/issues/13515.
(More precisely, fixes
https://github.com/emscripten-core/emscripten/issues/13515#issuecomment-784711318.)

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D97569

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[WebAssembly] Fix incorrect grouping and sorting of exceptions

This CL is not big but contains changes that span multiple analyses and
passes. This description is very long because it tries to expla

[WebAssembly] Fix incorrect grouping and sorting of exceptions

This CL is not big but contains changes that span multiple analyses and
passes. This description is very long because it tries to explain basics
on what each pass/analysis does and why we need this change on top of
that. Please feel free to skip parts that are not necessary for your
understanding.

---

`WasmEHFuncInfo` contains the mapping of <EH pad, the EH pad's next
unwind destination>. The value (unwind dest) here is where an exception
should end up when it is not caught by the key (EH pad). We record this
info in WasmEHPrepare to fix catch mismatches, because the CFG itself
does not have this info. A CFG only contains BBs and
predecessor-successor relationship between them, but in `WasmEHFuncInfo`
the unwind destination BB is not necessarily a successor or the key EH
pad BB. Their relationship can be intuitively explained by this C++ code
snippet:
```
try {
try {
foo();
} catch (int) { // EH pad
...
}
} catch (...) { // unwind destination
}
```
So when `foo()` throws, it goes to `catch (int)` first. But if it is not
caught by it, it ends up in the next unwind destination `catch (...)`.
This unwind destination is what you see in `catchswitch`'s
`unwind label %bb` part.

---

`WebAssemblyExceptionInfo` groups exceptions so that they can be sorted
continuously together in CFGSort, as we do for loops. What this analysis
does is very simple: it creates a single `WebAssemblyException` per EH
pad, and all BBs that are dominated by that EH pad are included in this
exception. We also identify subexception relationship in this way: if
EHPad A domiantes EHPad B, EHPad B's exception is a subexception of
EHPad A's exception.

This simple rule turns out to be incorrect in some cases. In
`WasmEHFuncInfo`, if EHPad A's unwind destination is EHPad B, it means
semantically EHPad B should not be included in EHPad A's exception,
because it does not make sense to rethrow/delegate to an inner scope.
This is what happened in CFGStackify as a result of this:
```
try
try
catch
... <- %dest_bb is among here!
end
delegate %dest_bb
```

So this patch adds a phase in `WebAssemblyExceptionInfo::recalculate` to
make sure excptions' unwind destinations are not subexceptions of
their unwind sources in `WasmEHFuncInfo`.

But this alone does not prevent `dest_bb` in the example above from
being sorted within the inner `catch`'s exception, even if its exception
is not a subexception of that `catch`'s exception anymore, because of
how CFGSort works, which will be explained below.

---

CFGSort places BBs within the same `SortRegion` (loop or exception)
continuously together so they can be demarcated with `loop`-`end_loop`
or `catch`-`end_try` in CFGStackify.

`SortRegion` is a wrapper for one of `MachineLoop` or
`WebAssemblyException`. `SortRegionInfo` already does some complicated
things because there discrepancies between those two data structures.
`WebAssemblyException` is what we control, and it is defined as an EH
pad as its header and BBs dominated by the header as its BBs (with a
newly added exception of unwind destinations explained in the previous
paragraph). But `MachineLoop` is an LLVM data structure and uses the
standard loop detection algorithm. So by the algorithm, BBs that are 1.
dominated by the loop header and 2. have a path back to its header.
Because of the second condition, many BBs that are dominated by the loop
header are not included in the loop. So BBs that contain `return` or
branches to outside of the loop are not technically included in
`MachineLoop`, but they can be sorted together with the loop with no
problem.

Maybe to relax the condition, in CFGSort, when we are in a `SortRegion`
we allow sorting of not only BBs that belong to the current innermost
region but also BBs that are by the current region header.
(This was written this way from the first version written by Dan, when
only loops existed.) But now, we have cases in exceptions when EHPad B
is the unwind destination for EHPad A, even if EHPad B is dominated by
EHPad A it should not be included in EHPad A's exception, and should not
be sorted within EHPad A.

One way to make things work, at least correctly, is change `dominates`
condition to `contains` condition for `SortRegion` when sorting BBs, but
this will change compilation results for existing non-EH code and I
can't be sure it will not degrade performance or code size. I think it
will degrade performance because it will force many BBs dominated by a
loop, which don't have the path back to the header, to be placed after
the loop and it will likely to create more branches and blocks.

So this does a little hacky check when adding BBs to `Preferred` list:
(`Preferred` list is a ready list. CFGSort maintains ready list in two
priority queues: `Preferred` and `Ready`. I'm not very sure why, but it
was written that way from the beginning. BBs are first added to
`Preferred` list and then some of them are pushed to `Ready` list, so
here we only need to guard condition for `Preferred` list.)

When adding a BB to `Preferred` list, we check if that BB is an unwind
destination of another BB. To do this, this adds the reverse mapping,
`UnwindDestToSrc`, and getter methods to `WasmEHFuncInfo`. And if the BB
is an unwind destination, it checks if the current stack of regions
(`Entries`) contains its source BB by traversing the stack backwards. If
we find its unwind source in there, we add the BB to its `Deferred`
list, to make sure that unwind destination BB is added to `Preferred`
list only after that region with the unwind source BB is sorted and
popped from the stack.

---

This does not contain a new test that crashes because of this bug, but
this fix changes the result for one of existing test case. This test
case didn't crash because it fortunately didn't contain `delegate` to
the incorrectly placed unwind destination BB.

Fixes https://github.com/emscripten-core/emscripten/issues/13514.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D97247

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[WebAssembly] Remap branch dests after fixCatchUnwindMismatches

Fixing catch unwind mismatches can sometimes invalidate existing branch
destinations. This CL remaps those destinations after placing

[WebAssembly] Remap branch dests after fixCatchUnwindMismatches

Fixing catch unwind mismatches can sometimes invalidate existing branch
destinations. This CL remaps those destinations after placing
try-delegates.

Fixes https://github.com/emscripten-core/emscripten/issues/13515.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D97178

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[WebAssembly] Misc. fixes in cfg-stackify-eh.ll

- Fix `preds` comments
- Delete nonexistent attributes in instructions (They used to exist in
clang-generated files, but I removed most of them to m

[WebAssembly] Misc. fixes in cfg-stackify-eh.ll

- Fix `preds` comments
- Delete nonexistent attributes in instructions (They used to exist in
clang-generated files, but I removed most of them to make the tests
tidy. We have only `nounwind` and `noreturn` left here.)
- Add missing `Function Attrs` comments in function declarations

None of these affect test function semantics or test results for now.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D97179

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[WebAssemblly] Fix EHPadStack update in fixCallUnwindMismatches

Updating `EHPadStack` with respect to `TRY` and `CATCH` instructions
have to be done after checking all other conditions, not before.

[WebAssemblly] Fix EHPadStack update in fixCallUnwindMismatches

Updating `EHPadStack` with respect to `TRY` and `CATCH` instructions
have to be done after checking all other conditions, not before. Because
we did this before checking other conditions, when we encounter `TRY`
and we want to record the current mismatching range, we already have
popped up the entry from `EHPadStack`, which we need to access to record
the range.

The `baz` call in the added test needs try-delegate because the previous
TRY marker placement for `quux` was placed before `baz`, because `baz`'s
return value was stackified in RegStackify. If this wasn't stackified
this try-delegate is not strictly necessary, but at the moment it is not
easy to identify cases like this. I plan to transfer `nounwind`
attributes from the LLVM IR to prevent cases like this. The call in the
test does not have `unwind` attribute in order to test this bug, but in
many cases of this pattern the previous call has `nounwind` attribute.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D96711

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[WebAssemblly] Fix rethrow's argument computation

Previously we assumed `rethrow`'s argument was always 0, but it turned
out `rethrow` follows the same rule with `br` or `delegate`:
https://github.c

[WebAssemblly] Fix rethrow's argument computation

Previously we assumed `rethrow`'s argument was always 0, but it turned
out `rethrow` follows the same rule with `br` or `delegate`:
https://github.com/WebAssembly/exception-handling/pull/137
https://github.com/WebAssembly/exception-handling/issues/146#issuecomment-777349038

Currently `rethrow`s generated by our backend always rethrow the
exception caught by the innermost enclosing catch, so this adds a
function to compute that and replaces `rethrow`'s argument with its
computed result.

This also renames `EHPadStack` in `InstPrinter` to `TryStack`, because
in CFGStackify we use `EHPadStack` to mean the range between
`catch`~`end`, while in `InstPrinter` we used it to mean the range
between `try`~`catch`, so choosing different names would look clearer.
Doesn't contain any functional changes in `InstPrinter`.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D96595

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[WebAssembly] Fix delegate's argument computation

I previously assumed `delegate`'s immediate argument computation
followed a different rule than that of branches, but we agreed to make
it the same

[WebAssembly] Fix delegate's argument computation

I previously assumed `delegate`'s immediate argument computation
followed a different rule than that of branches, but we agreed to make
it the same
(https://github.com/WebAssembly/exception-handling/issues/146). This
removes the need for a separate `DelegateStack` in both CFGStackify and
InstPrinter.

When computing the immediate argument, we use a different function for
`delegate` computation because in MIR `DELEGATE`'s instruction's
destination is the destination catch BB or delegate BB, and when it is a
catch BB, we need an additional step of getting its corresponding `end`
marker.

Reviewed By: tlively, dschuff

Differential Revision: https://reviews.llvm.org/D96525

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[WebAssembly] Fix catch unwind mismatches

This fixes unwind destination mismatches caused by 'catch'es, which
occur when a foreign exception is not caught by the nearest `catch` and
the next outer `

[WebAssembly] Fix catch unwind mismatches

This fixes unwind destination mismatches caused by 'catch'es, which
occur when a foreign exception is not caught by the nearest `catch` and
the next outer `catch` is not the catch it should unwind to, or the next
unwind destination should be the caller instead. This kind of mismatches
didn't exist in the previous version of the spec, because in the
previous spec `catch` was effectively `catch_all`, catching all
exceptions.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D94049

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[WebAssembly] Fix call unwind mismatches

This adds `delegate` instruction and use it to fix unwind destination
mismatches created by marker placement in CFGStackify.

There are two kinds of unwind d

[WebAssembly] Fix call unwind mismatches

This adds `delegate` instruction and use it to fix unwind destination
mismatches created by marker placement in CFGStackify.

There are two kinds of unwind destination mismatches:
- Mismatches caused by throwing instructions (here we call it "call
unwind mismatches", even though `throw` and `rethrow` can also cause
mismatches)
- Mismatches caused by `catch`es, in case a foreign exception is not
caught by the nearest `catch` and the next outer `catch` is not the
catch it should unwind to. This kind of mismatches didn't exist in the
previous version of the spec, because in the previous spec `catch` was
effectively `catch_all`, catching all exceptions.

This implements routines to fix the first kind of unwind mismatches,
which we call "call unwind mismatches". The second mismatch (catch
unwind mismatches) will be fixed in a later CL.

This also reenables all previously disabled tests in cfg-stackify-eh.ll
and updates FileCheck lines to match the new spec. Two tests were
deleted because they specifically tested the way we fixed unwind
mismatches before using `exnref`s and branches, which we don't do
anymore.

Reviewed By: tlively

Differential Revision: https://reviews.llvm.org/D94048

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[WebAssembly] Remove more unnecessary brs in CFGStackify

After placing markers, we removed some unnecessary branches, but it only
handled the simplest case. This makes more unnecessary branches to b

[WebAssembly] Remove more unnecessary brs in CFGStackify

After placing markers, we removed some unnecessary branches, but it only
handled the simplest case. This makes more unnecessary branches to be
removed.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D94047

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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] Update WasmEHPrepare for the new spec

Clang generates `wasm.get.exception` and `wasm.get.ehselector`
intrinsics, which respectively return a caught exception value (a
pointer to some C

[WebAssembly] Update WasmEHPrepare for the new spec

Clang generates `wasm.get.exception` and `wasm.get.ehselector`
intrinsics, which respectively return a caught exception value (a
pointer to some C++ exception struct) and a selector (an integer value
that tells which C++ `catch` clause the current exception matches, or
does not match any).

WasmEHPrepare is a pass that does some IR-level preparation before
instruction selection. Previously one of things we did in this pass was
to convert `wasm.get.exception` intrinsic calls to
`wasm.extract.exception` intrinsics. Their semantics were the same
except `wasm.extract.exception` did not have a token argument. We
maintained these two separate intrinsics with the same semantics because
instruction selection couldn't handle token arguments. This
`wasm.extract.exception` intrinsic was later converted to
`extract_exception` instruction in instruction selection, which was a
pseudo instruction to implement `br_on_exn`. Because `br_on_exn` pushed
an extracted value onto the value stack after the `end` instruction of a
`block`, but LLVM does not have a way of modeling that kind of behavior,
so this pseudo instruction was used to pull an extracted value out of
thin air, like this:
```
block $l0
...
br_on_exn $cpp_exception $l0
...
end
extract_exception ;; pushes values onto the stack
```

In the new spec, we don't need this pseudo instruction anymore because
`catch` itself returns a value and we don't have `br_on_exn` anymore. In
the spec `catch` returns multiple values (like `br_on_exn`), but here we
assume it only returns a single i32, which is sufficient to support C++.

So this renames `wasm.get.exception` intrinsic to `wasm.catch`. Because
this CL does not yet contain instruction selection for `wasm.catch`
intrinsic, all `RUN` lines in exception.ll, eh-lsda.ll, and
cfg-stackify-eh.ll, and a single `RUN` line in wasm-eh.cpp (which is an
end-to-end test from C++ source to assembly) fail. So this CL
temporarily disables those `RUN` lines, and for those test files without
any valid remaining `RUN` lines, adds a dummy `RUN` line to make them
pass. These tests will be reenabled in later CLs.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D94039

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[WebAssembly] Rename wasm_rethrow_in_catch intrinsic/builtin

`wasm_rethrow_in_catch` intrinsic and builtin are used in order to
rethrow an exception when the exception is caught but there is no
matc

[WebAssembly] Rename wasm_rethrow_in_catch intrinsic/builtin

`wasm_rethrow_in_catch` intrinsic and builtin are used in order to
rethrow an exception when the exception is caught but there is no
matching clause within the current `catch`. For example,
```
try {
foo();
} catch (int n) {
...
}
```
If the caught exception does not correspond to C++ `int` type, it should
be rethrown. These intrinsic/builtin were renamed `rethrow_in_catch`
because at the time I thought there would be another intrinsic for C++'s
`throw` keyword, which rethrows an exception. It turned out that `throw`
keyword doesn't require wasm's `rethrow` instruction, so we rename
`rethrow_in_catch` to just `rethrow` here.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D94038

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[WebAssembly] Change label numbers to variables in test

cfg-stackify-eh.ll contains many `CHECK` lines specifying label / catch
comments with numbers. These numbers are subject to change every time

[WebAssembly] Change label numbers to variables in test

cfg-stackify-eh.ll contains many `CHECK` lines specifying label / catch
comments with numbers. These numbers are subject to change every time
any block/loop/try is added in the middle in existing functions or any
other function is added in the middle of the file, generating a large
number of lines in diffs. This change converts them to variables so they
can be more resistent to future changes.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D94037

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[WebAssembly] Fix fixEndsAtEndOfFunction for try-catch

When the function return type is non-void and `end` instructions are at
the very end of a function, CFGStackify's `fixEndsAtEndOfFunction`
func

[WebAssembly] Fix fixEndsAtEndOfFunction for try-catch

When the function return type is non-void and `end` instructions are at
the very end of a function, CFGStackify's `fixEndsAtEndOfFunction`
function fixes the corresponding block/loop/try's type to match the
function's return type. This is applied to consecutive `end` markers at
the end of a function. For example, when the function return type is
`i32`,
```
block i32 ;; return type is fixed to i32
...
loop i32 ;; return type is fixed to i32
...
end_loop
end_block
end_function
```

But try-catch is a little different, because it consists of two parts:
a try part and a catch part, and both parts' return type should satisfy
the function's return type. Which means,
```
try i32 ;; return type is fixed to i32
...
block i32 ;; this should be changed i32 too!
...
end_block
catch
...
end_try
end_function
```
As you can see in this example, it is not sufficient to only `end`
instructions at the end of a function; in case of `try`, we should
check instructions before `catch`es, in case their corresponding `try`'s
type has been fixed.

This changes `fixEndsAtEndOfFunction`'s algorithm to use a worklist
that contains a reverse iterator, each of which is a starting point for
a new backward `end` instruction search.

Fixes https://bugs.llvm.org/show_bug.cgi?id=47413.

Reviewed By: dschuff, tlively

Differential Revision: https://reviews.llvm.org/D87207

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[WebAssembly] Fix getBottom for loops

When it was first created, CFGSort only made sure BBs in each
`MachineLoop` are sorted together. After we added exception support,
CFGSort now also sorts BBs in

[WebAssembly] Fix getBottom for loops

When it was first created, CFGSort only made sure BBs in each
`MachineLoop` are sorted together. After we added exception support,
CFGSort now also sorts BBs in each `WebAssemblyException`, which
represents a `catch` block, together, and
`Region` class was introduced to be a thin wrapper for both
`MachineLoop` and `WebAssemblyException`.

But how we compute those loops and exceptions is different.
`MachineLoopInfo` is constructed using the standard loop computation
algorithm in LLVM; the definition of loop is "a set of BBs that are
dominated by a loop header and have a path back to the loop header". So
even if some BBs are semantically contained by a loop in the original
program, or in other words dominated by a loop header, if they don't
have a path back to the loop header, they are not considered a part of
the loop. For example, if a BB is dominated by a loop header but
contains `call abort()` or `rethrow`, it wouldn't have a path back to
the header, so it is not included in the loop.

But `WebAssemblyException` is wasm-specific data structure, and its
algorithm is simple: a `WebAssemblyException` consists of an EH pad and
all BBs dominated by the EH pad. So this scenario is possible: (This is
also the situation in the newly added test in cfg-stackify-eh.ll)

```
Loop L: header, A, ehpad, latch
Exception E: ehpad, latch, B
```
(B contains `abort()`, so it does not have a path back to the loop
header, so it is not included in L.)

And it is sorted in this order:
```
header
A
ehpad
latch
B
```

And when CFGStackify places `end_loop` or `end_try` markers, it
previously used `WebAssembly::getBottom()`, which returns the latest BB
in the sorted order, and placed the marker there. So in this case the
marker placements will be like this:
```
loop
header
try
A
catch
ehpad
latch
end_loop <-- misplaced!
B
end_try
```
in which nesting between the loop and the exception is not correct.
`end_loop` marker has to be placed after `B`, and also after `end_try`.

Maybe the fundamental way to solve this problem is to come up with our
own algorithm for computing loop region too, in which we include all BBs
dominated by a loop header in a loop. But this takes a lot more effort.
The only thing we need to fix is actually, `getBottom()`. If we make it
return the right BB, which means in case of a loop, the latest BB of the
loop itself and all exceptions contained in there, we are good.

This renames `Region` and `RegionInfo` to `SortRegion` and
`SortRegionInfo` and extracts them into their own file. And add
`getBottom` to `SortRegionInfo` class, from which it can access
`WebAssemblyExceptionInfo`, so that it can compute a correct bottom
block for loops.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D84724

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[WebAssembly] Remove TEEs when dests are unstackified

When created in RegStackify pass, `TEE` has two destinations, where
op0 is stackified and op1 is not. But it is possible that
op0 becomes unstac

[WebAssembly] Remove TEEs when dests are unstackified

When created in RegStackify pass, `TEE` has two destinations, where
op0 is stackified and op1 is not. But it is possible that
op0 becomes unstackified in `fixUnwindMismatches` function in
CFGStackify pass when a nested try-catch-end is introduced, violating
the invariant of `TEE`s destinations.

In this case we convert the `TEE` into two `COPY`s, which will
eventually be resolved in ExplicitLocals.

Reviewed By: dschuff

Differential Revision: https://reviews.llvm.org/D81851

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