This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated. The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.
This is part of an effort to migrate from llvm::Optional to
std::optional:
https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716
As suggested on D135572, return Optional<> from getAllocSizeArgs()
rather than the peculiar pair(0, 0) sentinel.
The method on Attribute itself does not return Optional, because
the attribute must exist in that case.
This includes a function name and a relevant instruction in error
messages when possible, making them more helpful.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D120678
This makes three thread local variables (`__THREW__`, `__threwValue`,
and `__wasm_lpad_context`) unconditionally thread local. If the target
doesn't support TLS, they will be downgraded to normal variables in
`stripThreadLocals`. This makes the object not linkable with other
objects using shared memory, which is what we intend here; these
variables should be thread local when used with shared memory. This is
what we initially tried in D88262.
But D88323 changed this: It only created these variables when threads
were supported, because `__THREW__` and `__threwValue` were always
generated even if Emscripten EH/SjLj was not used, making all objects
built without threads not linkable with shared memory, which was too
restrictive. But sometimes this is not safe. If we build an object using
variables such as `__THREW__` without threads, it can be linked to other
objects using shared memory, because the original object's `__THREW__`
was not created thread local to begin with.
So this CL basically reverts D88323 with some additional improvements:
- This checks each of the functions and global variables created within
`LowerEmscriptenEHSjLj` pass and removes it if it's not used at the
end of the pass. So only modules using those variables will be
affected.
- Moves `CoalesceFeaturesAndStripAtomics` and `AtomicExpand` passes
after all other IR pasess that can create thread local variables. It
is not sufficient to move them to the end of `addIRPasses`, because
`__wasm_lpad_context` is created in `WasmEHPrepare`, which runs inside
`addPassesToHandleExceptions`, which runs before `addISelPrepare`. So
we override `addISelPrepare` and move atomic/TLS stripping and
expanding passes there.
This also removes merges `TLS` and `NO-TLS` FileCheck lines into one
`CHECK` line, because in the bitcode level we always create them as
thread local. Also some function declarations are deleted `CHECK` lines
because they are unused.
Reviewed By: tlively, sbc100
Differential Revision: https://reviews.llvm.org/D120013
These global TLS symbols are shared across all shared libraries and
therefor should not be assumed to be local to the current module.
Also add new error in the linker when TLS relocations are used against
undefined symbols. TLS relocations are offsets into the current modules
tls data segment, and don't make sense for undefined symbols which are
modeled as global imports.
Fixes: https://github.com/emscripten-core/emscripten/issues/13398
Differential Revision: https://reviews.llvm.org/D119630
This is similar to D116619, but now it handles `invoke`s. The reason we
didn't handle `invoke`s back then was we didn't support Wasm EH + Wasm
SjLj together, and the only case SjLj transformation will see `invoke`s
is when we are using Wasm EH. (In Emscripten EH, they would have been
transformed to `call`s to invoke wrappers.)
But after D117610 we support Wasm EH + Wasm SjLj together and we can
nullify `invoke`s to `setjmp` when there is no other longjmpable calls
within the function. Actually this is very unlikely to happen in
practice, because we treat destructors as longjmpable and also treat
`__cxa_end_catch` as longjmpable even if it is not.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D118408
Wasm SjLj converts longjmpable calls into `invoke`s that unwind to
`%catch.longjmp.dispatch` BB, from where we check if the thrown
exception is a `longjmp`. But in case a call already has a `funclet`
attribute, i.e., it is within a catch scope, we have to unwind to its
unwind destination first to preserve the scoping structure. That will
eventually unwind to `%catch.longjmp.dispatch`, because all
`catchswitch` and `cleanupret` that unwind to caller are redirected to
`%catch.dispatch.longjmp` during Wasm SjLj transformation.
But the prevous code assumed `cleanuppad`'s parent pad was always an
instruction, and didn't handle when a `cleanuppad`'s parent is `none`.
This CL handles this case, and makes the `while` loop more intuitive by
removing `FromPad` condition and explicitly inserting `break`s.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D118407
Wasm EH, used with either of Emscripten SjLj or Wasm SjLj, does not
allow `setjmp` calls to be placed within a `catch` clause, because we
don't support jumping into a `catch` block. Emscripten EH does not have
this restriction. But I think this restriction wouldn't prevent most of
use cases. This CL errors out with a clear messsage for this case.
Reviewed By: dschuff, kripken
Differential Revision: https://reviews.llvm.org/D118286
When we create an invoke wrapper call, if the original call instruction
has a `noreturn` attribute, we shouldn't copy it, because we expect
invoke wrapper calls to return. This generated incorrect `free` call
before an invoke wrapper call that calls `__cxa_throw`, because
`__cxa_throw` has `noreturn` attribute.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D118274
In D117610 we treated `__cxa_end_catch` longjmpable even though it was
not to make unwind destination relationships correct. But we only need
to do this in Wasm SjLj, and doing this in Emscripten SjLj does not make
the code incorrect but add unnecessary invokes. This CL treats
`__cxa_end_catch` longjmpable only in Wasm SjLj.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D117943
D108960 added support for SjLj using Wasm EH instructions, which we call
Wasm SjLj going forward. (We call the old SjLj Emscripten SjLj) But it
did not support using Wasm EH and Wasm SjLj together. So far users of
Wasm EH had to use Wasm EH with Emscripten SjLj, which had a certain
limitation and it suffered from bigger code size increases as well.
This enables using Wasm EH and Wasm SjLj together.
1. This redirects `catchswitch` and `cleanupret` that unwind to caller
to `catch.dispatch.longjmp` BB, which is a `catchswitch` BB that
handles longjmps.
2. D108960 converted all longjmpable `call`s to `invokes` that unwind to
`catch.dispatch.longjmp`. This CL checks if the `call` is embedded
within another `catchpad`, and if so, makes it unwind to its nearest
parent's unwind destination, rather than `catch.dispatch.longjmp`.
This is necessary to preserve the scoping structure.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D117610
This uses `changeToCall` and `changeToInvokeAndSplitBasicBlock` from
`lib/Transforms/Utils`, replacing the custom logic. One difference of
those functions from our previous logic is they delete the original
`CallInst`/`InvokeInst`, which makes them tricky to use while iterating
through instructions/BBs. So this CL gathers the candidate calls first
and run them through `changeToInvokeAndSplitBasicBlock` later.
Also this renames some variables.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D116620
D107530 did a small optimization that, if a function contains `setjmp`
calls but not other calls that can `longjmp`, we don't do SjLj
transformation on those `setjmp` calls, because they don't have
possibilities of returning from `longjmp`.
But we should remove those `setjmp` calls even in that case, because
Emscripten doesn't provide that function, assuming it is lowered away by
SjLj transformation. `setjmp` always returns 0 when called directly, so
this CL replaces them with `i32 0`.
Fixes https://github.com/emscripten-core/emscripten/issues/15679.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D116619
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
This reverts commit b7b4ebbcfa.
Reason: This breaks several code-size tests in Emscripten test suite
because this exports `emscripten_longjmp` for programs that didn't do it
before.
This is a fix on top of D106525's Case 2. In D106525, in
`runEHOnFunction` which handles Emscripten EH, We rethrow `longjmp` only
when the module has any usage of `setjmp` or `longjmp`. But now Wasm
object files are linked using wasm-ld, the module this pass sees is not
the whole program, and even if this module does not contain any
`longjmp`, another file can contain it and can be linked with the
current module. This enables the rethrowing of longjmp whenever
Emscripten SjLj is enabled, regardless of whether it is used in this
module or not.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D109670
Both Wasm & Emscripten SjLj handling has a restriction that `setjmp`
cannot be called indirectly. I thought we have been erroring out on
indirect uses of `setjmp`, but some recent CL disrupted the logic and
we are not erroring out anymore.
We currently
1. Collect functions that contain `setjmp` calls in `SetjmpUsers`. This
only counts direct calls:
8f77dc459e/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp (L869-L878)
2. Run `runSjLjOnFunction` only on those `SetjmpUsers`. Within
`runSjLjOnFunction`, if we see an indirect use of `setjmp`, we error
out:
8f77dc459e/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp (L1218-L1221)
So if there are only indirect setjmp calls within the module,
`SetjmpUsers` will be empty, and `runSjLjOnFunction` is not even entered
once. And the indirect `setjmp` call will error out at link time. So in
this CL we check for the indirect uses of `setjmp` upfront before we
enter `runSjLjOnFunction`.
Also this currently errors out on `invoke @setjmp`, which can only occur
when using Wasm EH + Wasm SjLj within a function. We recently added Wasm
SjLj support but we don't support using Wasm EH + Wasm SjLj in the same
function yet. We plan to add this support very soon, so I don't think
it's worth creating another test file just for this. (This is an error
test so it needs its own file)
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D109375
This add support for SjLj using Wasm exception handling instructions:
https://github.com/WebAssembly/exception-handling/blob/master/proposals/exception-handling/Exceptions.md
This does not yet support the mixed use of EH and SjLj within a
function. It will be added in a follow-up CL.
This currently passes all SjLj Emscripten tests for wasm0/1/2/3/s,
except for the below:
- `test_longjmp_standalone`: Uses Node
- `test_dlfcn_longjmp`: Uses NodeRAWFS
- `test_longjmp_throw`: Mixes EH and SjLj
- `test_exceptions_longjmp1`: Mixes EH and SjLj
- `test_exceptions_longjmp2`: Mixes EH and SjLj
- `test_exceptions_longjmp3`: Mixes EH and SjLj
Reviewed By: dschuff, tlively
Differential Revision: https://reviews.llvm.org/D108960
This is an improvement over D107852. We don't need to enumerate specific
function names; we can just check for `noreturn` attribute. This also
requires us to make sure `__resumeExeption` and `emscripten_longjmp`
have `noreturn` attribute too; one of them is a JS function and the
other calls a JS function so Clang does not have a way to deduce they
don't return.
This is effectively NFC, because I'm not sure if there is an additional
case this case covers; if we add a custom function call that has
`noreturn` attribute, it will be processed within the SjLj handling and
turned into `__invoke` call. So this really applies to some special
functions like `emscripten_longjmp`.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D108955
There are three kinds of "rethrowing" BBs in this pass:
1. In Emscripten SjLj, after a possibly longjmping function call, we
check if the thrown longjmp corresponds to one of setjmps within the
current function. If not, we rethrow the longjmp by calling
`emscripten_longjmp`.
2. In Emscripten EH, after a possibly throwing function call, we check
if the thrown exception corresponds to the current `catch` clauses.
If not, we rethrow the exception by calling `__resumeException`.
3. When both Emscripten EH and SjLj are used, when we check for an
exception after a possibly throwing function call, it is possible
that we get not an exception but a longjmp. In this case, we
shouldn't swallow it; we should rethrow the longjmp by calling
`emscripten_longjmp`.
4. When both Emscripten EH and SjLj are used, when we check for a
longjmp after a possibly longjmping function call, it is possible
that we get not a longjmp but an exception. In this case, we
shouldn't swallot it; we should rethrow the exception by calling
`__resumeException`.
Case 1 is in Emscripten SjLj, 2 is in Emscripten EH, and 3 and 4 are
relevant when both Emscripten EH and SjLj are used. 3 and 4 were first
implemented in D106525.
We create BBs for 1, 3, and 4 in this pass. We create those BBs for
every throwing/longjmping function call, along with other BBs that
contain condition checks. What this CL does is to create a single BB
within a function for each of 1, 3, and 4 cases. These BBs are exiting
BBs in the function and thus don't have successors, so easy to be shared
between calls.
The names of BBs created are:
Case 1: `call.em.longjmp`
Case 3: `rethrow.exn`
Case 4: `rethrow.longjmp`
For the case 2 we don't currently create BBs; we only replace the
existing `resume` instruction with `call @__resumeException`. And Clang
already creates only a single `resume` BB per function and reuses it,
so we don't need to optimize this case.
Not sure what are good benchmarks for EH/SjLj, but this decreases the
size of the object file for `grfmt_jpeg.bc` (presumably from opencv) we
got from one of our users by 8.9%. Even after running `wasm-opt -O4` on
them, there is still 4.8% improvement.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D108945
When doing Emscritpen EH, if SjLj is also enabled and used and if the
thrown exception has a possiblity being a longjmp instead of an
exception, we shouldn't swallow it; we should rethrow, or relay it. It
was done in D106525 and the code is here:
8441a8eea8/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp (L858-L898)
Here is the pseudocode of that part: (copied from comments)
```
if (%__THREW__.val == 0 || %__THREW__.val == 1)
goto %tail
else
goto %longjmp.rethrow
longjmp.rethrow: ;; This is longjmp. Rethrow it
%__threwValue.val = __threwValue
emscripten_longjmp(%__THREW__.val, %__threwValue.val);
tail: ;; Nothing happened or an exception is thrown
... Continue exception handling ...
```
If the current BB (where the `invoke` is created) has successors that
has the current BB as its PHI incoming node, now that has to change to
`tail` in the pseudocode, because `tail` is the latest BB that is
connected with the next BB, but this was missing.
Reviewed By: tlively
Differential Revision: https://reviews.llvm.org/D108785
Emscripten SjLj transformation is done in four steps. This will be
mostly the same for the soon-to-be-added Wasm SjLj; the step 1, 3, and 4
will be shared and there will be separate way of doing step 2.
1. Initialize `setjmpTable` and `setjmpTableSize` in the entry BB
2. Handle `setjmp` callsites
3. Handle `longjmp` callsites
4. Cleanup and update SSA
We initialize `setjmpTable` and `setjmpTableSize` in the entry BB. But
if the entry BB contains a `setjmp` call, some `setjmp` handling
transformation will also happen in the entry BB, such as calling
`saveSetjmp`.
This is fine for Emscripten SjLj but not for Wasm SjLj, because in Wasm
SjLj we will add a dispatch BB that contains a `switch` right after the
entry BB, from which we jump to one of post-`setjmp` BBs. And this
dispatch BB should precede all `setjmp` calls.
Emscripten SjLj (current):
```
entry:
%setjmpTable = ...
%setjmpTableSize = ...
...
call @saveSetjmp(...)
```
Wasm SjLj (follow-up):
```
entry:
%setjmpTable = ...
%setjmpTableSize = ...
setjmp.dispatch:
...
; Jump to the right post-setjmp BB, if we are returning from a
; longjmp. If this is the first setjmp call, go to %entry.split.
switch i32 %no, label %entry.split [
i32 1, label %post.setjmp1
i32 2, label %post.setjmp2
...
i32 N, label %post.setjmpN
]
entry.split:
...
call @saveSetjmp(...)
```
So in Wasm SjLj we split the entry BB to make the entry block only for
`setjmpTable` and `setjmpTableSize` initialization and insert a
`setjmp.dispatch` BB. (This part is not in this CL. This will be a
follow-up.) But note that Emscripten SjLj and Wasm SjLj share all
steps except for the step 2. If we only split the entry BB only for Wasm
SjLj, there will be one more `if`-`else` and the code will be more
complicated.
So this CL splits the entry BB in Emscripten SjLj and put only
initialization stuff there as follows:
Emscripten SjLj (this CL):
```
entry:
%setjmpTable = ...
%setjmpTableSize = ...
br %entry.split
entry.split:
...
call @saveSetjmp(...)
```
This is just done to share code with Wasm SjLj. It adds an unnecessary
branch but this will be removed in later optimization passes anyway.
This is in effect NFC, meaning the program behavior will not change, but
existing ll tests files have changed because the entry block was split.
The reason I upload this in a separate CL is to make the Wasm SjLj diff
tidier, because this changes many existing Emscripten SjLj tests, which
can be confusing for the follow-up Wasm SjLj CL.
Reviewed By: tlively
Differential Revision: https://reviews.llvm.org/D108729
Emscripten SjLj and (soon-to-be-added) Wasm SjLj transformation share
many steps:
1. Initialize `setjmpTable` and `setjmpTableSize` in the entry BB
2. Handle `setjmp` callsites
3. Handle `longjmp` callsites
4. Cleanup and update SSA
1, 3, and 4 are identical for Emscripten SjLj and Wasm SjLj. Only the
step 2 is different. This CL extracts the current Emscripten SjLj's
longjmp callsites handling into a function. The reason to make this a
separate CL is, without this, the diff tool cannot compare things well
in the presence of moved code and added code in the followup Wasm SjLj
CL, and it ends up mixing them together, making the diff unreadable.
Also fixes some typos and variable names. So far we've been calling the
buffer argument to `setjmp` and `longjmp` `jmpbuf`, but the name used in
the man page for those functions is `env`, so updated them to be
consistent.
Reviewed By: tlively
Differential Revision: https://reviews.llvm.org/D108728
We update SSA in two steps in Emscripten SjLj:
1. Rewrite uses of `setjmpTable` and `setjmpTableSize` variables and
place `phi`s where necessary, which are updated where we call
`saveSetjmp`.
2. Do a whole function level SSA update for all variables, because we
split BBs where `setjmp` is called and there are possibly variable
uses that are not dominated by a def.
(See 955b91c19c/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp (L1314-L1324))
We have been using `SSAUpdater` to do this, but `SSAUpdaterBulk` class
was added after this pass was first created, and for the step 2 it looks
like a better alternative with a possible performance benefit. Not sure
the author is aware of it, but `SSAUpdaterBulk` seems to have a
limitation: it cannot handle a use within the same BB as a def but
before it. For example:
```
... = %a + 1
%a = foo();
```
or
```
%a = %a + 1
```
The uses `%a` in RHS should be rewritten with another SSA variable of
`%a`, most likely one generated from a `phi`. But `SSAUpdaterBulk`
thinks all uses of `%a` are below the def of `%a` within the same BB.
(`SSAUpdater` has two different functions of rewriting because of this:
`RewriteUse` and `RewriteUseAfterInsertions`.) This doesn't affect our
usage in the step 2 because that deals with possibly non-dominated uses
by defs after block splitting. But it does in the step 1, which still
uses `SSAUpdater`.
But this CL also simplifies the step 1 by using `make_early_inc_range`,
removing the need to advance the iterator before rewriting a use.
This is NFC; the test changes are just the order of PHI nodes.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D108583
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
For SjLj, we allocate a table to record setjmp buffer info in the entry
of each setjmp-calling function by inserting a `malloc` call, and insert
a `free` call to free the buffer before each `ret` instruction.
But this is not sufficient; we have to free the buffer before we throw.
In SjLj handling, normal functions that can possibly throw or longjmp
are wrapped with an invoke and caught within the function so they don't
end up escaping the function. But three functions throw and escape the
function:
- `__resumeException` (Emscripten library function used for Emscripten
EH)
- `emscripten_longjmp` (Emscripten library function used for Emscripten
SjLj)
- `__cxa_throw` (libc++abi function called when for C++ `throw` keyword)
The first two functions are used to rethrow the current
exception/longjmp when the caught exception/longjmp is not for the
current function. `__cxa_throw` is used for exception, and because we
consider that a function that cannot longjmp, it escapes the function
right away, before which we should free the buffer.
Currently `lsan.test_longjmp3` and `lsan.test_exceptions_longjmp3` fail
in Emscripten; this CL fixes these.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D107852
Currently, when Wasm EH is used with Emscripten SjLj, Emscripten SjLj
cannot handle `invoke` instructions - it assumes all `invoke`s have been
lowered away with Emscripten EH. But in Wasm EH they are lowered in
instruction selection, so they are still present in the IR stage. This
happens when
1. Wasm EH and Emscripten SjLj are used together
2. A function that calls `setjmp` uses exceptions, i.e., has `invoke`s
We were already erroring out with an assertion failure in this case, but
this CL makes it error out more properly with a valid error message.
Wasm EH + Wasm SjLj will not have this restrictions. (it will have
another restriction though, e.g., `setjmp` cannot be called within
`catch`. But why would anyone do that..)
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D107687
When there is a `setjmp` call in a function, we transform every callsite
of `setjmp` to record its information by calling `saveSetjmp` function,
and we also transform every callsite of a function that can longjmp to
to check if a longjmp occurred and if so jump to the corresponding
post-setjmp BB. Currently we are doing this for every function that
contains a call to `setjmp`, but if there is no other function call
within that function that can longjmp, this transformation of `setjmp`
callsite and all the preparation of `setjmpTable` in the entry of the
function are not necessary.
This checks if a setjmp-calling function has any other calls that can
longjmp, and if not, skips the function for the SjLj transformation.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D107530
- Rename `wasm.catch` intrinsic to `wasm.catch.exn`, because we are
planning to add a separate `wasm.catch.longjmp` intrinsic which
returns two values.
- Rename several variables
- Remove an unnecessary parameter from `canLongjmp` and `isEmAsmCall`
from LowerEmscriptenEHSjLj pass
- Add `-verify-machineinstrs` in a test for a safety measure
- Add more comments + fix some errors in comments
- Replace `std::vector` with `SmallVector` for cases likely with small
number of elements
- Renamed `EnableEH`/`EnableSjLj` to `EnableEmEH`/`EnableEmSjLj`: We are
soon going to add `EnableWasmSjLj`, so this makes the distincion
clearer
Reviewed By: tlively
Differential Revision: https://reviews.llvm.org/D107405
When Emscripten EH mixes with Emscripten SjLj, we are not currently
handling some of them correctly. There are three cases:
1. The current function calls `setjmp` and there is an `invoke` to a
function that can either throw or longjmp. In this case, we have to
check both for exception and longjmp. We are currently handling this
case correctly:
0c0eb76782/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp (L1058-L1090)
When inserting routines for functions that can longjmp, which we do
only for setjmp-calling functions, we check if the function was
previously an `invoke` and handle it correctly.
2. The current function does NOT call `setjmp` and there is an `invoke`
to a function that can either throw or longjmp. Because there is no
`setjmp` call, we haven't been doing any check for functions that can
longjmp. But in that case, for `invoke`, we only check for an
exception and if it is not an exception we reset `__THREW__` to 0,
which can silently swallow the longjmp:
0c0eb76782/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp (L70-L80)
This CL fixes this.
3. The current function calls `setjmp` and there is no `invoke`. Because
it is not an `invoke`, we haven't been doing any check for functions
that can throw, and only insert longjmp-checking routines for
functions that can longjmp. But in that case, if a longjmpable
function throws, we only check for a longjmp so if it is not a
longjmp we reset `__THREW__` to 0, which can silently swallow the
exception:
0c0eb76782/llvm/lib/Target/WebAssembly/WebAssemblyLowerEmscriptenEHSjLj.cpp (L156-L169)
This CL fixes this.
To do that, this moves around some code, so we register necessary
functions for both EH and SjLj and precompute some data (the set of
functions that contains `setjmp`) before doing actual EH or SjLj
transformation.
This CL makes 2nd and 3rd tests in
https://github.com/emscripten-core/emscripten/pull/14732 work.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D106525
Both `__THREW__` and `__threwValue` are global variables, and we have
been distinguishing the global variable `__THREW__` and the loaded value
`%__THREW__.val` in comments but not doing it for `__threwValue`. Made
the pseudocode comments consistent for both variables.
Reviewed By: dschuff
Differential Revision: https://reviews.llvm.org/D106524
We have been handling filters and landingpads incorrectly all along. We
pass clauses' (catches') types to `__cxa_find_matching_catch` in JS glue
code, which returns the thrown pointer and sets the selector using
`setTempRet0()`.
We apparently have been doing the same for filters' (exception specs')
types; we pass them to `__cxa_find_matching_catch` just the same way as
clauses. And `__cxa_find_matching_catch` treats all given types as
clauses. So it is a little surprising; maybe we intended to do something
from the JS side and didn't end up doing?
So anyway, I don't think supporting exception specs in Emscripten EH is
a priority, but this can actually cause incorrect results for normal
catches when functions are inlined and the inlined spec type has a
parent-child relationship with the catch's type.
---
The below is an example of a bug that can happen when inlining and class
hierarchy is mixed. If you are busy you can skip this part:
```
struct A {};
struct B : A {};
void bar() throw (B) { throw B(); }
void foo() {
try {
bar();
} catch (A &) {
fputs ("Expected result\n", stdout);
}
}
```
In the unoptimized code, `bar`'s landingpad will have a filter for `B`
and `foo`'s landingpad will have a clause for `A`. But when `bar` is
inlined into `foo`, `foo`'s landingpad has both a filter for `B` and a
clause for `A`, and it passes the both types to
`__cxa_find_matching_catch`:
```
__cxa_find_matching_catch(typeinfo for B, typeinfo for A)
```
`__cxa_find_matching_catch` thinks both are clauses, and looks at the
first type `B`, which belongs to a filter. And the thrown type is `B`,
so it thinks the first type `B` is caught. But this makes it return an
incorrect selector, because it is supposed to catch the exception using
the second type `A`, which is a parent of `B`. As a result, the `foo` in
the example program above does not print "Expected result" but just
throws the exception to the caller. (This wouldn't have happened if `A`
and `B` are completely disjoint types, such as `float` and `int`)
Fixes https://bugs.llvm.org/show_bug.cgi?id=50357.
Reviewed By: dschuff, kripken
Differential Revision: https://reviews.llvm.org/D102795
In wasm64, the signatures of some library functions and global variables
defined in Emscripten change:
- `emscripten_longjmp`: `(i32, i32) -> ()` -> `(i64, i32) -> ()`
This changes because the first argument is the address of a memory
buffer. This in turn causes more changes below.
- `setThrew`: `(i32, i32) -> ()` -> `(i64, i32) -> ()`
`emscripten_longjmp` calls `setThrew` with the i64 buffer argument as
the first parameter.
- `__THREW__` (global var): `i32` to `i64`
`setThrew`'s first argument is set to this `__THREW__` variable, so it
should change to i64 as well.
- `testSetjmp`: `(i32, i32*, i32) -> (i32)` -> `(i64, i32*, i32) -> (i32)`
In the code transformation done in this pass, the value of `__THREW__`
is passed as the first parameter of `testSetjmp`.
This patch creates some helper functions to easily get types that become
different depending on the wasm32/wasm64, and uses them to change
various function signatures and code transformations. Also updates the
tests with WASM32/WASM64 check lines.
(Untested) Emscripten side patch: https://github.com/emscripten-core/emscripten/pull/14108
Reviewed By: aardappel
Differential Revision: https://reviews.llvm.org/D101985
We explicitly made it error out in D101403, out of a good intention that
the error message will make people less confusing. Turns out, we weren't
failing all cases of wasm EH + SjLj; only a few cases were failing and
our client was able to get around by fixing source code, but now we made
it fail for all cases, even the cases that previously succeeded fail,
which we didn't intend. This reverts that change.
Reviewed By: tlively
Differential Revision: https://reviews.llvm.org/D102364
- Removes the mention of fastcomp, which is deprecated.
- Some functions in Emscripten have moved from JS glue code to
compiler-rt/emscripten_setjmp.c and
compiler-rt/emscripten_exception_builtins.c. This fixes comments about
that.
Reviewed By: sbc100
Differential Revision: https://reviews.llvm.org/D101812
- Error out when both Emscripten EH and wasm EH are used together, i.e.,
both `-enable-emscripten-cxx-exceptions` and `-exception-model=wasm`
are given together. This will not happen if you use Emscripten, but
this can happen when you call `llc` manually with wrong set of
arguments.
- Currently we don't yet support using wasm EH with Emscripten SjLj.
Unlike `-enable-emscripten-cxx-exceptions` which is turned on only
when you use `emcc -s DISABLE_EXCEPTION_CATCHING=0`,
`-enable-emscripten-sjlj` is turned on by Emscripten by default. So we
error out only when it is turned on and `setjmp` or `longjmp` is
actually used.
Reviewed By: tlively
Differential Revision: https://reviews.llvm.org/D101403
Kazu Hirata