| Commit message (Collapse) | Author | Age | Files | Lines |
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Implement support for both sequentially consistent and acquire-release
variants of `struct.atomic.get` and `struct.atomic.set`, as proposed by
shared-everything-threads. Introduce a new `MemoryOrdering` enum for
describing different levels of atomicity (or the lack thereof). This new
enum should eventually be adopted by linear memory atomic accessors as
well to support acquire-release semantics, but for now just use it in
`StructGet` and `StructSet`.
In addition to implementing parsing and emitting for the instructions,
validate that shared-everything is enabled to use them, mark them as
having synchronization side effects, and lightly optimize them by
relaxing acquire-release accesses to non-shared structs to normal,
unordered accesses. This is valid because such accesses cannot possibly
synchronize with other threads. Also update Precompute to avoid
optimizing out synchronization points.
There are probably other passes that need to be updated to avoid
incorrectly optimizing synchronizing accesses, but identifying and
fixing them is left as future work.
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* Add interpreter support for exnref values.
* Fix optimization passes to support try_table.
* Enable the interpreter (but not in V8, see code) on exceptions.
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Also use TableInit in the interpreter to initialize module's table
state, which will now handle traps properly, fixing #6431
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Rename instructions `extern.internalize` into `any.convert_extern` and
`extern.externalize` into `extern.convert_any` to follow more closely
the spec. This was changed in
https://github.com/WebAssembly/gc/issues/432.
The legacy name is still accepted in text inputs and in the C and JS
APIs.
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Without that logic we could end up dropping that particular effect. This actually
made a test pass when it should not: the modified test here has a function with
effects that are ok to remove, but it had a loop which adds MayNotReturn which
we should actually not remove, so it was removed erroneously.
To fix the test, add other effects there (local ones) that we can see are removable.
Also add a function with a loop to test that we do not remove an infinite loop,
which adds coverage for the fix here.
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The stringref proposal has been superseded by the imported JS strings proposal,
but the former has many more operations than the latter. To reduce complexity,
remove all operations that are part of stringref but not part of imported
strings.
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The stringview types from the stringref proposal have three irregularities that
break common invariants and require pervasive special casing to handle properly:
they are supertypes of `none` but not subtypes of `any`, they cannot be the
targets of casts, and they cannot be used to construct nullable references. At
the same time, the stringref proposal has been superseded by the imported
strings proposal, which does not have these irregularities. The cost of
maintaing and improving our support for stringview types is no longer worth the
benefit of supporting them.
Simplify the code base by entirely removing the stringview types and related
instructions that do not have analogues in the imported strings proposal and do
not make sense in the absense of stringviews.
Three remaining instructions, `stringview_wtf16.get_codeunit`,
`stringview_wtf16.slice`, and `stringview_wtf16.length` take stringview operands
in the stringref proposal but cannot be removed because they lower to operations
from the imported strings proposal. These instructions are changed to take
stringref operands in Binaryen IR, and to allow a graceful upgrade path for
users of these instructions, the text and binary parsers still accept but ignore
`string.as_wtf16`, which is the instruction used to convert stringrefs to
stringviews. The binary writer emits code sequences that use scratch locals and `string.as_wtf16` to keep the output valid.
Future PRs will further align binaryen with the imported strings proposal
instead of the stringref proposal, for example by making `string` a subtype of
`extern` instead of a subtype of `any` and by removing additional instructions
that do not have analogues in the imported strings proposal.
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With this you can do std::cout << effects and get something like
EffectAnalyzer {
writesMemory
hasSideEffects
}
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We added string.compare late in the spec process, and forgot to add effects for it.
Unlike string.eq, it can trap.
Also use makeTrappingRefUse in recent fuzzer string generation places that I
forgot, which should reduce the amount of traps in fuzzer output.
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This is a combined commit covering multiple PRs fixing the handling of return
calls in different areas. The PRs are all landed as a single commit to ensure
internal consistency and avoid problems with bisection.
Original PR descriptions follow:
* Fix inlining of `return_call*` (#6448)
Previously we transformed return calls in inlined function bodies into normal
calls followed by branches out to the caller code. Similarly, when inlining a
`return_call` callsite, we simply added a `return` after the body inlined at the
callsite. These transformations would have been correct if the semantics of
return calls were to call and then return, but they are not correct for the
actual semantics of returning and then calling.
The previous implementation is observably incorrect for return calls inside try
blocks, where the previous implementation would run the inlined body within the
try block, but the proper semantics would be to run the inlined body outside the
try block.
Fix the problem by transforming inlined return calls to branches followed by
calls rather than as calls followed by branches. For the case of inlined return
call callsites, insert branches out of the original body of the caller and
inline the body of the callee as a sibling of the original caller body. For the
other case of return calls appearing in inlined bodies, translate the return
calls to branches out to calls inserted as siblings of the original inlined
body.
In both cases, it would have been convenient to use multivalue block return to
send call parameters along the branches to the calls, but unfortunately in our
IR that would have required tuple-typed scratch locals to unpack the tuple of
operands at the call sites. It is simpler to just use locals to propagate the
operands in the first place.
* Fix interpretation of `return_call*` (#6451)
We previously interpreted return calls as calls followed by returns, but that is
not correct both because it grows the size of the execution stack and because it
runs the called functions in the wrong context, which can be observable in the
case of exception handling.
Update the interpreter to handle return calls correctly by adding a new
`RETURN_CALL_FLOW` that behaves like a return, but carries the arguments and
reference to the return-callee rather than normal return values.
`callFunctionInternal` is updated to intercept this flow and call return-called
functions in a loop until a function returns with some other kind of flow.
Pull in the upstream spec tests return_call.wast, return_call_indirect.wast, and
return_call_ref.wast with light editing so that we parse and validate them
successfully.
* Handle return calls in wasm-ctor-eval (#6464)
When an evaluated export ends in a return call, continue evaluating the
return-called function. This requires propagating the parameters, handling the
case that the return-called function might be an import, and fixing up local
indices in case the final function has different parameters than the original
function.
* Update effects.h to handle return calls correctly (#6470)
As far as their surrounding code is concerned return calls are no different from
normal returns. It's only from a caller's perspective that a function containing
a return call also has the effects of the return-callee. To model this more
precisely in EffectAnalyzer, stash the throw effect of return-callees on the
side and only merge it in at the end when analyzing the effects of a full
function body.
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This PR is part of a series that adds basic support for the [typed
continuations/wasmfx proposal](https://github.com/wasmfx/specfx).
This particular PR adds support for the `suspend` instruction for suspending
with a given tag, documented
[here](https://github.com/wasmfx/specfx/blob/main/proposals/continuations/Overview.md#instructions).
These instructions are of the form `(suspend $tag)`. Assuming that `$tag` is
defined with _n_ `param` types `t_1` to `t_n`, the instruction consumes _n_
arguments of types `t_1` to `t_n`. Its result type is the same as the `result`
type of the tag. Thus, the folded textual representation looks like
`(suspend $tag arg1 ... argn)`.
Support for the instruction is implemented in both the old and the new wat
parser.
Note that this PR does not implement validation of the new instruction.
This PR also fixes finalization of `cont.new`, `cont.bind` and `resume` nodes in
those cases where any of their children are unreachable.
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This PR is part of a series that adds basic support for the [typed
continuations/wasmfx proposal](https://github.com/wasmfx/specfx).
This particular PR adds support for the `cont.bind` instruction for partially
applying continuations, documented
[here](https://github.com/wasmfx/specfx/blob/main/proposals/continuations/Overview.md#instructions).
In short, these instructions are of the form `(cont.bind $ct_before $ct_after)`
where `$ct_before` and `$ct_after` are related continuation types. They must
only differ in the number of arguments, where `$ct_before` has _n_ additional
parameters as compared to `$ct_after`, for some _n_ ≥ 0. The idea is that
`(cont.bind $ct_before $ct_after)` then takes a reference to a continuation of
type `$ct_before` as well as _n_ operands and returns a (reference to a)
continuation of type `$ct_after`. Thus, the folded textual representation looks
like `(cont.bind $ct_before $ct_after arg1 ... argn c)`.
Support for the instruction is implemented in both the old and the new wat
parser.
Note that this PR does not implement validation of the new instruction.
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This PR is part of a series that adds basic support for the [typed
continuations/wasmfx proposal](https://github.com/wasmfx/specfx).
This particular PR adds support for the `cont.new` instruction for creating
continuations, documented [here(https://github.com/wasmfx/specfx/blob/main/proposals/continuations/Overview.md#instructions).
In short, these instructions are of the form `(cont.new $ct)` where `$ct` must
be a continuation type. The instruction takes a single (nullable) function
reference as its argument, which means that the folded representation of the
instruction is of the form `(cont.new $ct (foo ...))`.
Support for the instruction is implemented in both the old and the new wat
parser.
Note that this PR does not implement validation of the new instruction.
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This PR is part of a series that adds basic support for the [typed continuations proposal](https://github.com/wasmfx/specfx).
This particular PR adds support for the `resume` instruction. The most notable missing feature is validation, which is not implemented, yet.
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This adds basic support for the new instructions in the new EH proposal
passed at the Oct CG hybrid CG meeting:
https://github.com/WebAssembly/meetings/blob/main/main/2023/CG-10.md
https://github.com/WebAssembly/exception-handling/blob/main/proposals/exception-handling/Exceptions.md
This mainly adds two instructions: `try_table` and `throw_ref`. This is
the bare minimum required to read and write text and binary format, and
does not include analyses or optimizations. (It includes some analysis
required for validation of existing instructions.) Validation for
the new instructions is not yet included.
`try_table` faces the same problem with the `resume` instruction in
#6083 that without the module-level tag info, we are unable to know the
'sent types' of `try_table`. This solves it with a similar approach
taken in #6083: this adds `Module*` parameter to `finalize` methods,
which defaults to `nullptr` when not given. The `Module*` parameter is
given when called from the binary and text parser, and we cache those
tag types in `sentTypes` array within `TryTable` class. In later
optimization passes, as long as they don't touch tags, it is fine to
call `finalize` without the `Module*`. Refer to
https://github.com/WebAssembly/binaryen/pull/6083#issuecomment-1854634679
and #6096 for related discussions when `resume` was added.
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Helps #5951
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This instruction was standardized as part of the bulk memory proposal, but we
never implemented it until now. Leave similar instructions like table.copy as
future work.
Fixes #5939.
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Globally replace the source string "I31New" with "RefI31" in preparation for
renaming the instruction from "i31.new" to "ref.i31", as implemented in the spec
in https://github.com/WebAssembly/gc/pull/422. This would be NFC, except that it
also changes the string in the external-facing C APIs.
A follow-up PR will make the corresponding behavioral change.
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(#5764)
EffectAnalyzer::canReorder/invalidate now assume that the things from whom we
generated the effects both execute (or, rather, that if the first of them doesn't
transfer control flow then they execute). If they both execute then we can do more work
in TrapsNeverHappen mode, since we can then reorder this for example:
(global.set ..)
(i32.load ..)
The load may trap, but in TNH mode we assume it won't. So we can reorder those
two. However, if they did not both execute then we could be in this situation:
(global.set ..)
(br_if ..)
(i32.load)
Reordering the load and the set here would be invalid, because we could make the
load execute when it didn't execute before, and it could now start to actually
trap at runtime.
This new assumption seems obvious, since we don't compare the effects of
things unless they are adjacent and with no control flow between them - otherwise,
why compare them? To be sure, I manually reviewed every single use of
EffectAnalyzer::canReorder/invalidate in the entire codebase.
I've also been fuzzing this for several days (hundreds of thousands of iterations),
and have not seen any problem.
This was motivated by seeing that #5744 should be able to do more work in TNH
mode, but it wasn't. New tests show the benefits there in OptimizeCasts as well
as in SimplifyLocals.
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This PR removes a check for
transfersControlFlow() && other.trap
which is already checked higher up in the code, here:
transfersControlFlow() && other.hasSideEffects()
In
binaryen/src/ir/effects.h , lines 223 to 224
That last code handles the first code because trapping is part
of hasSideEffects().
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We depend on repeated calls to walk/visit accumulating effects, so this
was a bug; if we want to clear stuff then we create a new EffectAnalyzer.
Removing that fixes the attached testcase. Also added a unit test.
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See WebAssembly/stringref#46.
This format is already adopted by V8: https://chromium-review.googlesource.com/c/v8/v8/+/3892695.
The text format is left unchanged (see #5607 for a discussion on the subject).
I have also added support for string.encode_lossy_utf8 and
string.encode_lossy_utf8 array (by allowing the replace policy for
Binaryen's string.encode_wtf8 instruction).
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This changes loops from having the effect "may trap (timeout)" to having
"may not return." The only noticeable difference is in TrapsNeverHappen mode,
which ignores the former but not the latter. So after this PR, in TNH mode we do
not optimize away an infinite loop that seems to have no other side effects. We
may also use this for other things in the future, like continuations/stack switching.
There are upsides and downsides to allowing the optimizer to remove infinite
loops (the C and C++ communities have had interesting discussions on that topic
over the years...) but it seems safer to not optimize them out for now, to let the
most code work properly. If a need comes up to optimize such code, we can look
at various options then (like a flag to ignore infinite loops).
See discussion in #5228
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Data/Elem (#5692)
ArrayNewSeg => ArrayNewSegData, ArrayNewSegElem
ArrayInit => ArrayInitData, ArrayInitElem
Basically we remove the opcode and use the class type to differentiate them.
This adds some code but it makes the representation simpler and more compact in
memory, and it will help with #5690
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These complement array.copy, which we already supported, as an initial complete
set of bulk array operations. Replace the WIP spec tests with the upstream spec
tests, lightly edited for compatibility with Binaryen.
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To match the standard instruction name, rename the expression class without
changing any parsing or printing behavior. A follow-on PR will take care of the
functional side of this change while keeping support for parsing the old name.
This change will allow `ArrayInit` to be used as the expression class for the
upcoming `array.init_data` and `array.init_elem` instructions.
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* Replace `RefIs` with `RefIsNull`
The other `ref.is*` instructions are deprecated and expressible in terms of
`ref.test`. Update binary and text parsing to parse those instructions as
`RefTest` expressions. Also update the printing and emitting of `RefTest`
expressions to emit the legacy instructions for now to minimize test changes and
make this a mostly non-functional change. Since `ref.is_null` is the only
`RefIs` instruction left, remove the `RefIsOp` field and rename the expression
class to `RefIsNull`.
The few test changes are due to the fact that `ref.is*` instructions are now
subject to `ref.test` validation, and in particular it is no longer valid to
perform a `ref.is_func` on a value outside of the `func` type hierarchy.
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In order to test them, fix the binary and text parsers to accept passive data
segments even if a module has no memory. In addition to parsing and emitting the
new instructions, also implement their validation and interpretation. Test the
interpretation directly with wasm-shell tests adapted from the upstream spec
tests. Running the upstream spec tests directly would require fixing too many
bugs in the legacy text parser, so it will have to wait for the new text parser
to be ready.
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These types, `none`, `nofunc`, and `noextern` are uninhabited, so references to
them can only possibly be null. To simplify the IR and increase type precision,
introduce new invariants that all `ref.null` instructions must be typed with one
of these new bottom types and that `Literals` have a bottom type iff they
represent null values. These new invariants requires several additional changes.
First, it is now possible that the `ref` or `target` child of a `StructGet`,
`StructSet`, `ArrayGet`, `ArraySet`, or `CallRef` instruction has a bottom
reference type, so it is not possible to determine what heap type annotation to
emit in the binary or text formats. (The bottom types are not valid type
annotations since they do not have indices in the type section.)
To fix that problem, update the printer and binary emitter to emit unreachables
instead of the instruction with undetermined type annotation. This is a valid
transformation because the only possible value that could flow into those
instructions in that case is null, and all of those instructions trap on nulls.
That fix uncovered a latent bug in the binary parser in which new unreachables
within unreachable code were handled incorrectly. This bug was not previously
found by the fuzzer because we generally stop emitting code once we encounter an
instruction with type `unreachable`. Now, however, it is possible to emit an
`unreachable` for instructions that do not have type `unreachable` (but are
known to trap at runtime), so we will continue emitting code. See the new
test/lit/parse-double-unreachable.wast for details.
Update other miscellaneous code that creates `RefNull` expressions and null
`Literals` to maintain the new invariants as well.
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Also fix some formatting issue in the file.
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Recently we added logic to ignore effects that don't "escape" past the function call.
That is, e.g. local.set only affects the current function scope, and once the call stack
is unwound it no longer matters as an effect. This moves that logic to a shared place,
and uses it in the core Vacuum logic.
The new constructor in EffectAnalyzer receives a function and then scans it as
a whole. This works just like e.g. scanning a Block as a whole (if we see a break in
the block, that has an effect only inside it, and the Block + children doesn't have a
branch effect).
Various tests are updated so they don't optimize away trivially, by adding new
return values for them.
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due to timeout (#5039)
I think this simplifies the logic behind what we consider to trap. Before we had kind of
a hack in visitLoop that now has a more clear reasoning behind it: we consider as
trapping things that trap in all VMs all the time, or will eventually. So a single allocation
doesn't trap, but an unbounded amount can, and an infinite loop is considered to
trap as well (a timeout in a VM will be hit eventually, somehow).
This means we cannot optimize way a trivial infinite loop with no effects in it,
while (1) {}
But we can optimize it out in trapsNeverHappen mode. In any event, such a loop
is not a realistic situation; an infinite loop with some other effect in it, like a call to
an import, will not be optimized out, of course.
Also clarify some other things regarding traps and trapsNeverHappen following
recent discussions in https://github.com/emscripten-core/emscripten/issues/17732
Specifically, TNH will never be allowed to remove calls to imports.
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This adds a map of function name => the effects of that function to the
PassOptions structure. That lets us compute those effects once and then
use them in multiple passes afterwards. For example, that lets us optimize
away a call to a function that has no effects:
(drop (call $nothing))
[..]
(func $nothing
;; .. lots of stuff but no effects, only a returned value ..
)
Vacuum will remove that dropped call if we tell it that the called function has
no effects. Note that a nice result of adding this to the PassOptions struct
is that all passes will use the extra info automatically.
This is not enabled by default as the benefits seem rather minor, though it
does help in a small but noticeable way on J2Wasm code, where we use
call.without.effects and have situations like this:
(func $foo
(call $bar)
)
(func $bar
(call.without.effects ..)
)
The call to bar looks like it has effects, normally, but with global effect info
we know it actually doesn't.
To use this, one would do
--generate-global-effects [.. some passes that use the effects ..] --discard-global-effects
Discarding is not necessary, but if there is a pass later that adds effects, then not
discarding could lead to bugs, since we'd think there are fewer effects than there are.
(However, normal optimization passes never add effects, only remove them.)
It's also possible to call this multiple times:
--generate-global-effects -O3 --generate-global-effects -O3
That computes affects after the first -O3, and may find fewer effects than earlier.
This doesn't compute the full transitive closure of the effects across functions. That is,
when computing a function's effects, we don't look into its own calls. The simple case
so far is enough to handle the call.without.effects example from before (though it
may take multiple optimization cycles).
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We had some concerns about this not working in the past, but thinking about it
now, I believe it is safe to do. Specifically, a throw is either like a break or a return -
either it jumps out to an outer scope (like a break) or it jumps out of the function
(like a return), and both breaks and returns have already been handled here.
This change has some nice effects on J2Wasm output, where there are quite a
lot of throws, which we can now optimize around.
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We explicitly wrote out memory, table, and globals, but did not add structs. This switches
us to use readsMutableGlobalState which has the full list of all relevant global state,
including the memory, table, and globals as well as structs.
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These new GC instructions infallibly convert between `extern` and `any`
references now that those types are not in the same hierarchy.
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RTTs were removed from the GC spec and if they are added back in in the future,
they will be heap types rather than value types as in our implementation.
Updating our implementation to have RTTs be heap types would have been more work
than deleting them for questionable benefit since we don't know how long it will
be before they are specced again.
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This is not observable in practice atm since call_ref also does a call,
which has even more effects. However, future optimizations might benefit
from this, and it is more consistent to avoid marking the instruction as
trapping if it can't.
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Unfortunately one slice is the same as python [start:end], using 2 params,
and the other slice is one param, [CURR:CURR+num] (where CURR is implied
by the current state in the iter). So we can't use a single class here. Perhaps
a different name would be good, like slice vs substring (like JS does), but
I picked names to match the current spec.
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This is more work than a typical instruction because it also adds a new section:
all the (string.const "foo") strings are put in a new "strings" section in the binary, and
the instructions refer to them by index.
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This is the first instruction from the Strings proposal.
This includes everything but interpreter support.
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