commit c74387a3a29c6edefd8c423ba7025d298b5b45a0
author Ömer Sinan Ağacan <omersa@google.com> Mon May 22 08:32:12 2023 +0000
committer Commit Queue <dart-scoped@luci-project-accounts.iam.gserviceaccount.com> Mon May 22 08:32:12 2023 +0000
tree 18e30d0103f43cc5696d2f99cbfd109c4e46a0cd
parent 7419e25966758b11a5836cd3d7e8fe00f96f42cb

[dart2wasm] New async implementation

This CL re-implements the async function compilation without using JSPI
or any other platform features.

This implementation is faster than the JSPI-based one in all benchmarks,
in some cases up to 200x (benchmark results at the end). So we remove
the JSPI-based implementation as there's no point in maintaining a much
slower implementation and supporting two implementations at the same
time (which is tricky because these implementations need different
libraries, all scripts need to support two modes etc.) that also
requires experimental platform features.

# Main changes

- A new pass `AwaitTransformer` transforms `await` expressions to
  top-level statements in form `var <fresh variable> = await <simple
  expr>`, where `<simple expr>` is an expression without `await`.

  After this pass all `await` expressions have the simple continuation
  of "assign the value of the awaited future to this variable and
  continue with the next statement". This simplifies `await`
  compilation.

- A new code generator `AsyncCodeGenerator` (inherits from
  `CodeGenerator`) compiles `async` functions. The `_YieldFinder` class
  is copied from `sync*` code generator but modified to handle `async`
  expressions.

- Mentions to the V8 flag `--experimental-wasm-stack-switching` is
  removed from all scripts and documents.

# Future work

- Control flow handling in `AsyncCodeGenerator` needs to be implemented
  in a similar way in `SyncStarCodeGenerator`. Doing this without
  duplicating a lot of code will require some refactoring.

# New passing tests

- co19/Language/Statements/Yield_and_Yield_Each/Yield/execution_async_A05_t01
- co19/Language/Statements/For/Asynchronous_For_in/execution_A02_t02
- language/regress/regress23996_test
- language/sync_star/dcall_type_test

# Benchmarks

Current implementation:

```
AsyncLiveVars.LiveObj1(RunTime): 1586000.0 us.
AsyncLiveVars.LiveObj2(RunTime): 2114000.0 us.
AsyncLiveVars.LiveObj4(RunTime): 1972500.0 us.
AsyncLiveVars.LiveObj8(RunTime): 2212000.0 us.
AsyncLiveVars.LiveObj16(RunTime): 2238000.0 us.
AsyncLiveVars.LiveInt1(RunTime): 2362000.0 us.
AsyncLiveVars.LiveInt4(RunTime): 2470000.0 us.
AsyncLiveVars.LiveObj2Int2(RunTime): 2575000.0 us.
AsyncLiveVars.LiveObj4Int4(RunTime): 2820000.0 us.
Calls.AwaitAsyncCall(RunTimeRaw): 35676.15658362989 ns.
Calls.AwaitAsyncCallClosureTargetPolymorphic(RunTimeRaw): 38934.108527131786 ns.
Calls.AwaitAsyncCallInstanceTargetPolymorphic(RunTimeRaw): 42617.02127659575 ns.
Calls.AwaitFutureCall(RunTimeRaw): 2832.058906825262 ns.
Calls.AwaitFutureCallClosureTargetPolymorphic(RunTimeRaw): 3665.8125915080527 ns.
Calls.AwaitFutureCallInstanceTargetPolymorphic(RunTimeRaw): 4420.449537241076 ns.
Calls.AwaitFutureOrCall(RunTimeRaw): 3692.7621861152143 ns.
Calls.AwaitFutureOrCallClosureTargetPolymorphic(RunTimeRaw): 4625.346901017576 ns.
Calls.AwaitFutureOrCallInstanceTargetPolymorphic(RunTimeRaw): 4514.6726862302485 ns.
Calls.AwaitFutureOrCallInstanceTargetPolymorphicManyAwaits(RunTimeRaw): 345172.4137931034 ns.
Calls.AwaitForAsyncStarStreamPolymorphic(RunTimeRaw): 697000.0 ns.
Calls.AwaitForAsyncStarStreamPolymorphicManyYields(RunTimeRaw): 704666.6666666666 ns.
Calls.AwaitForManualStreamPolymorphic(RunTimeRaw): 11010.989010989011 ns.
Calls.SyncCall(RunTimeRaw): 0.40275240996973316 ns.
Calls.SyncCallClosureTarget(RunTimeRaw): 0.3989591156672242 ns.
Calls.SyncCallInstanceTargetPolymorphic(RunTimeRaw): 3.2632549336335526 ns.
Calls.IterableSyncStarIterablePolymorphic(RunTimeRaw): 353.3980582524272 ns.
Calls.IterableManualIterablePolymorphic(RunTimeRaw): 332.1161825726141 ns.
Calls.IterableManualIterablePolymorphicManyYields(RunTimeRaw): 354.28067078552516 ns.
```

New implementation:

```
AsyncLiveVars.LiveObj1(RunTime): 11327.683615819209 us.
AsyncLiveVars.LiveObj2(RunTime): 10923.91304347826 us.
AsyncLiveVars.LiveObj4(RunTime): 10956.284153005465 us.
AsyncLiveVars.LiveObj8(RunTime): 11286.516853932584 us.
AsyncLiveVars.LiveObj16(RunTime): 11445.714285714286 us.
AsyncLiveVars.LiveInt1(RunTime): 11016.483516483517 us.
AsyncLiveVars.LiveInt4(RunTime): 11327.683615819209 us.
AsyncLiveVars.LiveObj2Int2(RunTime): 10918.478260869566 us.
AsyncLiveVars.LiveObj4Int4(RunTime): 10737.967914438503 us.
Calls.AwaitAsyncCall(RunTimeRaw): 1082.2510822510822 ns.
Calls.AwaitAsyncCallClosureTargetPolymorphic(RunTimeRaw): 1056.4124234100993 ns.
Calls.AwaitAsyncCallInstanceTargetPolymorphic(RunTimeRaw): 1134.1726210729273 ns.
Calls.AwaitFutureCall(RunTimeRaw): 865.6509695290858 ns.
Calls.AwaitFutureCallClosureTargetPolymorphic(RunTimeRaw): 841.3967185527977 ns.
Calls.AwaitFutureCallInstanceTargetPolymorphic(RunTimeRaw): 839.066957543212 ns.
Calls.AwaitFutureOrCall(RunTimeRaw): 397.9941096871766 ns.
Calls.AwaitFutureOrCallClosureTargetPolymorphic(RunTimeRaw): 406.17384240454913 ns.
Calls.AwaitFutureOrCallInstanceTargetPolymorphic(RunTimeRaw): 393.7472929873607 ns.
Calls.AwaitFutureOrCallInstanceTargetPolymorphicManyAwaits(RunTimeRaw): 1095.0503723171266 ns.
Calls.AwaitForAsyncStarStreamPolymorphic(RunTimeRaw): 6643.426294820717 ns.
Calls.AwaitForAsyncStarStreamPolymorphicManyYields(RunTimeRaw): 7178.750897343863 ns.
Calls.AwaitForManualStreamPolymorphic(RunTimeRaw): 1456.23998835008 ns.
Calls.SyncCall(RunTimeRaw): 0.3919935321067202 ns.
Calls.SyncCallClosureTarget(RunTimeRaw): 0.3906669661780074 ns.
Calls.SyncCallInstanceTargetPolymorphic(RunTimeRaw): 3.1676143112814583 ns.
Calls.IterableSyncStarIterablePolymorphic(RunTimeRaw): 104.4932079414838 ns.
Calls.IterableManualIterablePolymorphic(RunTimeRaw): 104.57516339869281 ns.
Calls.IterableManualIterablePolymorphicManyYields(RunTimeRaw): 116.92487576731949 ns.
```

TEST=ci
CoreLibraryReviewExempt: Added entry-point pragmas.
Change-Id: I02fbd08141f51c00fb37b6fa0304dc25d6afdb71
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/301020
Commit-Queue: Ömer Ağacan <omersa@google.com>
Reviewed-by: William Hesse <whesse@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Reviewed-by: Joshua Litt <joshualitt@google.com>