commit 2742d90033d0f486217b19758a1436dcbe24b27b
author Zach Anderson <zra@google.com> Fri Sep 30 21:51:59 2022 +0000
committer Commit Queue <dart-scoped@luci-project-accounts.iam.gserviceaccount.com> Fri Sep 30 21:51:59 2022 +0000
tree a0109ebee55753ff631673d5c9c417fbe4a57a98
parent cb45aa8a939df848b738dd176a3af7cacce65b54

Revert "[vm/ffi] Throw on returning `Error` in `Handle`"

This reverts commit d9c442bce8d13bb4db977e738d795b753ce84168.

Reason for revert: https://github.com/flutter/flutter/issues/112726

Original change's description:
> [vm/ffi] Throw on returning `Error` in `Handle`
>
> Makes `Dart_Handle` FFI returns behave as the following snippet:
>
> ```
> Dart_Handle ExampleSnippet() {
>   Dart_Handle result;
>   if (Dart_IsError(result)) {
>     Dart_PropagateError(result);
>   }
>   return result;
> }
> ```
>
> Also makes FFI consistent with Dart_NativeFunctions, which will
> automatically throw upon return if Dart_SetReturnValue set the result
> to an error.
>
> `UnhandledExceptions` cannot flow out into Dart generated code. So,
> the implementation needs to be in `FfiCallInstr::EmitNativeCode`.
>
> Using `Dart_IsError` is slow compared to a machine code class id
> check. So, we should do the handle unwrapping and class id check in
> machine code.
>
> Unwrapping Handles in machine code is only safe when the GC is
> guaranteed to not run: Either (1) in `kThreadInGenerated`, or (2) in
> `kThreadInNative`, but only when transitioned into safepoint. So, the
> handle cannot be unwrapped immediately after the FFI call in machine code. We first need to transition back to generated.
>
> This means we need to transition again to native to do the actual
> `Dart_PropagateError` call. We can do so without the stub in JIT
> because we never return with normal control flow.
>
> Performance impact of this change is within benchmark noise in both
> JIT and AOT.
> Size impact is 42 bytes on x64, which is 10% in AOT and 12% in JIT.
>
> For more numbers see: go/dart-ffi-handle-error
>
> TEST=runtime/bin/ffi_test/ffi_test_functions_vmspecific.cc
> TEST=tests/ffi/vmspecific_handle_test.dart
>
> Closes: https://github.com/dart-lang/sdk/issues/49936
> Change-Id: Ie8fabeb6d53bc80689541bc4470cb37ee2200581
> Cq-Include-Trybots: luci.dart.try:vm-canary-linux-debug-try,vm-ffi-android-debug-arm64c-try,vm-ffi-android-debug-arm-try,vm-kernel-gcc-linux-try,vm-kernel-linux-debug-x64-try,vm-kernel-linux-debug-x64c-try,vm-kernel-msvc-windows-try,vm-kernel-optcounter-threshold-linux-release-x64-try,vm-kernel-precomp-asan-linux-release-x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-kernel-reload-linux-debug-x64-try,vm-kernel-reload-rollback-linux-debug-x64-try,vm-kernel-tsan-linux-release-x64-try,vm-kernel-win-debug-x64-try,vm-kernel-win-debug-ia32-try,vm-precomp-ffi-qemu-linux-release-arm-try,vm-precomp-ffi-qemu-linux-release-riscv64-try,vm-kernel-linux-debug-ia32-try,vm-kernel-mac-release-arm64-try,vm-kernel-precomp-win-debug-x64c-try
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/261603
> Reviewed-by: Ryan Macnak <rmacnak@google.com>
> Reviewed-by: Martin Kustermann <kustermann@google.com>
> Commit-Queue: Daco Harkes <dacoharkes@google.com>

TBR=kustermann@google.com,rmacnak@google.com,dacoharkes@google.com,dart-scoped@luci-project-accounts.iam.gserviceaccount.com

Change-Id: I94cc63de16b54db2b0a4f92759c39a1e569b8e63
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Cq-Include-Trybots: luci.dart.try:vm-canary-linux-debug-try,vm-ffi-android-debug-arm64c-try,vm-ffi-android-debug-arm-try,vm-kernel-gcc-linux-try,vm-kernel-linux-debug-x64-try,vm-kernel-linux-debug-x64c-try,vm-kernel-msvc-windows-try,vm-kernel-optcounter-threshold-linux-release-x64-try,vm-kernel-precomp-asan-linux-release-x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-kernel-reload-linux-debug-x64-try,vm-kernel-reload-rollback-linux-debug-x64-try,vm-kernel-tsan-linux-release-x64-try,vm-kernel-win-debug-x64-try,vm-kernel-win-debug-ia32-try,vm-precomp-ffi-qemu-linux-release-arm-try,vm-precomp-ffi-qemu-linux-release-riscv64-try,vm-kernel-linux-debug-ia32-try,vm-kernel-mac-release-arm64-try,vm-kernel-precomp-win-debug-x64c-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/262270
Reviewed-by: Zach Anderson <zra@google.com>
Reviewed-by: Liam Appelbe <liama@google.com>
Commit-Queue: Zach Anderson <zra@google.com>