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Daco Harkes b113fffb65 Reland "[vm/ffi] Throw on returning Error in Handle"
Fix: Check handle contents for Smi.
Closes: https://github.com/flutter/flutter/issues/112726

Orignal CL description:

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: Id8edfd841a7d6246438386007d83747868a0a151
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/+/262342
Reviewed-by: Martin Kustermann <kustermann@google.com>
Auto-Submit: Daco Harkes <dacoharkes@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>
2022-10-03 12:25:08 +00:00
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benchmarks Reland "[vm/ffi] Throw on returning Error in Handle" 2022-10-03 12:25:08 +00:00
build
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pkg [cfe] Pass --no-sound-null-safety explicitly 2022-10-03 11:52:58 +00:00
runtime Reland "[vm/ffi] Throw on returning Error in Handle" 2022-10-03 12:25:08 +00:00
samples
sdk [dart2wasm] Correctly handle null when jsifying maps. 2022-09-30 21:09:29 +00:00
tests Reland "[vm/ffi] Throw on returning Error in Handle" 2022-10-03 12:25:08 +00:00
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