This CL adds passing structs by value in FFI trampolines.
Nested structs and inline arrays are future work.
C defines passing empty structs as undefined behavior, so that is not
supported in this CL.
Suggested review order:
1) commit message
2) ffi/marshaller (decisions for what is done in IL and what in MC)
3) frontend/kernel_to_il (IL construction)
4) backend/il (MC generation from IL)
5) rest in VM
Overall architecture is that structs are split up into word-size chunks
in IL when this is possible: 1 definition in IL per chunk, 1 Location in
IL per chunk, and 1 NativeLocation for the backend per chunk.
In some cases it is not possible or less convenient to split into
chunks. In these cases TypedDataBase objects are stored into and loaded
from directly in machine code.
The various cases:
- FFI call arguments which are not passed as pointers: pass individual
chunks to FFI call which already have the right location.
- FFI call arguments which are passed as pointers: Pass in TypedDataBase
to FFI call, allocate space on the stack, and make a copy on the stack
and pass the copies' address to the callee.
- FFI call return value: pass in TypedData to FFI call, and copy result
in machine code.
- FFI callback arguments which are not passed as pointers: IL definition
for each chunk, and populate a new TypedData with those chunks.
- FFI callback arguments which are passed as pointer: IL definition for
the pointer, and copying of contents in IL.
- FFI return value when location is pointer: Copy data to callee result
location in IL.
- FFI return value when location is not a pointer: Copy data in machine
code to the right registers.
Some other notes about the implementation:
- Due to Store/LoadIndexed loading doubles from float arrays, we use
a int32 instead and use the BitCastInstr.
- Linux ia32 uses `ret 4` when returning structs by value. This requires
special casing in the FFI callback trampolines to either use `ret` or
`ret 4` when returning.
- The 1 IL definition, 1 Location, and 1 NativeLocation approach does
not remove the need for special casing PairLocations in the machine
code generation because they are 1 Location belonging to 1 definition.
Because of the amount of corner cases in the calling conventions that
need to be covered, the tests are generated, rather than hand-written.
ABIs tested on CQ: x64 (Linux, MacOS, Windows), ia32 (Linux, Windows),
arm (Android softFP, Linux hardFP), arm64 Android.
ABIs tested locally through Flutter: ia32 Android (emulator), x64 iOS
(simulator), arm64 iOS.
ABIs not tested: arm iOS.
TEST=runtime/bin/ffi_test/ffi_test_functions_generated.cc
TEST=runtime/bin/ffi_test/ffi_test_functions.cc
TEST=tests/{ffi,ffi_2}/function_structs_by_value_generated_test.dart
TEST=tests/{ffi,ffi_2}/function_callbacks_structs_by_value_generated_tes
TEST=tests/{ffi,ffi_2}/function_callbacks_structs_by_value_test.dart
TEST=tests/{ffi,ffi_2}/vmspecific_static_checks_test.dart
Closes https://github.com/dart-lang/sdk/issues/36730.
Change-Id: I474d3a4ee1faadbe767ddadd1b696e24d8dc364c
Cq-Include-Trybots: luci.dart.try:dart-sdk-linux-try,dart-sdk-mac-try,dart-sdk-win-try,vm-ffi-android-debug-arm-try,vm-ffi-android-debug-arm64-try,vm-kernel-asan-linux-release-x64-try,vm-kernel-mac-debug-x64-try,vm-kernel-linux-debug-ia32-try,vm-kernel-linux-debug-x64-try,vm-kernel-nnbd-linux-debug-x64-try,vm-kernel-nnbd-linux-debug-ia32-try,vm-kernel-nnbd-mac-release-x64-try,vm-kernel-nnbd-win-debug-x64-try,vm-kernel-precomp-linux-debug-x64-try,vm-kernel-precomp-linux-debug-simarm_x64-try,vm-kernel-precomp-nnbd-linux-debug-x64-try,vm-kernel-precomp-win-release-x64-try,vm-kernel-reload-linux-debug-x64-try,vm-kernel-reload-rollback-linux-debug-x64-try,vm-kernel-win-debug-x64-try,vm-kernel-win-debug-ia32-try,vm-precomp-ffi-qemu-linux-release-arm-try,vm-kernel-precomp-obfuscate-linux-release-x64-try,vm-kernel-msan-linux-release-x64-try,vm-kernel-precomp-msan-linux-release-x64-try,vm-kernel-precomp-android-release-arm_x64-try,analyzer-analysis-server-linux-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/140290
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
Daco Harkes
3e7cda8a4e