dart:ffi Struct support on 32-bit systems

[sjindel-google]

We need to update the alignment and sizing rules appropriately for the ARM32 and Intel 32-bit ABIs.

Also, we should consider in the implementation how to accommodate using information from Clang in the future.

[sjindel-google]

At the least, we need to lockout struct support on 32-bit systems for the Preview.

[dcharkes]

Why did we move this back to Flutter MVP?

[dcharkes]

(Note to self, and for later reference.)

The ABI lookup at runtime reliably crashes with --enable-interpreter on the swarming bots, but locally it reliably never crashes.

On the swarming bot it reaches the native entry for _abi(), instead of having _abi()'s body replaced with IL before calling it:

../../runtime/lib/ffi.cc: 613: error: unreachable code
version=2.5.0-edge.d1fcefc13a1e638d8e4d2dcff4d538adaa92e289 (Thu Jul 11 08:18:19 2019 +0000) on "linux_x64"
thread=13632, isolate=main(0x56032b0e8c00)
  pc 0x00005603285a5b1c fp 0x00007f5043778e40 dart::Profiler::DumpStackTrace(void*)
  pc 0x00005603281c6752 fp 0x00007f5043778f20 dart::Assert::Fail(char const*, ...)
  pc 0x00005603283cd3a3 fp 0x00007f5043778f40 out/DebugX64/dart+0x18ef3a3
  pc 0x00005603283cd2ac fp 0x00007f5043778fa0 dart::BootstrapNatives::DN_Ffi_abi(_Dart_NativeArguments*)
  pc 0x0000560328477284 fp 0x00007f50437790d0 out/DebugX64/dart+0x1999284
^^^ enters native entry instead of compiling function ^^^
  pc 0x0000560328466d57 fp 0x00007f504377a0a0 dart::Interpreter::Call(dart::RawFunction*, dart::RawArray*, long, dart::RawObject* const*, dart::Thread*)
  pc 0x0000560328428212 fp 0x00007f504377a140 dart::DartEntry::InvokeFunction(dart::Function const&, dart::Array const&, dart::Array const&, unsigned long)
  pc 0x0000560328516bd7 fp 0x00007f504377a1b0 dart::Field::EvaluateInitializer() const
  pc 0x0000560328516877 fp 0x00007f504377a1f0 dart::Field::Initialize() const
  pc 0x000056032861c179 fp 0x00007f504377a2a0 dart::DRT_InitStaticField(dart::NativeArguments)
  pc 0x000056032846060c fp 0x00007f504377a3f0 out/DebugX64/dart+0x198260c
  pc 0x0000560328473332 fp 0x00007f504377b3c0 dart::Interpreter::Call(dart::RawFunction*, dart::RawArray*, long, dart::RawObject* const*, dart::Thread*)
  pc 0x0000560328428212 fp 0x00007f504377b460 dart::DartEntry::InvokeFunction(dart::Function const&, dart::Array const&, dart::Array const&, unsigned long)
  pc 0x00005603283cd485 fp 0x00007f504377b490 out/DebugX64/dart+0x18ef485
  pc 0x00005603283c8199 fp 0x00007f504377b510 dart::BootstrapNatives::DN_Ffi_allocate(_Dart_NativeArguments*)
...

Break point locally with -d0 on the first time we hit IL:

dart::kernel::FlowGraphBuilder::BuildGraphOfRecognizedMethod(dart::kernel::FlowGraphBuilder * this, const dart::Function & function) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/compiler/frontend/kernel_to_il.cc:1067)
dart::kernel::StreamingFlowGraphBuilder::BuildGraph(dart::kernel::StreamingFlowGraphBuilder * this) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/compiler/frontend/kernel_binary_flowgraph.cc:991)
dart::kernel::FlowGraphBuilder::BuildGraph(dart::kernel::FlowGraphBuilder * this) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/compiler/frontend/kernel_to_il.cc:728)
dart::DartCompilationPipeline::BuildFlowGraph(dart::DartCompilationPipeline * this, dart::Zone * zone, dart::ParsedFunction * parsed_function, dart::ZoneGrowableArray<dart::ICData const*> * ic_data_array, intptr_t osr_id, bool optimized) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/compiler/jit/compiler.cc:147)
dart::CompileParsedFunctionHelper::Compile(dart::CompileParsedFunctionHelper * this, dart::DartCompilationPipeline * pipeline) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/compiler/jit/compiler.cc:608)
dart::CompileFunctionHelper(dart::DartCompilationPipeline * pipeline, const dart::Function & function, volatile bool optimized, intptr_t osr_id) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/compiler/jit/compiler.cc:797)
dart::Compiler::CompileFunction(dart::Thread * thread, const dart::Function & function) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/compiler/jit/compiler.cc:939)
dart::DRT_HelperCompileFunction(dart::Isolate * isolate, dart::Thread * thread, dart::Zone * zone, dart::NativeArguments arguments) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/compiler/jit/compiler.cc:246)
dart::DRT_CompileFunction(dart::NativeArguments arguments) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/compiler/jit/compiler.cc:222)
dart::InvokeRuntime(dart::Thread * thread, dart::Interpreter * interpreter, dart::RuntimeFunction drt, const dart::NativeArguments & args) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/interpreter.cc:533)
dart::Interpreter::Invoke(dart::Interpreter * this, dart::Thread * thread, dart::RawObject ** call_base, dart::RawObject ** call_top, const dart::KBCInstr ** pc, dart::RawObject *** FP, dart::RawObject *** SP) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/interpreter.cc:703)
^^^ properly compiles function ^^^
dart::Interpreter::Call(dart::Interpreter * this, dart::RawFunction * function, dart::RawArray * argdesc, const uint32_t argc, dart::RawObject * const * argv, dart::Thread * thread) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/interpreter.cc:1967)
dart::Interpreter::Call(dart::Interpreter * this, const dart::Function & function, const dart::Array & arguments_descriptor, const dart::Array & arguments, dart::Thread * thread) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/interpreter.cc:1368)
dart::DartEntry::InvokeFunction(const dart::Function & function, const dart::Array & arguments, const dart::Array & arguments_descriptor, dart::uword current_sp) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/dart_entry.cc:159)
dart::DartEntry::InvokeFunction(const dart::Function & function, const dart::Array & arguments) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/dart_entry.cc:35)
dart::Field::EvaluateInitializer(const dart::Field * this) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/object.cc:8814)
dart::Field::Initialize(const dart::Field * this) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/object.cc:8789)
dart::DRT_HelperInitStaticField(dart::Isolate * isolate, dart::Thread * thread, dart::Zone * zone, dart::NativeArguments arguments) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/runtime_entry.cc:2842)
dart::DRT_InitStaticField(dart::NativeArguments arguments) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/runtime_entry.cc:2840)
dart::InvokeRuntime(dart::Thread * thread, dart::Interpreter * interpreter, dart::RuntimeFunction drt, const dart::NativeArguments & args) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/interpreter.cc:533)
dart::Interpreter::Call(dart::Interpreter * this, dart::RawFunction * function, dart::RawArray * argdesc, intptr_t argc, dart::RawObject * const * argv, dart::Thread * thread) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/interpreter.cc:3265)
dart::Interpreter::Call(dart::Interpreter * this, const dart::Function & function, const dart::Array & arguments_descriptor, const dart::Array & arguments, dart::Thread * thread) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/interpreter.cc:1368)
dart::DartEntry::InvokeFunction(const dart::Function & function, const dart::Array & arguments, const dart::Array & arguments_descriptor, dart::uword current_sp) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/dart_entry.cc:159)
dart::DartEntry::InvokeFunction(const dart::Function & function, const dart::Array & arguments) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/dart_entry.cc:35)
dart::Class::InvokeGetter(const dart::Class * this, const dart::String & getter_name, bool throw_nsm_if_absent, bool respect_reflectable, bool check_is_entrypoint) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/vm/object.cc:3381)
dart::SizeOf(const dart::Type & type) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/lib/ffi.cc:189)
dart::DN_HelperFfi_allocate(dart::Isolate * isolate, dart::Thread * thread, dart::Zone * zone, dart::NativeArguments * arguments) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/lib/ffi.cc:203)
dart::BootstrapNatives::DN_Ffi_allocate(Dart_NativeArguments args) (/usr/local/google/home/dacoharkes/dart-sdk/sdk/runtime/lib/ffi.cc:199)
[Unknown/Just-In-Time compiled code] (Unknown Source:0)

[sjindel-google]

You need to build your vm_platform.dill with bytecode bodies for core library methods. Pass --bytecode to gn.py to reproduce this issue.

[dcharkes]

Got reverted with a build failure on iOS: flutter/engine#9817 (comment)