☂️ Development modular AOT compiler targeting iOS/arm64

[alexmarkov]

It becomes increasingly difficult to use JIT for development on iOS (https://github.com/flutter/flutter/issues/163984, https://github.com/flutter/flutter/issues/175962). Eventually we would like to step away from using JIT and replace it with a new AOT compiler along with bytecode interpreter for debugging and hot reload.

This is an umbrella issue for implementation of a new modular AOT compiler for development on iOS (for Flutter debug mode).

Approximate plan to bring up the new compiler:

• First run:

  • [x] Implement essential parts of CFG IR (types, constants, functions, subset of instructions).
  • [x] Partially implement translation of AST to CFG IR.
  • [x] Implement SSA computation and a few optimization passes.
  • [ ] Implement arm64 assembler.
  • [ ] Sketch register allocation and code generation.
  • [ ] Implement module snapshot writer in the compiler and module snapshot reader in the VM.
  • [ ] Implement Mach-O image writer.

• [x] Milestone 1. Run "hello, world" (on mac/arm64).

• Feature completeness and correctness track:

  • [ ] Implement closures and captured variables (depends on https://github.com/dart-lang/sdk/issues/61572).
  • [ ] Implement late variables and fields.
  • [ ] Implement async/async*/sync* functions.
  • [ ] Implement super invocations.
  • [ ] Implement list, set and map literals.
  • [ ] Implement records.
  • [ ] Implement dart:ffi.
  • [ ] Implement deferred libraries.
  • [ ] Implement all recognized methods for correctness.
  • [ ] Implement all necessary stubs in the new compiler.

• [ ] Milestone 2. 90% of language tests are passing (on mac/arm64).
• [ ] Milestone 3. All core libraries are fully compiled with the new compiler.
• [ ] Milestone 4. 95+% of all tests are passing (on mac/arm64).

• Performance track:

  • [ ] Compare performance against JIT and production AOT on Golem micro-benchmarks.
  • [ ] Implement all recognized methods for performance.
  • [ ] Implement devirtualization and inlining.
  • [ ] Implement LICM.
  • [ ] Implement DCE.
  • [ ] Revise calling conventions (requires compiling all core libraries with the new compiler).
  • [ ] Profile compiler and fix low-hanging fruits to improve compilation speed.
  • [ ] (Optional) implement load/store forwarding.
  • [ ] (Optional) implement allocation sinking.
  • [ ] (Optional) implement write barrier elimination.

• Integration with bytecode interpreter:

  • [ ] Suport deoptimization from native code to bytecode.
    • [ ] Generate deoptimization info in the new compiler.
    • [ ] Implement switching from native code to bytecode in the VM in case of debugging or hot reload.
    • [ ] Add stress testing mode to deoptimize random functions to bytecode.

• Integration with Flutter:

  • [ ] Integrate new compiler into front-end server.
  • [ ] Support modular compilation and new compiler in Flutter tools.
  • [ ] Support multiple app dynamic libraries in the Flutter engine on iOS.

• [ ] Milestone 5. Flutter apps can run on iOS without JIT, with debugging and hot reload.