ecmascript/compiler/assembler

Provides architecture-specific assembler and macro-assembler primitives that emit machine instructions programmatically, used by the baseline compiler, trampoline generators, and stub builders. Primary Language: C++

Design

The assembler is structured in two layers per architecture:

  Assembler (abstract base)
       │
       ├── AssemblerAarch64     ──▶ raw ARM64 instruction encoding
       │       └── ExtendAssembler  ──▶ extended ARM64 helpers
       │
       └── AssemblerX64         ──▶ raw x86-64 instruction encoding
               └── ExtendedAssemblerX64 ──▶ extended x64 helpers

  MacroAssembler (abstract base)
       │
       ├── MacroAssemblerAarch64  ──▶ high-level ARM64 patterns (push, call, etc.)
       └── MacroAssemblerX64      ──▶ high-level x64 patterns

Assembler handles raw instruction encoding (opcode + operands → bytes). MacroAssembler provides higher-level patterns (function prologues, stack operations, conditional branches) built on top of the assembler.

The baseline compiler and trampoline generators use MacroAssembler directly. The stub compiler uses it through BaselineStubBuilder.

Key Files

File	Role
assembler.h	Abstract assembler base class
macro_assembler.h	Abstract macro-assembler base class
aarch64/assembler_aarch64.cpp/.h	ARM64 instruction encoding
aarch64/macro_assembler_aarch64.cpp/.h	ARM64 high-level emission
x64/assembler_x64.cpp/.h	x86-64 instruction encoding
x64/macro_assembler_x64.cpp/.h	x86-64 high-level emission
aarch64/assembler_aarch64_constants.h	ARM64 ISA constants

How to Modify

Add a new instruction:

1. Add encoding logic to the architecture-specific assembler (e.g., assembler_aarch64.cpp)
2. If it's a common pattern, add a macro-assembler wrapper
3. Add test cases in tests/assembler_*_test.cpp

Add support for a new architecture:

1. Create a new subdirectory (e.g., riscv64/)
2. Implement Assembler and MacroAssembler subclasses
3. Wire into BUILD.gn with appropriate CPU gating
4. Update trampoline generators to use the new assembler

Building

Standalone repo (from repo root ../../):

python ark.py x64.debug

Full OHOS tree:

./build.sh --product-name <product-name> --build-target ark_js_host_linux_tools_packages

Tests

Standalone repo (from repo root ../../):

python ark.py x64.debug unittest   # all unit tests (includes assembler tests)

Full OHOS tree:

./build.sh --product-name <product-name> --build-target ecmascript/compiler/tests:host_unittest

Test files: tests/assembler_aarch64_test.cpp, tests/assembler_x64_test.cpp, tests/extended_assembler_x64_test.cpp, tests/macro_assembler_x64_test.cpp.

Tests are registered as AssemblerTest in ecmascript/compiler/tests/BUILD.gn.

Boundaries

• Keep instruction encoding changes scoped to the correct architecture directory (aarch64/ vs x64/).
• ABI/register conventions are shared with trampoline/ and stubs/ — changes must be synchronized.
• This module only emits instructions; it does not decide what to emit — that's the job of baseline compiler, trampoline generators, and stub builders.