plan9asm

github.com/xgo-dev/plan9asm

Plan 9 assembly parser and LLVM IR translator, extracted as an independent module.

Repository layout

• github.com/xgo-dev/plan9asm: parser + lowering library.
• cmd/plan9asm: package/file oriented helper (list, transpile), moved from llgo-stdlib-opt/chore/plan9asm.
• cmd/plan9asmll: stdlib-oriented converter/test tool (.s -> .ll, optional llc compile).

Current status

• Library parser/lowering targets: 386, amd64, arm, arm64, wasm.
• Tool targets (cmd/plan9asmll -all-targets):
  • darwin/amd64, darwin/arm64
  • linux/amd64, linux/arm64, linux/386
  • windows/amd64, windows/arm64, windows/386
• The package-oriented cmd/plan9asm and coverage-oriented cmd/plan9asmscan additionally support the official js/wasm and wasip1/wasm standard-library corpora. linux/arm is covered by the same corpus path; it is not part of plan9asmll -all-targets.
• 386 currently reuses the x86 lowering path from amd64 backend logic.
• arm64 does not include arm (32-bit). They are separate architectures.
• Instruction coverage is tracked by architecture, family, opcode, and operand form against Go's official encoder tables, positive assembler testdata, and executable real-world regressions. See Plan 9 assembly instruction coverage.

LLVM backend

• TranslateModule builds an in-memory llvm.Module (github.com/xgo-dev/llvm).
• Translate keeps compatibility and returns textual IR from that module.
• Root module dependency stays small (goplus/llvm).
• golang.org/x/tools/go/packages is used only in cmd/plan9asmll submodule.
• cmd/plan9asm does not depend on llgo/internal/build or llgo/internal/packages.

Quick test

go test ./...

Some tests require local LLVM/Clang tools (llc, clang) and skip when unavailable.

The executable cases under testdata/conformance use the native Go assembler as an oracle, then compile and run the same assembly through plan9asm/LLVM. Run them with:

go test . -run 'Test.*Conformance'

The separate cross-version instruction coverage gate compares Go's assembler corpus and encoder forms against the checked-in baseline:

scripts/check-go-asm-coverage.sh

On a Linux/amd64 host with the Debian cross GCC toolchains and QEMU user-mode emulators installed, run the cross-architecture link and execution smoke test:

PLAN9ASM_CROSS_EXEC=1 go test . -run '^TestCrossLinuxRuntimeMatrix$' -count=1 -v

cmd/plan9asmll usage

Show flags:

go run -C cmd/plan9asmll . -h

List selected asm files only:

go run -C cmd/plan9asmll . -patterns=std -goos=linux -goarch=386 -list-only

Convert one target (.s -> .ll):

go run -C cmd/plan9asmll . \
  -patterns=std \
  -goos=linux -goarch=amd64 \
  -out _out/plan9asmll/linux-amd64 \
  -report /tmp/plan9asmll-linux-amd64.json

Convert and compile (.ll -> .o) via llc:

go run -C cmd/plan9asmll . \
  -all-targets \
  -patterns=std \
  -compile \
  -out _out/plan9asmll/all-targets \
  -report /tmp/plan9asmll-all-targets.json

Run only x86 (386) targets:

go run -C cmd/plan9asmll . \
  -patterns=std \
  -targets=linux/386,windows/386 \
  -compile \
  -out _out/plan9asmll/x86 \
  -report /tmp/plan9asmll-x86.json

Output behavior

• Every asm file is printed with explicit status (OK or FAIL).
• On failure, tool prints:
  • the primary reason line,
  • unsupported opcode set (if detected),
  • per-hit location as file line number + source line.
• -keep-going=true (default) continues through all files and summarizes at the end.

Notes

• The stdlib asm corpus depends on your local Go toolchain version (go tool dist list, GOROOT content).
• If -compile is enabled, llc must be discoverable in PATH or set via -llc.
• Design notes and migration details are in doc/llvm-module-migration.md.

cmd/plan9asm usage

List packages/files containing .s:

go run -C cmd/plan9asm . list -goos=linux -goarch=amd64 std

transpile package mode uses positional patterns (go build/test style) and supports multiple patterns.

Transpile package selected .s files:

go run -C cmd/plan9asm . transpile \
  -dir _out/plan9asm/runtime-linux-amd64 \
  -goos=linux -goarch=amd64 \
  runtime

Transpile one .s file:

go run -C cmd/plan9asm . transpile \
  -i /path/to/file.s \
  -o /tmp/file.ll \
  -goos=linux -goarch=amd64