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asmgen
Roadmap

Roadmap

asmgen — Roadmap

go-asmgen grew along two axes: wider type support within an architecture, and more architectures over a shared ABI0 layout model. Both were broadly covered by v0.5.0. Later releases brought:

  • the wasm-SIMD kernel catalogue (see the wasm roadmap);
  • the amd64 CPU feature probes (AVX2, POPCNT, AVX512F, FMA) and a CPUID vendor probe (VendorProbe, v0.12.0) for tuning;
  • vector float64 arithmetic on arm64 (v0.10.0), ppc64le (v0.13.0) and loong64 (v0.14.0), each run bit-identical to Go’s arithmetic and math.FMA on hardware.

v0.15.0 returns to cmd/asm encoding wherever Go allows it. The arm64 methods emit VFADD… (Go 1.27; the minimum is 1.27.1 since v0.15.2) and the loong64 broadcast load emits VMOVQ off(R), V.V2. Instructions Go cannot assemble yet are registered, patched and watched; see Instructions cmd/asm lacks.

v0.16.0 adds the arm64 float32 vector methods (VFADD4S … VFMLS4S, VFNEG4S), as cmd/asm mnemonics.

v0 — proof of pipeline — done

  • arm64, ABI0, sequences of 8-byte int/ptr arguments and results.
  • ISA-agnostic emit text writer.
  • End-to-end go:generate example, validated by asmdecl + a native arm64 runtime test, with the library held to 100% coverage.

Widen arm64 scalar support — done

  • 1/2/4/8-byte signed and unsigned integers and pointers, with correct move selection (MOVB/MOVBU, MOVH/MOVHU, MOVW/MOVWU, MOVD) and sub-word sign/zero extension.
  • Floating-point registers (F0..) with FMOVS/FMOVD.
  • Word-aligned result area and per-type argument alignment.
  • Every case validated against go vet asmdecl and runtime tests on native arm64 (see examples/types).

Shared ABI0 model + more architectures — done

  • Extracted the architecture-independent ABI0 layout into abi; arm64 re-exports it with no behaviour change.
  • Added riscv64 (page), loong64 (page), amd64 (page), ppc64le (page) and s390x (page) as thin architectures over the shared model — each only a move table. 100% coverage, asmdecl + cmd/asm validated, and runtime-proven (natively on amd64/arm64, under qemu-user for riscv64/loong64/ppc64le/s390x, the s390x run exercising the big-endian path).
  • Promoted abi and emit out of internal/ so the library is importable.

Aggregates — done

  • Struct, slice, and string parameters laid out by Go’s struct rules, each field addressed as name_field+offset(FP), asmdecl- and runtime-validated. See Aggregates.

Arrays — done

  • Fixed-size [n]T arrays passed by value, addressed element-wise (name_0 … name_(n-1)) via abi.Array; Signature.Slot for offset lookup. asmdecl-clean and runtime-proven. See Aggregates.

ppc64le + s390x — done — v0.5.0

  • Added ppc64le (page) and s390x (page) as the fifth and sixth targets, completing all six 64-bit Go SIMD architectures. Both use the move table MOVD / FMOVS / FMOVD; s390x is big-endian, and its runtime job deliberately exercises that path. Validated under qemu-user on ubuntu-latest (default CPU for ppc64le; QEMU_CPU=max for s390x), asmdecl + cmd/asm clean, 100% coverage. Released as v0.5.0.

SIMD — done (via Raw)

  • Packed-add examples on all six targets, runtime-proven, including the 256-bit widths: SSE2 + AVX2 (amd64), NEON (arm64), RVV (riscv64), LSX + LASX (loong64), VSX (ppc64le), vector facility (s390x). Emitted through Raw over pointer arguments — see SIMD. A single vector load of a whole by-value array is not asmdecl-clean, so passing vectors by value is not pursued.
  • Possible future work: a typed vector-load helper that emits the pointer-based load/op/store sequence, removing the Raw boilerplate.

Stack frames and TEXT flags — done

  • NewFuncFlags emits any Plan 9 TEXT flags (NOSPLIT, NOSPLIT|NOFRAME, or none); frameSize > 0 reserves stack locals addressed name-N(SP) via Raw. See TEXT flags and stack frames and examples/frame — a non-NOSPLIT function that spills to a 16-byte frame, runtime-proven.

Adding another architecture

  • Any further 64-bit target follows the same recipe: re-export the shared abi types and add one loadMnemonic/storeMnemonic pair.

Possible future work

  • Derive instruction-mnemonic tables from cmd/internal/obj to catch typos at generation time — still delegating actual encoding to cmd/asm.
  • Differential encoding checks wired into CI as an additional guard against emit-layer regressions.
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