A generated, flattened instruction reference for hover tooltips. table.json.gz (gzip-compressed JSON) is embedded at build time and looked up by mnemonic via asmref.Lookup.

The table holds the factual "API" — brief title, description, syntax forms and per-operand meanings — plus x86 per-microarchitecture performance data (uops, ports, latency, throughput). Bit encodings and execution pseudocode are dropped. The Go-pseudocode effects shown in tooltips come from internal/asmhelp, not from here; asmref only fills in reference text asmhelp doesn't already cover.

The full table (all mnemonics, all measured microarchitectures) is ~15MB of JSON that gzips to ~0.6MB, hence the compressed embed.

Regenerating

go generate ./internal/asmref

With no arguments the generator reads the small checked-in fixtures under gen/testdata, so a bare run stays reproducible. To build the full table, download the sources (data/download.sh) and point it at them:

go run ./internal/asmref/gen \
  -arm  data/arm64/ISA_A64_xml_A_profile-2025-12 \
  -x86  data/x86/instructions.xml \
  -out  internal/asmref/table.json.gz

The generator also prints (to stderr) any mnemonics that golang.org/x/arch's decoders know but the table is missing — a coverage hint, not an error.

Sources

ARM AArch64 — the official "Exploration tools / ISA XML" release from developer.arm.com (the ISA_A64_xml_* bundle, one XML file per instruction). Files starting with sysreg_ (system registers) and AArch64- (shared pseudocode) are skipped.
x86 / AMD64 — instructions.xml from https://uops.info (XED-derived, ~140MB). It is a benchmark dataset, not a manual: there are no description or syntax elements, so the summary attribute becomes the brief and the string attribute (e.g. ADD (R32, M32)) becomes a syntax form. Per-operand descriptions are not emitted — they restate the token already in the form. For every operand form and every measured microarchitecture, the first <measurement> yields uops, ports (uops.info notation, e.g. 1*p0156), throughput and worst-case latency; <IACA> estimate nodes are skipped in favour of the real measurements.

data/download.sh fetches both dumps (URLs/version pinned to match golang.org/x/arch/arm64/instgen/xmlspec). They are large and gitignored; record the release version you used so regeneration stays reproducible.