env GOARCH=riscv64
env GORISCV64=rva20u64
go list -f '{{context.ToolTags}}'
stdout 'riscv64.rva20u64'

env GOARCH=riscv64
env GORISCV64=rva22u64
go list -f '{{context.ToolTags}}'
stdout 'riscv64.rva20u64 riscv64.rva22u64'

env GOARCH=riscv64
env GORISCV64=rva22
! go list -f '{{context.ToolTags}}'
stderr 'go: invalid GORISCV64: must be rva20u64, rva22u64'

env GOARCH=riscv64
env GORISCV64=

	if goamd64(); Error == nil {
		t.Errorf("Wrong parsing of GOAMD64=1")
	}

	os.Setenv("GORISCV64", "rva20u64")
	if goriscv64() != 20 {
		t.Errorf("Wrong parsing of RISCV64=rva20u64")
	}
	os.Setenv("GORISCV64", "rva22u64")
	if goriscv64() != 22 {
		t.Errorf("Wrong parsing of RISCV64=rva22u64")
	}
	Error = nil
	os.Setenv("GORISCV64", "rva22")
	if _ = goriscv64(); Error == nil {

The `GORISCV64` environment variable defaults to `rva20u64`.

### Wasm {#wasm}

<!-- go.dev/issue/63718 -->
The `go_wasip1_wasm_exec` script in `GOROOT/misc/wasm` has dropped support

	return int(defaultGOPPC64[len("power")] - '0')
}

func goriscv64() int {
	switch v := envOr("GORISCV64", defaultGORISCV64); v {
	case "rva20u64":
		return 20
	case "rva22u64":
		return 22
	}
	Error = fmt.Errorf("invalid GORISCV64: must be rva20u64, rva22u64")
	v := defaultGORISCV64[len("rva"):]
	i := strings.IndexFunc(v, func(r rune) bool {
		return r < '0' || r > '9'
	})
	year, _ := strconv.Atoi(v[:i])

	  ppc64.power8, ppc64.power9, and ppc64.power10
	  (or ppc64le.power8, ppc64le.power9, and ppc64le.power10)
	  feature build tags.
	- For GOARCH=riscv64,
	  GORISCV64=rva20u64 and rva22u64 correspond to the riscv64.rva20u64
	  and riscv64.rva22u64 build tags.
	- For GOARCH=wasm, GOWASM=satconv and signext
	  correspond to the wasm.satconv and wasm.signext feature build tags.

//     (or ppc64le.power8, ppc64le.power9, and ppc64le.power10)
//     feature build tags.
//   - For GOARCH=riscv64,
//     GORISCV64=rva20u64 and rva22u64 correspond to the riscv64.rva20u64
//     and riscv64.rva22u64 build tags.
//   - For GOARCH=wasm, GOWASM=satconv and signext
//     correspond to the wasm.satconv and wasm.signext feature build tags.
//

		"ppc64le": {"GOPPC64", "power8", "power9", "power10"},
		"ppc64x":  {}, // A pseudo-arch representing both ppc64 and ppc64le
		"s390x":   {},
		"wasm":    {},
		"riscv64": {"GORISCV64", "rva20u64", "rva22u64"},
	}
)

// wantedAsmOpcode is a single asmcheck check
type wantedAsmOpcode struct {
	fileline string         // original source file/line (eg: "/path/foo.go:45")

	if b == "" {
		b = "hardfloat"
	}
	gomips64 = b

	b = os.Getenv("GOPPC64")
	if b == "" {
		b = "power8"
	}
	goppc64 = b

	b = os.Getenv("GORISCV64")
	if b == "" {
		b = "rva20u64"
	}
	goriscv64 = b

	if p := pathf("%s/src/all.bash", goroot); !isfile(p) {
		fatalf("$GOROOT is not set correctly or not exported\n"+
			"\tGOROOT=%s\n"+
			"\t%s does not exist", goroot, p)
	}