### ARM64 {#arm64}

<!-- go.dev/issue/60905, CL 559555 -->
Go 1.23 introduces a new `GOARM64` environment variable, which specifies the minimum target version of the ARM64 architecture at compile time. Allowed values are `v8.{0-9}` and `v9.{0-5}`. This may be followed by an option specifying extensions implemented by target hardware. Valid options are `,lse` and `,crypto`.

The `GOARM64` environment variable defaults to `v8.0`.

### RISC-V {#riscv}

	case "amd64":
		telemetry.Inc("go/platform/target/goamd64:" + cfg.GOAMD64)
	case "arm":
		telemetry.Inc("go/platform/target/goarm:" + cfg.GOARM)
	case "arm64":
		telemetry.Inc("go/platform/target/goarm64:" + cfg.GOARM64)
	case "mips":
		telemetry.Inc("go/platform/target/gomips:" + cfg.GOMIPS)
	case "ppc64":
		telemetry.Inc("go/platform/target/goppc64:" + cfg.GOPPC64)
	case "riscv64":

	GOBIN                         = Getenv("GOBIN")
	GOMODCACHE, GOMODCACHEChanged = EnvOrAndChanged("GOMODCACHE", gopathDir("pkg/mod"))

	// Used in envcmd.MkEnv and build ID computations.
	GOARM64, goARM64Changed     = EnvOrAndChanged("GOARM64", fmt.Sprint(buildcfg.GOARM64))
	GOARM, goARMChanged         = EnvOrAndChanged("GOARM", fmt.Sprint(buildcfg.GOARM))
	GO386, go386Changed         = EnvOrAndChanged("GO386", buildcfg.GO386)

	if find(goos, okgoos) < 0 {
		fatalf("unknown $GOOS %s", goos)
	}

	b = os.Getenv("GOARM")
	if b == "" {
		b = xgetgoarm()
	}
	goarm = b

	b = os.Getenv("GOARM64")
	if b == "" {
		b = "v8.0"
	}
	goarm64 = b

	b = os.Getenv("GO386")
	if b == "" {
		b = "sse2"
	}
	go386 = b

	b = os.Getenv("GOAMD64")
	if b == "" {
		b = "v1"
	}
	goamd64 = b

	GOARM64
		For GOARCH=arm64, the ARM64 architecture for which to compile.
		Valid values are v8.0 (default), v8.{1-9}, v9.{0-5}.
		The value can be followed by an option specifying extensions implemented by target hardware.
		Valid options are ,lse and ,crypto.
		Note that some extensions are enabled by default starting from a certain GOARM64 version;

			args = append(args, "-D", "GOARM_6")
			fallthrough
		default:
			args = append(args, "-D", "GOARM_5")
		}
	}

	if cfg.Goarch == "arm64" {
		g, err := buildcfg.ParseGoarm64(cfg.GOARM64)
		if err == nil && g.LSE {
			args = append(args, "-D", "GOARM64_LSE")
		}
	}

	return args
}

func (gcToolchain) asm(b *Builder, a *Action, sfiles []string) ([]string, error) {
	p := a.Package

//	GOARM64
//		For GOARCH=arm64, the ARM64 architecture for which to compile.
//		Valid values are v8.0 (default), v8.{1-9}, v9.{0-5}.
//		The value can be followed by an option specifying extensions implemented by target hardware.
//		Valid options are ,lse and ,crypto.
//		Note that some extensions are enabled by default starting from a certain GOARM64 version;

	makeAtomicGuardedIntrinsicARM64 := func(op0, op1 ssa.Op, typ types.Kind, emit atomicOpEmitter) intrinsicBuilder {

		return func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
			if buildcfg.GOARM64.LSE {
				emit(s, n, args, op1, typ)
			} else {
				// Target Atomic feature is identified by dynamic detection
				addr := s.entryNewValue1A(ssa.OpAddr, types.Types[types.TBOOL].PtrTo(), ir.Syms.ARM64HasATOMICS, s.sb)