cmd/go: add GORISCV64 environment variable

The variable represents the RISC-V user-mode application profile for
which to compile.  Valid values are rva20u64 (the default) and
rva22u64.

Setting GORISCV64=rva20u64 defines the riscv64.rva20u64 build tag,
sets the internal variable buildcfg.GORISCV64 to 20 and defines the
macro GORISCV64_rva20u64 for use in assembly language code.

Setting GORISCV64=rva22u64 defines the riscv64.rva20u64 and
riscv64.rva22u64 build tags, sets the internal variable
buildcfg.GORISCV64 to 22 and defines the macro GORISCV64_rva22u64
for use in assembly language code.

This patch only provides a mechanism for the compiler and hand-coded
assembly language functions to take advantage of the RISC-V
extensions mandated by the application profiles.  Further patches
will be required to get the compiler/assembler and assembly language
functions to actually generate and use these extensions.

Fixes #61476

Change-Id: I9195ae6ee71703cd2112160e89157ab63b8391af
Reviewed-on: https://go-review.googlesource.com/c/go/+/541135
Reviewed-by: M Zhuo <mengzhuo1203@gmail.com>
Reviewed-by: Joel Sing <joel@sing.id.au>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Wang Yaduo <wangyaduo@linux.alibaba.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: M Zhuo <mengzhuo1203@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/dist/build.go

@@ -38,6 +38,7 @@ var (
 	gomips           string
 	gomips64         string
 	goppc64          string
+	goriscv64        string
 	goroot           string
 	goroot_final     string
 	goextlinkenabled string
@@ -177,6 +178,12 @@ func xinit() {
 	}
 	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"+
@@ -236,6 +243,7 @@ func xinit() {
 	os.Setenv("GOMIPS", gomips)
 	os.Setenv("GOMIPS64", gomips64)
 	os.Setenv("GOPPC64", goppc64)
+	os.Setenv("GORISCV64", goriscv64)
 	os.Setenv("GOROOT", goroot)
 	os.Setenv("GOROOT_FINAL", goroot_final)
 
@@ -891,6 +899,10 @@ func runInstall(pkg string, ch chan struct{}) {
 			asmArgs = append(asmArgs, "-D", "GOPPC64_power8")
 		}
 	}
+	if goarch == "riscv64" {
+		// Define GORISCV64_value from goriscv64
+		asmArgs = append(asmArgs, "-D", "GORISCV64_"+goriscv64)
+	}
 	goasmh := pathf("%s/go_asm.h", workdir)
 
 	// Collect symabis from assembly code.
@@ -1236,6 +1248,9 @@ func cmdenv() {
 	if goarch == "ppc64" || goarch == "ppc64le" {
 		xprintf(format, "GOPPC64", goppc64)
 	}
+	if goarch == "riscv64" {
+		xprintf(format, "GORISCV64", goriscv64)
+	}
 	xprintf(format, "GOWORK", "off")
 
 	if *path {

src/cmd/dist/buildruntime.go

@@ -57,6 +57,7 @@ func mkbuildcfg(file string) {
 	fmt.Fprintf(&buf, "const defaultGOMIPS = `%s`\n", gomips)
 	fmt.Fprintf(&buf, "const defaultGOMIPS64 = `%s`\n", gomips64)
 	fmt.Fprintf(&buf, "const defaultGOPPC64 = `%s`\n", goppc64)
+	fmt.Fprintf(&buf, "const defaultGORISCV64 = `%s`\n", goriscv64)
 	fmt.Fprintf(&buf, "const defaultGOEXPERIMENT = `%s`\n", goexperiment)
 	fmt.Fprintf(&buf, "const defaultGO_EXTLINK_ENABLED = `%s`\n", goextlinkenabled)
 	fmt.Fprintf(&buf, "const defaultGO_LDSO = `%s`\n", defaultldso)

src/cmd/go/alldocs.go

@@ -2001,10 +2001,13 @@
 //     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.
 //
-// For GOARCH=amd64, arm, ppc64, and ppc64le, a particular feature level
+// For GOARCH=amd64, arm, ppc64, ppc64le, and riscv64, a particular feature level
 // sets the feature build tags for all previous levels as well.
 // For example, GOAMD64=v2 sets the amd64.v1 and amd64.v2 feature flags.
 // This ensures that code making use of v2 features continues to compile
@@ -2300,6 +2303,10 @@
 //	GOPPC64
 //		For GOARCH=ppc64{,le}, the target ISA (Instruction Set Architecture).
 //		Valid values are power8 (default), power9, power10.
+//	GORISCV64
+//		For GOARCH=riscv64, the RISC-V user-mode application profile for which
+//		to compile. Valid values are rva20u64 (default), rva22u64.
+//		See https://github.com/riscv/riscv-profiles/blob/main/profiles.adoc
 //	GOWASM
 //		For GOARCH=wasm, comma-separated list of experimental WebAssembly features to use.
 //		Valid values are satconv, signext.

src/cmd/go/internal/cfg/cfg.go

@@ -414,6 +414,7 @@ var (
 	GOMIPS    = envOr("GOMIPS", buildcfg.GOMIPS)
 	GOMIPS64  = envOr("GOMIPS64", buildcfg.GOMIPS64)
 	GOPPC64   = envOr("GOPPC64", fmt.Sprintf("%s%d", "power", buildcfg.GOPPC64))
+	GORISCV64 = envOr("GORISCV64", fmt.Sprintf("rva%du64", buildcfg.GORISCV64))
 	GOWASM    = envOr("GOWASM", fmt.Sprint(buildcfg.GOWASM))
 
 	GOPROXY    = envOr("GOPROXY", "")
@@ -445,6 +446,8 @@ func GetArchEnv() (key, val string) {
 		return "GOMIPS64", GOMIPS64
 	case "ppc64", "ppc64le":
 		return "GOPPC64", GOPPC64
+	case "riscv64":
+		return "GORISCV64", GORISCV64
 	case "wasm":
 		return "GOWASM", GOWASM
 	}

src/cmd/go/internal/help/helpdoc.go

@@ -619,6 +619,10 @@ Architecture-specific environment variables:
 	GOPPC64
 		For GOARCH=ppc64{,le}, the target ISA (Instruction Set Architecture).
 		Valid values are power8 (default), power9, power10.
+	GORISCV64
+		For GOARCH=riscv64, the RISC-V user-mode application profile for which
+		to compile. Valid values are rva20u64 (default), rva22u64.
+		See https://github.com/riscv/riscv-profiles/blob/main/profiles.adoc
 	GOWASM
 		For GOARCH=wasm, comma-separated list of experimental WebAssembly features to use.
 		Valid values are satconv, signext.
@@ -907,10 +911,13 @@ The defined architecture feature build tags are:
 	  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.
 
-For GOARCH=amd64, arm, ppc64, and ppc64le, a particular feature level
+For GOARCH=amd64, arm, ppc64, ppc64le, and riscv64, a particular feature level
 sets the feature build tags for all previous levels as well.
 For example, GOAMD64=v2 sets the amd64.v1 and amd64.v2 feature flags.
 This ensures that code making use of v2 features continues to compile

src/cmd/go/internal/work/gc.go

@@ -361,6 +361,11 @@ func asmArgs(a *Action, p *load.Package) []any {
 		}
 	}
 
+	if cfg.Goarch == "riscv64" {
+		// Define GORISCV64_value from cfg.GORISCV64.
+		args = append(args, "-D", "GORISCV64_"+cfg.GORISCV64)
+	}
+
 	if cfg.Goarch == "arm" {
 		// Define GOARM_value from cfg.GOARM.
 		switch cfg.GOARM {

src/cmd/go/testdata/script/tooltags.txt

@@ -40,6 +40,26 @@ env GOPPC64=power10
 go list -f '{{context.ToolTags}}'
 stdout 'ppc64le.power8 ppc64le.power9 ppc64le.power10'
 
+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=
+go list -f '{{context.ToolTags}}'
+stdout 'riscv64.rva20u64'
+
 env GOARCH=386
 env GO386=sse2
 go list -f '{{context.ToolTags}}'

src/cmd/internal/testdir/testdir_test.go

@@ -1468,7 +1468,7 @@ var (
 		"ppc64x":  {}, // A pseudo-arch representing both ppc64 and ppc64le
 		"s390x":   {},
 		"wasm":    {},
-		"riscv64": {},
+		"riscv64": {"GORISCV64", "rva20u64", "rva22u64"},
 	}
 )
 

src/internal/buildcfg/cfg.go

@@ -30,6 +30,7 @@ var (
 	GOMIPS    = gomips()
 	GOMIPS64  = gomips64()
 	GOPPC64   = goppc64()
+	GORISCV64 = goriscv64()
 	GOWASM    = gowasm()
 	ToolTags  = toolTags()
 	GO_LDSO   = defaultGO_LDSO
@@ -157,6 +158,22 @@ func goppc64() int {
 	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])
+	return year
+}
+
 type gowasmFeatures struct {
 	SatConv bool
 	SignExt bool
@@ -260,6 +277,12 @@ func gogoarchTags() []string {
 			list = append(list, fmt.Sprintf("%s.power%d", GOARCH, i))
 		}
 		return list
+	case "riscv64":
+		list := []string{GOARCH + "." + "rva20u64"}
+		if GORISCV64 >= 22 {
+			list = append(list, GOARCH+"."+"rva22u64")
+		}
+		return list
 	case "wasm":
 		var list []string
 		if GOWASM.SatConv {

src/internal/buildcfg/cfg_test.go

@@ -23,4 +23,18 @@ func TestConfigFlags(t *testing.T) {
 	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 {
+		t.Errorf("Wrong parsing of RISCV64=rva22")
+	}
 }

src/internal/cfg/cfg.go

@@ -57,6 +57,7 @@ const KnownEnv = `
 	GOPPC64
 	GOPRIVATE
 	GOPROXY
+	GORISCV64
 	GOROOT
 	GOSUMDB
 	GOTMPDIR