cmd/compile: add softfloat support to mips64{,le}

mips64 softfloat support is based on mips implementation and introduces
new enviroment variable GOMIPS64.

GOMIPS64 is a GOARCH=mips64{,le} specific option, for a choice between
hard-float and soft-float. Valid values are 'hardfloat' (default) and
'softfloat'. It is passed to the assembler as
'GOMIPS64_{hardfloat,softfloat}'.

Change-Id: I7f73078627f7cb37c588a38fb5c997fe09c56134
Reviewed-on: https://go-review.googlesource.com/108475
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

doc/asm.html

@@ -939,6 +939,12 @@ The value of <code>GOMIPS</code> environment variable (<code>hardfloat</code> or
 <code>GOMIPS_hardfloat</code> or <code>GOMIPS_softfloat</code>.
 </p>
 
+<p>
+The value of <code>GOMIPS64</code> environment variable (<code>hardfloat</code> or
+<code>softfloat</code>) is made available to assembly code by predefining either
+<code>GOMIPS64_hardfloat</code> or <code>GOMIPS64_softfloat</code>.
+</p>
+
 <h3 id="unsupported_opcodes">Unsupported opcodes</h3>
 
 <p>

src/cmd/compile/internal/mips64/galign.go

@@ -18,7 +18,7 @@ func Init(arch *gc.Arch) {
 	}
 	arch.REGSP = mips.REGSP
 	arch.MAXWIDTH = 1 << 50
-
+	arch.SoftFloat = objabi.GOMIPS64 == "softfloat"
 	arch.ZeroRange = zerorange
 	arch.ZeroAuto = zeroAuto
 	arch.Ginsnop = ginsnop

src/cmd/dist/build.go

@@ -31,6 +31,7 @@ var (
 	goarm            string
 	go386            string
 	gomips           string
+	gomips64         string
 	goroot           string
 	goroot_final     string
 	goextlinkenabled string
@@ -145,6 +146,12 @@ func xinit() {
 	}
 	gomips = b
 
+	b = os.Getenv("GOMIPS64")
+	if b == "" {
+		b = "hardfloat"
+	}
+	gomips64 = b
+
 	if p := pathf("%s/src/all.bash", goroot); !isfile(p) {
 		fatalf("$GOROOT is not set correctly or not exported\n"+
 			"\tGOROOT=%s\n"+
@@ -202,6 +209,7 @@ func xinit() {
 	os.Setenv("GOHOSTOS", gohostos)
 	os.Setenv("GOOS", goos)
 	os.Setenv("GOMIPS", gomips)
+	os.Setenv("GOMIPS64", gomips64)
 	os.Setenv("GOROOT", goroot)
 	os.Setenv("GOROOT_FINAL", goroot_final)
 
@@ -822,6 +830,11 @@ func runInstall(dir string, ch chan struct{}) {
 			compile = append(compile, "-D", "GOMIPS_"+gomips)
 		}
 
+		if goarch == "mips64" || goarch == "mipsle64" {
+			// Define GOMIPS64_value from gomips64.
+			compile = append(compile, "-D", "GOMIPS64_"+gomips64)
+		}
+
 		doclean := true
 		b := pathf("%s/%s", workdir, filepath.Base(p))
 
@@ -1063,6 +1076,9 @@ func cmdenv() {
 	if goarch == "mips" || goarch == "mipsle" {
 		xprintf(format, "GOMIPS", gomips)
 	}
+	if goarch == "mips64" || goarch == "mips64le" {
+		xprintf(format, "GOMIPS64", gomips64)
+	}
 
 	if *path {
 		sep := ":"

src/cmd/dist/buildruntime.go

@@ -44,6 +44,7 @@ func mkzversion(dir, file string) {
 //	const defaultGO386 = <go386>
 //	const defaultGOARM = <goarm>
 //	const defaultGOMIPS = <gomips>
+//	const defaultGOMIPS64 = <gomips64>
 //	const defaultGOOS = runtime.GOOS
 //	const defaultGOARCH = runtime.GOARCH
 //	const defaultGO_EXTLINK_ENABLED = <goextlinkenabled>
@@ -71,6 +72,7 @@ func mkzbootstrap(file string) {
 	fmt.Fprintf(&buf, "const defaultGO386 = `%s`\n", go386)
 	fmt.Fprintf(&buf, "const defaultGOARM = `%s`\n", goarm)
 	fmt.Fprintf(&buf, "const defaultGOMIPS = `%s`\n", gomips)
+	fmt.Fprintf(&buf, "const defaultGOMIPS64 = `%s`\n", gomips64)
 	fmt.Fprintf(&buf, "const defaultGOOS = runtime.GOOS\n")
 	fmt.Fprintf(&buf, "const defaultGOARCH = runtime.GOARCH\n")
 	fmt.Fprintf(&buf, "const defaultGO_EXTLINK_ENABLED = `%s`\n", goextlinkenabled)

src/cmd/go/alldocs.go

@@ -1094,6 +1094,9 @@
 // 	GOMIPS
 // 		For GOARCH=mips{,le}, whether to use floating point instructions.
 // 		Valid values are hardfloat (default), softfloat.
+//	GOMIPS64
+//		For GOARCH=mips64{,le}, whether to use floating point instructions.
+//		Valid values are hardfloat (default), softfloat.
 //
 // Special-purpose environment variables:
 //

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

@@ -87,6 +87,7 @@ var (
 	GOARM    = fmt.Sprint(objabi.GOARM)
 	GO386    = objabi.GO386
 	GOMIPS   = objabi.GOMIPS
+	GOMIPS64 = objabi.GOMIPS64
 )
 
 // Update build context to use our computed GOROOT.

src/cmd/go/internal/envcmd/env.go

@@ -78,6 +78,8 @@ func MkEnv() []cfg.EnvVar {
 		env = append(env, cfg.EnvVar{Name: "GO386", Value: cfg.GO386})
 	case "mips", "mipsle":
 		env = append(env, cfg.EnvVar{Name: "GOMIPS", Value: cfg.GOMIPS})
+	case "mips64", "mips64le":
+		env = append(env, cfg.EnvVar{Name: "GOMIPS64", Value: cfg.GOMIPS64})
 	}
 
 	cc := cfg.DefaultCC(cfg.Goos, cfg.Goarch)

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

@@ -527,6 +527,9 @@ Architecture-specific environment variables:
 	GOMIPS
 		For GOARCH=mips{,le}, whether to use floating point instructions.
 		Valid values are hardfloat (default), softfloat.
+	GOMIPS64
+		For GOARCH=mips64{,le}, whether to use floating point instructions.
+		Valid values are hardfloat (default), softfloat.
 
 Special-purpose environment variables:
 

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

@@ -233,6 +233,11 @@ func (gcToolchain) asm(b *Builder, a *Action, sfiles []string) ([]string, error)
 		args = append(args, "-D", "GOMIPS_"+cfg.GOMIPS)
 	}
 
+	if cfg.Goarch == "mips64" || cfg.Goarch == "mips64le" {
+		// Define GOMIPS64_value from cfg.GOMIPS64.
+		args = append(args, "-D", "GOMIPS64_"+cfg.GOMIPS64)
+	}
+
 	var ofiles []string
 	for _, sfile := range sfiles {
 		ofile := a.Objdir + sfile[:len(sfile)-len(".s")] + ".o"

src/cmd/internal/objabi/util.go

@@ -27,6 +27,7 @@ var (
 	GO386    = envOr("GO386", defaultGO386)
 	GOARM    = goarm()
 	GOMIPS   = gomips()
+	GOMIPS64 = gomips64()
 	Version  = version
 )
 
@@ -53,6 +54,15 @@ func gomips() string {
 	panic("unreachable")
 }
 
+func gomips64() string {
+	switch v := envOr("GOMIPS64", defaultGOMIPS64); v {
+	case "hardfloat", "softfloat":
+		return v
+	}
+	log.Fatalf("Invalid GOMIPS64 value. Must be hardfloat or softfloat.")
+	panic("unreachable")
+}
+
 func Getgoextlinkenabled() string {
 	return envOr("GO_EXTLINK_ENABLED", defaultGO_EXTLINK_ENABLED)
 }

src/runtime/cgo/asm_mips64x.s

@@ -17,7 +17,11 @@ TEXT crosscall2(SB),NOSPLIT|NOFRAME,$0
 	 * Also note that at procedure entry in gc world, 8(R29) will be the
 	 *  first arg.
 	 */
+#ifndef GOMIPS64_softfloat
 	ADDV	$(-8*23), R29
+#else
+	ADDV	$(-8*15), R29
+#endif
 	MOVV	R5, (8*1)(R29) // void*
 	MOVW	R6, (8*2)(R29) // int32
 	MOVV	R7, (8*3)(R29) // uintptr
@@ -32,6 +36,7 @@ TEXT crosscall2(SB),NOSPLIT|NOFRAME,$0
 	MOVV	RSB, (8*12)(R29)
 	MOVV	g, (8*13)(R29)
 	MOVV	R31, (8*14)(R29)
+#ifndef GOMIPS64_softfloat
 	MOVD	F24, (8*15)(R29)
 	MOVD	F25, (8*16)(R29)
 	MOVD	F26, (8*17)(R29)
@@ -40,7 +45,7 @@ TEXT crosscall2(SB),NOSPLIT|NOFRAME,$0
 	MOVD	F29, (8*20)(R29)
 	MOVD	F30, (8*21)(R29)
 	MOVD	F31, (8*22)(R29)
-
+#endif
 	// Initialize Go ABI environment
 	// prepare SB register = PC & 0xffffffff00000000
 	BGEZAL	R0, 1(PC)
@@ -60,6 +65,7 @@ TEXT crosscall2(SB),NOSPLIT|NOFRAME,$0
 	MOVV	(8*12)(R29), RSB
 	MOVV	(8*13)(R29), g
 	MOVV	(8*14)(R29), R31
+#ifndef GOMIPS64_softfloat
 	MOVD	(8*15)(R29), F24
 	MOVD	(8*16)(R29), F25
 	MOVD	(8*17)(R29), F26
@@ -69,4 +75,7 @@ TEXT crosscall2(SB),NOSPLIT|NOFRAME,$0
 	MOVD	(8*21)(R29), F30
 	MOVD	(8*22)(R29), F31
 	ADDV	$(8*23), R29
+#else
+	ADDV	$(8*15), R29
+#endif
 	RET

src/runtime/cgo/gcc_mips64x.S

@@ -14,7 +14,11 @@
 .globl crosscall1
 .set noat
 crosscall1:
+#ifndef __mips_soft_float
 	daddiu	$29, $29, -160
+#else
+	daddiu	$29, $29, -96 // For soft-float, no need to make room for FP registers
+#endif
 	sd	$31, 0($29)
 	sd	$16, 8($29)
 	sd	$17, 16($29)
@@ -26,6 +30,7 @@ crosscall1:
 	sd	$23, 64($29)
 	sd	$28, 72($29)
 	sd	$30, 80($29)
+#ifndef __mips_soft_float
 	sdc1	$f24, 88($29)
 	sdc1	$f25, 96($29)
 	sdc1	$f26, 104($29)
@@ -34,6 +39,7 @@ crosscall1:
 	sdc1	$f29, 128($29)
 	sdc1	$f30, 136($29)
 	sdc1	$f31, 144($29)
+#endif
 
 	// prepare SB register = pc & 0xffffffff00000000
 	bal	1f
@@ -56,6 +62,7 @@ crosscall1:
 	ld	$23, 64($29)
 	ld	$28, 72($29)
 	ld	$30, 80($29)
+#ifndef __mips_soft_float
 	ldc1	$f24, 88($29)
 	ldc1	$f25, 96($29)
 	ldc1	$f26, 104($29)
@@ -64,9 +71,13 @@ crosscall1:
 	ldc1	$f29, 128($29)
 	ldc1	$f30, 136($29)
 	ldc1	$f31, 144($29)
+#endif
 	ld	$31, 0($29)
-
+#ifndef __mips_soft_float
 	daddiu	$29, $29, 160
+#else
+	daddiu	$29, $29, 96
+#endif
 	jr	$31
 
 .set at

test/codegen/math.go

@@ -40,7 +40,8 @@ func sqrt(x float64) float64 {
 	// 386/387:"FSQRT" 386/sse2:"SQRTSD"
 	// arm64:"FSQRTD"
 	// arm/7:"SQRTD"
-	// mips/hardfloat:"SQRTD" mips64:"SQRTD"
+	// mips/hardfloat:"SQRTD" mips/softfloat:-"SQRTD"
+	// mips64/hardfloat:"SQRTD" mips64/softfloat:-"SQRTD"
 	return math.Sqrt(x)
 }
 

test/run.go

@@ -1301,7 +1301,7 @@ var (
 		"arm":     {"GOARM", "5", "6", "7"},
 		"arm64":   {},
 		"mips":    {"GOMIPS", "hardfloat", "softfloat"},
-		"mips64":  {},
+		"mips64":  {"GOMIPS64", "hardfloat", "softfloat"},
 		"ppc64":   {},
 		"ppc64le": {},
 		"s390x":   {},