cmd/compile: add support for Abs and Copysign intrinsics on riscv64

Also, add the FABSS and FABSD pseudo instructions to the assembler.
The compiler could use FSGNJX[SD] directly but there doesn't seem
to be much advantage to doing so and the pseudo instructions are
easier to understand.

Change-Id: Ie8825b8aa8773c69cc4f07a32ef04abf4061d80d
Reviewed-on: https://go-review.googlesource.com/c/go/+/348989
Trust: Michael Munday <mike.munday@lowrisc.org>
Run-TryBot: Michael Munday <mike.munday@lowrisc.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Joel Sing <joel@sing.id.au>

src/cmd/asm/internal/asm/testdata/riscv64.s

@@ -382,10 +382,12 @@ start:
 	SNEZ	X15, X15				// b337f000
 
 	// F extension
+	FABSS	F0, F1					// d3200020
 	FNEGS	F0, F1					// d3100020
 	FNES	F0, F1, X7				// d3a300a093c31300
 
 	// D extension
+	FABSD	F0, F1					// d3200022
 	FNEGD	F0, F1					// d3100022
 	FNED	F0, F1, X5				// d3a200a293c21200
 	FLTD	F0, F1, X5				// d39200a2

src/cmd/compile/internal/riscv64/ssa.go

@@ -272,7 +272,8 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		ssa.OpRISCV64FADDS, ssa.OpRISCV64FSUBS, ssa.OpRISCV64FMULS, ssa.OpRISCV64FDIVS,
 		ssa.OpRISCV64FEQS, ssa.OpRISCV64FNES, ssa.OpRISCV64FLTS, ssa.OpRISCV64FLES,
 		ssa.OpRISCV64FADDD, ssa.OpRISCV64FSUBD, ssa.OpRISCV64FMULD, ssa.OpRISCV64FDIVD,
-		ssa.OpRISCV64FEQD, ssa.OpRISCV64FNED, ssa.OpRISCV64FLTD, ssa.OpRISCV64FLED:
+		ssa.OpRISCV64FEQD, ssa.OpRISCV64FNED, ssa.OpRISCV64FLTD, ssa.OpRISCV64FLED,
+		ssa.OpRISCV64FSGNJD:
 		r := v.Reg()
 		r1 := v.Args[0].Reg()
 		r2 := v.Args[1].Reg()
@@ -329,7 +330,7 @@ func ssaGenValue(s *ssagen.State, v *ssa.Value) {
 		p.SetRestArgs([]obj.Addr{{Type: obj.TYPE_REG, Reg: r3}})
 		p.To.Type = obj.TYPE_REG
 		p.To.Reg = r
-	case ssa.OpRISCV64FSQRTS, ssa.OpRISCV64FNEGS, ssa.OpRISCV64FSQRTD, ssa.OpRISCV64FNEGD,
+	case ssa.OpRISCV64FSQRTS, ssa.OpRISCV64FNEGS, ssa.OpRISCV64FABSD, ssa.OpRISCV64FSQRTD, ssa.OpRISCV64FNEGD,
 		ssa.OpRISCV64FMVSX, ssa.OpRISCV64FMVDX,
 		ssa.OpRISCV64FCVTSW, ssa.OpRISCV64FCVTSL, ssa.OpRISCV64FCVTWS, ssa.OpRISCV64FCVTLS,
 		ssa.OpRISCV64FCVTDW, ssa.OpRISCV64FCVTDL, ssa.OpRISCV64FCVTWD, ssa.OpRISCV64FCVTLD, ssa.OpRISCV64FCVTDS, ssa.OpRISCV64FCVTSD,

src/cmd/compile/internal/ssa/gen/RISCV64.rules

@@ -96,6 +96,10 @@
 (Sqrt ...) => (FSQRTD ...)
 (Sqrt32 ...) => (FSQRTS ...)
 
+(Copysign ...) => (FSGNJD ...)
+
+(Abs ...) => (FABSD ...)
+
 (FMA ...) => (FMADDD ...)
 
 // Sign and zero extension.

src/cmd/compile/internal/ssa/gen/RISCV64Ops.go

@@ -432,6 +432,8 @@ func init() {
 		{name: "FNMSUBD", argLength: 3, reg: fp31, asm: "FNMSUBD", commutative: true, typ: "Float64"},                                       // -(arg0 * arg1) - arg2
 		{name: "FSQRTD", argLength: 1, reg: fp11, asm: "FSQRTD", typ: "Float64"},                                                            // sqrt(arg0)
 		{name: "FNEGD", argLength: 1, reg: fp11, asm: "FNEGD", typ: "Float64"},                                                              // -arg0
+		{name: "FABSD", argLength: 1, reg: fp11, asm: "FABSD", typ: "Float64"},                                                              // abs(arg0)
+		{name: "FSGNJD", argLength: 2, reg: fp21, asm: "FSGNJD", typ: "Float64"},                                                            // copy sign of arg1 to arg0
 		{name: "FMVDX", argLength: 1, reg: gpfp, asm: "FMVDX", typ: "Float64"},                                                              // reinterpret arg0 as float
 		{name: "FCVTDW", argLength: 1, reg: gpfp, asm: "FCVTDW", typ: "Float64"},                                                            // float64(low 32 bits of arg0)
 		{name: "FCVTDL", argLength: 1, reg: gpfp, asm: "FCVTDL", typ: "Float64"},                                                            // float64(arg0)

src/cmd/compile/internal/ssa/opGen.go

@@ -2183,6 +2183,8 @@ const (
 	OpRISCV64FNMSUBD
 	OpRISCV64FSQRTD
 	OpRISCV64FNEGD
+	OpRISCV64FABSD
+	OpRISCV64FSGNJD
 	OpRISCV64FMVDX
 	OpRISCV64FCVTDW
 	OpRISCV64FCVTDL
@@ -29187,6 +29189,33 @@ var opcodeTable = [...]opInfo{
 			},
 		},
 	},
+	{
+		name:   "FABSD",
+		argLen: 1,
+		asm:    riscv.AFABSD,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 9223372034707292160}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 F26 F27 F28 F29 F30 F31
+			},
+			outputs: []outputInfo{
+				{0, 9223372034707292160}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 F26 F27 F28 F29 F30 F31
+			},
+		},
+	},
+	{
+		name:   "FSGNJD",
+		argLen: 2,
+		asm:    riscv.AFSGNJD,
+		reg: regInfo{
+			inputs: []inputInfo{
+				{0, 9223372034707292160}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 F26 F27 F28 F29 F30 F31
+				{1, 9223372034707292160}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 F26 F27 F28 F29 F30 F31
+			},
+			outputs: []outputInfo{
+				{0, 9223372034707292160}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 F24 F25 F26 F27 F28 F29 F30 F31
+			},
+		},
+	},
 	{
 		name:   "FMVDX",
 		argLen: 1,

src/cmd/compile/internal/ssa/rewriteRISCV64.go

@@ -8,6 +8,9 @@ import "cmd/compile/internal/types"
 
 func rewriteValueRISCV64(v *Value) bool {
 	switch v.Op {
+	case OpAbs:
+		v.Op = OpRISCV64FABSD
+		return true
 	case OpAdd16:
 		v.Op = OpRISCV64ADD
 		return true
@@ -134,6 +137,9 @@ func rewriteValueRISCV64(v *Value) bool {
 	case OpConvert:
 		v.Op = OpRISCV64MOVconvert
 		return true
+	case OpCopysign:
+		v.Op = OpRISCV64FSGNJD
+		return true
 	case OpCvt32Fto32:
 		v.Op = OpRISCV64FCVTWS
 		return true

src/cmd/compile/internal/ssagen/ssa.go

@@ -4212,12 +4212,12 @@ func InitTables() {
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			return s.newValue1(ssa.OpAbs, types.Types[types.TFLOAT64], args[0])
 		},
-		sys.ARM64, sys.ARM, sys.PPC64, sys.Wasm)
+		sys.ARM64, sys.ARM, sys.PPC64, sys.RISCV64, sys.Wasm)
 	addF("math", "Copysign",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			return s.newValue2(ssa.OpCopysign, types.Types[types.TFLOAT64], args[0], args[1])
 		},
-		sys.PPC64, sys.Wasm)
+		sys.PPC64, sys.RISCV64, sys.Wasm)
 	addF("math", "FMA",
 		func(s *state, n *ir.CallExpr, args []*ssa.Value) *ssa.Value {
 			return s.newValue3(ssa.OpFMA, types.Types[types.TFLOAT64], args[0], args[1], args[2])

src/cmd/internal/obj/riscv/anames.go

@@ -236,6 +236,8 @@ var Anames = []string{
 	"BLEZ",
 	"BLTZ",
 	"BNEZ",
+	"FABSD",
+	"FABSS",
 	"FNEGD",
 	"FNEGS",
 	"FNED",

src/cmd/internal/obj/riscv/cpu.go

@@ -590,6 +590,8 @@ const (
 	ABLEZ
 	ABLTZ
 	ABNEZ
+	AFABSD
+	AFABSS
 	AFNEGD
 	AFNEGS
 	AFNED

src/cmd/internal/obj/riscv/obj.go

@@ -1998,6 +1998,16 @@ func instructionsForProg(p *obj.Prog) []*instruction {
 		ins.as = ASLTU
 		ins.rs1 = REG_ZERO
 
+	case AFABSS:
+		// FABSS rs, rd -> FSGNJXS rs, rs, rd
+		ins.as = AFSGNJXS
+		ins.rs1 = uint32(p.From.Reg)
+
+	case AFABSD:
+		// FABSD rs, rd -> FSGNJXD rs, rs, rd
+		ins.as = AFSGNJXD
+		ins.rs1 = uint32(p.From.Reg)
+
 	case AFNEGS:
 		// FNEGS rs, rd -> FSGNJNS rs, rs, rd
 		ins.as = AFSGNJNS

test/codegen/math.go

@@ -73,6 +73,7 @@ func abs(x, y float64) {
 	// s390x:"LPDFR\t",-"MOVD\t"     (no integer load/store)
 	// ppc64:"FABS\t"
 	// ppc64le:"FABS\t"
+	// riscv64:"FABSD\t"
 	// wasm:"F64Abs"
 	// arm/6:"ABSD\t"
 	sink64[0] = math.Abs(x)
@@ -96,6 +97,7 @@ func copysign(a, b, c float64) {
 	// s390x:"CPSDR",-"MOVD"         (no integer load/store)
 	// ppc64:"FCPSGN"
 	// ppc64le:"FCPSGN"
+	// riscv64:"FSGNJD"
 	// wasm:"F64Copysign"
 	sink64[0] = math.Copysign(a, b)
 
@@ -103,6 +105,7 @@ func copysign(a, b, c float64) {
 	// s390x:"LNDFR\t",-"MOVD\t"     (no integer load/store)
 	// ppc64:"FCPSGN"
 	// ppc64le:"FCPSGN"
+	// riscv64:"FSGNJD"
 	// arm64:"ORR", -"AND"
 	sink64[1] = math.Copysign(c, -1)
 
@@ -115,6 +118,7 @@ func copysign(a, b, c float64) {
 	// s390x:"CPSDR\t",-"MOVD\t"     (no integer load/store)
 	// ppc64:"FCPSGN"
 	// ppc64le:"FCPSGN"
+	// riscv64:"FSGNJD"
 	sink64[3] = math.Copysign(-1, c)
 }