cmd/internal/obj/riscv: implement floating point instructions

Add support for assembling various single-precision and double-precision
floating point instructions.

Based on the riscv-go port.

Updates #27532

Change-Id: Iac1aec9b03bb6cbf116b229daeef944d4df550fa
Reviewed-on: https://go-review.googlesource.com/c/go/+/196839Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -95,7 +95,7 @@ TEXT asmtest(SB),DUPOK|NOSPLIT,$0
 	SB	$0, X5, X6				// 23005300
 	SB	$4, X5, X6				// 23025300
 
-        // 5.2: Integer Computational Instructions (RV64I)
+	// 5.2: Integer Computational Instructions (RV64I)
 	ADDIW	$1, X5, X6				// 1b831200
 	SLLIW	$1, X5, X6				// 1b931200
 	SRLIW	$1, X5, X6				// 1bd31200
@@ -132,6 +132,75 @@ TEXT asmtest(SB),DUPOK|NOSPLIT,$0
 	RDTIME		X5				// f32210c0
 	RDINSTRET	X5				// f32220c0
 
+	// 11.5: Single-Precision Load and Store Instructions
+	FLW	$0, X5, F0				// 07a00200
+	FLW	$4, X5, F0				// 07a04200
+	FSW	$0, F0, X5				// 27a00200
+	FSW	$4, F0, X5				// 27a20200
+
+	// 11.6: Single-Precision Floating-Point Computational Instructions
+	FADDS	F1, F0, F2				// 53011000
+	FSUBS	F1, F0, F2				// 53011008
+	FMULS	F1, F0, F2				// 53011010
+	FDIVS	F1, F0, F2				// 53011018
+	FMINS	F1, F0, F2				// 53011028
+	FMAXS	F1, F0, F2				// 53111028
+	FSQRTS	F0, F1					// d3000058
+
+	// 11.7: Single-Precision Floating-Point Conversion and Move Instructions
+	FCVTWS	F0, X5					// d31200c0
+	FCVTLS	F0, X5					// d31220c0
+	FCVTSW	X5, F0					// 538002d0
+	FCVTSL	X5, F0					// 538022d0
+	FCVTWUS	F0, X5					// d31210c0
+	FCVTLUS	F0, X5					// d31230c0
+	FCVTSWU	X5, F0					// 538012d0
+	FCVTSLU	X5, F0					// 538032d0
+	FSGNJS	F1, F0, F2				// 53011020
+	FSGNJNS	F1, F0, F2				// 53111020
+	FSGNJXS	F1, F0, F2				// 53211020
+	FMVXS	F0, X5					// d30200e0
+	FMVSX	X5, F0					// 538002f0
+	FMVXW	F0, X5					// d30200e0
+	FMVWX	X5, F0					// 538002f0
+
+	// 11.8: Single-Precision Floating-Point Compare Instructions
+	FEQS	F0, F1, X7				// d3a300a0
+	FLTS	F0, F1, X7				// d39300a0
+	FLES	F0, F1, X7				// d38300a0
+
+	// 12.3: Double-Precision Load and Store Instructions
+	FLD	$0, X5, F0				// 07b00200
+	FLD	$4, X5, F0				// 07b04200
+	FSD	$0, F0, X5				// 27b00200
+	FSD	$4, F0, X5				// 27b20200
+
+	// 12.4: Double-Precision Floating-Point Computational Instructions
+	FADDD	F1, F0, F2				// 53011002
+	FSUBD	F1, F0, F2				// 5301100a
+	FMULD	F1, F0, F2				// 53011012
+	FDIVD	F1, F0, F2				// 5301101a
+	FMIND	F1, F0, F2				// 5301102a
+	FMAXD	F1, F0, F2				// 5311102a
+	FSQRTD	F0, F1					// d300005a
+
+	// 12.5: Double-Precision Floating-Point Conversion and Move Instructions
+	FCVTWD	F0, X5					// d31200c2
+	FCVTLD	F0, X5					// d31220c2
+	FCVTDW	X5, F0					// 538002d2
+	FCVTDL	X5, F0					// 538022d2
+	FCVTWUD F0, X5					// d31210c2
+	FCVTLUD F0, X5					// d31230c2
+	FCVTDWU X5, F0					// 538012d2
+	FCVTDLU X5, F0					// 538032d2
+	FCVTSD	F0, F1					// d3001040
+	FCVTDS	F0, F1					// d3000042
+	FSGNJD	F1, F0, F2				// 53011022
+	FSGNJND	F1, F0, F2				// 53111022
+	FSGNJXD	F1, F0, F2				// 53211022
+	FMVXD	F0, X5					// d30200e2
+	FMVDX	X5, F0					// 538002f2
+
 	// Privileged ISA
 
 	// 3.2.1: Environment Call and Breakpoint

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

@@ -133,10 +133,10 @@ var Anames = []string{
 	"FSGNJS",
 	"FSGNJNS",
 	"FSGNJXS",
-	"FMVSX",
 	"FMVXS",
-	"FMVWX",
+	"FMVSX",
 	"FMVXW",
+	"FMVWX",
 	"FEQS",
 	"FLTS",
 	"FLES",

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

@@ -368,10 +368,10 @@ const (
 	AFSGNJS
 	AFSGNJNS
 	AFSGNJXS
-	AFMVSX
 	AFMVXS
-	AFMVWX
+	AFMVSX
 	AFMVXW
+	AFMVWX
 
 	// 11.8: Single-Precision Floating-Point Compare Instructions
 	AFEQS

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

@@ -96,6 +96,16 @@ func progedit(ctxt *obj.Link, p *obj.Prog, newprog obj.ProgAlloc) {
 		if p.To.Type == obj.TYPE_NONE {
 			p.To.Type, p.To.Reg = obj.TYPE_REG, REG_ZERO
 		}
+
+	case AFSQRTS, AFSQRTD:
+		// These instructions expect a zero (i.e. float register 0)
+		// to be the second input operand.
+		p.Reg = p.From.Reg
+		p.From = obj.Addr{Type: obj.TYPE_REG, Reg: REG_F0}
+
+	case AFCVTWS, AFCVTLS, AFCVTWUS, AFCVTLUS, AFCVTWD, AFCVTLD, AFCVTWUD, AFCVTLUD:
+		// Set the rounding mode in funct3 to round to zero.
+		p.Scond = 1
 	}
 }
 
@@ -159,6 +169,11 @@ func regI(r int16) uint32 {
 	return regVal(r, REG_X0, REG_X31)
 }
 
+// regF returns a float register.
+func regF(r int16) uint32 {
+	return regVal(r, REG_F0, REG_F31)
+}
+
 // regAddr extracts a register from an Addr.
 func regAddr(a obj.Addr, min, max int16) uint32 {
 	if a.Type != obj.TYPE_REG {
@@ -172,6 +187,11 @@ func regIAddr(a obj.Addr) uint32 {
 	return regAddr(a, REG_X0, REG_X31)
 }
 
+// regFAddr extracts the float register from an Addr.
+func regFAddr(a obj.Addr) uint32 {
+	return regAddr(a, REG_F0, REG_F31)
+}
+
 // immFits reports whether immediate value x fits in nbits bits as a
 // signed integer.
 func immFits(x int64, nbits uint) bool {
@@ -213,6 +233,11 @@ func wantIntReg(p *obj.Prog, pos string, r int16) {
 	wantReg(p, pos, "integer", r, REG_X0, REG_X31)
 }
 
+// wantFloatReg checks that r is a floating-point register.
+func wantFloatReg(p *obj.Prog, pos string, r int16) {
+	wantReg(p, pos, "float", r, REG_F0, REG_F31)
+}
+
 func wantRegAddr(p *obj.Prog, pos string, a *obj.Addr, descr string, min int16, max int16) {
 	if a == nil {
 		p.Ctxt.Diag("%v\texpected register in %s position but got nothing", p, pos)
@@ -232,24 +257,68 @@ func wantIntRegAddr(p *obj.Prog, pos string, a *obj.Addr) {
 	wantRegAddr(p, pos, a, "integer", REG_X0, REG_X31)
 }
 
+// wantFloatRegAddr checks that a contains a floating-point register.
+func wantFloatRegAddr(p *obj.Prog, pos string, a *obj.Addr) {
+	wantRegAddr(p, pos, a, "float", REG_F0, REG_F31)
+}
+
 func validateRIII(p *obj.Prog) {
 	wantIntRegAddr(p, "from", &p.From)
 	wantIntReg(p, "reg", p.Reg)
 	wantIntRegAddr(p, "to", &p.To)
 }
 
+func validateRFFF(p *obj.Prog) {
+	wantFloatRegAddr(p, "from", &p.From)
+	wantFloatReg(p, "reg", p.Reg)
+	wantFloatRegAddr(p, "to", &p.To)
+}
+
+func validateRFFI(p *obj.Prog) {
+	wantFloatRegAddr(p, "from", &p.From)
+	wantFloatReg(p, "reg", p.Reg)
+	wantIntRegAddr(p, "to", &p.To)
+}
+
+func validateRFI(p *obj.Prog) {
+	wantFloatRegAddr(p, "from", &p.From)
+	wantIntRegAddr(p, "to", &p.To)
+}
+
+func validateRIF(p *obj.Prog) {
+	wantIntRegAddr(p, "from", &p.From)
+	wantFloatRegAddr(p, "to", &p.To)
+}
+
+func validateRFF(p *obj.Prog) {
+	wantFloatRegAddr(p, "from", &p.From)
+	wantFloatRegAddr(p, "to", &p.To)
+}
+
 func validateII(p *obj.Prog) {
 	wantImm(p, "from", p.From, 12)
 	wantIntReg(p, "reg", p.Reg)
 	wantIntRegAddr(p, "to", &p.To)
 }
 
+func validateIF(p *obj.Prog) {
+	wantImm(p, "from", p.From, 12)
+	wantIntReg(p, "reg", p.Reg)
+	wantFloatRegAddr(p, "to", &p.To)
+}
+
 func validateSI(p *obj.Prog) {
 	wantImm(p, "from", p.From, 12)
 	wantIntReg(p, "reg", p.Reg)
 	wantIntRegAddr(p, "to", &p.To)
 }
 
+func validateSF(p *obj.Prog) {
+	wantImm(p, "from", p.From, 12)
+	wantFloatReg(p, "reg", p.Reg)
+	wantIntRegAddr(p, "to", &p.To)
+}
+
 func validateRaw(p *obj.Prog) {
 	// Treat the raw value specially as a 32-bit unsigned integer.
 	// Nobody wants to enter negative machine code.
@@ -282,6 +351,26 @@ func encodeRIII(p *obj.Prog) uint32 {
 	return encodeR(p, regI(p.Reg), regIAddr(p.From), regIAddr(p.To))
 }
 
+func encodeRFFF(p *obj.Prog) uint32 {
+	return encodeR(p, regF(p.Reg), regFAddr(p.From), regFAddr(p.To))
+}
+
+func encodeRFFI(p *obj.Prog) uint32 {
+	return encodeR(p, regF(p.Reg), regFAddr(p.From), regIAddr(p.To))
+}
+
+func encodeRFI(p *obj.Prog) uint32 {
+	return encodeR(p, regFAddr(p.From), 0, regIAddr(p.To))
+}
+
+func encodeRIF(p *obj.Prog) uint32 {
+	return encodeR(p, regIAddr(p.From), 0, regFAddr(p.To))
+}
+
+func encodeRFF(p *obj.Prog) uint32 {
+	return encodeR(p, regFAddr(p.From), 0, regFAddr(p.To))
+}
+
 // encodeI encodes an I-type RISC-V instruction.
 func encodeI(p *obj.Prog, rd uint32) uint32 {
 	imm := immI(p.From, 12)
@@ -298,6 +387,10 @@ func encodeII(p *obj.Prog) uint32 {
 	return encodeI(p, regIAddr(p.To))
 }
 
+func encodeIF(p *obj.Prog) uint32 {
+	return encodeI(p, regFAddr(p.To))
+}
+
 // encodeS encodes an S-type RISC-V instruction.
 func encodeS(p *obj.Prog, rs2 uint32) uint32 {
 	imm := immI(p.From, 12)
@@ -313,6 +406,10 @@ func encodeSI(p *obj.Prog) uint32 {
 	return encodeS(p, regI(p.Reg))
 }
 
+func encodeSF(p *obj.Prog) uint32 {
+	return encodeS(p, regF(p.Reg))
+}
+
 // encodeRaw encodes a raw instruction value.
 func encodeRaw(p *obj.Prog) uint32 {
 	// Treat the raw value specially as a 32-bit unsigned integer.
@@ -346,10 +443,17 @@ var (
 	// indicates an S-type instruction with rs2 being a float register.
 
 	rIIIEncoding = encoding{encode: encodeRIII, validate: validateRIII, length: 4}
+	rFFFEncoding = encoding{encode: encodeRFFF, validate: validateRFFF, length: 4}
+	rFFIEncoding = encoding{encode: encodeRFFI, validate: validateRFFI, length: 4}
+	rFIEncoding  = encoding{encode: encodeRFI, validate: validateRFI, length: 4}
+	rIFEncoding  = encoding{encode: encodeRIF, validate: validateRIF, length: 4}
+	rFFEncoding  = encoding{encode: encodeRFF, validate: validateRFF, length: 4}
 
 	iIEncoding = encoding{encode: encodeII, validate: validateII, length: 4}
+	iFEncoding = encoding{encode: encodeIF, validate: validateIF, length: 4}
 
 	sIEncoding = encoding{encode: encodeSI, validate: validateSI, length: 4}
+	sFEncoding = encoding{encode: encodeSF, validate: validateSF, length: 4}
 
 	// rawEncoding encodes a raw instruction byte sequence.
 	rawEncoding = encoding{encode: encodeRaw, validate: validateRaw, length: 4}
@@ -436,6 +540,76 @@ var encodingForAs = [ALAST & obj.AMask]encoding{
 	ARDTIME & obj.AMask:    iIEncoding,
 	ARDINSTRET & obj.AMask: iIEncoding,
 
+	// 11.5: Single-Precision Load and Store Instructions
+	AFLW & obj.AMask: iFEncoding,
+	AFSW & obj.AMask: sFEncoding,
+
+	// 11.6: Single-Precision Floating-Point Computational Instructions
+	AFADDS & obj.AMask:  rFFFEncoding,
+	AFSUBS & obj.AMask:  rFFFEncoding,
+	AFMULS & obj.AMask:  rFFFEncoding,
+	AFDIVS & obj.AMask:  rFFFEncoding,
+	AFMINS & obj.AMask:  rFFFEncoding,
+	AFMAXS & obj.AMask:  rFFFEncoding,
+	AFSQRTS & obj.AMask: rFFFEncoding,
+
+	// 11.7: Single-Precision Floating-Point Conversion and Move Instructions
+	AFCVTWS & obj.AMask:  rFIEncoding,
+	AFCVTLS & obj.AMask:  rFIEncoding,
+	AFCVTSW & obj.AMask:  rIFEncoding,
+	AFCVTSL & obj.AMask:  rIFEncoding,
+	AFCVTWUS & obj.AMask: rFIEncoding,
+	AFCVTLUS & obj.AMask: rFIEncoding,
+	AFCVTSWU & obj.AMask: rIFEncoding,
+	AFCVTSLU & obj.AMask: rIFEncoding,
+	AFSGNJS & obj.AMask:  rFFFEncoding,
+	AFSGNJNS & obj.AMask: rFFFEncoding,
+	AFSGNJXS & obj.AMask: rFFFEncoding,
+	AFMVXS & obj.AMask:   rFIEncoding,
+	AFMVSX & obj.AMask:   rIFEncoding,
+	AFMVXW & obj.AMask:   rFIEncoding,
+	AFMVWX & obj.AMask:   rIFEncoding,
+
+	// 11.8: Single-Precision Floating-Point Compare Instructions
+	AFEQS & obj.AMask: rFFIEncoding,
+	AFLTS & obj.AMask: rFFIEncoding,
+	AFLES & obj.AMask: rFFIEncoding,
+
+	// 12.3: Double-Precision Load and Store Instructions
+	AFLD & obj.AMask: iFEncoding,
+	AFSD & obj.AMask: sFEncoding,
+
+	// 12.4: Double-Precision Floating-Point Computational Instructions
+	AFADDD & obj.AMask:  rFFFEncoding,
+	AFSUBD & obj.AMask:  rFFFEncoding,
+	AFMULD & obj.AMask:  rFFFEncoding,
+	AFDIVD & obj.AMask:  rFFFEncoding,
+	AFMIND & obj.AMask:  rFFFEncoding,
+	AFMAXD & obj.AMask:  rFFFEncoding,
+	AFSQRTD & obj.AMask: rFFFEncoding,
+
+	// 12.5: Double-Precision Floating-Point Conversion and Move Instructions
+	AFCVTWD & obj.AMask:  rFIEncoding,
+	AFCVTLD & obj.AMask:  rFIEncoding,
+	AFCVTDW & obj.AMask:  rIFEncoding,
+	AFCVTDL & obj.AMask:  rIFEncoding,
+	AFCVTWUD & obj.AMask: rFIEncoding,
+	AFCVTLUD & obj.AMask: rFIEncoding,
+	AFCVTDWU & obj.AMask: rIFEncoding,
+	AFCVTDLU & obj.AMask: rIFEncoding,
+	AFCVTSD & obj.AMask:  rFFEncoding,
+	AFCVTDS & obj.AMask:  rFFEncoding,
+	AFSGNJD & obj.AMask:  rFFFEncoding,
+	AFSGNJND & obj.AMask: rFFFEncoding,
+	AFSGNJXD & obj.AMask: rFFFEncoding,
+	AFMVXD & obj.AMask:   rFIEncoding,
+	AFMVDX & obj.AMask:   rIFEncoding,
+
+	// 12.6: Double-Precision Floating-Point Compare Instructions
+	AFEQD & obj.AMask: rFFIEncoding,
+	AFLTD & obj.AMask: rFFIEncoding,
+	AFLED & obj.AMask: rFFIEncoding,
+
 	// Privileged ISA
 
 	// 3.2.1: Environment Call and Breakpoint