cmd/internal/obj/riscv: implement AUIPC and LUI instructions

Add support for assembling AUIPC and LUI instructions.

Based on the riscv-go port.

Updates #27532

Change-Id: I178868b6dcc6fdc6b8527454569a3538ed50723e
Reviewed-on: https://go-review.googlesource.com/c/go/+/196840Reviewed-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

@@ -57,6 +57,15 @@ TEXT asmtest(SB),DUPOK|NOSPLIT,$0
 	XOR	$1, X5, X6				// 13c31200
 	XOR	$1, X5					// 93c21200
 
+	AUIPC	$0, X10					// 17050000
+	AUIPC	$0, X11					// 97050000
+	AUIPC	$1, X10					// 17150000
+	AUIPC	$1048575, X10				// 17f5ffff
+
+	LUI	$0, X15					// b7070000
+	LUI	$167, X15				// b7770a00
+	LUI	$1048575, X15				// b7f7ffff
+
 	SLL	X6, X5, X7				// b3936200
 	SLL	X5, X6					// 33135300
 	SLL	$1, X5, X6				// 13931200

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

@@ -192,33 +192,61 @@ 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 {
+// immIFits reports whether immediate value x fits in nbits bits
+// as a signed integer.
+func immIFits(x int64, nbits uint) bool {
 	nbits--
 	var min int64 = -1 << nbits
 	var max int64 = 1<<nbits - 1
 	return min <= x && x <= max
 }
 
-// immI extracts the integer literal of the specified size from an Addr.
+// immUFits reports whether immediate value x fits in nbits bits
+// as an unsigned integer.
+func immUFits(x int64, nbits uint) bool {
+	var max int64 = 1<<nbits - 1
+	return 0 <= x && x <= max
+}
+
+// immI extracts the signed integer literal of the specified size from an Addr.
 func immI(a obj.Addr, nbits uint) uint32 {
 	if a.Type != obj.TYPE_CONST {
 		panic(fmt.Sprintf("ill typed: %+v", a))
 	}
-	if !immFits(a.Offset, nbits) {
-		panic(fmt.Sprintf("immediate %d in %v cannot fit in %d bits", a.Offset, a, nbits))
+	if !immIFits(a.Offset, nbits) {
+		panic(fmt.Sprintf("signed immediate %d in %v cannot fit in %d bits", a.Offset, a, nbits))
+	}
+	return uint32(a.Offset)
+}
+
+// immU extracts the unsigned integer literal of the specified size from an Addr.
+func immU(a obj.Addr, nbits uint) uint32 {
+	if a.Type != obj.TYPE_CONST {
+		panic(fmt.Sprintf("ill typed: %+v", a))
+	}
+	if !immUFits(a.Offset, nbits) {
+		panic(fmt.Sprintf("unsigned immediate %d in %v cannot fit in %d bits", a.Offset, a, nbits))
 	}
 	return uint32(a.Offset)
 }
 
-func wantImm(p *obj.Prog, pos string, a obj.Addr, nbits uint) {
+func wantImmI(p *obj.Prog, pos string, a obj.Addr, nbits uint) {
+	if a.Type != obj.TYPE_CONST {
+		p.Ctxt.Diag("%v\texpected immediate in %s position but got %s", p, pos, obj.Dconv(p, &a))
+		return
+	}
+	if !immIFits(a.Offset, nbits) {
+		p.Ctxt.Diag("%v\tsigned immediate in %s position cannot be larger than %d bits but got %d", p, pos, nbits, a.Offset)
+	}
+}
+
+func wantImmU(p *obj.Prog, pos string, a obj.Addr, nbits uint) {
 	if a.Type != obj.TYPE_CONST {
 		p.Ctxt.Diag("%v\texpected immediate in %s position but got %s", p, pos, obj.Dconv(p, &a))
 		return
 	}
-	if !immFits(a.Offset, nbits) {
-		p.Ctxt.Diag("%v\timmediate in %s position cannot be larger than %d bits but got %d", p, pos, nbits, a.Offset)
+	if !immUFits(a.Offset, nbits) {
+		p.Ctxt.Diag("%v\tunsigned immediate in %s position cannot be larger than %d bits but got %d", p, pos, nbits, a.Offset)
 	}
 }
 
@@ -296,29 +324,34 @@ func validateRFF(p *obj.Prog) {
 }
 
 func validateII(p *obj.Prog) {
-	wantImm(p, "from", p.From, 12)
+	wantImmI(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)
+	wantImmI(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)
+	wantImmI(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)
+	wantImmI(p, "from", p.From, 12)
 	wantFloatReg(p, "reg", p.Reg)
 	wantIntRegAddr(p, "to", &p.To)
 }
 
+func validateU(p *obj.Prog) {
+	wantImmU(p, "from", p.From, 20)
+	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.
@@ -395,11 +428,11 @@ func encodeIF(p *obj.Prog) uint32 {
 func encodeS(p *obj.Prog, rs2 uint32) uint32 {
 	imm := immI(p.From, 12)
 	rs1 := regIAddr(p.To)
-	i := encode(p.As)
-	if i == nil {
+	ins := encode(p.As)
+	if ins == nil {
 		panic("encodeS: could not encode instruction")
 	}
-	return (imm>>5)<<25 | rs2<<20 | rs1<<15 | i.funct3<<12 | (imm&0x1f)<<7 | i.opcode
+	return (imm>>5)<<25 | rs2<<20 | rs1<<15 | ins.funct3<<12 | (imm&0x1f)<<7 | ins.opcode
 }
 
 func encodeSI(p *obj.Prog) uint32 {
@@ -410,6 +443,21 @@ func encodeSF(p *obj.Prog) uint32 {
 	return encodeS(p, regF(p.Reg))
 }
 
+// encodeU encodes a U-type RISC-V instruction.
+func encodeU(p *obj.Prog) uint32 {
+	// The immediates for encodeU are the upper 20 bits of a 32 bit value.
+	// Rather than have the user/compiler generate a 32 bit constant, the
+	// bottommost bits of which must all be zero, instead accept just the
+	// top bits.
+	imm := immU(p.From, 20)
+	rd := regIAddr(p.To)
+	ins := encode(p.As)
+	if ins == nil {
+		panic("encodeU: could not encode instruction")
+	}
+	return imm<<12 | rd<<7 | ins.opcode
+}
+
 // encodeRaw encodes a raw instruction value.
 func encodeRaw(p *obj.Prog) uint32 {
 	// Treat the raw value specially as a 32-bit unsigned integer.
@@ -455,6 +503,8 @@ var (
 	sIEncoding = encoding{encode: encodeSI, validate: validateSI, length: 4}
 	sFEncoding = encoding{encode: encodeSF, validate: validateSF, length: 4}
 
+	uEncoding = encoding{encode: encodeU, validate: validateU, length: 4}
+
 	// rawEncoding encodes a raw instruction byte sequence.
 	rawEncoding = encoding{encode: encodeRaw, validate: validateRaw, length: 4}
 
@@ -483,6 +533,8 @@ var encodingForAs = [ALAST & obj.AMask]encoding{
 	ASLLI & obj.AMask:  iIEncoding,
 	ASRLI & obj.AMask:  iIEncoding,
 	ASRAI & obj.AMask:  iIEncoding,
+	ALUI & obj.AMask:   uEncoding,
+	AAUIPC & obj.AMask: uEncoding,
 	AADD & obj.AMask:   rIIIEncoding,
 	ASLT & obj.AMask:   rIIIEncoding,
 	ASLTU & obj.AMask:  rIIIEncoding,