cmd/internal/obj/arm: support BFX/BFXU instructions

BFX extracts given bits from the source register, sign extends them
to 32-bit, and writes to destination register. BFXU does the similar
operation with zero extention.

They were introduced in ARMv6T2.

Change-Id: I6822ebf663497a87a662d3645eddd7c611de2b1e
Reviewed-on: https://go-review.googlesource.com/56071
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/asm/internal/arch/arm.go

@@ -122,6 +122,15 @@ func IsARMMRC(op obj.As) bool {
 	return false
 }
 
+// IsARMBFX reports whether the op is arm.BFX or arm.BFXU
+func IsARMBFX(op obj.As) bool {
+	switch op {
+	case arm.ABFX, arm.ABFXU:
+		return true
+	}
+	return false
+}
+
 // IsARMFloatCmp reports whether the op is a floating comparison instruction.
 func IsARMFloatCmp(op obj.As) bool {
 	switch op {

src/cmd/asm/internal/asm/asm.go

@@ -564,6 +564,13 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 				prog.To = a[2]
 				break
 			}
+			if arch.IsARMBFX(op) {
+				// a[0] and a[1] must be constants, a[2] must be a register
+				prog.From = a[0]
+				prog.From3 = newAddr(a[1])
+				prog.To = a[2]
+				break
+			}
 			// Otherwise the 2nd operand (a[1]) must be a register.
 			prog.From = a[0]
 			prog.Reg = p.getRegister(prog, op, &a[1])
@@ -635,7 +642,16 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			return
 		}
 	case 4:
-		if p.arch.Family == sys.ARM && arch.IsARMMULA(op) {
+		if p.arch.Family == sys.ARM {
+			if arch.IsARMBFX(op) {
+				// a[0] and a[1] must be constants, a[2] and a[3] must be registers
+				prog.From = a[0]
+				prog.From3 = newAddr(a[1])
+				prog.Reg = p.getRegister(prog, op, &a[2])
+				prog.To = a[3]
+				break
+			}
+			if arch.IsARMMULA(op) {
 				// All must be registers.
 				p.getRegister(prog, op, &a[0])
 				r1 := p.getRegister(prog, op, &a[1])
@@ -648,6 +664,7 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 				prog.Reg = r1
 				break
 			}
+		}
 		if p.arch.Family == sys.AMD64 {
 			// 4 operand instruction have form  ymm1, ymm2, ymm3/m256, imm8
 			// So From3 is always just a register, so we store imm8 in Offset field,

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

@@ -1007,6 +1007,12 @@ jmp_label_3:
 	SWI	$65535         // ffff00ef
 	SWI	               // 000000ef
 
+// BFX/BFXU
+	BFX	$16, $8, R1, R2 // BFX $16, R1, $8, R2   // 5124afe7
+	BFX	$29, $2, R8                              // 5881bce7
+	BFXU	$16, $8, R1, R2 // BFXU $16, R1, $8, R2  // 5124efe7
+	BFXU	$29, $2, R8                              // 5881fce7
+
 // synthetic arithmatic
 	ADD	$0xffffffaa, R2, R3 // ADD $4294967210, R2, R3   // 55b0e0e30b3082e0
 	ADD	$0xffffff55, R5     // ADD $4294967125, R5       // aab0e0e30b5085e0

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

@@ -124,5 +124,12 @@ TEXT errors(SB),$0
 	MOVFW	CPSR, R2           // ERROR "illegal combination"
 	MOVDW	R1, CPSR           // ERROR "illegal combination"
 	MOVFW	R1, CPSR           // ERROR "illegal combination"
+	BFX	$12, $41, R2, R3   // ERROR "wrong width or LSB"
+	BFX	$12, $-2, R2       // ERROR "wrong width or LSB"
+	BFXU	$40, $4, R2, R3    // ERROR "wrong width or LSB"
+	BFXU	$-40, $4, R2       // ERROR "wrong width or LSB"
+	BFX	$-2, $4, R2, R3    // ERROR "wrong width or LSB"
+	BFXU	$4, R2, R5, R2     // ERROR "missing or wrong LSB"
+	BFXU	$4, R2, R5         // ERROR "missing or wrong LSB"
 
 	END

src/cmd/internal/obj/arm/a.out.go

@@ -294,6 +294,9 @@ const (
 	AREVSH
 	ARBIT
 
+	ABFX
+	ABFXU
+
 	AMULWT
 	AMULWB
 	AMULBB

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

@@ -107,6 +107,8 @@ var Anames = []string{
 	"REV16",
 	"REVSH",
 	"RBIT",
+	"BFX",
+	"BFXU",
 	"MULWT",
 	"MULWB",
 	"MULBB",

src/cmd/internal/obj/arm/asm5.go

@@ -180,6 +180,8 @@ var optab = []Optab{
 	{ADIVHW, C_REG, C_REG, C_REG, 105, 4, 0, 0, 0},
 	{ADIVHW, C_REG, C_NONE, C_REG, 105, 4, 0, 0, 0},
 	{AMULL, C_REG, C_REG, C_REGREG, 17, 4, 0, 0, 0},
+	{ABFX, C_LCON, C_REG, C_REG, 18, 4, 0, 0, 0},  // width in From, LSB in From3
+	{ABFX, C_LCON, C_NONE, C_REG, 18, 4, 0, 0, 0}, // width in From, LSB in From3
 	{AMOVW, C_REG, C_NONE, C_SAUTO, 20, 4, REGSP, 0, 0},
 	{AMOVW, C_REG, C_NONE, C_SOREG, 20, 4, 0, 0, 0},
 	{AMOVB, C_REG, C_NONE, C_SAUTO, 20, 4, REGSP, 0, 0},
@@ -1691,6 +1693,9 @@ func buildop(ctxt *obj.Link) {
 			opset(AMMULA, r0)
 			opset(AMMULS, r0)
 
+		case ABFX:
+			opset(ABFXU, r0)
+
 		case ACLZ:
 			opset(AREV, r0)
 			opset(AREV16, r0)
@@ -2038,6 +2043,24 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		r := int(p.Reg)
 		o1 |= (uint32(rf)&15)<<8 | (uint32(r)&15)<<0 | (uint32(rt)&15)<<16 | (uint32(rt2)&15)<<12
 
+	case 18: /* BFX/BFXU */
+		o1 = c.oprrr(p, p.As, int(p.Scond))
+		rt := int(p.To.Reg)
+		r := int(p.Reg)
+		if r == 0 {
+			r = rt
+		}
+		if p.From3 == nil || p.From3.Type != obj.TYPE_CONST {
+			c.ctxt.Diag("%v: missing or wrong LSB", p)
+			break
+		}
+		lsb := p.From3.Offset
+		width := p.From.Offset
+		if lsb < 0 || lsb > 31 || width <= 0 || (lsb+width) > 31 {
+			c.ctxt.Diag("%v: wrong width or LSB", p)
+		}
+		o1 |= (uint32(r)&15)<<0 | (uint32(rt)&15)<<12 | uint32(lsb)<<7 | uint32(width-1)<<16
+
 	case 20: /* mov/movb/movbu R,O(R) */
 		c.aclass(&p.To)
 
@@ -2911,6 +2934,12 @@ func (c *ctxt5) oprrr(p *obj.Prog, a obj.As, sc int) uint32 {
 	case -ACMP: // cmp imm
 		return o | 0x3<<24 | 0x5<<20
 
+	case ABFX:
+		return o | 0x3d<<21 | 0x5<<4
+
+	case ABFXU:
+		return o | 0x3f<<21 | 0x5<<4
+
 		// CLZ doesn't support .nil
 	case ACLZ:
 		return o&(0xf<<28) | 0x16f<<16 | 0xf1<<4