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>

4 files changed, 51 insertions, 12 deletions

diff --git a/src/cmd/asm/internal/arch/arm.go b/src/cmd/asm/internal/arch/arm.go
index 40443d5eca..4ee494a74c 100644
--- a/src/cmd/asm/internal/arch/arm.go
+++ b/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 {
diff --git a/src/cmd/asm/internal/asm/asm.go b/src/cmd/asm/internal/asm/asm.go
index df23856c47..7e9e59daf4 100644
--- a/src/cmd/asm/internal/asm/asm.go
+++ b/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])
@@ -635,18 +642,28 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 			return
 		}
 	case 4:
-		if p.arch.Family == sys.ARM && arch.IsARMMULA(op) {
-			// All must be registers.
-			p.getRegister(prog, op, &a[0])
-			r1 := p.getRegister(prog, op, &a[1])
-			r2 := p.getRegister(prog, op, &a[2])
-			p.getRegister(prog, op, &a[3])
-			prog.From = a[0]
-			prog.To = a[3]
-			prog.To.Type = obj.TYPE_REGREG2
-			prog.To.Offset = int64(r2)
-			prog.Reg = r1
-			break
+		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])
+				r2 := p.getRegister(prog, op, &a[2])
+				p.getRegister(prog, op, &a[3])
+				prog.From = a[0]
+				prog.To = a[3]
+				prog.To.Type = obj.TYPE_REGREG2
+				prog.To.Offset = int64(r2)
+				prog.Reg = r1
+				break
+			}
 		}
 		if p.arch.Family == sys.AMD64 {
 			// 4 operand instruction have form  ymm1, ymm2, ymm3/m256, imm8
diff --git a/src/cmd/asm/internal/asm/testdata/arm.s b/src/cmd/asm/internal/asm/testdata/arm.s
index cd1d11f518..662ab180d7 100644
--- a/src/cmd/asm/internal/asm/testdata/arm.s
+++ b/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
diff --git a/src/cmd/asm/internal/asm/testdata/armerror.s b/src/cmd/asm/internal/asm/testdata/armerror.s
index 2959a2f47b..a0bb13ed8b 100644
--- a/src/cmd/asm/internal/asm/testdata/armerror.s
+++ b/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