cmd/internal/obj/arm: fix illegal forms of ARM VFP instruction

"ADDF F0, R1, F2" is silently accepted by the arm assembler and
assembled to the same binary code of "ADDF F0, F1, F2". So does
"CMPF F0, R1".

"ABSF F0, F1, F2" is also silently accepted and assembled to a
different instruction.

This patch reports those illegal forms and adds test cases.

fix #20464

Change-Id: I88b80dc29de24c6266ac7bf7bce1578c5adbc68c
Reviewed-on: https://go-review.googlesource.com/43931
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/asm/endtoend_test.go

@@ -305,7 +305,7 @@ func testErrors(t *testing.T, goarch, file string) {
 			continue
 		}
 		fileline := m[1]
-		if errors[fileline] != "" {
+		if errors[fileline] != "" && errors[fileline] != line {
 			t.Errorf("multiple errors on %s:\n\t%s\n\t%s", fileline, errors[fileline], line)
 			continue
 		}

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

@@ -7,4 +7,17 @@ TEXT errors(SB),$0
 	ADD.P	R1, R2, R3         // ERROR "invalid .P suffix"
 	SUB.W	R2, R3             // ERROR "invalid .W suffix"
 	BL	4(R4)              // ERROR "non-zero offset"
+	ADDF	F0, R1, F2         // ERROR "illegal combination"
+	SWI	(R0)               // ERROR "illegal combination"
+	NEGF	F0, F1, F2         // ERROR "illegal combination"
+	NEGD	F0, F1, F2         // ERROR "illegal combination"
+	ABSF	F0, F1, F2         // ERROR "illegal combination"
+	ABSD	F0, F1, F2         // ERROR "illegal combination"
+	SQRTF	F0, F1, F2         // ERROR "illegal combination"
+	SQRTD	F0, F1, F2         // ERROR "illegal combination"
+	MOVF	F0, F1, F2         // ERROR "illegal combination"
+	MOVD	F0, F1, F2         // ERROR "illegal combination"
+	MOVDF	F0, F1, F2         // ERROR "illegal combination"
+	MOVFD	F0, F1, F2         // ERROR "illegal combination"
+
 	END

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

@@ -228,8 +228,9 @@ var optab = []Optab{
 	{AMOVF, C_FREG, C_NONE, C_ADDR, 68, 8, 0, LTO | LPCREL, 4},
 	{AMOVF, C_ADDR, C_NONE, C_FREG, 69, 8, 0, LFROM | LPCREL, 4},
 	{AADDF, C_FREG, C_NONE, C_FREG, 54, 4, 0, 0, 0},
-	{AADDF, C_FREG, C_REG, C_FREG, 54, 4, 0, 0, 0},
-	{AMOVF, C_FREG, C_NONE, C_FREG, 54, 4, 0, 0, 0},
+	{AADDF, C_FREG, C_FREG, C_FREG, 54, 4, 0, 0, 0},
+	{AMOVF, C_FREG, C_NONE, C_FREG, 55, 4, 0, 0, 0},
+	{ANEGF, C_FREG, C_NONE, C_FREG, 55, 4, 0, 0, 0},
 	{AMOVW, C_REG, C_NONE, C_FCR, 56, 4, 0, 0, 0},
 	{AMOVW, C_FCR, C_NONE, C_REG, 57, 4, 0, 0, 0},
 	{AMOVW, C_SHIFT, C_NONE, C_REG, 59, 4, 0, 0, 0},
@@ -284,7 +285,7 @@ var optab = []Optab{
 	{ASTREX, C_SOREG, C_REG, C_REG, 78, 4, 0, 0, 0},
 	{AMOVF, C_ZFCON, C_NONE, C_FREG, 80, 8, 0, 0, 0},
 	{AMOVF, C_SFCON, C_NONE, C_FREG, 81, 4, 0, 0, 0},
-	{ACMPF, C_FREG, C_REG, C_NONE, 82, 8, 0, 0, 0},
+	{ACMPF, C_FREG, C_FREG, C_NONE, 82, 8, 0, 0, 0},
 	{ACMPF, C_FREG, C_NONE, C_NONE, 83, 8, 0, 0, 0},
 	{AMOVFW, C_FREG, C_NONE, C_FREG, 84, 4, 0, 0, 0},
 	{AMOVWF, C_FREG, C_NONE, C_FREG, 85, 4, 0, 0, 0},
@@ -1325,7 +1326,14 @@ func (c *ctxt5) oplook(p *obj.Prog) *Optab {
 	a3--
 	a2 := C_NONE
 	if p.Reg != 0 {
+		switch {
+		case REG_F0 <= p.Reg && p.Reg <= REG_F15:
+			a2 = C_FREG
+		case REG_R0 <= p.Reg && p.Reg <= REG_R15:
 			a2 = C_REG
+		default:
+			c.ctxt.Diag("invalid register in %v", p)
+		}
 	}
 
 	// If current instruction has a .S suffix (flags update),
@@ -1353,8 +1361,7 @@ func (c *ctxt5) oplook(p *obj.Prog) *Optab {
 		}
 	}
 
-	c.ctxt.Diag("illegal combination %v; %v %v %v, %d %d", p, DRconv(a1), DRconv(a2), DRconv(a3), p.From.Type, p.To.Type)
-	c.ctxt.Diag("from %d %d to %d %d\n", p.From.Type, p.From.Name, p.To.Type, p.To.Name)
+	c.ctxt.Diag("illegal combination %v; %v %v %v; from %d %d; to %d %d", p, DRconv(a1), DRconv(a2), DRconv(a3), p.From.Type, p.From.Name, p.To.Type, p.To.Name)
 	if ops == nil {
 		ops = optab
 	}
@@ -1590,14 +1597,15 @@ func buildop(ctxt *obj.Link) {
 			opset(AMULD, r0)
 			opset(ADIVF, r0)
 			opset(ADIVD, r0)
+
+		case ANEGF:
+			opset(ANEGD, r0)
 			opset(ASQRTF, r0)
 			opset(ASQRTD, r0)
 			opset(AMOVFD, r0)
 			opset(AMOVDF, r0)
 			opset(AABSF, r0)
 			opset(AABSD, r0)
-			opset(ANEGF, r0)
-			opset(ANEGD, r0)
 
 		case ACMPF:
 			opset(ACMPD, r0)
@@ -2167,13 +2175,18 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		r := int(p.Reg)
 		if r == 0 {
 			r = rt
-			if p.As == AMOVF || p.As == AMOVD || p.As == AMOVFD || p.As == AMOVDF || p.As == ASQRTF || p.As == ASQRTD || p.As == AABSF || p.As == AABSD || p.As == ANEGF || p.As == ANEGD {
-				r = 0
-			}
 		}
 
 		o1 |= (uint32(rf)&15)<<0 | (uint32(r)&15)<<16 | (uint32(rt)&15)<<12
 
+	case 55: /* negf freg, freg */
+		o1 = c.oprrr(p, p.As, int(p.Scond))
+
+		rf := int(p.From.Reg)
+		rt := int(p.To.Reg)
+
+		o1 |= (uint32(rf)&15)<<0 | (uint32(rt)&15)<<12
+
 	case 56: /* move to FP[CS]R */
 		o1 = ((uint32(p.Scond)&C_SCOND)^C_SCOND_XOR)<<28 | 0xe<<24 | 1<<8 | 1<<4