cmd/internal/obj/arm: fix constant decomposition

There are two issues in constant decomposition.

1. A typo in "func immrot2s" blocks "case 107" of []optab be triggered.

2. Though "ADD $0xffff, R0, R0" is decomposed to "ADD $0xff00, R0, R0" and
   "ADD $0x00ff, R0, R0" as expected, "ADD $0xffff, R0" still uses the
   constant pool, which should be the same as "ADD $0xffff, R0, R0".

This patch fixes them and adds more instruction encoding tests.

fix #20516

Change-Id: Icd7bdfa1946b29db15580dcb429111266f1384c6
Reviewed-on: https://go-review.googlesource.com/44335
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

2 files changed, 127 insertions, 1 deletions

diff --git a/src/cmd/asm/internal/asm/testdata/arm.s b/src/cmd/asm/internal/asm/testdata/arm.s
index 1e26075611..30d24ac805 100644
--- a/src/cmd/asm/internal/asm/testdata/arm.s
+++ b/src/cmd/asm/internal/asm/testdata/arm.s
@@ -963,9 +963,13 @@ jmp_label_3:
 
 // MUL
 	MUL	R2, R3, R4           // 930204e0
+	MUL	R2, R4               // 920404e0
 	MUL.S	R2, R3, R4           // 930214e0
+	MUL.S	R2, R4               // 920414e0
 	MULU	R5, R6, R7           // 960507e0
+	MULU	R5, R7               // 950707e0
 	MULU.S	R5, R6, R7           // 960517e0
+	MULU.S	R5, R7               // 950717e0
 	MULLU	R1, R2, (R4, R3)     // 923184e0
 	MULLU.S	R1, R2, (R4, R3)     // 923194e0
 	MULL	R1, R2, (R4, R3)     // 9231c4e0
@@ -1003,6 +1007,119 @@ jmp_label_3:
 	SWI	$65535         // ffff00ef
 	SWI	               // 000000ef
 
+// synthetic arithmatic
+	ADD	$0xffffffaa, R2, R3 // ADD $4294967210, R2, R3   // 55b0e0e30b3082e0
+	ADD	$0xffffff55, R5     // ADD $4294967125, R5       // aab0e0e30b5085e0
+	ADD.S	$0xffffffab, R2, R3 // ADD.S $4294967211, R2, R3 // 54b0e0e30b3092e0
+	ADD.S	$0xffffff54, R5     // ADD.S $4294967124, R5     // abb0e0e30b5095e0
+	ADC	$0xffffffac, R2, R3 // ADC $4294967212, R2, R3   // 53b0e0e30b30a2e0
+	ADC	$0xffffff53, R5     // ADC $4294967123, R5       // acb0e0e30b50a5e0
+	ADC.S	$0xffffffad, R2, R3 // ADC.S $4294967213, R2, R3 // 52b0e0e30b30b2e0
+	ADC.S	$0xffffff52, R5     // ADC.S $4294967122, R5     // adb0e0e30b50b5e0
+	SUB	$0xffffffae, R2, R3 // SUB $4294967214, R2, R3   // 51b0e0e30b3042e0
+	SUB	$0xffffff51, R5     // SUB $4294967121, R5       // aeb0e0e30b5045e0
+	SUB.S	$0xffffffaf, R2, R3 // SUB.S $4294967215, R2, R3 // 50b0e0e30b3052e0
+	SUB.S	$0xffffff50, R5     // SUB.S $4294967120, R5     // afb0e0e30b5055e0
+	SBC	$0xffffffb0, R2, R3 // SBC $4294967216, R2, R3   // 4fb0e0e30b30c2e0
+	SBC	$0xffffff4f, R5     // SBC $4294967119, R5       // b0b0e0e30b50c5e0
+	SBC.S	$0xffffffb1, R2, R3 // SBC.S $4294967217, R2, R3 // 4eb0e0e30b30d2e0
+	SBC.S	$0xffffff4e, R5     // SBC.S $4294967118, R5     // b1b0e0e30b50d5e0
+	RSB	$0xffffffb2, R2, R3 // RSB $4294967218, R2, R3   // 4db0e0e30b3062e0
+	RSB	$0xffffff4d, R5     // RSB $4294967117, R5       // b2b0e0e30b5065e0
+	RSB.S	$0xffffffb3, R2, R3 // RSB.S $4294967219, R2, R3 // 4cb0e0e30b3072e0
+	RSB.S	$0xffffff4c, R5     // RSB.S $4294967116, R5     // b3b0e0e30b5075e0
+	RSC	$0xffffffb4, R2, R3 // RSC $4294967220, R2, R3   // 4bb0e0e30b30e2e0
+	RSC	$0xffffff4b, R5     // RSC $4294967115, R5       // b4b0e0e30b50e5e0
+	RSC.S	$0xffffffb5, R2, R3 // RSC.S $4294967221, R2, R3 // 4ab0e0e30b30f2e0
+	RSC.S	$0xffffff4a, R5     // RSC.S $4294967114, R5     // b5b0e0e30b50f5e0
+	AND	$0xffffffaa, R2, R3 // AND $4294967210, R2, R3   // 55b0e0e30b3002e0
+	AND	$0xffffff55, R5     // AND $4294967125, R5       // aab0e0e30b5005e0
+	AND.S	$0xffffffab, R2, R3 // AND.S $4294967211, R2, R3 // 54b0e0e30b3012e0
+	AND.S	$0xffffff54, R5     // AND.S $4294967124, R5     // abb0e0e30b5015e0
+	ORR	$0xffffffaa, R2, R3 // ORR $4294967210, R2, R3   // 55b0e0e30b3082e1
+	ORR	$0xffffff55, R5     // ORR $4294967125, R5       // aab0e0e30b5085e1
+	ORR.S	$0xffffffab, R2, R3 // ORR.S $4294967211, R2, R3 // 54b0e0e30b3092e1
+	ORR.S	$0xffffff54, R5     // ORR.S $4294967124, R5     // abb0e0e30b5095e1
+	EOR	$0xffffffaa, R2, R3 // EOR $4294967210, R2, R3   // 55b0e0e30b3022e0
+	EOR	$0xffffff55, R5     // EOR $4294967125, R5       // aab0e0e30b5025e0
+	EOR.S	$0xffffffab, R2, R3 // EOR.S $4294967211, R2, R3 // 54b0e0e30b3032e0
+	EOR.S	$0xffffff54, R5     // EOR.S $4294967124, R5     // abb0e0e30b5035e0
+	BIC	$0xffffffaa, R2, R3 // BIC $4294967210, R2, R3   // 55b0e0e30b30c2e1
+	BIC	$0xffffff55, R5     // BIC $4294967125, R5       // aab0e0e30b50c5e1
+	BIC.S	$0xffffffab, R2, R3 // BIC.S $4294967211, R2, R3 // 54b0e0e30b30d2e1
+	BIC.S	$0xffffff54, R5     // BIC.S $4294967124, R5     // abb0e0e30b50d5e1
+	CMP	$0xffffffab, R2     // CMP $4294967211, R2       // 54b0e0e30b0052e1
+	CMN	$0xffffffac, R3     // CMN $4294967212, R3       // 53b0e0e30b0073e1
+	TST	$0xffffffad, R4     // TST $4294967213, R4       // 52b0e0e30b0014e1
+	TEQ	$0xffffffae, R5     // TEQ $4294967214, R5       // 51b0e0e30b0035e1
+
+// immediate decomposition
+	ADD	$0xff0000ff, R0, R1 // ADD $4278190335, R0, R1 // ff1080e2ff1481e2
+	EOR	$0xff0000ff, R0, R1 // EOR $4278190335, R0, R1 // ff1020e2ff1421e2
+	ORR	$0xff0000ff, R0, R1 // ORR $4278190335, R0, R1 // ff1080e3ff1481e3
+	SUB	$0xff0000ff, R0, R1 // SUB $4278190335, R0, R1 // ff1040e2ff1441e2
+	BIC	$0xff0000ff, R0, R1 // BIC $4278190335, R0, R1 // ff10c0e3ff14c1e3
+	RSB	$0xff0000ff, R0, R1 // RSB $4278190335, R0, R1 // ff1060e2ff1481e2
+	ADC	$0xff0000ff, R0, R1 // ADC $4278190335, R0, R1 // ff10a0e2ff1481e2
+	SBC	$0xff0000ff, R0, R1 // SBC $4278190335, R0, R1 // ff10c0e2ff1441e2
+	RSC	$0xff0000ff, R0, R1 // RSC $4278190335, R0, R1 // ff10e0e2ff1481e2
+	ADD	$0x000fffff, R0, R1 // ADD $1048575, R0, R1    // 011680e2011041e2
+	ADC	$0x000fffff, R0, R1 // ADC $1048575, R0, R1    // 0116a0e2011041e2
+	SUB	$0x000fffff, R0, R1 // SUB $1048575, R0, R1    // 011640e2011081e2
+	SBC	$0x000fffff, R0, R1 // SBC $1048575, R0, R1    // 0116c0e2011081e2
+	RSB	$0x000fffff, R0, R1 // RSB $1048575, R0, R1    // 011660e2011041e2
+	RSC	$0x000fffff, R0, R1 // RSC $1048575, R0, R1    // 0116e0e2011041e2
+	ADD	$0xff0000ff, R1     // ADD $4278190335, R1     // ff1081e2ff1481e2
+	EOR	$0xff0000ff, R1     // EOR $4278190335, R1     // ff1021e2ff1421e2
+	ORR	$0xff0000ff, R1     // ORR $4278190335, R1     // ff1081e3ff1481e3
+	SUB	$0xff0000ff, R1     // SUB $4278190335, R1     // ff1041e2ff1441e2
+	BIC	$0xff0000ff, R1     // BIC $4278190335, R1     // ff10c1e3ff14c1e3
+	RSB	$0xff0000ff, R1     // RSB $4278190335, R1     // ff1061e2ff1481e2
+	ADC	$0xff0000ff, R1     // ADC $4278190335, R1     // ff10a1e2ff1481e2
+	SBC	$0xff0000ff, R1     // SBC $4278190335, R1     // ff10c1e2ff1441e2
+	RSC	$0xff0000ff, R1     // RSC $4278190335, R1     // ff10e1e2ff1481e2
+	ADD	$0x000fffff, R1     // ADD $1048575, R1        // 011681e2011041e2
+	ADC	$0x000fffff, R1     // ADC $1048575, R1        // 0116a1e2011041e2
+	SUB	$0x000fffff, R1     // SUB $1048575, R1        // 011641e2011081e2
+	SBC	$0x000fffff, R1     // SBC $1048575, R1        // 0116c1e2011081e2
+	RSB	$0x000fffff, R1     // RSB $1048575, R1        // 011661e2011041e2
+	RSC	$0x000fffff, R1     // RSC $1048575, R1        // 0116e1e2011041e2
+
+// MVN
+	MVN	$0xff, R1        // MVN $255, R1          // ff10e0e3
+	MVN	$0xff000000, R1  // MVN $4278190080, R1   // ff14e0e3
+	MVN.S	$0xff, R1        // MVN.S $255, R1        // ff10f0e3
+	MVN.S	$0xff000000, R1  // MVN.S $4278190080, R1 // ff14f0e3
+	MVN	R9<<30, R7       // 097fe0e1
+	MVN	R9>>30, R7       // 297fe0e1
+	MVN	R9->30, R7       // 497fe0e1
+	MVN	R9@>30, R7       // 697fe0e1
+	MVN.S	R9<<30, R7       // 097ff0e1
+	MVN.S	R9>>30, R7       // 297ff0e1
+	MVN.S	R9->30, R7       // 497ff0e1
+	MVN.S	R9@>30, R7       // 697ff0e1
+	MVN	R9<<R8, R7       // 1978e0e1
+	MVN	R9>>R8, R7       // 3978e0e1
+	MVN	R9->R8, R7       // 5978e0e1
+	MVN	R9@>R8, R7       // 7978e0e1
+	MVN.S	R9<<R8, R7       // 1978f0e1
+	MVN.S	R9>>R8, R7       // 3978f0e1
+	MVN.S	R9->R8, R7       // 5978f0e1
+	MVN.S	R9@>R8, R7       // 7978f0e1
+	MVN	$0xffffffae, R5  // MVN $4294967214, R5   // 51b0e0e30b50e0e1
+	MVN.S	$0xffffffae, R5  // MVN.S $4294967214, R5 // 51b0e0e30b50f0e1
+
+// MOVW
+mov_label_0:
+	MOVW	$0xff, R9            // MOVW $255, R9             // ff90a0e3
+	MOVW	$0xff000000, R9      // MOVW $4278190080, R9      // ff94a0e3
+	MOVW	R3, R4               // 0340a0e1
+	MOVW	$0xff(R0), R1        // MOVW $255(R0), R1         // ff1080e2
+	MOVW	$-0xff(R0), R1       // MOVW $-255(R0), R1        // ff1040e2
+	MOVW	$0xffffffae, R1      // MOVW $4294967214, R1      // 5110e0e3
+	MOVW	$0xaaaaaaaa, R1      // MOVW $2863311530, R1
+	MOVW	$mov_label_0(SB), R2 // MOVW $mov_label_0(SB), R2
+
 //
 // END
 //
diff --git a/src/cmd/internal/obj/arm/asm5.go b/src/cmd/internal/obj/arm/asm5.go
index c27b470817..e17d312987 100644
--- a/src/cmd/internal/obj/arm/asm5.go
+++ b/src/cmd/internal/obj/arm/asm5.go
@@ -154,8 +154,11 @@ var optab = []Optab{
 	{AMVN, C_SCON, C_NONE, C_REG, 13, 8, 0, 0, 0},
 	{ACMP, C_SCON, C_REG, C_NONE, 13, 8, 0, 0, 0},
 	{AADD, C_RCON2A, C_REG, C_REG, 106, 8, 0, 0, 0},
+	{AADD, C_RCON2A, C_NONE, C_REG, 106, 8, 0, 0, 0},
 	{AORR, C_RCON2A, C_REG, C_REG, 106, 8, 0, 0, 0},
+	{AORR, C_RCON2A, C_NONE, C_REG, 106, 8, 0, 0, 0},
 	{AADD, C_RCON2S, C_REG, C_REG, 107, 8, 0, 0, 0},
+	{AADD, C_RCON2S, C_NONE, C_REG, 107, 8, 0, 0, 0},
 	{AADD, C_LCON, C_REG, C_REG, 13, 8, 0, LFROM, 0},
 	{AADD, C_LCON, C_NONE, C_REG, 13, 8, 0, LFROM, 0},
 	{AAND, C_LCON, C_REG, C_REG, 13, 8, 0, LFROM, 0},
@@ -1063,7 +1066,7 @@ func immrot2a(v uint32) (uint32, uint32) {
 // such that the encoded constants y, x satisfy y-x==v, y&x==0.
 // Returns 0,0 if no such decomposition of v exists.
 func immrot2s(v uint32) (uint32, uint32) {
-	if immrot(v) == 0 {
+	if immrot(v) != 0 {
 		return v, 0
 	}
 	// suppose v in the form of {leading 00, upper effective bits, lower 8 effective bits, trailing 00}
@@ -1717,6 +1720,9 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		c.aclass(&p.From)
 		r := int(p.Reg)
 		rt := int(p.To.Reg)
+		if r == 0 {
+			r = rt
+		}
 		x, y := immrot2a(uint32(c.instoffset))
 		var as2 obj.As
 		switch p.As {
@@ -1744,6 +1750,9 @@ func (c *ctxt5) asmout(p *obj.Prog, o *Optab, out []uint32) {
 		c.aclass(&p.From)
 		r := int(p.Reg)
 		rt := int(p.To.Reg)
+		if r == 0 {
+			r = rt
+		}
 		y, x := immrot2s(uint32(c.instoffset))
 		var as2 obj.As
 		switch p.As {