8a, 8l: add EMMS instruction

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5673081

src/cmd/8a/lex.c

@@ -666,6 +666,7 @@ struct
 	"LFENCE",	LTYPE0, ALFENCE,
 	"MFENCE",	LTYPE0, AMFENCE,
 	"SFENCE",	LTYPE0, ASFENCE,
+	"EMMS",		LTYPE0, AEMMS,
 
 	0
 };

src/cmd/8l/8.out.h

@@ -449,6 +449,8 @@ enum	as
 	AMFENCE,
 	ASFENCE,
 
+	AEMMS,
+
 	ALAST
 };
 

src/cmd/8l/optab.c

@@ -759,5 +759,7 @@ Optab optab[] =
 	{ AMFENCE, ynone, Pm, 0xae,0xf0 },
 	{ ASFENCE, ynone, Pm, 0xae,0xf8 },
 
+	{ AEMMS, ynone, Pm, 0x77 },
+
 	0
 };

src/libmach/8db.c

@@ -688,6 +688,7 @@ static Optable optab0F[256]=
 [0x74] =	{ RM,0,		"PCMPEQB %m,%M" },
 [0x75] =	{ RM,0,		"PCMPEQW %m,%M" },
 [0x76] =	{ RM,0,		"PCMPEQL %m,%M" },
+[0x77] =	{ 0,0,		"EMMS" },
 [0x7E] =	{ RM,0,		"MOV%S %M,%e" },
 [0x7F] =	{ RM,0,		"MOVQ %M,%m" },
 [0xAE] =	{ RMOP,0,		optab0FAE },

src/pkg/sync/atomic/asm_386.s

@@ -108,8 +108,7 @@ TEXT ·LoadUint64(SB),7,$0
 	BYTE $0x0f; BYTE $0x6f; BYTE $0x00
 	// MOVQ %MM0, 0x8(%ESP)
 	BYTE $0x0f; BYTE $0x7f; BYTE $0x44; BYTE $0x24; BYTE $0x08
-	// EMMS
-	BYTE $0x0F; BYTE $0x77
+	EMMS
 	RET
 
 TEXT ·LoadUintptr(SB),7,$0
@@ -137,8 +136,7 @@ TEXT ·StoreUint64(SB),7,$0
 	BYTE $0x0f; BYTE $0x6f; BYTE $0x44; BYTE $0x24; BYTE $0x08
 	// MOVQ %MM0, (%EAX)
 	BYTE $0x0f; BYTE $0x7f; BYTE $0x00 
-	// EMMS
-	BYTE $0x0F; BYTE $0x77
+	EMMS
 	// This is essentially a no-op, but it provides required memory fencing.
 	// It can be replaced with MFENCE, but MFENCE was introduced only on the Pentium4 (SSE2).
 	XORL	AX, AX