8a/8l: add PCMPEQB and PMOVMSKB to 386.

Used by CL 8056043 for fast string equals.

R=bradfitz
CC=golang-dev
https://golang.org/cl/8102044

src/cmd/8a/lex.c

@@ -760,10 +760,12 @@ struct
 	"ORPS",		LTYPE3,	AORPS,
 	"PADDQ",	LTYPE3,	APADDQ,
 	"PAND",		LTYPE3,	APAND,
+	"PCMPEQB",	LTYPE3,	APCMPEQB,
 	"PMAXSW",	LTYPE3,	APMAXSW,
 	"PMAXUB",	LTYPE3,	APMAXUB,
 	"PMINSW",	LTYPE3,	APMINSW,
 	"PMINUB",	LTYPE3,	APMINUB,
+	"PMOVMSKB",	LTYPE3,	APMOVMSKB,
 	"PSADBW",	LTYPE3,	APSADBW,
 	"PSHUFB",	LTYPE3, APSHUFB,
 	"PSUBB",	LTYPE3,	APSUBB,

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

@@ -534,10 +534,12 @@ enum	as
 	AORPS,
 	APADDQ,
 	APAND,
+	APCMPEQB,
 	APMAXSW,
 	APMAXUB,
 	APMINSW,
 	APMINUB,
+	APMOVMSKB,
 	APSADBW,
 	APSUBB,
 	APSUBL,

src/cmd/8l/optab.c

@@ -364,6 +364,12 @@ uchar	ysvrs[] =
 	Ym,	Ynone,	Zm_o,	2,
 	0
 };
+uchar	ymskb[] =
+{
+	Yxr,	Yrl,	Zm_r_xm,	2,
+	Ymr,	Yrl,	Zm_r_xm,	1,
+	0
+};
 uchar	yxm[] = 
 {
 	Yxm,	Yxr,	Zm_r_xm,	1,
@@ -950,10 +956,12 @@ Optab optab[] =
 	{ AORPS,	yxm,	Pm, 0x56 },
 	{ APADDQ,	yxm,	Pe, 0xd4 },
 	{ APAND,	yxm,	Pe, 0xdb },
+	{ APCMPEQB,	yxmq,	Pe ,0x74 },
 	{ APMAXSW,	yxm,	Pe, 0xee },
 	{ APMAXUB,	yxm,	Pe, 0xde },
 	{ APMINSW,	yxm,	Pe, 0xea },
 	{ APMINUB,	yxm,	Pe, 0xda },
+	{ APMOVMSKB,	ymskb,	Px, Pe,0xd7,0xd7 },
 	{ APSADBW,	yxm,	Pq, 0xf6 },
 	{ APSUBB,	yxm,	Pe, 0xf8 },
 	{ APSUBL,	yxm,	Pe, 0xfa },