cmd/asm: add amd64 PALIGNR instruction

3rd change out of 3 to cover AMD64 SSSE3 instruction set in Go asm.
This commit adds instruction that do require new ytab variable.

Change-Id: I0bc7d9401c9176eb3760c3d59494ef082e97af84
Reviewed-on: https://go-review.googlesource.com/56870
Run-TryBot: Iskander Sharipov <iskander.sharipov@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ilya Tocar <ilya.tocar@intel.com>
Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/asm/internal/asm/testdata/amd64enc.s

@@ -3315,14 +3315,14 @@ TEXT asmtest(SB),DUPOK|NOSPLIT,$0
 	//TODO: PALIGNR $7, (R11), M3           // 410f3a0f1b07
 	//TODO: PALIGNR $7, M2, M3              // 0f3a0fda07
 	//TODO: PALIGNR $7, M3, M3              // 0f3a0fdb07
-	//TODO: PALIGNR $7, (BX), X2            // 660f3a0f1307
-	//TODO: PALIGNR $7, (R11), X2           // 66410f3a0f1307
-	//TODO: PALIGNR $7, X2, X2              // 660f3a0fd207
-	//TODO: PALIGNR $7, X11, X2             // 66410f3a0fd307
-	//TODO: PALIGNR $7, (BX), X11           // 66440f3a0f1b07
-	//TODO: PALIGNR $7, (R11), X11          // 66450f3a0f1b07
-	//TODO: PALIGNR $7, X2, X11             // 66440f3a0fda07
-	//TODO: PALIGNR $7, X11, X11            // 66450f3a0fdb07
+	PALIGNR $7, (BX), X2                    // 660f3a0f1307
+	PALIGNR $7, (R11), X2                   // 66410f3a0f1307
+	PALIGNR $7, X2, X2                      // 660f3a0fd207
+	PALIGNR $7, X11, X2                     // 66410f3a0fd307
+	PALIGNR $7, (BX), X11                   // 66440f3a0f1b07
+	PALIGNR $7, (R11), X11                  // 66450f3a0f1b07
+	PALIGNR $7, X2, X11                     // 66440f3a0fda07
+	PALIGNR $7, X11, X11                    // 66450f3a0fdb07
 	PAND (BX), M2                           // 0fdb13
 	PAND (R11), M2                          // 410fdb13
 	PAND M2, M2                             // 0fdbd2

src/cmd/internal/obj/x86/a.out.go

@@ -627,6 +627,7 @@ const (
 	APADDUSB
 	APADDUSW
 	APADDW
+	APALIGNR
 	APAND
 	APANDN
 	APAVGB

src/cmd/internal/obj/x86/anames.go

@@ -570,6 +570,7 @@ var Anames = []string{
 	"PADDUSB",
 	"PADDUSW",
 	"PADDW",
+	"PALIGNR",
 	"PAND",
 	"PANDN",
 	"PAVGB",

src/cmd/internal/obj/x86/asm6.go

@@ -786,6 +786,10 @@ var ylddqu = []ytab{
 	{Ym, Ynone, Yxr, Zm_r, 1},
 }
 
+var ypalignr = []ytab{
+	{Yu8, Yxm, Yxr, Zibm_r, 2},
+}
+
 // VEX instructions that come in two forms:
 //	VTHING xmm2/m128, xmmV, xmm1
 //	VTHING ymm2/m256, ymmV, ymm1
@@ -1274,6 +1278,7 @@ var optab =
 	{APADDUSB, ymm, Py1, [23]uint8{0xdc, Pe, 0xdc}},
 	{APADDUSW, ymm, Py1, [23]uint8{0xdd, Pe, 0xdd}},
 	{APADDW, ymm, Py1, [23]uint8{0xfd, Pe, 0xfd}},
+	{APALIGNR, ypalignr, Pq, [23]uint8{0x3a, 0x0f}},
 	{APAND, ymm, Py1, [23]uint8{0xdb, Pe, 0xdb}},
 	{APANDN, ymm, Py1, [23]uint8{0xdf, Pe, 0xdf}},
 	{APAUSE, ynone, Px, [23]uint8{0xf3, 0x90}},