cmd/internal/obj/ppc64: add support for vmrgow,vmrgew

This adds support for ppc64 instructions vmrgow and vmrgew which
are needed for an improved implementation of chacha20.

Change-Id: I967a2de54236bcc573a99f7e2b222d5a8bb29e03
Reviewed-on: https://go-review.googlesource.com/c/go/+/192117
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>

src/cmd/asm/internal/asm/testdata/ppc64.s

@@ -900,6 +900,13 @@ label1:
 //	<mnemonic> VRT,VRA,VRB,SHB
 	VSLDOI	$4, V2, V1, V0
 
+//	Vector merge odd and even word
+//	<MNEMONIC> VRA,VRB,VRT produces
+//	<mnemonic> VRT,VRA,VRB
+
+	VMRGOW	V4,V5,V6
+	VMRGEW	V4,V5,V6
+
 //	Vector count, VX-form
 //	<MNEMONIC> VRB,VRT produces
 //	<mnemonic> VRT,VRB

src/cmd/internal/obj/ppc64/a.out.go

@@ -929,6 +929,8 @@ const (
 	AVSHASIGMA
 	AVSHASIGMAW
 	AVSHASIGMAD
+	AVMRGEW
+	AVMRGOW
 
 	/* VSX */
 	ALXV

src/cmd/internal/obj/ppc64/anames.go

@@ -519,6 +519,8 @@ var Anames = []string{
 	"VSHASIGMA",
 	"VSHASIGMAW",
 	"VSHASIGMAD",
+	"VMRGEW",
+	"VMRGOW",
 	"LXV",
 	"LXVD2X",
 	"LXVDSX",

src/cmd/internal/obj/ppc64/asm9.go

@@ -449,6 +449,9 @@ var optab = []Optab{
 	{AVCMPGT, C_VREG, C_VREG, C_NONE, C_VREG, 82, 4, 0},   /* vector compare greater than, vc-form */
 	{AVCMPNEZB, C_VREG, C_VREG, C_NONE, C_VREG, 82, 4, 0}, /* vector compare not equal, vx-form */
 
+	/* Vector merge */
+	{AVMRGOW, C_VREG, C_VREG, C_NONE, C_VREG, 82, 4, 0}, /* vector merge odd word, vx-form */
+
 	/* Vector permute */
 	{AVPERM, C_VREG, C_VREG, C_VREG, C_VREG, 83, 4, 0}, /* vector permute, va-form */
 
@@ -1354,6 +1357,9 @@ func buildop(ctxt *obj.Link) {
 			opset(AVANDC, r0)
 			opset(AVNAND, r0)
 
+		case AVMRGOW: /* vmrgew, vmrgow */
+			opset(AVMRGEW, r0)
+
 		case AVOR: /* vor, vorc, vxor, vnor, veqv */
 			opset(AVOR, r0)
 			opset(AVORC, r0)
@@ -4406,6 +4412,11 @@ func (c *ctxt9) oprrr(a obj.As) uint32 {
 	case AVRLD:
 		return OPVX(4, 196, 0, 0) /* vrld - v2.07 */
 
+	case AVMRGOW:
+		return OPVX(4, 1676, 0, 0) /* vmrgow - v2.07 */
+	case AVMRGEW:
+		return OPVX(4, 1932, 0, 0) /* vmrgew - v2.07 */
+
 	case AVSLB:
 		return OPVX(4, 260, 0, 0) /* vslh - v2.03 */
 	case AVSLH: