cmd/internal/obj/x86: fix PINSRD with mem in from3

Change-Id: I3a2b17e218aa05cfb67d7561e0b52a6df766924d
Reviewed-on: https://go-review.googlesource.com/6897
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

src/cmd/internal/obj/x86/obj6.go

@@ -609,6 +609,13 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 		if a == obj.NAME_PARAM {
 			p.From.Offset += int64(deltasp) + int64(pcsize)
 		}
+		a = int(p.From3.Name)
+		if a == obj.NAME_AUTO {
+			p.From3.Offset += int64(deltasp) - int64(bpsize)
+		}
+		if a == obj.NAME_PARAM {
+			p.From3.Offset += int64(deltasp) + int64(pcsize)
+		}
 		a = int(p.To.Name)
 		if a == obj.NAME_AUTO {
 			p.To.Offset += int64(deltasp) - int64(bpsize)