cmd/5g: fix build

The line in cgen.go was lost during the ginscmp CL.
The ggen.go change is not strictly necessary, but
it makes the 5g -S output for x[0] match what it said
before the ginscmp CL.

Change-Id: I5890a9ec1ac69a38509416eda5aea13b8b12b94a
Reviewed-on: https://go-review.googlesource.com/9929Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/5g/ggen.go

@@ -480,20 +480,28 @@ func ginscon(as int, c int64, n *gc.Node) {
 }
 
 func ginscmp(op int, t *gc.Type, n1, n2 *gc.Node, likely int) *obj.Prog {
+	if gc.Isint[t.Etype] && n1.Op == gc.OLITERAL && gc.Mpgetfix(n1.Val.U.Xval) == 0 && n2.Op != gc.OLITERAL {
+		op = gc.Brrev(op)
+		n1, n2 = n2, n1
+	}
 	var r1, r2, g1, g2 gc.Node
 	gc.Regalloc(&r1, t, n1)
 	gc.Regalloc(&g1, n1.Type, &r1)
 	gc.Cgen(n1, &g1)
 	gmove(&g1, &r1)
-	gc.Regalloc(&r2, t, n2)
-	gc.Regalloc(&g2, n1.Type, &r2)
-	gc.Cgen(n2, &g2)
-	gmove(&g2, &r2)
-	gins(optoas(gc.OCMP, t), &r1, &r2)
+	if gc.Isint[t.Etype] && n2.Op == gc.OLITERAL && gc.Mpgetfix(n2.Val.U.Xval) == 0 {
+		gins(arm.ACMP, &r1, n2)
+	} else {
+		gc.Regalloc(&r2, t, n2)
+		gc.Regalloc(&g2, n1.Type, &r2)
+		gc.Cgen(n2, &g2)
+		gmove(&g2, &r2)
+		gins(optoas(gc.OCMP, t), &r1, &r2)
+		gc.Regfree(&g2)
+		gc.Regfree(&r2)
+	}
 	gc.Regfree(&g1)
 	gc.Regfree(&r1)
-	gc.Regfree(&g2)
-	gc.Regfree(&r2)
 	return gc.Gbranch(optoas(op, t), nil, likely)
 }
 

src/cmd/internal/gc/cgen.go

@@ -1045,6 +1045,7 @@ func Agenr(n *Node, a *Node, res *Node) {
 						n1.Op = OINDREG
 						n1.Type = Types[Tptr]
 						n1.Xoffset = int64(Array_nel)
+						Nodconst(&n2, Types[TUINT32], int64(v))
 						p1 := Thearch.Ginscmp(OGT, Types[TUINT32], &n1, &n2, +1)
 						Ginscall(Panicindex, -1)
 						Patch(p1, Pc)