8g: fix opt bug

Was trying to optimize a duplicate float64 move
by registerizing an int64.

Fixes #2588.

R=ken2
CC=golang-dev
https://golang.org/cl/5645086

src/cmd/8g/reg.c

@@ -220,6 +220,9 @@ regopt(Prog *firstp)
 		 * funny
 		 */
 		case ALEAL:
+		case AFMOVL: 
+		case AFMOVW:
+		case AFMOVV:
 			setaddrs(bit);
 			break;
 
@@ -741,7 +744,7 @@ addmove(Reg *r, int bn, int rn, int f)
 	p1->as = AMOVL;
 	switch(v->etype) {
 	default:
-		fatal("unknown type\n");
+		fatal("unknown type %E", v->etype);
 	case TINT8:
 	case TUINT8:
 	case TBOOL:

test/fixedbugs/bug411.go

+// $G $D/$F.go
+
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 2588.  Used to trigger internal compiler error on 8g,
+// because the compiler tried to registerize the int64 being
+// used as a memory operand of a int64->float64 move.
+
+package p
+
+func f1(a int64) {
+	f2(float64(a), float64(a))
+}
+
+func f2(a,b float64) {
+}
+