cmd/8g: add a few missing splitclean

Fixes #887.

R=ken2
CC=golang-dev
https://golang.org/cl/7303061

src/cmd/8g/ggen.c

@@ -704,6 +704,7 @@ cgen_shift(int op, int bounded, Node *nl, Node *nr, Node *res)
 			regalloc(&n1, types[TUINT32], &n1);		// to hold the shift type in CX
 			split64(&nt, &lo, &hi);
 			gmove(&lo, &n1);
+			splitclean();
 		}
 	} else {
 		if(nr->type->width > 4) {
@@ -716,6 +717,7 @@ cgen_shift(int op, int bounded, Node *nl, Node *nr, Node *res)
 			p2 = gbranch(optoas(ONE, types[TUINT32]), T, +1);
 			gins(optoas(OCMP, types[TUINT32]), &n1, ncon(w));
 			p1 = gbranch(optoas(OLT, types[TUINT32]), T, +1);
+			splitclean();
 			patch(p2, pc);
 		} else {
 			gins(optoas(OCMP, nr->type), &n1, ncon(w));

src/cmd/8g/gsubr.c

@@ -1168,9 +1168,9 @@ split64(Node *n, Node *lo, Node *hi)
 	if(!is64(n->type))
 		fatal("split64 %T", n->type);
 
-	sclean[nsclean].op = OEMPTY;
 	if(nsclean >= nelem(sclean))
 		fatal("split64 clean");
+	sclean[nsclean].op = OEMPTY;
 	nsclean++;
 	switch(n->op) {
 	default:

test/fixedbugs/issue887.go

+// compile
+
+// Copyright 2013 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.
+
+// Used to leak registers on 8g.
+
+package p
+
+func f(x byte, y uint64) {
+	var r byte
+	switch y {
+	case 1:
+		r = x << y // '>>' triggers it too
+	case 2:
+		r = x << y
+	case 3:
+		r = x << y
+	case 4:
+		r = x << y
+	case 5:
+		r = x << y
+	case 6:
+		r = x << y
+	case 7:
+		r = x << y
+	case 8:
+		r = x << y
+	case 9:
+		r = x << y
+	case 10:
+		r = x << y
+	}
+	_ = r
+}