gc: implement new shift rules

The change is that 1.0<<2 is now okay.

R=ken2
CC=golang-dev
https://golang.org/cl/4524084

src/cmd/gc/const.c

@@ -103,6 +103,8 @@ convlit1(Node **np, Type *t, int explicit)
 	case ORSH:
 		convlit1(&n->left, t, explicit && isideal(n->left->type));
 		t = n->left->type;
+		if(t != T && t->etype == TIDEAL && n->val.ctype != CTINT)
+			n->val = toint(n->val);
 		if(t != T && !isint[t->etype]) {
 			yyerror("invalid operation: %#N (shift of type %T)", n, t);
 			t = T;
@@ -514,6 +516,8 @@ evconst(Node *n)
 		n->right = nr;
 		if(nr->type && (issigned[nr->type->etype] || !isint[nr->type->etype]))
 			goto illegal;
+		nl->val = toint(nl->val);
+		nr->val = toint(nr->val);
 		break;
 	}
 

test/golden.out

@@ -40,21 +40,6 @@ hello, world
 -9223372036854775808
 9223372036854775807
 
-=========== ./shift1.go
-BUG: errchk: ./shift1.go:33: error message does not match 'overflow'
-errchk: ./shift1.go:34: error message does not match 'overflow'
-errchk: ./shift1.go:35: error message does not match 'overflow'
-
-=========== ./shift2.go
-./shift2.go:22: illegal constant expression: ideal LSH uint
-./shift2.go:35: illegal constant expression: ideal LSH uint
-./shift2.go:36: illegal constant expression: ideal LSH uint
-./shift2.go:36: invalid operation: 2 << c (shift of type float64)
-./shift2.go:39: illegal constant expression: ideal LSH uint
-./shift2.go:40: illegal constant expression: ideal LSH uint
-./shift2.go:40: invalid operation: 2 << c (shift of type float64)
-./shift2.go:40: cannot use 2 << c as type interface { } in function argument
-
 =========== ./sigchld.go
 survived SIGCHLD
 

test/shift2.go

-// $G $D/$F.go && $L $F.$A && ./$A.out
+// $G $D/$F.go || echo BUG: shift2
 
 // Copyright 2011 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style