floating point constant errors in 6g

R=r
OCL=19379
CL=19379

test/bugs/bug120.go

+// $G $D/$F.go && $L $F.$A && ./$A.out || echo BUG: bug120
+
+// Copyright 2009 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.
+
+package main
+
+import "strconv";
+
+type Test struct {
+	f float64;
+	in string;
+	out string;
+}
+
+var tests = []Test {
+	Test{ 123.5, "123.5", "123.5" },
+	Test{ 456.7, "456.7", "456.7" },
+	Test{ 1e23+8.5e6, "1e23+8.5e6", "1.0000000000000001e+23" },
+	Test{ 100000000000000008388608, "100000000000000008388608", "1.0000000000000001e+23" },
+	Test{ 1e23+8.388608e6, "1e23+8.388608e6", "1.0000000000000001e+23" },
+	Test{ 1e23+8.388609e6, "1e23+8.388609e6", "1.0000000000000001e+23" },
+}
+
+func main() {
+	ok := true;
+	for i := 0; i < len(tests); i++ {
+		t := tests[i];
+		v := strconv.ftoa64(t.f, 'g', -1);
+		if v != t.out {
+			println("Bad float64 const:", t.in, "want", t.out, "got", v);
+			ok = false;
+		}
+	}
+	if !ok {
+		panicln("bug120");
+	}
+}