[dev.debug] cmd/compile: keep float names in the Names list

Fix an oversight in decompose that caused floats to be missing from the
Names list.

Change-Id: I5db9c9498e9a4421742389eb929752fdac873b38
Reviewed-on: https://go-review.googlesource.com/50877Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

src/cmd/compile/internal/ssa/decompose.go

@@ -98,6 +98,7 @@ func decomposeBuiltIn(f *Func) {
 			delete(f.NamedValues, name)
 		case t.IsFloat():
 			// floats are never decomposed, even ones bigger than RegSize
+			newNames = append(newNames, name)
 		case t.Size() > f.Config.RegSize:
 			f.Fatalf("undecomposed named type %v %v", name, t)
 		default: