[PATCH] Fix PR optimization/13653

[Richard Kenner]

    Right.  And presumably that's what's happening in this case -- ie, we
    have a reg which is set by the initialization in a loop and we're
    somehow determining that the initialization sequence looks like a GIV.
    And we're doing this even though we've set TREE_READONLY on the
    object.  Right?

Eric explained this.  We have something like:

	for (i = 0; i < j; i++)
	  {
	     const int k = i * 4;

K is a giv.  But it's also readonly.