On Sat, Jun 11, 2011 at 10:01 PM, Jason Merrill <ja...@redhat.com> wrote: > On 06/10/2011 10:20 AM, Richard Guenther wrote: >> >> no, a VIEW_CONVERT_EXPR is generally not an lvalue (fold for example >> would turn the above to (volatile int) a[1]). > > The gimplifier seems to consider it an lvalue: gimplify_expr uses > gimplify_compound_lval for it, and gimplify_addr_expr handles taking its > address. And get_inner_reference handles it. So I think fold should be > changed, and we should clarify that VIEW_CONVERT_EXPR is an lvalue. > > If not, we need a new tree code for treating an lvalue as an lvalue of a > different type without having to take its address; that's what I thought > VIEW_CONVERT_EXPR was for.
The please provide a specification on what a VIEW_CONVERT_EXPR does to type-based alias analysis. We are trying to avoid that by the rvalue rule. Also you can always avoid VIEW_CONVERT_EXPRs for lvalues by simply moving the conversion to the rvalue side. Yes, we do handle lvalue VIEW_CONVERT_EXPRs, but that is for Ada which uses it for aggregates. I don't want us to add more lvalue VIEW_CONVERT_EXPR cases, especially not for register types. Richard. > Jason >
