Re: [patch] expr.c: Fix PR middle-end/18008.

[Jeffrey A Law <law at redhat dot com>]

On Mon, 2004-10-18 at 15:54, Jason Merrill wrote:
> >> After the tree optimizers run, I get
> >> 
> >>   b->b = (<unnamed type>) (unsigned char) v;
> >> 
> >> where <unnamed type> is a 2-bit integer type.  The problem is that we
> >> get ANDs from two places.  The first one is generated by the cast to
> >> (<unnamed type>).  The second one is from the assignment, more
> >> specifically store_bit_field.
> >> 
> >> The patch fixes the problem by stripping a narrowing conversion.
> 
> It seems to me that the right fix is to avoid generating an AND in
> store_bit_field if the value assigned is already appropriately narrow.
Yes.  However, it's probably still worth simplifying the code in
the optimizers.

Jeff