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Re: Widening multiplication limitations
- From: Frederic Riss <frederic dot riss at gmail dot com>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: gcc <gcc at gcc dot gnu dot org>
- Date: Wed, 27 Mar 2013 11:24:24 +0100
- Subject: Re: Widening multiplication limitations
- References: <CAKk_3s_MTY7KUw_h_d68x05do5_XcG0DOOveGYPEbVKzsz4jRg at mail dot gmail dot com> <CAFiYyc0o6FwZeqwePTLOnWzT00O_fAe4o8L5o07dM_uqhAkfrg at mail dot gmail dot com>
On 27 March 2013 10:05, Richard Biener <richard.guenther@gmail.com> wrote:
> On Tue, Mar 26, 2013 at 6:30 PM, Frederic Riss <frederic.riss@gmail.com> wrote:
>> Here, the code trying to expand a signed by unsigned widening multiply
>> explicitly checks that the operand isn't a constant. Why is that? I
>> removed that condition to try to find the failing cases, but the few
>> million random multiplies that I threw at it didn't fail in any
>> visible way.
>
> Not sure, the limitation does not make sense to me. Probably the
> code assumes that it would have been easy to convert the constant
> to the same signedness as treeop0. Simply removing the check
> seems correct to me.
Thanks for the confirmation. I'll try to see if these modifications
pass regstrap on a primary target and then maybe submit a patch.
Fred