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Re: [C PATCH] Discard P - (P + CST) optimization in pointer_diff (PR c/61240)
- From: Jeff Law <law at redhat dot com>
- To: Richard Biener <rguenther at suse dot de>, Marek Polacek <polacek at redhat dot com>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, "Joseph S. Myers" <joseph at codesourcery dot com>, Jakub Jelinek <jakub at redhat dot com>
- Date: Wed, 06 Aug 2014 10:04:53 -0600
- Subject: Re: [C PATCH] Discard P - (P + CST) optimization in pointer_diff (PR c/61240)
- Authentication-results: sourceware.org; auth=none
- References: <20140804101856 dot GB24292 at redhat dot com> <alpine dot LSU dot 2 dot 11 dot 1408041224210 dot 20733 at zhemvz dot fhfr dot qr> <20140804113836 dot GD24292 at redhat dot com> <alpine dot LSU dot 2 dot 11 dot 1408041404040 dot 20733 at zhemvz dot fhfr dot qr> <20140805143652 dot GG24292 at redhat dot com> <53E13B1D dot 5050401 at redhat dot com> <20140806082219 dot GI24292 at redhat dot com> <alpine dot LSU dot 2 dot 11 dot 1408061021280 dot 20733 at zhemvz dot fhfr dot qr>
On 08/06/14 02:27, Richard Biener wrote:
Well, at least on the mn102, I defined both a zero and sign extension
for PSI -> SI. So whichever one the generic parts of the compiler
needed, the backend provided.
which we may restrict better with checking whether the pointer
uses a partial integer mode. Not sure how PSImode -> SImode
"extends" on RTL?
As to what bits are modified, that's target dependent as the precise
size of the partial modes is target dependent. That's one of the things
that would be largely made irrelevant by DJ's proposed changes. Instead
of using PSImode, we'd be able to define modes of precisely the number
of bits one of these targets needs.