Re: [C PATCH] Discard P - (P + CST) optimization in pointer_diff (PR c/61240)

[Jeff Law <law at redhat dot com>]

On 08/06/14 02:27, Richard Biener wrote:

> which we may restrict better with checking whether the pointer
> uses a partial integer mode.  Not sure how PSImode -> SImode
> "extends" on RTL?
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.

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.

Jeff