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


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


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