Messages in this thread | | | Subject | RE: [ANNOUNCE][PATCH 2.6.11 2/3] megaraid_sas: Announcing new mod ule for LSI Logic's SAS based MegaRAID controllers | From | Arjan van de Ven <> | Date | Wed, 09 Mar 2005 19:19:35 +0100 |
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On Wed, 2005-03-09 at 12:44 -0500, Bagalkote, Sreenivas wrote: > >> > > >> >> . And since this is compile time > >> >> system-wide property, I kept it as driver global. > >> > > >> >that step I don't understand... why is it a global > >*VARIABLE* if it's > >> >compile time system-wide property... > >> > > >> > >> I see your point! Are you saying I should use > >if(sizeof(dma_addr_t)==8) > >> instead of the shortcut if(is_dma64)? > >yep > >well you can use a preprocessor define of something to make it slightly > >more readable (eg shortcut) if you want, but that's what I mean yeah.. > > > >gcc will optimize the entire unused code away this way, including the > >actual conditional jump, so for performance and bloat-ness > >point of view > >it's nice.... and of course generic design beauty ;) > > > > Great. Thanks! I will change it. If I understand you correctly, I should > #define IS_DMA64 (sizeof(dma_addr_t)==8).
that's one way to do it yeah. > > Is this better than declaring is_dma64 global variable const? (Excuse the > oxymoron).
in C yes; in C "const" doesn't quite mean what you want it to mean with this and as a result gcc I think can't optimize this the way it can with the define.
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