Messages in this thread | | | Date | Wed, 9 Jul 2008 18:50:55 -0700 | From | Arjan van de Ven <> | Subject | Re: [PATCH 02/34] AMD IOMMU: add header file for driver data structures and defines |
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On Wed, 9 Jul 2008 18:38:23 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:
> On Thu, 26 Jun 2008 21:27:38 +0200 Joerg Roedel > <joerg.roedel@amd.com> wrote: > > > +/* helper macros */ > > +#define LOW_U32(x) ((x) & ((1ULL << 32)-1)) > > +#define HIGH_U32(x) (LOW_U32((x) >> 32)) > > Please avoid putting general-purpose helpers into private header > files.
especially broken helpers.
A >> 32 on something that may be a 32 bit entry is bad; int32 >> 32... gcc can (and does!) optimize that out.
(because it first gets translated into a SHR x86 instruction which then notices it's encoded as a zero shift.. which then gets deleted)
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