Messages in this thread | | | Date | Fri, 25 Jul 2008 17:39:21 -0400 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] introduce lower_32_bits() macro |
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Roland Dreier wrote: > > There's some readability benefit. Sometimes it is hard to understand > > why some random open-coded cast was used. But I seem to recall that > > there was another reason why we decided we needed this. I forget, and > > so apparently did the changelog author ;) > > The guy who added the macro explained it in a comment ;) > > * A basic shift-right of a 64- or 32-bit quantity. Use this to suppress > * the "right shift count >= width of type" warning when that quantity is > * 32-bits.
That was for upper_32_bits() -- and can also be done with an internal (u64) cast; it would be interesting to find out if that would generate better code.
-hpa
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