On Mon, Nov 25, 2002 at 11:29:01AM -0500, Dan Sugalski wrote: > At 4:04 PM +0000 11/25/02, Nicholas Clark wrote:
> >Is there any speed advantage in truncating by casting via a C type > >[eg a = (int)(short) b] > >rather than and on a bitmask > >[eg a = b & 0xFFFF] > >? > > > >We're going to have to do that latter to make it work on Crays anyway, so is > >a conditional compile to chose between the two worth it? > > The bitmask doesn't sign-extend where the casting will, which could > be an issue. That still lets us halve our conditional code. :-) (do all the unsigned with masks) And we ought to make a generic "safe" version of the code for signed truncation that works for platforms that are any or all of the following holds 1: no type of that size (eg Crays) 2: signed integer truncation (UTS) [and other OSes on S/390 processors?] 3: not 2s complement [no examples] Nicholas Clark
