------- Comment #21 from michael dot meissner at amd dot com 2005-10-04 20:46 ------- Subject: RE: variable rotate and long long rotate should be better optimized
Sorry, I got mixed up as to who the original poster was. SSE2 is harder to use because it deals with 128 bit items instead of 64 bit (unless you are in 64-bit and working on TImode values). Ultimately, it is a matter whether it is important enough for somebody to spend a week or two of work to use the multimedia instructions for this case. I suspect in most cases, it might be better to isolate the code and use #ifdef's and builtin functions/asm's. -----Original Message----- From: ak at muc dot de [mailto:[EMAIL PROTECTED] Sent: Tuesday, October 04, 2005 4:40 PM To: Meissner, Michael Subject: [Bug middle-end/17886] variable rotate and long long rotate should be better optimized ------- Comment #20 from ak at muc dot de 2005-10-04 20:39 ------- Newer linux does that of course, although not always in older releases. But even in user space it's not a good idea to use SSE2 unless you really need it because it increases the cost of the context switch and costs an exception each time first in a timeslice. P.S.: I was the original poster, but the application wasn't a kernel but I doubt it's a good idea to use SSE2. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17886
