------- Comment #18 from michael dot meissner at amd dot com 2005-10-04 20:32 ------- Subject: RE: variable rotate and long long rotate should be better optimized
Yep, all valid points. So I don't think it should be done by default. But I suspect the original poster's application may be well behaved to be able to use it. Certainly if the only reason for doing long long is to do heavy duty bit banging (shift/rotate/and/or/test), but no arithmetic it would speed up since it could do one instruction instead of multiple, and it would lesson the register pressure that long longs put on the x86. -----Original Message----- From: ak at muc dot de [mailto:[EMAIL PROTECTED] Sent: Tuesday, October 04, 2005 4:20 PM To: Meissner, Michael Subject: [Bug middle-end/17886] variable rotate and long long rotate should be better optimized ------- Comment #17 from ak at muc dot de 2005-10-04 20:20 ------- The code now looks fine to me thanks I would prefer if it didn't generate SSE2/MMX code because that would be a problem for kernels. Also in many x86 implementations moving things between normal integer registers and SIMD registers is quite slow and would likely eat all advantages -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17886
