------- Comment #14 from michael dot meissner at amd dot com 2005-10-04 18:59
-------
Created an attachment (id=9876)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9876&action=view)
Patch for x86 double word shifts
This patch fixes the bug from the x86 side of things instead of from the
machine independent, by adding direct expanders for the best code (for doing 64
bit rotates in 32-bit mode and 128 bit rotates in 64-bit mode). On a machine
with conditional move (all recent processors), the code becomes:
movl %edx, %ebx
shldl %eax, %edx
shldl %ebx, %eax
movl %edx, %ebx
andl $32, %ecx
cmovne %eax, %edx
cmovne %ebx, %eax
However, I suspect using MMX or SSE2 instructions will provide even more of a
speedup, since there are direct 64-bit shifts, and, or, load/store directly
(but no direct rotate). In the MMX space you have to be careful not to have
active floating point going on, and to switch out of MMX mode before doing
calls or returns.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17886
