http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53346
Uros Bizjak <ubizjak at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |hjl.tools at gmail dot com
--- Comment #14 from Uros Bizjak <ubizjak at gmail dot com> 2012-05-18 17:17:45
UTC ---
Compile and execute slow assembly:
gfortran rnflow.s && time ./a.out
real 0m24.454s
user 0m24.167s
sys 0m0.231s
Apply following patch that changes cmove in very fast loops (cptrf2) to jumps:
--cut here--
--- rnflow.s 2012-05-18 19:00:22.314102061 +0200
+++ rnflow1.s 2012-05-18 19:10:59.363428625 +0200
@@ -1305,7 +1305,9 @@
movslq %edx, %rbx
movss -4(%rdi,%rbx,4), %xmm0
ucomiss (%r9), %xmm0
- cmova %ecx, %edx
+ jbe .L183x
+ movl %ecx, %edx
+.L183x:
subl $1, %ecx
subq $4, %r9
cmpl %r10d, %ecx
@@ -1329,7 +1331,9 @@
movslq %ecx, %r10
movss -4(%rdi,%r10,4), %xmm0
ucomiss (%r9), %xmm0
- cmova %r11d, %ecx
+ jbe .L192x
+ movl %r11d, %ecx
+.L192x:
subl $1, %r11d
subq $4, %r9
cmpl %eax, %r11d
@@ -1485,7 +1489,9 @@
movslq %edx, %r10
movss -4(%rdi,%r10,4), %xmm0
ucomiss (%r9), %xmm0
- cmova %ecx, %edx
+ jbe .L179x
+ movl %ecx, %edx
+.L179x:
subq $4, %r9
subl $1, %ecx
jne .L179
--cut here--
gfortran rnflow.s && time ./a.out
real 0m18.170s
user 0m17.907s
sys 0m0.223s
WTF happened here?!
Relevant part of my /proc/cpuinfo:
vendor_id : GenuineIntel
cpu family : 6
model : 42
Adding CC.
