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Subject: [Bug tree-optimization/53346] [4.6/4.7/4.8 Regression] Bad vectorization in the proc cptrf2 of rnflow.f90
Date: Fri, 18 May 2012 17:46:00 -0000
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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.