[Bug tree-optimization/56309] -O3 optimizer generates conditional moves instead of compare and branch resulting in almost 2x slower code

[arturomdn at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56309



--- Comment #14 from arturomdn at gmail dot com 2013-02-14 17:30:54 UTC ---

I also did the experiment, with the same results... it got faster but not as

fast as the version with

conditional branch instead of conditional moves:



./by-ref-O3

Took 6.65 seconds total.



./by-val-O3 

Took 11.64 seconds total.



./by-val-fixed-O3 

Took 9.94 seconds total.



--- by-val-O3.s 2013-02-14 11:27:28.109856000 -0600

+++ by-val-fixed-O3.s   2013-02-14 11:11:07.312317000 -0600

@@ -679,13 +679,12 @@

        shrq    $32, %rdi

        .loc 4 25 0

        andl    $4294967295, %ecx

+       addq    $1, %rax

        cmpq    %r8, %rdx

        cmovbe  %r11, %rdi

 .LVL43:

        .loc 4 29 0

-       addq    $1, %rax

 .LVL44:

-       cmpq    %r8, %rdx

        cmovbe  %rdx, %rcx

 .LVL45:

        .loc 4 21 0