http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56175
--- Comment #2 from Uros Bizjak <ubizjak at gmail dot com> 2013-02-02 12:01:56
UTC ---
(In reply to comment #1)
> Created attachment 29330 [details]
> testcase
>
> This test must be compiled with the following options:
> "-O2 -ffast-math -msse2 -mfpmath=sse -m32 -march=atom -mtune=atom
> -ftree-loop-if-convert"
Compiling attached test with above flags, I got:
foo:
movl 4(%esp), %eax
movl 8(%esp), %edx
testb %al, %al
je .L3
testw %dx, %dx
je .L3
shrb %al
shrw %dx
xorl %edx, %eax
andl $1, %eax
ret
.L3:
xorl %eax, %eax
ret
which looks the same as your optimal assembly in Description - maybe due to the
fact that the attached test source is the same as the source in Description.
BTW: This is probably the case of missing CSE in tree optimizers. Combine pass
is not powerful enough to figure out optimal sequence, it more-or-less blindly
combines various patterns.
Please provide the test that exposes this missing optimization.
