https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88271
--- Comment #10 from Daniel Fruzynski ---
Here is possible code transformation to equivalent form, where this
optimization can be simply applied. This change also has a bit surprising side
effect, second nested while loop is unrolled.
[code]
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88271
--- Comment #9 from Daniel Fruzynski ---
I have idea about alternate approach to this. gcc could try to look for
relations between loop control statement, and other statements which modify
variables used in that control statement. With such
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88271
--- Comment #8 from Daniel Fruzynski ---
I have results from Callgrind. Cycle estimation for MoveRows function (without
children) is 58.29%. This is for app without test instruction. So in synthetic
benchmark for this function only speed change
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88271
--- Comment #7 from Daniel Fruzynski ---
One more note: this particular function creates matrices with all possible
permutations of row order of original matrix, which satisfies some additional
criteria. So this optimization may be applicable to
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88271
--- Comment #6 from Daniel Fruzynski ---
Average for version with test is 246.313ms, I deleted too many digits.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88271
--- Comment #5 from Daniel Fruzynski ---
How to use perf? I did not have change to use it yet, I usually use time
command or callgrind.
I have run my app compiled with AVX2 instructions on Xeon E5-2683 v3, CentOS
7.6, on idle CPU. I run it 3
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88271
--- Comment #4 from Uroš Bizjak ---
(In reply to Daniel Fruzynski from comment #3)
> What about adding new pass at the end? It would look for various possible
> optimizations, which were missed earlier because they are cross-basic block.
We do
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88271
--- Comment #3 from Daniel Fruzynski ---
What about adding new pass at the end? It would look for various possible
optimizations, which were missed earlier because they are cross-basic block.
In my case this example code is part of tight loop.
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88271
Jakub Jelinek changed:
What|Removed |Added
CC||jakub at gcc dot gnu.org
--- Comment #2
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88271
--- Comment #1 from Daniel Fruzynski ---
I checked that in simple case when bit shift is used in "if", it is optimized:
[code]
void f();
void g();
void test(int n)
{
if (n << 1)
f();
else
g();
}
[/code]
[asm]
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