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* [Bug tree-optimization/91540] missed value-replacement in phiopt
[not found] <bug-91540-4@http.gcc.gnu.org/bugzilla/>
@ 2021-05-24 6:20 ` pinskia at gcc dot gnu.org
2021-06-15 0:34 ` pinskia at gcc dot gnu.org
2021-06-15 0:36 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-05-24 6:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91540
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Currently on the trunk we get:
andl %edi, %esi
movl $43, %eax
movzbl %sil, %esi
subl %esi, %eax
Which is close.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/91540] missed value-replacement in phiopt
[not found] <bug-91540-4@http.gcc.gnu.org/bugzilla/>
2021-05-24 6:20 ` [Bug tree-optimization/91540] missed value-replacement in phiopt pinskia at gcc dot gnu.org
@ 2021-06-15 0:34 ` pinskia at gcc dot gnu.org
2021-06-15 0:36 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-06-15 0:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91540
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
On the trunk we get:
_5 = cond1_2(D) & cond2_3(D);
_6 = (int) _5;
_7 = 43 - _6;
If we replace the minus with xor, we would get what clang gives.
I think we do this with or though.
I looked into a slightly different case:
int Test(bool cond1, bool cond2)
{
if (cond1)
{
if (cond2)
{
return 43;
}
}
return 42;
}
int Test1(bool cond1, bool cond2)
{
int t = 0;
if (cond1)
{
if (cond2)
{
t = 1;
}
}
return 42 + t;
}
int Test0(bool cond1, bool cond2)
{
int t = 0;
if (cond1)
{
if (cond2)
{
t = 1;
}
}
return 42 + t;
}
int Test2(bool cond1, bool cond2)
{
int t = cond1 & cond2;
return 42 + t;
}
int Test3(bool cond1, bool cond2)
{
int t = (cond1 & cond2);
return 42 | t;
}
---- CUT ----
GCC produces the decent code for all of the Tests here while clang produces
produces decent for Test2 and Test3.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/91540] missed value-replacement in phiopt
[not found] <bug-91540-4@http.gcc.gnu.org/bugzilla/>
2021-05-24 6:20 ` [Bug tree-optimization/91540] missed value-replacement in phiopt pinskia at gcc dot gnu.org
2021-06-15 0:34 ` pinskia at gcc dot gnu.org
@ 2021-06-15 0:36 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-06-15 0:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91540
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
In summary, clang is trying to produce xor always for similar value reductions
(or still branches) while GCC produce plus and minus; though producing xor or
ior might lead to better code in general.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-06-15 0:36 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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[not found] <bug-91540-4@http.gcc.gnu.org/bugzilla/>
2021-05-24 6:20 ` [Bug tree-optimization/91540] missed value-replacement in phiopt pinskia at gcc dot gnu.org
2021-06-15 0:34 ` pinskia at gcc dot gnu.org
2021-06-15 0:36 ` pinskia at gcc dot gnu.org
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