[Bug tree-optimization/110087] Missing if conversion

[ubizjak at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110087

--- Comment #9 from Uroš Bizjak  ---
(In reply to Andrew Pinski from comment #8)
> Please file this separately, since it is a different issue.
PR110155.

[Bug tree-optimization/110087] Missing if conversion

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110087

--- Comment #8 from Andrew Pinski  ---
(In reply to Uroš Bizjak from comment #7)
> Similar conversion, not performed by gcc:
> 
> --cut here--
> #include 
> 
> _Bool foo (void);
> 
> int bar (int r)
> {
>   if (foo ())
> r++;
> 
>   return r;
> }
> --cut here--
> 
> gcc -O2:
> 
> movl%edi, %ebx
> callfoo
> cmpb$1, %al
> sbbl$-1, %ebx
> movl%ebx, %eax
> 
> could be:
> 
> movl%edi, %ebx
> callq   foo
> movzbl  %al, %eax
> addl%ebx, %eax

Please file this separately, since it is a different issue. Though I think
there are dups of that one too.

[Bug tree-optimization/110087] Missing if conversion

[ubizjak at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110087

--- Comment #7 from Uroš Bizjak  ---
Similar conversion, not performed by gcc:

--cut here--
#include 

_Bool foo (void);

int bar (int r)
{
  if (foo ())
r++;

  return r;
}
--cut here--

gcc -O2:

movl%edi, %ebx
callfoo
cmpb$1, %al
sbbl$-1, %ebx
movl%ebx, %eax

could be:

movl%edi, %ebx
callq   foo
movzbl  %al, %eax
addl%ebx, %eax

[Bug tree-optimization/110087] Missing if conversion

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110087

--- Comment #6 from Andrew Pinski  ---
(In reply to Richard Biener from comment #2) 
> there?  There's zero_one_valued_p we could use for both the
> tested value and the value or-ed into.
> 
> We already have
> 
> /* ((x & 0x1) == 0) ? y : z  y -> (-(typeof(y))(x & 0x1) & z)  y */
> 
> and
> 
> /* ((x & 0x1) == 0) ? z  y : y -> (-(typeof(y))(x & 0x1) & z)  y */

That is exactly what my patch does (I put it in PR 89263), I was going to
submit this patch a couple of days ago but got side tracked with other fixes
not to add the testcases to the patch and submit it.

[Bug tree-optimization/110087] Missing if conversion

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110087

Andrew Pinski  changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
 Resolution|--- |DUPLICATE

--- Comment #5 from Andrew Pinski  ---
Really this is a dup of bug 89263.

*** This bug has been marked as a duplicate of bug 89263 ***

[Bug tree-optimization/110087] Missing if conversion

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110087

Andrew Pinski  changed:

   What|Removed |Added

   Assignee|unassigned at gcc dot gnu.org  |pinskia at gcc dot 
gnu.org
 Status|NEW |ASSIGNED

--- Comment #4 from Andrew Pinski  ---
I have a patch that converts this into the or.

[Bug tree-optimization/110087] Missing if conversion

[amonakov at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110087

Alexander Monakov  changed:

   What|Removed |Added

 CC||amonakov at gcc dot gnu.org

--- Comment #3 from Alexander Monakov  ---
(In reply to Uroš Bizjak from comment #1)
> BTW: If the result of foo is random, then cmove gets badly predicted.
> Considering the problems with cmove on x86 (even without bad prediction),
> the above optimization can be quite important. Clang does it.

There is no prediction involved in execution of CMOV. It is one ALU uop with
latency 1 on any recent x86, or two uops with latency 1 on Haswell, going back
to Intel Core: https://uops.info/html-instr/CMOVZ_R32_R32.html

If you convert a control dependency to a data dependency with CMOV you may end
up with slower code due to longer dependency chains, but this is not the case
here.

[Bug tree-optimization/110087] Missing if conversion

[rguenth at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110087

Richard Biener  changed:

   What|Removed |Added

  Component|rtl-optimization|tree-optimization
 Ever confirmed|0   |1
 Status|UNCONFIRMED |NEW
   Keywords||missed-optimization
   Last reconfirmed||2023-06-02
 CC||pinskia at gcc dot gnu.org

--- Comment #2 from Richard Biener  ---
  _Bool _1;

   :
  _1 = foo ();
  if (_1 != 0)
goto ; [INV]
  else
goto ; [INV]

   :

   :
  # r_2 = PHI 
  return r_2;

I wonder if we should address this in PHI-OPT and transform it to

 r_2 = r_5(D) | _1;

there?  There's zero_one_valued_p we could use for both the
tested value and the value or-ed into.

We already have

/* ((x & 0x1) == 0) ? y : z  y -> (-(typeof(y))(x & 0x1) & z)  y */

and

/* ((x & 0x1) == 0) ? z  y : y -> (-(typeof(y))(x & 0x1) & z)  y */