[Bug tree-optimization/109960] New: [10/11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[Bug tree-optimization/109960] New: [10/11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

            Bug ID: 109960
           Summary: [10/11/12/13/14 Regression] missing combining of
                    `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take the following C++ code (reduced from stmt_can_terminate_bb_p):
```
static inline bool f1(unsigned *a)
{
        return (*a&1);
}
static inline bool f2(unsigned *a)
{
        return (*a&2);
}

bool f(int c, unsigned *a)
{
  if (c)
    return 0;
  return f2(a) || f1(a) ;
}
```

At -O1 we can produce:
```
        movl    $0, %eax
        testl   %edi, %edi
        jne     .L1
        testb   $3, (%rsi)
        setne   %al
.L1:
        ret
```
But at -O2 we get:
        xorl    %eax, %eax
        testl   %edi, %edi
        jne     .L1
        movl    (%rsi), %edx
        movl    %edx, %eax
        andl    $1, %eax
        andl    $2, %edx
        movl    $1, %edx
        cmovne  %edx, %eax
.L1:
        ret

Which is just so much worse.
This started in GCC 9.

[Bug tree-optimization/109960] [10/11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |8.5.0
      Known to fail|                            |9.1.0
   Target Milestone|---                         |10.5

[Bug tree-optimization/109960] [10/11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
We could have a pattern that does:

`(a & CST) != 0 ? 1: (bool)a` -> `a & (CST|1) != 0` to fix this I think.

[Bug tree-optimization/109960] [10/11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-05-25
             Status|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot gnu.org

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Or maybe extend recognize_single_bit_test to recognize (bool)a != 0 is the same
as a & 1 != 0.

Let me try that.

[Bug tree-optimization/109960] [10/11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|1                           |0
             Status|ASSIGNED                    |UNCONFIRMED
           Assignee|pinskia at gcc dot gnu.org         |unassigned at gcc dot gnu.org

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Nope not working, even tried to figure out how to modify tree-ssa-reassoc.cc to
teach it about `(bool)a` being the same as `(a & 1) != 0` But I could not
figure out how.

[Bug tree-optimization/109960] [10/11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I happened to notice this because I am working on a match patch that transform
`a ? 1 : b` into `a | b`.

In the case of stmt_can_terminate_bb_p, I noticed we had:
  <bb 31> [local count: 330920071]:
  _48 = MEM[(const struct gasm *)t_22(D)].D.129035.D.128905.D.128890.subcode;
  _49 = _48 & 2;
  if (_49 != 0)
    goto <bb 33>; [34.00%]
  else
    goto <bb 32>; [66.00%]

  <bb 32> [local count: 218407246]:
  _50 = (bool) _48;

  <bb 33> [local count: 940291388]:
  # _13 = PHI <0(14), _50(32), _12(29), 0(11), 0(30), 1(2), 1(31), 0(25)>

And the patch to match would do:
  <bb 31> [local count: 330920071]:
  _48 = MEM[(const struct gasm *)t_22(D)].D.129035.D.128905.D.128890.subcode;
  _49 = _48 & 2;
  _50 = (bool) _48;
  _127 = _49 != 0;
  _44 = _50 | _127;

  <bb 32> [local count: 940291388]:
  # _13 = PHI <0(14), 0(25), _12(29), 0(11), 0(30), 1(2), _44(31)>

Which is definitely better than before but I was like isn't that the same as:
  _49 = _48 & 3;
  _44 = _49 != 0;

[Bug tree-optimization/109960] [10/11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
ifcombine was supposed to handle this but I guess we mess up before it

[Bug tree-optimization/109960] [11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|10.5                        |11.5

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 10 branch is being closed.

[Bug tree-optimization/109960] [11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot gnu.org

--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Mine.

[Bug tree-optimization/109960] [11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

--- Comment #8 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 55913
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55913&action=edit
part of the ifcombine fixes

It does not catch:
 _10 = _5 >> 1;
  _11 = (_Bool) _10;
  if (_11 != 0)

Though. I will add that in a bit. That is used for PR 108370.

[Bug tree-optimization/109960] [11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 55915
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55915&action=edit
match pattern for the non-ifcombine case

sometimes we need to handle this outside of ifcombine due to phiopt or other
passes. So this adds that pattern.

[Bug tree-optimization/109960] [11/12/13/14 Regression] missing combining of `(a&1) != 0 || (a&2)!=0` into `(a&3)!=0`

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109960

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2