[Bug tree-optimization/112096] New: `(a || b) ? a : b` should be simplified to a

[Bug tree-optimization/112096] New: `(a || b) ? a : b` should be simplified to a

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112096

            Bug ID: 112096
           Summary: `(a || b) ? a : b` should be simplified to a
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
int t0(int x, int y)
{
  _Bool t = x == 0 && y == 0;
  if (t) return x; return y;
} // y

int t0_(int x, int y)
{
  _Bool t = x == 0 && y == 0;
  if (t) return 0; return y;
} // y

int t1(int x, int y)
{
  _Bool t = x || y;
  if (t) return x; return y;
} // x
int t1_(int x, int y)
{
  _Bool t = x || y;
  if (t) return x; return 0;
} // x
```
These should be simplified as the comment says

All 4 of these are caught by LLVM.

[Bug tree-optimization/112096] `(a || b) ? a : b` should be simplified to a

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112096

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note we already handle the bool case on the trunk.

[Bug tree-optimization/112096] `(a || b) ? a : b` should be simplified to a

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112096

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-10-26
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |pinskia at gcc dot gnu.org

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
```
int t01(int x, int y)
{
  bool t = x == 5 && y == 5;
  if (t) return 5; return y;
} // y
```
Is able to be detected in phiopt2.  Just not the == 0/!=0 case.

Nor:
```
int t1(int x, int y)
{
  bool t = x != 5 || y != 5;
  if (t) return x; return 5;
} // x
```
I have to look at where phiopt is able to detect this and improve it for these
2 cases ...

[Bug tree-optimization/112096] `(a || b) ? a : b` should be simplified to a

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112096

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> ```
> int t01(int x, int y)
> {
>   bool t = x == 5 && y == 5;
>   if (t) return 5; return y;
> } // y
> ```
> Is able to be detected in phiopt2.  Just not the == 0/!=0 case.

r0-125639-gc9ef86a1717dd6 added that code.
https://inbox.sourceware.org/gcc-patches/000001cebdbf$a3155310$e93ff930$@arm.com/

I really have not read this code in over 10 years and I forgot I even reviewed
it slightly.

Anyways I am thinking about ways of improving this even further ...
And maybe even rewriting part of it since it has got way too complex.

[Bug tree-optimization/112096] `(a || b) ? a : b` should be simplified to a

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112096

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Another testcase:
```
int f(int a, int b, int d)
{
        bool t = a == 0;
        bool t1 = d == 0;
        int c = a + b;
        if (t & t1) return b;
        return c;
}

int f1(int a, int b, int d)
{
        bool t = a == 0;
        bool t1 = d == 43;
        int c = a + b;
        if (t & t1) return b;
        return c;
}
```

I have a patch which handles this one. I have to check on the != cases next.