[Bug target/112454] csinc (csel is though) is not being used when there is matches twice

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112454

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2023-11-18
     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> ---
Mine, looks like a cost issue not recording that 1 (and ~0) are free to create.

you can see the cost issue if we look at combine for the case of 1 csel:
Trying 37 -> 39:
   37: r98:SI=0x1
   39: r92:SI={(cc:CC!=0)?r100:SI:r98:SI}
      REG_DEAD r100:SI
      REG_DEAD cc:CC
      REG_DEAD r98:SI
Successfully matched this instruction:
(set (reg:SI 92 [ <retval> ])
    (if_then_else:SI (ne (reg:CC 66 cc)
            (const_int 0 [0]))
        (reg:SI 100)
        (const_int 1 [0x1])))
allowing combination of insns 37 and 39
original costs 4 + 4 = 8
replacement cost 8
deferring deletion of insn with uid = 37.
modifying insn i3    39: r92:SI={(cc:CC!=0)?r100:SI:0x1}
      REG_DEAD cc:CC
      REG_DEAD r100:SI
deferring rescan insn with uid = 39.

The replacement cost should be still 4.