[Bug middle-end/120372] New: canonicalize_comparison uses gen_move_insn to calcualate the cost of the constant formation

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120372

            Bug ID: 120372
           Summary: canonicalize_comparison uses gen_move_insn to
                    calcualate the cost of the constant formation
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: middle-end
          Assignee: pinskia at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64

Take:
```
int check1 (int x)
{
  return x > 0xaa9fff;
}
```

Currently canonicalize_comparison gives:
;; cmp: gt, old cst: (const_int 11182079 [0xaa9fff]) new cst: (const_int
11182080 [0xaaa000])
;; old cst cost: 8, new cst cost: 8

Which is correct if we are forming a constant by itself. But the cmp
instruction can take a different constant than if we are just forming the
constant.

Note the middle-end also checks:
rtx_cost (x, mode, COMPARE, 0, optimize_insn_for_speed_p ())

In a different code. So maybe canonicalize_comparison should use that instead.