[Bug tree-optimization/126689] New: Missed removal of nested copysigns

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126689

            Bug ID: 126689
           Summary: Missed removal of nested copysigns
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: easyhack
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ktkachov at gcc dot gnu.org
  Target Milestone: ---

double f1 (double x, double y, double z)
{
  return __builtin_copysign (x, __builtin_copysign (y, z));
}
float f2 (float x, float y, float z)
{
  return __builtin_copysignf (x, __builtin_copysignf (y, z));
}

On aarch64 generates:
f1:
        movi    v31.4s, 0
        fneg    v31.2d, v31.2d
        bit     v1.8b, v2.8b, v31.8b
        bit     v0.8b, v1.8b, v31.8b
        ret
f2:
        movi    v31.4s, 0x80, lsl 24
        bit     v1.8b, v2.8b, v31.8b
        bit     v0.8b, v1.8b, v31.8b
        ret

but should do like Clang:
f1:
        movi    v1.2d, #0xffffffffffffffff
        fneg    v1.2d, v1.2d
        bif     v0.16b, v2.16b, v1.16b
        ret

f2:
        mvni    v1.4s, #128, lsl #24
        bif     v0.16b, v2.16b, v1.16b
        ret