[Bug target/103959] New: float64x1_t not using fmov to generate some float values

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103959

            Bug ID: 103959
           Summary: float64x1_t not using fmov to generate some float
                    values
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64-*-*

#include <arm_neon.h>
Take:
double ff(void)
{
  return 2.0;
}
float64x1_t g(void)
{
  return (float64x1_t){2.0};
}
---- CUT ----
These should produce the same code but currently does not.
ff:
        fmov    d0, 2.0e+0
        ret
g:
        mov     x0, 4611686018427387904
        fmov    d0, x0
        ret

I Noticed this while working on PR 64821 where we now fold sqrt but get g.