[flang] Avoid unnecessary looping for constants (#156403)HEADmain

Going through and doing `convertToAttribute` for all elements, if they
are the same can be costly. If the elements are the same, we can just
call `convertToAttribute` once.

This does give us a significant speed-up:
```console
$ hyperfine --warmup 1 --runs 5 ./slow.sh ./fast.sh
Benchmark 1: ./slow.sh
  Time (mean ± σ):      1.606 s ±  0.014 s    [User: 1.393 s, System: 0.087 s]
  Range (min … max):    1.591 s …  1.628 s    5 runs

Benchmark 2: ./fast.sh
  Time (mean ± σ):     452.9 ms ±   7.6 ms    [User: 249.9 ms, System: 83.3 ms]
  Range (min … max):   443.9 ms … 461.7 ms    5 runs

Summary
  ./fast.sh ran
    3.55 ± 0.07 times faster than ./slow.sh
```

Fixes #125444

0 files changed, 0 insertions, 0 deletions