[AArch64] Improve lowering of scalar abs(sub(a, b)). (#151180)

This patch avoids a comparison against zero when lowering abs(sub(a, b))
patterns, instead reusing the condition codes generated by a subs of the
operands directly.

For example, currently:
```
  sxtb w8, w0
  sub w8, w8, w1, sxtb
  cmp w8, #0
  cneg w0, w8, mi
```
becomes:
```
  sxtb w8, w0
  subs w8, w8, w1, sxtb
  cneg w0, w8, mi
```

Together with #151177, this should handle the remaining patterns in
#118413.

0 files changed, 0 insertions, 0 deletions