[flang] Clean-up for fir.do_loop generation in lowering. (#160630)

This patch changes two things:
  1. We do not need to use the loop counter's last value
     for regular do-loops in Lowering.
  2. The loop counter's increment is implied by fir.do_loop
     operation, so there is no need to increment it explicitly.

The last point has been especially confusing to me, because it was
unclear why we have an explicit increment if it is implied.
It looks like CFGConversion somehow still makes the final code
correct, i.e. the counter is not incremented twice.
Anyway, the new lowering should look more concise.

0 files changed, 0 insertions, 0 deletions