Question on register renaming in rtl loop unroll pass

[Bin.Cheng]

Hi, I have a question about register renaming in rtl loop unroll.
For an example loop:
.L1:
  [r162] <-  x
  r162 <- r162 + 4
  ...
  b .L1

After unrolling:
.L1:
  [r162] <-  x
  r197 <- r162 + 4
  r162 <- r197
  ...
  [r162] <- y
  r162 <- r197 + 4
  ...
  b .L1
Why not:
.L1:
  [r162] <-  x
  r162 <- r162 + 4
  ...
  [r162] <- y
  r162 <- r162 + 4
  ...
  b .L1

Thus less copy instructions and can take advantage of auto-increment.
Any ideas?

Thanks.
bin