arch-power: Add zero count instructions

This introduces new helpers for finding the count of
leading and trailing zero bits in a given value and adds
the following instructions.
  * Count Trailing Zeros Word (cnttzw[.])
  * Count Leading Zeros Doubleword (cntlzd[.])
  * Count Trailing Zeros Doubleword (cnttzd[.])

Change-Id: I69dad34bc2cffb2ac70ecd3dba7301fa1cdcb340
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/40920
Reviewed-by: Boris Shingarov <shingarov@labware.com>
Maintainer: Boris Shingarov <shingarov@labware.com>
Tested-by: kokoro <noreply+kokoro@google.com>
3 files changed