[SystemZ] Improved handling of the @llvm.ctlz intrinsic.
Since SystemZ supports counting of leading zeros with the FLOGR instruction,
isCheapToSpeculateCtlz() should return true, which it now does.
ISD::CTLZ_ZERO_UNDEF i32 is now handled the same way as ISD::CTLZ is, which
is needed since promotion to i64 is required and CTLZ_ZERO_UNDEF is only
expanded to CTLZ if it is Legal or Custom.
Review: Ulrich Weigand
https://reviews.llvm.org/D57710
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@353330
91177308-0d34-0410-b5e6-
96231b3b80d8