[NVPTX] Improve lowering of llvm.ctlz.
Summary:
* Disable "ctlz speculation", which inserts a branch on every ctlz(x) which
has defined behavior on x == 0 to check whether x is, in fact zero.
* Add DAG patterns that avoid re-truncating or re-expanding the result
of the 16- and 64-bit ctz instructions.
Reviewers: tra
Subscribers: llvm-commits, jholewinski
Differential Revision: https://reviews.llvm.org/D28719
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292299 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed