[BypassSlowDivision] Improve our handling of divisions by constants

Summary:
Don't bail out on constant divisors for divisions that can be narrowed without
introducing control flow .  This gives us a 32 bit multiply instead of an
emulated 64 bit multiply in the generated PTX assembly.

Reviewers: jlebar

Subscribers: jholewinski, mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D38265

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@314253 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed