tree bad4e98e3d1233a98588fc9c32c6dc47be5cf75c
parent 03f53c0c4dc904789fe791eb97bcedaca852fe4a
author Florian Hahn <flo@fhahn.com> 1555516663 +0000
committer Florian Hahn <flo@fhahn.com> 1555516663 +0000

[LoopUnroll] Allow unrolling if the unrolled size does not exceed loop size.

Summary:
In the following cases, unrolling can be beneficial, even when
optimizing for code size:
 1) very low trip counts
 2) potential to constant fold most instructions after fully unrolling.

We can unroll in those cases, by setting the unrolling threshold to the
loop size. This might highlight some cost modeling issues and fixing
them will have a positive impact in general.

Reviewers: vsk, efriedma, dmgreen, paquette

Reviewed By: paquette

Differential Revision: https://reviews.llvm.org/D60265

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358586 91177308-0d34-0410-b5e6-96231b3b80d8