[LoopFusion] Restrict loop fusion to rotated loops.

Authored by kbarton on Dec 16 2019, 8:57 AM.


[LoopFusion] Restrict loop fusion to rotated loops.

This patch restricts loop fusion to only consider rotated loops as valid candidates.
This simplifies the analysis and transformation and aligns with other loop optimizations.

Reviewers: jdoerfert, Meinersbur, dmgreen, etiotto, Whitney, fhahn, hfinkel

Reviewed By: Meinersbur

Subscribers: ormris, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D71025