tree 9a572915866e1e73abb34e6bc0ff138b31965abf
parent 4fe807c8084658ab761096f816d1d6c95675e0f6
author Kit Barton <kbarton@ca.ibm.com> 1555527207 +0000
committer Kit Barton <kbarton@ca.ibm.com> 1555527207 +0000

Add basic loop fusion pass.

This patch adds a basic loop fusion pass. It will fuse loops that conform to the
following 4 conditions:
  1. Adjacent (no code between them)
  2. Control flow equivalent (if one loop executes, the other loop executes)
  3. Identical bounds (both loops iterate the same number of iterations)
  4. No negative distance dependencies between the loop bodies.

The pass does not make any changes to the IR to create opportunities for fusion.
Instead, it checks if the necessary conditions are met and if so it fuses two
loops together.

The pass has not been added to the pass pipeline yet, and thus is not enabled by
default. It can be run stand alone using the -loop-fusion option.

Differential Revision: https://reviews.llvm.org/D55851

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@358607 91177308-0d34-0410-b5e6-96231b3b80d8