If a loop has a loop exiting latch, it can be profitable
to rotate the loop if it leads to the simplification of
a phi node. Perform rotation in these cases even if loop
rotate itself didnt simplify the loop to get there.
Differential Revision: https://reviews.llvm.org/D44199
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328933 91177308-0d34-0410-b5e6-96231b3b80d8
The existing LoopRotation.cpp is implemented as one of loop passes instead of
being a utility. The user cannot easily perform the loop rotation selectively
(or on demand) under different optimization level. For example, the loop
rotation is needed as part of the logic to convert a loop into a loop with
bottom test for a transformation. If the loop rotation is simply added as a
loop pass before the transformation, the pass is skipped if it is compiled at
–O0 or if it is explicitly disabled by the user, causing the compiler to
generate incorrect code. Furthermore, as a loop pass it will rotate all loops
instead of just the relevant loops.
We provide a utility interface for the loop rotation so that the loop rotation
can be called on demand. The changeset is as follows:
- Create a new file lib/Transforms/Utils/LoopRotationUtils.cpp and move the main
implementation of class LoopRotate into this file.
- Create a new file llvm/include/Transform/Utils/LoopRotationUtils.h with the
interface LoopRotation(...).
- Original LoopRotation.cpp is changed to use the utility function LoopRotation
in LoopRotationUtils.cpp. This is done in the same way community did for
mem-to-reg implementation.
Patch by Jin Lin!
Differential Revision: https://reviews.llvm.org/D44595
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@328766 91177308-0d34-0410-b5e6-96231b3b80d8
