[PATCH] D60144: [SCEV] Add option to forget everything in SCEV.

[Alina Sbirlea via Phabricator via llvm-commits]

asbirlea created this revision.
asbirlea added a reviewer: sanjoy.
Herald added subscribers: jdoerfert, dmgreen, javed.absar, zzheng, jlebar, mehdi_amini.
Herald added a project: LLVM.

Create a method to forget everything in SCEV.
Add a cl::opt and PassManagerBuilder option to use this in LoopUnroll.

Motivation: Certain Halide applications spend a very long time compiling in forgetLoop, and prefer to forget everything and rebuild SCEV from scratch.
Sample difference in compile time reduction: 21.04 to 14.78 using current ToT release build.
Testcase showcasing this cannot be opensourced and is fairly large.
I don't have evidence now that this compile time reduction is true for other applications, hence leaving the option disabled by default.


Repository:
  rL LLVM

https://reviews.llvm.org/D60144

Files:
  include/llvm/Analysis/ScalarEvolution.h
  include/llvm/Transforms/IPO/PassManagerBuilder.h
  include/llvm/Transforms/Scalar.h
  include/llvm/Transforms/Utils/UnrollLoop.h
  lib/Analysis/ScalarEvolution.cpp
  lib/Transforms/IPO/PassManagerBuilder.cpp
  lib/Transforms/Scalar/LoopUnrollPass.cpp
  lib/Transforms/Utils/LoopUnroll.cpp
  lib/Transforms/Utils/LoopUnrollAndJam.cpp
  lib/Transforms/Utils/LoopUnrollRuntime.cpp
  unittests/Transforms/Utils/UnrollLoopTest.cpp

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