[PATCH] D17443: [LPM] Document the new helpers to make it easy to get consistent require and preserve behavior from loop passes.

[Chandler Carruth via llvm-commits]

chandlerc created this revision.
chandlerc added a reviewer: jmolloy.
chandlerc added a subscriber: llvm-commits.
Herald added a subscriber: mcrosier.

Note that I'm pretty terrible at documentation. If what I've written isn't
helping, please just suggest what would make sense here. Happy to iterate and
get something useful.

http://reviews.llvm.org/D17443

Files:
  docs/WritingAnLLVMPass.rst

Index: docs/WritingAnLLVMPass.rst
===================================================================
--- docs/WritingAnLLVMPass.rst
+++ docs/WritingAnLLVMPass.rst
@@ -525,6 +525,14 @@
 these methods should return ``true`` if they modified the program, or ``false``
 if they didn't.
 
+A ``LoopPass`` subclass which is intended to run as part of the main loop pass
+pipeline needs to preserve all of the same *function* analyses that the other
+loop passes in its pipeline require. To make that easier,
+a ``getLoopAnalysisUsage`` function is provided by ``LoopUtils.h``. It can be
+called within the subclass's ``getAnalysisUsage`` override to get consistent
+and correct behavior. Analogously, ``INITIALIZE_PASS_DEPENDENCY(LoopPass)``
+will initialize this set of function analyses.
+
 The ``doInitialization(Loop *, LPPassManager &)`` method
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 


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