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| -rw-r--r-- | llvm/docs/WritingAnLLVMPass.rst | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/llvm/docs/WritingAnLLVMPass.rst b/llvm/docs/WritingAnLLVMPass.rst index 241066842b7..4e5f8a90a93 100644 --- a/llvm/docs/WritingAnLLVMPass.rst +++ b/llvm/docs/WritingAnLLVMPass.rst @@ -525,6 +525,14 @@ interface. Implementing a loop pass is usually straightforward. 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 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
