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Diffstat (limited to 'llvm/docs/AliasAnalysis.rst')
| -rw-r--r-- | llvm/docs/AliasAnalysis.rst | 33 |
1 files changed, 3 insertions, 30 deletions
diff --git a/llvm/docs/AliasAnalysis.rst b/llvm/docs/AliasAnalysis.rst index 0a5cb00a48d..14decfeca6e 100644 --- a/llvm/docs/AliasAnalysis.rst +++ b/llvm/docs/AliasAnalysis.rst @@ -389,11 +389,6 @@ in its ``getAnalysisUsage`` that it does so. Some passes attempt to use ``AU.addPreserved<AliasAnalysis>``, however this doesn't actually have any effect. -``AliasAnalysisCounter`` (``-count-aa``) are implemented as ``ModulePass`` -classes, so if your alias analysis uses ``FunctionPass``, it won't be able to -use these utilities. If you try to use them, the pass manager will silently -route alias analysis queries directly to ``BasicAliasAnalysis`` instead. - Similarly, the ``opt -p`` option introduces ``ModulePass`` passes between each pass, which prevents the use of ``FunctionPass`` alias analysis passes. @@ -408,17 +403,10 @@ before it appears in an alias query. However, popular clients such as ``GVN`` don't support this, and are known to trigger errors when run with the ``AliasAnalysisDebugger``. -Due to several of the above limitations, the most obvious use for the -``AliasAnalysisCounter`` utility, collecting stats on all alias queries in a -compilation, doesn't work, even if the ``AliasAnalysis`` implementations don't -use ``FunctionPass``. There's no way to set a default, much less a default -sequence, and there's no way to preserve it. - The ``AliasSetTracker`` class (which is used by ``LICM``) makes a -non-deterministic number of alias queries. This can cause stats collected by -``AliasAnalysisCounter`` to have fluctuations among identical runs, for -example. Another consequence is that debugging techniques involving pausing -execution after a predetermined number of queries can be unreliable. +non-deterministic number of alias queries. This can cause debugging techniques +involving pausing execution after a predetermined number of queries to be +unreliable. Many alias queries can be reformulated in terms of other alias queries. When multiple ``AliasAnalysis`` queries are chained together, it would make sense to @@ -676,21 +664,6 @@ you're using the ``AliasSetTracker`` class. To use it, use something like: % opt -ds-aa -print-alias-sets -disable-output -The ``-count-aa`` pass -^^^^^^^^^^^^^^^^^^^^^^ - -The ``-count-aa`` pass is useful to see how many queries a particular pass is -making and what responses are returned by the alias analysis. As an example: - -.. code-block:: bash - - % opt -basicaa -count-aa -ds-aa -count-aa -licm - -will print out how many queries (and what responses are returned) by the -``-licm`` pass (of the ``-ds-aa`` pass) and how many queries are made of the -``-basicaa`` pass by the ``-ds-aa`` pass. This can be useful when debugging a -transformation or an alias analysis implementation. - The ``-aa-eval`` pass ^^^^^^^^^^^^^^^^^^^^^ |
