optimization-passes.rst

Optimization passes

.. currentmodule:: llvmlite.binding

LLVM gives you the opportunity to fine-tune optimization passes. Optimization passes are managed by a pass manager. There are 2 kinds of pass managers:

• :class:`FunctionPassManager`, for optimizations that work on single functions.
• :class:`ModulePassManager`, for optimizations that work on whole modules.

To instantiate either of these pass managers, you first need to create and configure a :class:`PassManagerBuilder`.

Create a new pass manager builder. This object centralizes optimization settings.

The populate method is available:

.. method:: populate(pm)

  Populate the pass manager *pm* with the optimization passes
  configured in this pass manager builder.

  The following writable attributes are available:

  * .. attribute:: disable_unroll_loops

        If ``True``, disable loop unrolling.

  * .. attribute:: inlining_threshold

        The integer threshold for inlining one function into
        another. The higher the number, the more likely that
        inlining will occur. This attribute is write-only.

  * .. attribute:: loop_vectorize

        If ``True``, allow vectorizing loops.

  * .. attribute:: opt_level

        The general optimization level, as an integer between 0
        and 3.

  * .. attribute:: size_level

        Whether and how much to optimize for size, as an integer
        between 0 and 2.

  * .. attribute:: slp_vectorize

        If ``True``, enable the SLP vectorizer, which uses a
        different algorithm than the loop vectorizer. Both may
        be enabled at the same time.

The base class for pass managers. Use individual add_* methods or :meth:`PassManagerBuilder.populate` to add optimization passes.

• .. function:: add_constant_merge_pass()
  
     See `constmerge pass documentation <http://llvm.org/docs/Passes.html#constmerge-merge-duplicate-global-constants>`_.
  
  

• .. function:: add_dead_arg_elimination_pass()
  
     See `deadargelim pass documentation <http://llvm.org/docs/Passes.html#deadargelim-dead-argument-elimination>`_.
  
  

• .. function:: add_function_attrs_pass()
  
     See `functionattrs pass documentation <http://llvm.org/docs/Passes.html#functionattrs-deduce-function-attributes>`_.
  
  

• .. function:: add_function_inlining_pass(self, )
  
     See `inline pass documentation <http://llvm.org/docs/Passes.html#inline-function-integration-inlining>`_.
  
  

• .. function:: add_global_dce_pass()
  
     See `globaldce pass documentation <http://llvm.org/docs/Passes.html#globaldce-dead-global-elimination>`_.
  
  

• .. function:: add_global_optimizer_pass()
  
     See `globalopt pass documentation <http://llvm.org/docs/Passes.html#globalopt-global-variable-optimizer>`_.
  
  

• .. function:: add_ipsccp_pass()
  
     See `ipsccp pass documentation <http://llvm.org/docs/Passes.html#ipsccp-interprocedural-sparse-conditional-constant-propagation>`_.
  
  

• .. function:: add_dead_code_elimination_pass()
  
     See `dce pass documentation <http://llvm.org/docs/Passes.html#dce-dead-code-elimination>`_.
  
  

• .. function:: add_cfg_simplification_pass()
  
     See `simplifycfg pass documentation <http://llvm.org/docs/Passes.html#simplifycfg-simplify-the-cfg>`_.
  
  

• .. function:: add_gvn_pass()
  
     See `gvn pass documentation <http://llvm.org/docs/Passes.html#gvn-global-value-numbering>`_.
  
  

• .. function:: add_instruction_combining_pass()
  
     See `instcombine pass documentation <http://llvm.org/docs/Passes.html#passes-instcombine>`_.
  
  

• .. function:: add_licm_pass()
  
     See `licm pass documentation <http://llvm.org/docs/Passes.html#licm-loop-invariant-code-motion>`_.
  
  

• .. function:: add_sccp_pass()
  
     See `sccp pass documentation <http://llvm.org/docs/Passes.html#sccp-sparse-conditional-constant-propagation>`_.
  
  

• .. function:: add_sroa_pass()
  
     See `scalarrepl pass documentation <http://llvm.org/docs/Passes.html#scalarrepl-scalar-replacement-of-aggregates>`_.
  
     While the scalarrepl pass documentation describes the
     transformation performed by the pass added by this
     function, the pass corresponds to the ``opt -sroa``
     command-line option and not to ``opt -scalarrepl``.
  
  

• .. function:: add_type_based_alias_analysis_pass()
  
     See `tbaa metadata documentation <http://llvm.org/docs/LangRef.html#tbaa-metadata>`_.
  
  

• .. function:: add_basic_alias_analysis_pass()
  
     See `basicaa pass documentation <http://llvm.org/docs/AliasAnalysis.html#the-basicaa-pass>`_.
  

Create a new pass manager to run optimization passes on a module.

The run method is available:

.. method:: run(module)

   Run optimization passes on the
   *module*, a :class:`ModuleRef` instance.

   Returns ``True`` if the optimizations made any modification
   to the module. Otherwise returns ``False``.

Create a new pass manager to run optimization passes on a function of the given module, a :class:`ModuleRef` instance.

The following methods are available:

• .. method:: finalize()
  
     Run all the finalizers of the optimization passes.
  
  

• .. method:: initialize()
  
     Run all the initializers of the optimization passes.
  
  

• .. method:: run(function)
  
     Run optimization passes on *function*, a
     :class:`ValueRef` instance.
  
     Returns ``True`` if the optimizations made any
     modification to the module. Otherwise returns ``False``.