7eb899cbcd
We peform runtime folding, but do not currently emit remarks when it is performed. This is because it comes from the runtime library and is beyond the users control. However, people may still wish to view this and similar information easily, so we can enable this behaviour using a special flag to enable verbose remarks. Reviewed By: jdoerfert Differential Revision: https://reviews.llvm.org/D109627
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3.7 KiB
ReStructuredText
114 lines
3.7 KiB
ReStructuredText
OpenMP Optimization Remarks
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===========================
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The :doc:`OpenMP-Aware optimization pass </optimizations/OpenMPOpt>` is able to
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generate compiler remarks for performed and missed optimisations. To emit them,
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pass ``-Rpass=openmp-opt``, ``-Rpass-analysis=openmp-opt``, and
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``-Rpass-missed=openmp-opt`` to the Clang invocation. For more information and
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features of the remark system the clang documentation should be consulted:
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+ `Clang options to emit optimization reports <https://clang.llvm.org/docs/UsersManual.html#options-to-emit-optimization-reports>`_
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+ `Clang diagnostic and remark flags <https://clang.llvm.org/docs/ClangCommandLineReference.html#diagnostic-flags>`_
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+ The `-foptimization-record-file flag
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<https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-foptimization-record-file>`_
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and the `-fsave-optimization-record flag
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<https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang1-fsave-optimization-record>`_
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OpenMP Remarks
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--------------
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.. toctree::
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:hidden:
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:maxdepth: 1
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OMP100
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OMP101
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OMP102
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OMP110
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OMP111
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OMP112
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OMP113
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OMP120
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OMP121
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OMP130
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OMP131
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OMP132
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OMP133
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OMP140
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OMP150
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OMP160
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OMP170
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OMP180
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.. list-table::
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:widths: 15 15 70
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:header-rows: 1
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* - Diagnostics Number
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- Diagnostics Kind
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- Diagnostics Description
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* - :ref:`OMP100 <omp100>`
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- Analysis
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- Potentially unknown OpenMP target region caller.
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* - :ref:`OMP101 <omp101>`
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- Analysis
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- Parallel region is used in unknown / unexpected ways. Will not attempt to
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rewrite the state machine.
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* - :ref:`OMP102 <omp102>`
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- Analysis
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- Parallel region is not called from a unique kernel. Will not attempt to
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rewrite the state machine.
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* - :ref:`OMP110 <omp110>`
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- Optimization
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- Moving globalized variable to the stack.
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* - :ref:`OMP111 <omp111>`
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- Optimization
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- Replaced globalized variable with X bytes of shared memory.
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* - :ref:`OMP112 <omp112>`
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- Missed
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- Found thread data sharing on the GPU. Expect degraded performance due to
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data globalization.
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* - :ref:`OMP113 <omp113>`
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- Missed
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- Could not move globalized variable to the stack. Variable is potentially
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captured in call. Mark parameter as `__attribute__((noescape))` to
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override.
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* - :ref:`OMP120 <omp120>`
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- Optimization
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- Transformed generic-mode kernel to SPMD-mode.
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* - :ref:`OMP121 <omp121>`
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- Analysis
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- Value has potential side effects preventing SPMD-mode execution. Add
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`__attribute__((assume(\"ompx_spmd_amenable\")))` to the called function
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to override.
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* - :ref:`OMP130 <omp130>`
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- Optimization
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- Removing unused state machine from generic-mode kernel.
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* - :ref:`OMP131 <omp131>`
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- Optimization
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- Rewriting generic-mode kernel with a customized state machine.
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* - :ref:`OMP132 <omp132>`
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- Analysis
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- Generic-mode kernel is executed with a customized state machine that
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requires a fallback.
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* - :ref:`OMP133 <omp133>`
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- Analysis
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- Call may contain unknown parallel regions. Use
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`__attribute__((assume("omp_no_parallelism")))` to override.
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* - :ref:`OMP140 <omp140>`
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- Analysis
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- Could not internalize function. Some optimizations may not be possible.
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* - :ref:`OMP150 <omp150>`
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- Optimization
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- Parallel region merged with parallel region at <location>.
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* - :ref:`OMP160 <omp160>`
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- Optimization
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- Removing parallel region with no side-effects.
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* - :ref:`OMP170 <omp170>`
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- Optimization
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- OpenMP runtime call <call> deduplicated.
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* - :ref:`OMP180 <omp180>`
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- Optimization
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- Replacing OpenMP runtime call <call> with <value>.
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