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Update the docs about the fact that the loop vectorizer is enabled by default for -O3.

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llvm-svn: 179060
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Nadav Rotem 2013-04-08 21:34:49 +00:00
parent ad3e40ef0b
commit cedc2f5e24
1 changed files with 4 additions and 9 deletions
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docs/Vectorizers.rst
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@ -21,19 +21,14 @@ The Loop Vectorizer
Usage
-----
LLVM's Loop Vectorizer is now available and will be useful for many people.
It is not enabled by default, but can be enabled through clang using the
command line flag:
LLVM's Loop Vectorizer is now enabled by default for -O3.
The vectorizer can be disabled using the command line:
.. code-block:: console
$ clang -fvectorize -O3 file.c
$ clang ... -fno-vectorize file.c
If the ``-fvectorize`` flag is used then the loop vectorizer will be enabled
when running with ``-O3``, ``-O2``. When ``-Os`` is used, the loop vectorizer
will only vectorize loops that do not require a major increase in code size.
We plan to enable the Loop Vectorizer by default as part of the LLVM 3.3 release.
At this point the loop vectorizer is only enabled for -O3, and will not work for -O2 or -Os.
Command line flags
^^^^^^^^^^^^^^^^^^