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Fix a grammar mistake, and add a line about the two phases that the BB/SLP vectorizers have (top-down and bottom-up). 

llvm-svn: 179566
This commit is contained in:
Nadav Rotem 2013-04-15 22:21:25 +00:00
parent c875cc1273
commit 136d50adb2
1 changed files with 5 additions and 3 deletions
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8
llvm/docs/Vectorizers.rst
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@ -5,11 +5,11 @@ Auto-Vectorization in LLVM
.. contents::
:local:
LLVM has two kind vectorizers: The :ref:`Loop Vectorizer <loop-vectorizer>`,
LLVM has two vectorizers: The :ref:`Loop Vectorizer <loop-vectorizer>`,
which operates on Loops, and the :ref:`SLP Vectorizer
<slp-vectorizer>`, which optimizes straight-line code. These vectorizers
focus on different optimization opportunities and use different techniques.
The BB vectorizer merges multiple scalars that are found in the code into
The SLP vectorizer merges multiple scalars that are found in the code into
vectors while the Loop Vectorizer widens instructions in the original loop
to operate on multiple consecutive loop iterations.
@ -318,6 +318,8 @@ into vector operations.
A[1] = a2*(a2 + b2)/b2 + 50*b2/a2;
}
The SLP-vectorizer has two phases, bottom-up, and top-down. The top-down vectorization
phase is more aggressive, but takes more time to run.
Usage
------
@ -329,7 +331,7 @@ through clang using the command line flag:
$ clang -fslp-vectorize file.c
LLVM has a second phase basic block vectorization phase
LLVM has a second basic block vectorization phase
which is more compile-time intensive (The BB vectorizer). This optimization
can be enabled through clang using the command line flag: