doc: add subsections.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170568 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/Vectorizers.rst b/docs/Vectorizers.rst
index 9507fd6953bff43212987522957b9371e65314e7..f585c630f94ef5bcde4747850ecbf4ab9bb24585 100644 (file)
--- a/docs/Vectorizers.rst
+++ b/docs/Vectorizers.rst
@@ -12,6 +12,9 @@ original loop to operate on multiple consecutive loop iterations.
 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:
@@ -208,6 +211,9 @@ The Y-axis shows time in msec. Lower is better.
 The Basic Block Vectorizer
 ==========================
 
+Usage
+^^^^^^
+
 The Basic Block Vectorizer is not enabled by default, but it can be enabled
 through clang using the command line flag:
 
@@ -215,6 +221,9 @@ through clang using the command line flag:
 
    $ clang -fslp-vectorize file.c 
 
+Details
+^^^^^^^
+
 The goal of basic-block vectorization (a.k.a. superword-level parallelism) is
 to combine similar independent instructions within simple control-flow regions
 into vector instructions. Memory accesses, arithemetic operations, comparison