Revise llvm.vectorizer.width documentation

- clarify that vectorizer.width only applies if the vectorizer decides to
  vectorize.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182938 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/LangRef.rst b/docs/LangRef.rst
index 72648edbcb28e36648af3f1803fe6eeaf73a9b78..e07d8fe8dba1a84e5271f7bb06060d15e37793f0 100644 (file)
--- a/docs/LangRef.rst
+++ b/docs/LangRef.rst
@@ -2680,8 +2680,10 @@ determined automatically.
 '``llvm.vectorizer.width``' Metadata
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-This metadata forces the loop vectorizer to widen scalar values to a vector
-width of ``N`` rather than computing the width using a cost model.
+This metadata sets the target width of the vectorizer to ``N``. Without
+this metadata, the vectorizer will choose a width automatically.
+Regardless of this metadata, the vectorizer will only vectorize loops if
+it believes it is valid to do so.
 
 The first operand is the string ``llvm.vectorizer.width`` and the second
 operand is an integer specifying the width. For example: