[Docs] Add a note clarifying how to get good test performances.

Differential Revision:  https://reviews.llvm.org/D56337

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351885 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/docs/TestingGuide.rst b/docs/TestingGuide.rst
index e3db60dd9e788de898bf97c9d2f96e82e961db2d..ceb2023e750a59f3e3fdee8adc184e5681d6b744 100644 (file)
--- a/docs/TestingGuide.rst
+++ b/docs/TestingGuide.rst
@@ -107,6 +107,13 @@ To run all of the LLVM regression tests use the check-llvm target:
 
     % make check-llvm
 
+In order to get reasonable testing performance, build LLVM and subprojects
+in release mode, i.e.
+
+.. code-block:: bash
+
+    % cmake -DCMAKE_BUILD_TYPE="Release"
+
 If you have `Clang <http://clang.llvm.org/>`_ checked out and built, you
 can run the LLVM and Clang tests simultaneously using: