[ThinLTO] Correct documentation on default number of threads

teresajohnson · teresajohnson · commit c9818ebc02b9 · 2018-08-17T13:19:36.000Z
Summary: The number of threads used for ThinLTO backend parallelism was dropped to the number of cores in r284618 to avoid oversubscribing physical cores due to hyperthreading. This updates the documentation to reflect that change. Fixes PR38610. Reviewers: pcc Subscribers: mehdi_amini, inglorion, eraman, steven_wu, dexonsmith, cfe-commits Differential Revision: https://reviews.llvm.org/D50882 llvm-svn: 340021
diff --git a/clang/docs/ThinLTO.rst b/clang/docs/ThinLTO.rst
@@ -105,7 +105,9 @@ Controlling Backend Parallelism
 -------------------------------
 .. _parallelism:
 
-By default, the ThinLTO link step will launch up to
+By default, the ThinLTO link step will launch as many
+threads in parallel as there are cores. If the number of
+cores can't be computed for the architecture, then it will launch
 ``std::thread::hardware_concurrency`` number of threads in parallel.
 For machines with hyper-threading, this is the total number of
 virtual cores. For some applications and machine configurations this
