Remove FAQ about increasing inlining threshold for Clang.
- Changing the inlining threshold for Clang as described has a minimal
effect on user performance.
- The problem that originally prompted the belief that it did was
due to an erroneous CXX flag configuration (in user code).
Change-Id: I03017241c0f87b8dcefb8c984ec3b192afd97fc2
diff --git a/docs/source/faqs.rst b/docs/source/faqs.rst
index badf90a..d851038 100644
--- a/docs/source/faqs.rst
+++ b/docs/source/faqs.rst
@@ -33,44 +33,6 @@
NDK. It has worse performance than the full fledged glog library
and is much harder to control and use.
-#. Increase the inlining threshold in Clang for Eigen.
-
- By default, the inlining threshold (evaluated on a heuristic used by LLVM to
- guess how expensive a function will be to inline) can hobble Eigen, resulting in
- poor performance.
-
- Ceres itself will always be compiled with an increased inline threshold
- (currently 600) when compiled with Clang. To experiment with this in your
- own code, you can use the following:
-
-.. code-block:: cmake
-
- # If using CMake >= 2.8.12:
- # We recommend you use target_compile_options() to add the inlining flags
- # to specific targets for fine grained control:
- #
- # Use a larger inlining threshold for Clang, since it can hobble Eigen,
- # resulting in reduced performance. The -Qunused-arguments is needed because
- # CMake passes the inline threshold to the linker and clang complains about
- # it (and dies, if compiling with -Werror).
- target_compile_options(<YOUR_TARGET_NAME> PUBLIC
- $<$<CXX_COMPILER_ID:Clang>:-Qunused-arguments -mllvm -inline-threshold=600>)
-
-.. code-block:: cmake
-
- # If using CMake < 2.8.12:
- # On CMake < 2.8.12 target_compile_options() is not available, so you
- # cannot add the flags only on a per-target level and must instead set them
- # for all targets declared after the flags are updated:
- #
- # Use a larger inlining threshold for Clang, since it can hobble Eigen,
- # resulting in reduced performance. The -Qunused-arguments is needed because
- # CMake passes the inline threshold to the linker and clang complains about
- # it (and dies, if compiling with -Werror).
- if (CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
- set(CMAKE_CXX_FLAGS
- "${CMAKE_CXX_FLAGS} -Qunused-arguments -mllvm -inline-threshold=600")
- endif()
Modeling
========
