Merge topic 'optimize-static-library-deps'

2e42651dff Add option to optimize link dependencies for static libraries

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !5103

5 files changed, 51 insertions, 0 deletions

diff --git a/Help/manual/cmake-properties.7.rst b/Help/manual/cmake-properties.7.rst
index 30b2a05..afdf78c 100644
--- a/Help/manual/cmake-properties.7.rst
+++ b/Help/manual/cmake-properties.7.rst
@@ -307,6 +307,7 @@ Properties on Targets
    /prop_tgt/OBJCXX_EXTENSIONS
    /prop_tgt/OBJCXX_STANDARD
    /prop_tgt/OBJCXX_STANDARD_REQUIRED
+   /prop_tgt/OPTIMIZE_DEPENDENCIES
    /prop_tgt/OSX_ARCHITECTURES_CONFIG
    /prop_tgt/OSX_ARCHITECTURES
    /prop_tgt/OUTPUT_NAME_CONFIG
diff --git a/Help/manual/cmake-variables.7.rst b/Help/manual/cmake-variables.7.rst
index d780a65..4b40917 100644
--- a/Help/manual/cmake-variables.7.rst
+++ b/Help/manual/cmake-variables.7.rst
@@ -437,6 +437,7 @@ Variables that Control the Build
    /variable/CMAKE_NINJA_OUTPUT_PATH_PREFIX
    /variable/CMAKE_NO_BUILTIN_CHRPATH
    /variable/CMAKE_NO_SYSTEM_FROM_IMPORTED
+   /variable/CMAKE_OPTIMIZE_DEPENDENCIES
    /variable/CMAKE_OSX_ARCHITECTURES
    /variable/CMAKE_OSX_DEPLOYMENT_TARGET
    /variable/CMAKE_OSX_SYSROOT
diff --git a/Help/prop_tgt/OPTIMIZE_DEPENDENCIES.rst b/Help/prop_tgt/OPTIMIZE_DEPENDENCIES.rst
new file mode 100644
index 0000000..533cf6a
--- /dev/null
+++ b/Help/prop_tgt/OPTIMIZE_DEPENDENCIES.rst
@@ -0,0 +1,38 @@
+OPTIMIZE_DEPENDENCIES
+---------------------
+
+Activates dependency optimization of static and object libraries.
+
+When this property is set to true, some dependencies for a static or object
+library may be removed at generation time if they are not necessary to build
+the library, since static and object libraries don't actually link against
+anything.
+
+If a static or object library has dependency optimization enabled, it first
+discards all dependencies. Then, it looks through all of the direct and
+indirect dependencies that it initially had, and adds them back if they meet
+any of the following criteria:
+
+* The dependency was added to the library by :command:`add_dependencies`.
+* The dependency was added to the library through a source file in the library
+  generated by a custom command that uses the dependency.
+* The dependency has any ``PRE_BUILD``, ``PRE_LINK``, or ``POST_BUILD`` custom
+  commands associated with it.
+* The dependency contains any source files that were generated by a custom
+  command.
+* The dependency contains any languages which produce side effects that are
+  relevant to the library. Currently, all languages except C, C++, Objective-C,
+  Objective-C++, assembly, and CUDA are assumed to produce side effects.
+  However, side effects from one language are assumed not to be relevant to
+  another (for example, a Fortran library is assumed to not have any side
+  effects that are relevant for a Swift library.)
+
+As an example, assume you have a static Fortran library which depends on a
+static C library, which in turn depends on a static Fortran library. The
+top-level Fortran library has optimization enabled, but the middle C library
+does not. If you build the top Fortran library, the bottom Fortran library will
+also build, but not the middle C library, since the C library does not have any
+side effects that are relevant for the Fortran library. However, if you build
+the middle C library, the bottom Fortran library will also build, even though
+it does not have any side effects that are relevant to the C library, since the
+C library does not have optimization enabled.
diff --git a/Help/release/dev/optimize-link-dependencies.rst b/Help/release/dev/optimize-link-dependencies.rst
new file mode 100644
index 0000000..cfda826
--- /dev/null
+++ b/Help/release/dev/optimize-link-dependencies.rst
@@ -0,0 +1,7 @@
+optimize-link-dependencies
+--------------------------
+
+* A new target property, :prop_tgt:`OPTIMIZE_DEPENDENCIES`, was added to
+  avoid unnecessarily building dependencies for a static library.
+* A new variable, :variable:`CMAKE_OPTIMIZE_DEPENDENCIES`, was added to
+  initialize the :prop_tgt:`OPTIMIZE_DEPENDENCIES` target property.
diff --git a/Help/variable/CMAKE_OPTIMIZE_DEPENDENCIES.rst b/Help/variable/CMAKE_OPTIMIZE_DEPENDENCIES.rst
new file mode 100644
index 0000000..eed352a
--- /dev/null
+++ b/Help/variable/CMAKE_OPTIMIZE_DEPENDENCIES.rst
@@ -0,0 +1,4 @@
+CMAKE_OPTIMIZE_DEPENDENCIES
+---------------------------
+
+Initializes the :prop_tgt:`OPTIMIZE_DEPENDENCIES` target property.