From d1085af3ac626603be61d069baa0277575da29b6 Mon Sep 17 00:00:00 2001
From: Carles Fernandez <carles.fernandez@gmail.com>
Date: Fri, 21 Aug 2020 16:31:57 +0200
Subject: [PATCH] Activate usage of cpu_features

---
 CMakeLists.txt                                           | 5 +++++
 docs/changelog.md                                        | 9 +++++++++
 .../libs/volk_gnsssdr_module/volk_gnsssdr/CMakeLists.txt | 1 -
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6a7621b8f..3d25ff1c5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1168,6 +1168,11 @@ if(NOT VOLKGNSSSDR_FOUND)
             INTERFACE_INCLUDE_DIRECTORIES "${VOLK_GNSSSDR_INCLUDE_DIRS}"
             INTERFACE_LINK_LIBRARIES "${VOLK_GNSSSDR_LIBRARIES}"
         )
+        if(CMAKE_VERSION VERSION_GREATER 3.0) # and GCC, and Clang and PYTHON...
+            set_target_properties(Volkgnsssdr::volkgnsssdr PROPERTIES
+                INTERFACE_LINK_LIBRARIES ${CMAKE_BINARY_DIR}/volk_gnsssdr_module/install/lib/${CMAKE_FIND_LIBRARY_PREFIXES}cpu_features${CMAKE_STATIC_LIBRARY_SUFFIX}
+            )
+        endif()
     endif()
 
     if(CMAKE_VERSION VERSION_LESS 3.2)
diff --git a/docs/changelog.md b/docs/changelog.md
index ce8bcd36d..32c6239c6 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -31,6 +31,15 @@ SPDX-FileCopyrightText: 2011-2020 Carles Fernandez-Prades <carles.fernandez@cttc
 - Replaced `git://` by `https://` as the used protocol when downloading Gflags,
   so it can work through firewalls requiring authentication.
 - Fixed static linking of the matio library when downloaded and built by CMake.
+- Improved CPU feature detection by switching to Google's
+  [cpu_features](https://github.com/google/cpu_features) library: The
+  `volk_gnsssdr` library had its own CPU feature detection methods, which were
+  not totally reliable and difficult to implement across compilers and OSes.
+  This is now handled by the `cpu_features` library, thus building upon that
+  expertise. Since that library has higher dependency version requirements than
+  GNSS-SDR, the old method is still used in old development environments. No
+  extra dependency is needed. This change is transparent to the user, since
+  everything is managed by the CMake scripts.
 
 ### Improvements in Usability:
 
diff --git a/src/algorithms/libs/volk_gnsssdr_module/volk_gnsssdr/CMakeLists.txt b/src/algorithms/libs/volk_gnsssdr_module/volk_gnsssdr/CMakeLists.txt
index 73cd2b17b..41f3ad2c0 100644
--- a/src/algorithms/libs/volk_gnsssdr_module/volk_gnsssdr/CMakeLists.txt
+++ b/src/algorithms/libs/volk_gnsssdr_module/volk_gnsssdr/CMakeLists.txt
@@ -234,7 +234,6 @@ if(CMAKE_VERSION VERSION_GREATER 3.0)
     set(USE_CPU_FEATURES ON)
     add_subdirectory(cpu_features)
 endif()
-set(USE_CPU_FEATURES OFF)
 
 # Python
 include(VolkPython) # sets PYTHON_EXECUTABLE