From 105ac14b2f671f7d448f621290404098189f424d Mon Sep 17 00:00:00 2001
From: Yangqing Jia <jiayq84@gmail.com>
Date: Mon, 23 Apr 2018 12:57:03 -0700
Subject: [PATCH] Add caching for cxx_feature_check (#573)

---
 cmake/CXXFeatureCheck.cmake | 38 +++++++++++++++++++------------------
 1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/cmake/CXXFeatureCheck.cmake b/cmake/CXXFeatureCheck.cmake
index b2a82171..c4c4d660 100644
--- a/cmake/CXXFeatureCheck.cmake
+++ b/cmake/CXXFeatureCheck.cmake
@@ -27,25 +27,27 @@ function(cxx_feature_check FILE)
     return()
   endif()
 
-  message("-- Performing Test ${FEATURE}")
-  if(CMAKE_CROSSCOMPILING)
-    try_compile(COMPILE_${FEATURE}
-            ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
-            CMAKE_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS}
-            LINK_LIBRARIES ${BENCHMARK_CXX_LIBRARIES})
-    if(COMPILE_${FEATURE})
-      message(WARNING
-            "If you see build failures due to cross compilation, try setting HAVE_${VAR} to 0")
-      set(RUN_${FEATURE} 0)
-    else()
-      set(RUN_${FEATURE} 1)
-    endif()
-  else()
+  if (NOT DEFINED COMPILE_${FEATURE})
     message("-- Performing Test ${FEATURE}")
-    try_run(RUN_${FEATURE} COMPILE_${FEATURE}
-            ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
-            CMAKE_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS}
-            LINK_LIBRARIES ${BENCHMARK_CXX_LIBRARIES})
+    if(CMAKE_CROSSCOMPILING)
+      try_compile(COMPILE_${FEATURE}
+              ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
+              CMAKE_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS}
+              LINK_LIBRARIES ${BENCHMARK_CXX_LIBRARIES})
+      if(COMPILE_${FEATURE})
+        message(WARNING
+              "If you see build failures due to cross compilation, try setting HAVE_${VAR} to 0")
+        set(RUN_${FEATURE} 0)
+      else()
+        set(RUN_${FEATURE} 1)
+      endif()
+    else()
+      message("-- Performing Test ${FEATURE}")
+      try_run(RUN_${FEATURE} COMPILE_${FEATURE}
+              ${CMAKE_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/cmake/${FILE}.cpp
+              CMAKE_FLAGS ${BENCHMARK_CXX_LINKER_FLAGS}
+              LINK_LIBRARIES ${BENCHMARK_CXX_LIBRARIES})
+    endif()
   endif()
 
   if(RUN_${FEATURE} EQUAL 0)