added optimization for normal static libraries Tokutek/mongo#983

cmake/merge_archives_unix.cmake.in

@@ -40,23 +40,38 @@ FOREACH(LIB ${STATIC_LIBS})
     )
   STRING(REGEX REPLACE "\n" ";" LIB_OBJ_LIST "${LIB_OBJS}")
   STRING(REGEX REPLACE ";$" "" LIB_OBJ_LIST "${LIB_OBJ_LIST}")
-  LIST(SORT LIB_OBJ_LIST)
-  SET(SAME_OBJ_COUNT 1)
-  SET(LAST_OBJ_NAME)
-  FOREACH(OBJ ${LIB_OBJ_LIST})
-    IF(OBJ STREQUAL LAST_OBJ_NAME)
-      GET_FILENAME_COMPONENT(OBJ_NO_EXT ${OBJ} NAME_WE)
-      FILE(RENAME "${TEMP_SUBDIR}/${OBJ}" "${TEMP_SUBDIR}/${OBJ_NO_EXT}.${SAME_OBJ_COUNT}.o")
-      MATH(EXPR SAME_OBJ_COUNT "${SAME_OBJ_COUNT}+1")
-    ELSE()
-      SET(SAME_OBJ_COUNT 1)
-    ENDIF()
-    SET(LAST_OBJ_NAME "${OBJ}")
+
+  LIST(LENGTH LIB_OBJ_LIST LENGTH_WITH_DUPS)
+  SET(LIB_OBJ_LIST_NO_DUPS ${LIB_OBJ_LIST})
+  LIST(REMOVE_DUPLICATES LIB_OBJ_LIST_NO_DUPS)
+  LIST(LENGTH LIB_OBJ_LIST_NO_DUPS LENGTH_WITHOUT_DUPS)
+
+  IF(LENGTH_WITH_DUPS EQUAL LENGTH_WITHOUT_DUPS)
+    # Optimization for when lib doesn't actually have duplicate object
+    # names, we can just extract everything.
     EXECUTE_PROCESS(
-      COMMAND ${CMAKE_AR} -xN ${SAME_OBJ_COUNT} ${LIB} ${OBJ}
+      COMMAND ${CMAKE_AR} -x ${LIB}
       WORKING_DIRECTORY ${TEMP_SUBDIR}
       )
-  ENDFOREACH()
+  ELSE()
+    LIST(SORT LIB_OBJ_LIST)
+    SET(SAME_OBJ_COUNT 1)
+    SET(LAST_OBJ_NAME)
+    FOREACH(OBJ ${LIB_OBJ_LIST})
+      IF(OBJ STREQUAL LAST_OBJ_NAME)
+        GET_FILENAME_COMPONENT(OBJ_NO_EXT ${OBJ} NAME_WE)
+        FILE(RENAME "${TEMP_SUBDIR}/${OBJ}" "${TEMP_SUBDIR}/${OBJ_NO_EXT}.${SAME_OBJ_COUNT}.o")
+        MATH(EXPR SAME_OBJ_COUNT "${SAME_OBJ_COUNT}+1")
+      ELSE()
+        SET(SAME_OBJ_COUNT 1)
+      ENDIF()
+      SET(LAST_OBJ_NAME "${OBJ}")
+      EXECUTE_PROCESS(
+        COMMAND ${CMAKE_AR} -xN ${SAME_OBJ_COUNT} ${LIB} ${OBJ}
+        WORKING_DIRECTORY ${TEMP_SUBDIR}
+        )
+    ENDFOREACH()
+  ENDIF()
 
   FILE(GLOB_RECURSE LIB_OBJECTS "${TEMP_SUBDIR}/*.o")
   SET(OBJECTS ${OBJECTS} ${LIB_OBJECTS})