[Freeciv-Dev] (PR#7195) inlining map_pos_to_index

["Jason Short" <jshort@xxxxxxxxxxxxxx>]

<URL: http://rt.freeciv.org/Ticket/Display.html?id=7195 >

The attached patch inlines map_pos_to_index.  This speeds up the server 
by 5-10% as well as making the code smaller and more readible.

This is a special case of a piece of code that NEEDS to be 
inlined/macrod, but for which macros are much inferior to inlining.  In 
a discussion some weeks ago, the maintainers decided that inlining was 
allowed but could not agree on the exact criteria for what should be 
inlined.  We agreed that function-like macros and inlining should only 
be used when it gives a helpful increase in overall speed - which 
probably means most of our current macros should be (non-inline) 
functions instead.  I think we all agreed this piece of code was a good 
candidate for inlining.

jason

Index: common/map.h
===================================================================
RCS file: /home/freeciv/CVS/freeciv/common/map.h,v
retrieving revision 1.165
diff -u -r1.165 map.h
--- common/map.h        2003/11/28 17:37:21     1.165
+++ common/map.h        2004/01/04 23:23:17
@@ -222,21 +222,7 @@
       *(pnat_x) = (2 * (map_x) - *(pnat_y) - (*(pnat_y) & 1)) / 2)          \
    : (*(pnat_x) = (map_x), *(pnat_y) = (map_y)))
 
-/* Use map_to_native_pos instead unless you know what you're doing. */
-#define map_pos_to_native_x(map_x, map_y)                                   \
-  (topo_has_flag(TF_ISO)                                                    \
-   ? (((map_x) - (map_y) + map.xsize                                        \
-       - (((map_x) + (map_y) - map.xsize) & 1)) / 2)                        \
-   : (map_x))
-#define map_pos_to_native_y(map_x, map_y)                                   \
-  (topo_has_flag(TF_ISO)                                                    \
-   ? ((map_x) + (map_y) - map.xsize)                                        \
-   : (map_y))
-
-#define map_pos_to_index(map_x, map_y)        \
-  (CHECK_MAP_POS((map_x), (map_y)),           \
-   (map_pos_to_native_x(map_x, map_y)         \
-    + map_pos_to_native_y(map_x, map_y) * map.xsize))
+static inline int map_pos_to_index(int map_x, int map_y);
 
 /* index_to_map_pos(int *, int *, int) inverts map_pos_to_index */
 #define index_to_map_pos(pmap_x, pmap_y, index) \
@@ -683,5 +669,21 @@
 #define MAP_DEFAULT_SEPARATE_POLES   TRUE
 #define MAP_MIN_SEPARATE_POLES       FALSE
 #define MAP_MAX_SEPARATE_POLES       TRUE
+
+
+/*
+ * Inline function definitions.  These are at the bottom because they may use
+ * elements defined above.
+ */
+
+static inline int map_pos_to_index(int map_x, int map_y)
+{
+  /* Note: writing this as a macro is hard; it needs temp variables. */
+  int nat_x, nat_y;
+
+  CHECK_MAP_POS(map_x, map_y);
+  map_to_native_pos(&nat_x, &nat_y, map_x, map_y);
+  return nat_x + nat_y * map.xsize;
+}
 
 #endif  /* FC__MAP_H */