dispatch: Try harder to avoid calling the resolver

Our caller may load (eg) epoxy_glAlphaFunc, which is a function pointer, and then call through that value multiple times. Until the caller re-examines the value of that function pointer, which is a copy relocation in the executable, repeated calls mean repeated work resolving the GL function. We can't make the caller reinspect the variable, but the resolver function can avoid doing redundant work. Fixes: #171 Signed-off-by: Adam Jackson <[email protected]>
anholt · May 17, 2018 · 707f50e · 707f50e
1 parent c00c889
commit 707f50e
Showing 1 changed file with 5 additions and 3 deletions.
diff --git a/src/dispatch_common.h b/src/dispatch_common.h
@@ -85,18 +85,20 @@
 #define WRAPPER(x) x ## _wrapped
 
 #define GEN_GLOBAL_REWRITE_PTR(name, args, passthrough)          \
-    static void EPOXY_CALLSPEC                                        \
+    static void EPOXY_CALLSPEC                                   \
     name##_global_rewrite_ptr args                               \
     {                                                            \
-        name = (void *)name##_resolver();                        \
+        if (name == (void *)name##_global_rewrite_ptr)           \
+            name = (void *)name##_resolver();                    \
         name passthrough;                                        \
     }
 
 #define GEN_GLOBAL_REWRITE_PTR_RET(ret, name, args, passthrough) \
     static ret EPOXY_CALLSPEC                                    \
     name##_global_rewrite_ptr args                               \
     {                                                            \
-        name = (void *)name##_resolver();                        \
+        if (name == (void *)name##_global_rewrite_ptr)           \
+            name = (void *)name##_resolver();                    \
         return name passthrough;                                 \
     }