glx/glvnd: rework dispatch functions/indices tables lookup

Rather than checking if the function name maps to a valid entry in the
respective table, just create a dummy entry at the end of each table.

This allows us to remove some unnessesary "index >= 0" checks, which get
executed quite often.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>

2 files changed, 13 insertions, 13 deletions

diff --git a/src/glx/g_glxglvnddispatchfuncs.c b/src/glx/g_glxglvnddispatchfuncs.c
index 13fbc5e..72f0f68 100644
--- a/src/glx/g_glxglvnddispatchfuncs.c
+++ b/src/glx/g_glxglvnddispatchfuncs.c
@@ -9,7 +9,8 @@
 #include "g_glxglvnddispatchindices.h"
 
 const int DI_FUNCTION_COUNT = DI_LAST_INDEX;
-int __glXDispatchTableIndices[DI_LAST_INDEX];
+/* Allocate an extra 'dummy' to ease lookup. See FindGLXFunction() */
+int __glXDispatchTableIndices[DI_LAST_INDEX + 1];
 const __GLXapiExports *__glXGLVNDAPIExports;
 
 const char * const __glXDispatchTableStrings[DI_LAST_INDEX] = {
@@ -922,7 +923,8 @@ static Bool dispatch_glXWaitForSbcOML(Display *dpy, GLXDrawable drawable,
 #undef __FETCH_FUNCTION_PTR
 
 
-const void * const __glXDispatchFunctions[DI_LAST_INDEX] = {
+/* Allocate an extra 'dummy' to ease lookup. See FindGLXFunction() */
+const void * const __glXDispatchFunctions[DI_LAST_INDEX + 1] = {
 #define __ATTRIB(field) \
     [DI_##field] = (void *)dispatch_##field
 
@@ -972,5 +974,6 @@ const void * const __glXDispatchFunctions[DI_LAST_INDEX] = {
     __ATTRIB(glXWaitForMscOML),
     __ATTRIB(glXWaitForSbcOML),
 
+    [DI_LAST_INDEX] = NULL,
 #undef __ATTRIB
 };
diff --git a/src/glx/glxglvnd.c b/src/glx/glxglvnd.c
index 96cd1fd..b7252a7 100644
--- a/src/glx/glxglvnd.c
+++ b/src/glx/glxglvnd.c
@@ -17,7 +17,7 @@ static void *__glXGLVNDGetProcAddress(const GLubyte *procName)
     return glXGetProcAddressARB(procName);
 }
 
-static int FindGLXFunction(const GLubyte *name)
+static unsigned FindGLXFunction(const GLubyte *name)
 {
     unsigned first = 0;
     unsigned last = DI_FUNCTION_COUNT - 1;
@@ -34,26 +34,23 @@ static int FindGLXFunction(const GLubyte *name)
         else
             return middle;
     }
-    return -1;
+
+    /* Just point to the dummy entry at the end of the respective table */
+    return DI_FUNCTION_COUNT;
 }
 
 static void *__glXGLVNDGetDispatchAddress(const GLubyte *procName)
 {
-    int internalIndex = FindGLXFunction(procName);
-
-    if (internalIndex >= 0) {
-        return __glXDispatchFunctions[internalIndex];
-    }
+    unsigned internalIndex = FindGLXFunction(procName);
 
-    return NULL;
+    return __glXDispatchFunctions[internalIndex];
 }
 
 static void __glXGLVNDSetDispatchIndex(const GLubyte *procName, int index)
 {
-    int internalIndex = FindGLXFunction(procName);
+    unsigned internalIndex = FindGLXFunction(procName);
 
-    if (internalIndex >= 0)
-        __glXDispatchTableIndices[internalIndex] = index;
+    __glXDispatchTableIndices[internalIndex] = index;
 }
 
 _X_EXPORT Bool __glx_Main(uint32_t version, const __GLXapiExports *exports,