From 09a2b2ed3189fe12483cbd673c24ceddc2c20f3f Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 27 Jul 2009 10:14:24 +0100
Subject: [PATCH] [xlib] Fast-path the likely case of retrieving a known
 xrender_format

If we know the CPU can read pointers atomically, then we can simply peek
into the cached_xrender_formats to see if we already have a match, before
taking the mutex. (Acquiring the mutex here is a minor nuisance that
appears on the callgrind profiles.)
---
 src/cairo-xlib-display.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/cairo-xlib-display.c b/src/cairo-xlib-display.c
index 92e96bab5..d9ee90483 100644
--- a/src/cairo-xlib-display.c
+++ b/src/cairo-xlib-display.c
@@ -514,6 +514,12 @@ _cairo_xlib_display_get_xrender_format (cairo_xlib_display_t	*display,
 {
     XRenderPictFormat *xrender_format;
 
+#if ! ATOMIC_OP_NEEDS_MEMORY_BARRIER
+    xrender_format = display->cached_xrender_formats[format];
+    if (likely (xrender_format != NULL))
+	return xrender_format;
+#endif
+
     CAIRO_MUTEX_LOCK (display->mutex);
     xrender_format = display->cached_xrender_formats[format];
     if (xrender_format == NULL) {