From f5939399f04ac96b71fae16413241d38d032ff10 Mon Sep 17 00:00:00 2001
From: Henri Verbeet <hverbeet@codeweavers.com>
Date: Wed, 10 Dec 2014 13:26:34 +0100
Subject: [PATCH] wined3d: Use __builtin_clz() in wined3d_log2i() when
 available.

---
 configure            | 33 +++++++++++++++++++++++++++++++++
 configure.ac         |  9 +++++++++
 dlls/wined3d/utils.c |  5 +++++
 include/config.h.in  |  3 +++
 4 files changed, 50 insertions(+)

diff --git a/configure b/configure
index 2677e43cc04..e67969645f6 100755
--- a/configure
+++ b/configure
@@ -16448,6 +16448,39 @@ done
 
 LIBS="$ac_save_LIBS"
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_clz" >&5
+$as_echo_n "checking for __builtin_clz... " >&6; }
+if ${ac_cv_have___builtin_clz+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+return __builtin_clz(1)
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_have___builtin_clz="yes"
+else
+  ac_cv_have___builtin_clz="no"
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_have___builtin_clz" >&5
+$as_echo "$ac_cv_have___builtin_clz" >&6; }
+if test "$ac_cv_have___builtin_clz" = "yes"
+then
+
+$as_echo "#define HAVE___BUILTIN_CLZ 1" >>confdefs.h
+
+fi
+
 
 case $host_cpu in
   *i[3456789]86*) { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether we need to define __i386__" >&5
diff --git a/configure.ac b/configure.ac
index 8110995ccc9..6f4e7194fb2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2595,6 +2595,15 @@ AC_CHECK_FUNCS(\
 )
 LIBS="$ac_save_LIBS"
 
+dnl Check for __builtin_clz
+AC_CACHE_CHECK([for __builtin_clz], ac_cv_have___builtin_clz,
+               AC_LINK_IFELSE([AC_LANG_PROGRAM(,[[return __builtin_clz(1)]])],
+               [ac_cv_have___builtin_clz="yes"], [ac_cv_have___builtin_clz="no"]))
+if test "$ac_cv_have___builtin_clz" = "yes"
+then
+    AC_DEFINE(HAVE___BUILTIN_CLZ, 1, [Define to 1 if you have the `__builtin_clz' built-in function.])
+fi
+
 dnl *** check for the need to define platform-specific symbols
 
 case $host_cpu in
diff --git a/dlls/wined3d/utils.c b/dlls/wined3d/utils.c
index d3fb1d69736..566d9211bc0 100644
--- a/dlls/wined3d/utils.c
+++ b/dlls/wined3d/utils.c
@@ -3929,8 +3929,12 @@ const struct wine_rb_functions wined3d_ffp_vertex_program_rb_functions =
     wined3d_ffp_vertex_program_key_compare,
 };
 
+/* Return the integer base-2 logarithm of x. Undefined for x == 0. */
 UINT wined3d_log2i(UINT32 x)
 {
+#ifdef HAVE___BUILTIN_CLZ
+    return __builtin_clz(x) ^ 0x1f;
+#else
     static const UINT l[] =
     {
         ~0U, 0, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
@@ -3953,6 +3957,7 @@ UINT wined3d_log2i(UINT32 x)
     UINT32 i;
 
     return (i = x >> 16) ? (x = i >> 8) ? l[x] + 24 : l[i] + 16 : (i = x >> 8) ? l[i] + 8 : l[x];
+#endif
 }
 
 const struct blit_shader *wined3d_select_blitter(const struct wined3d_gl_info *gl_info, enum wined3d_blit_op blit_op,
diff --git a/include/config.h.in b/include/config.h.in
index 0370c6d34ad..a8ae6c576bf 100644
--- a/include/config.h.in
+++ b/include/config.h.in
@@ -1281,6 +1281,9 @@
 /* Define to 1 if you have the `_vsnprintf' function. */
 #undef HAVE__VSNPRINTF
 
+/* Define to 1 if you have the `__builtin_clz' built-in function. */
+#undef HAVE___BUILTIN_CLZ
+
 /* Define to 1 if you have the `__res_getservers' function. */
 #undef HAVE___RES_GETSERVERS