@@ -, +, @@ 
---
 configure.ac                        | 1 +
 scons/gallium.py                    | 2 ++
 src/gallium/auxiliary/util/u_math.h | 2 +-
 3 files changed, 4 insertions(+), 1 deletion(-)
--- a/configure.ac	
+++ a/configure.ac	
@@ -171,6 +171,7 @@ fi
 dnl Check for compiler builtins
 AX_GCC_BUILTIN([__builtin_bswap32])
 AX_GCC_BUILTIN([__builtin_bswap64])
+AX_GCC_BUILTIN([__builtin_clrsb])
 AX_GCC_BUILTIN([__builtin_clz])
 AX_GCC_BUILTIN([__builtin_clzll])
 AX_GCC_BUILTIN([__builtin_ctz])
--- a/scons/gallium.py	
+++ a/scons/gallium.py	
@@ -607,6 +607,8 @@ def generate(env):
             ]
         if distutils.version.LooseVersion(ccversion) >= distutils.version.LooseVersion('4.5'):
             cppdefines += ['HAVE___BUILTIN_UNREACHABLE']
+        if distutils.version.LooseVersion(ccversion) >= distutils.version.LooseVersion('4.7'):
+            cppdefines += ['HAVE___BUILTIN_CLRSB']
 
     # Load tools
     env.Tool('lex')
--- a/src/gallium/auxiliary/util/u_math.h	
+++ a/src/gallium/auxiliary/util/u_math.h	
@@ -561,7 +561,7 @@ util_last_bit(unsigned u)
 static INLINE unsigned
 util_last_bit_signed(int i)
 {
-#if defined(__GNUC__) && ((__GNUC__ * 100 + __GNUC_MINOR__) >= 407) && !defined(__INTEL_COMPILER)
+#ifdef HAVE___BUILTIN_CLRSB
    return 31 - __builtin_clrsb(i);
 #else
    if (i >= 0)
--