based from gentoo
http://bugs.gentoo.org/show_bug.cgi?id=94664

--- ./configure.orig	2005-05-05 08:15:43.000000000 +0100
+++ ./configure	2005-05-31 23:32:26.000000000 +0100
@@ -9,6 +9,7 @@
 x86_cpus="i386,i486,i586,i686,pentium,pentiumpro,${x86_mmx_cpus}"
 x86_cmov_cpus="i686,pentiumpro,pentium2,pentium3,pentium3m,pentium-m,pentium4,"
 x86_cmov_cpus="pentium4m,prescott,athlon,athlon-xp,c3-2"
+x86_64_cpus="x86-64,athlon64,k8,opteron,athlon-fx"
 
 # default parameters
 compile_type="release"
@@ -223,6 +224,14 @@
     cpu="x86"
 fi
 
+is_x86_64_cpu() {
+    expr ",${x86_64_cpus}," : ".*,$1," > /dev/null
+}
+
+if is_x86_64_cpu "$cpu" ; then
+    cpu="x86_64"
+fi
+
 case "$cpu" in
   x86)
   ;;
--- ./configure~	2005-09-04 11:48:59.000000000 +0300
+++ ./configure	2005-09-04 11:49:01.000000000 +0300
@@ -237,12 +237,13 @@
   x86)
   ;;
   x86_64)
-    if [ "`$cc -dumpmachine | grep x86_64 | cut -d- -f1`" = "x86_64" -a \
-         -z "`echo $CFLAGS | grep -- -m32`"  ]; then
-      cpu="x86_64"
-    else
-      cpu="x86"
-    fi
+	if [ "`$cc -dumpmachine | grep x86_64 | cut -d- -f1`" = "x86_64" ]; then
+		if [ -z "`echo $CFLAGS | grep -- -m32`"  ]; then
+			cpu="x86_64"
+		else
+			cpu="x86"
+		fi
+	fi
   ;;
   # armv4l is a subset of armv5tel
   armv4l|armv5tel)