--- configure.orig	2014-02-11 23:45:49.000000000 +0100
+++ configure	2014-02-11 23:50:50.000000000 +0100
@@ -19096,24 +19096,30 @@
 	esac
     fi
 
+    if $CC -v 2>&1 | grep clang > /dev/null; then
+	CLANG=yes
+    else
+	CLANG=no
+    fi
+
     case "$optimize" in
 	-O|"-O "*)
 	    optimize="-O"
 	    optimize="$optimize -fforce-mem"
-	    optimize="$optimize -fforce-addr"
+	    test $CLANG = no && optimize="$optimize -fforce-addr"
 	    : #x optimize="$optimize -finline-functions"
 	    : #- optimize="$optimize -fstrength-reduce"
-	    optimize="$optimize -fthread-jumps"
-	    optimize="$optimize -fcse-follow-jumps"
-	    optimize="$optimize -fcse-skip-blocks"
+	    test $CLANG = no && optimize="$optimize -fthread-jumps"
+	    test $CLANG = no && optimize="$optimize -fcse-follow-jumps"
+	    test $CLANG = no && optimize="$optimize -fcse-skip-blocks"
 	    : #x optimize="$optimize -frerun-cse-after-loop"
 	    : #x optimize="$optimize -frerun-loop-opt"
 	    : #x optimize="$optimize -fgcse"
 	    optimize="$optimize -fexpensive-optimizations"
-	    optimize="$optimize -fregmove"
+	    test $CLANG = no && optimize="$optimize -fregmove"
 	    : #* optimize="$optimize -fdelayed-branch"
 	    : #x optimize="$optimize -fschedule-insns"
-	    optimize="$optimize -fschedule-insns2"
+	    test $CLANG = no && optimize="$optimize -fschedule-insns2"
 	    : #? optimize="$optimize -ffunction-sections"
 	    : #? optimize="$optimize -fcaller-saves"
 	    : #> optimize="$optimize -funroll-loops"