--- old/src/cpu/x86/vm/vm_version_x86.cpp	2014-02-07 00:45:28.000000000 -0800
+++ new/src/cpu/x86/vm/vm_version_x86.cpp	2014-02-07 00:45:28.000000000 -0800
@@ -600,13 +600,6 @@
       }
     }
 
-    // Use count leading zeros count instruction if available.
-    if (supports_lzcnt()) {
-      if (FLAG_IS_DEFAULT(UseCountLeadingZerosInstruction)) {
-        UseCountLeadingZerosInstruction = true;
-      }
-    }
-
     // some defaults for AMD family 15h
     if ( cpu_family() == 0x15 ) {
       // On family 15h processors default is no sw prefetch
@@ -692,6 +685,29 @@
     }
 #endif // COMPILER2
 
+  // Use count leading zeros count instruction if available.
+  if (supports_lzcnt()) {
+    if (FLAG_IS_DEFAULT(UseCountLeadingZerosInstruction)) {
+      UseCountLeadingZerosInstruction = true;
+    }
+  }
+
+  //Use count trailing zeros instruction if available
+  if (FLAG_IS_DEFAULT(UseCountTrailingZerosInstruction)) {
+    if (supports_bmi1()) {
+      UseCountTrailingZerosInstruction = true;
+    }
+  }
+
+  if (supports_bmi1()) {
+    if (FLAG_IS_DEFAULT(UseBMI1Instructions)) {
+      UseBMI1Instructions = true;
+    }
+  } else if (UseBMI1Instructions) {
+    warning("BMI1 instructions are not available on this CPU");
+    FLAG_SET_DEFAULT(UseBMI1Instructions, false);
+  }
+
   // Use population count instruction if available.
   if (supports_popcnt()) {
     if (FLAG_IS_DEFAULT(UsePopCountInstruction)) {