diff -r dfe27f03244a -r e9ff18c4ace7 src/share/vm/opto/matcher.cpp
--- a/src/share/vm/opto/matcher.cpp	Tue Jun 01 11:48:33 2010 -0700
+++ b/src/share/vm/opto/matcher.cpp	Wed Jun 02 22:45:42 2010 -0700
@@ -1334,7 +1334,7 @@
       if( j == max_scan )       // No post-domination before scan end?
         return true;            // Then break the match tree up
     }
-    if (m->is_DecodeN() && Matcher::clone_shift_expressions) {
+    if (m->is_DecodeN() && Matcher::narrow_oop_use_complex_address()) {
       // These are commonly used in address expressions and can
       // efficiently fold into them on X64 in some cases.
       return false;
@@ -2110,8 +2110,8 @@
         _null_check_tests.push(proj);
         Node* val = cmp->in(1);
 #ifdef _LP64
-        if (UseCompressedOops && !Matcher::clone_shift_expressions &&
-            val->bottom_type()->isa_narrowoop()) {
+        if (val->bottom_type()->isa_narrowoop() &&
+            !Matcher::narrow_oop_use_complex_address()) {
           //
           // Look for DecodeN node which should be pinned to orig_proj.
           // On platforms (Sparc) which can not handle 2 adds
@@ -2127,6 +2127,9 @@
             if (d->is_DecodeN() && d->in(1) == val) {
               val = d;
               val->set_req(0, NULL); // Unpin now.
+              // Mark this as special case to distinguish from
+              // a regular case: CmpP(DecodeN, NULL).
+              val = (Node*)(((intptr_t)val) | 1);
               break;
             }
           }
@@ -2146,9 +2149,21 @@
   for( uint i=0; i < cnt; i+=2 ) {
     Node *test = _null_check_tests[i];
     Node *val = _null_check_tests[i+1];
+    bool is_decoden = ((intptr_t)val) & 1;
+    val = (Node*)(((intptr_t)val) & ~1);
     if (has_new_node(val)) {
+      Node* new_val = new_node(val);
+      if (is_decoden) {
+        assert(val->is_DecodeN() && val->in(0) == NULL, "sanity");
+        // Note: new_val may have a control edge if
+        // the original ideal node DecodeN was matched before
+        // it was unpinned in Matcher::collect_null_checks().
+        // Unpin the mach node and mark it.
+        new_val->set_req(0, NULL);
+        new_val = (Node*)(((intptr_t)new_val) | 1);
+      }
       // Is a match-tree root, so replace with the matched value
-      _null_check_tests.map(i+1, new_node(val));
+      _null_check_tests.map(i+1, new_val);
     } else {
       // Yank from candidate list
       _null_check_tests.map(i+1,_null_check_tests[--cnt]);