# HG changeset patch
# User Christos Kotselidis <christos.kotselidis@oracle.com>
# Date 1371807257 -7200
# Node ID 34444b095a51731b193937b2f24ea80561b29c31
# Parent  e98e021d1e7ec3c5de2c875e4c3ba10306d68095
Read nodes with attached barrier (G1) can not float

diff -r e98e021d1e7e -r 34444b095a51 graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/extended/FloatableAccessNode.java
--- a/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/extended/FloatableAccessNode.java	Fri Jun 21 11:08:10 2013 +0200
+++ b/graal/com.oracle.graal.nodes/src/com/oracle/graal/nodes/extended/FloatableAccessNode.java	Fri Jun 21 11:34:17 2013 +0200
@@ -22,6 +22,7 @@
  */
 package com.oracle.graal.nodes.extended;
 
+import com.oracle.graal.api.meta.*;
 import com.oracle.graal.nodes.*;
 import com.oracle.graal.nodes.type.*;
 
@@ -43,4 +44,13 @@
     }
 
     public abstract FloatingAccessNode asFloatingNode(ValueNode lastLocationAccess);
+
+    /**
+     * AccessNodes can float only if their location identities are not ANY_LOCATION. Furthermore, in
+     * case G1 is enabled any access (read) to the java.lang.ref.Reference.referent field which has
+     * an attached write barrier with pre-semantics can not also float.
+     */
+    public boolean canFloat() {
+        return location().getLocationIdentity() != LocationIdentity.ANY_LOCATION && getWriteBarrierType() == WriteBarrierType.NONE;
+    }
 }
diff -r e98e021d1e7e -r 34444b095a51 graal/com.oracle.graal.phases.common/src/com/oracle/graal/phases/common/FloatingReadPhase.java
--- a/graal/com.oracle.graal.phases.common/src/com/oracle/graal/phases/common/FloatingReadPhase.java	Fri Jun 21 11:08:10 2013 +0200
+++ b/graal/com.oracle.graal.phases.common/src/com/oracle/graal/phases/common/FloatingReadPhase.java	Fri Jun 21 11:34:17 2013 +0200
@@ -175,7 +175,7 @@
             StructuredGraph graph = accessNode.graph();
             assert accessNode.getNullCheck() == false;
             LocationIdentity locationIdentity = accessNode.location().getLocationIdentity();
-            if (locationIdentity != ANY_LOCATION) {
+            if (accessNode.canFloat()) {
                 ValueNode lastLocationAccess = state.getLastLocationAccess(locationIdentity);
                 FloatingAccessNode floatingNode = accessNode.asFloatingNode(lastLocationAccess);
                 floatingNode.setNullCheck(accessNode.getNullCheck());