# HG changeset patch
# User Christian Wimmer <christian.wimmer@oracle.com>
# Date 1363659661 25200
# Node ID 98b90a7bb764c9a2eaec524b5f3b8a94da2f4401
# Parent  63f909f4ba3a265cb9db90e99e898f70077122a5
Only stack slots in caller frame are method arguments.  Also optimize object arguments when the runtime supports it.

diff -r 63f909f4ba3a -r 98b90a7bb764 graal/com.oracle.graal.compiler/src/com/oracle/graal/compiler/alloc/LinearScan.java
--- a/graal/com.oracle.graal.compiler/src/com/oracle/graal/compiler/alloc/LinearScan.java	Mon Mar 18 20:04:50 2013 +0100
+++ b/graal/com.oracle.graal.compiler/src/com/oracle/graal/compiler/alloc/LinearScan.java	Mon Mar 18 19:21:01 2013 -0700
@@ -1051,8 +1051,7 @@
     static RegisterPriority registerPriorityOfOutputOperand(LIRInstruction op) {
         if (op instanceof MoveOp) {
             MoveOp move = (MoveOp) op;
-            if (isStackSlot(move.getInput()) && move.getInput().getKind() != Kind.Object) {
-                // method argument (condition must be equal to handleMethodArguments)
+            if (optimizeMethodArgument(move.getInput())) {
                 return RegisterPriority.None;
             }
         }
@@ -1073,6 +1072,10 @@
         return RegisterPriority.MustHaveRegister;
     }
 
+    private static boolean optimizeMethodArgument(Value value) {
+        return isStackSlot(value) && asStackSlot(value).isInCallerFrame() && (GraalOptions.IncomingMethodArgumentsGCSafe || value.getKind() != Kind.Object);
+    }
+
     /**
      * Optimizes moves related to incoming stack based arguments. The interval for the destination
      * of such moves is assigned the stack slot (which is in the caller's frame) as its spill slot.
@@ -1080,8 +1083,8 @@
     void handleMethodArguments(LIRInstruction op) {
         if (op instanceof MoveOp) {
             MoveOp move = (MoveOp) op;
-            if (isStackSlot(move.getInput()) && move.getInput().getKind() != Kind.Object) {
-                StackSlot slot = (StackSlot) move.getInput();
+            if (optimizeMethodArgument(move.getInput())) {
+                StackSlot slot = asStackSlot(move.getInput());
                 if (GraalOptions.DetailedAsserts) {
                     assert op.id() > 0 : "invalid id";
                     assert blockForId(op.id()).getPredecessorCount() == 0 : "move from stack must be in first block";
diff -r 63f909f4ba3a -r 98b90a7bb764 graal/com.oracle.graal.phases/src/com/oracle/graal/phases/GraalOptions.java
--- a/graal/com.oracle.graal.phases/src/com/oracle/graal/phases/GraalOptions.java	Mon Mar 18 20:04:50 2013 +0100
+++ b/graal/com.oracle.graal.phases/src/com/oracle/graal/phases/GraalOptions.java	Mon Mar 18 19:21:01 2013 -0700
@@ -212,6 +212,12 @@
     public static boolean IntrinsifyAESMethods               = true;
 
     /**
+     * Method arguments that are passed on the stack can be optimized by the register allocator to avoid spilling 
+     * and reloading. However, this requires that the runtime visits method arguments during stack walking.  
+     */
+    public static boolean IncomingMethodArgumentsGCSafe      = true;
+
+    /**
      * Counts the various paths taken through snippets.
      */
     public static boolean SnippetCounters = false;