SUGGESTED FIX

repo:       /net/jano2.sfbay/export2/hotspot/hg/hotspot-comp.clean
changeset:  51:daf38130e60d
user:       never
date:       Tue Mar 18 23:44:46 2008 -0700
description:
6676841: ClearArrayNode::Identity is incorrect for 64-bit
Summary: ClearArrayNode::Identity should use TypeX instead of TypeInt
Reviewed-by: jrose, kvn, sgoldman

files:
src/share/vm/opto/memnode.cpp
                                     

SUGGESTED FIX

diff -r 6dbf1a175d6b src/share/vm/opto/memnode.cpp
--- a/src/share/vm/opto/memnode.cpp     Fri Mar 14 16:40:42 2008 -0700
+++ b/src/share/vm/opto/memnode.cpp     Tue Mar 18 11:01:12 2008 -0700
@@ -1881,7 +1881,7 @@ uint ClearArrayNode::match_edge(uint idx
 //------------------------------Identity---------------------------------------
 // Clearing a zero length array does nothing
 Node *ClearArrayNode::Identity( PhaseTransform *phase ) {
-  return phase->type(in(2))->higher_equal(TypeInt::ZERO)  ? in(1) : this;
+  return phase->type(in(2))->higher_equal(TypeX::ZERO)  ? in(1) : this;
 }

 //------------------------------Idealize---------------------------------------
@@ -1954,6 +1954,11 @@ Node* ClearArrayNode::clear_memory(Node*
                                    Node* start_offset,
                                    Node* end_offset,
                                    PhaseGVN* phase) {
+  if (start_offset == end_offset) {
+    // nothing to do
+    return mem;
+  }
+
   Compile* C = phase->C;
   int unit = BytesPerLong;
   Node* zbase = start_offset;
@@ -1979,6 +1984,11 @@ Node* ClearArrayNode::clear_memory(Node*
                                    intptr_t start_offset,
                                    intptr_t end_offset,
                                    PhaseGVN* phase) {
+  if (start_offset == end_offset) {
+    // nothing to do
+    return mem;
+  }
+
   Compile* C = phase->C;
   assert((end_offset % BytesPerInt) == 0, "odd end offset");
   intptr_t done_offset = end_offset;
                                     

EVALUATION

do as suggested.