--- a/graal/com.oracle.graal.hotspot.amd64/src/com/oracle/graal/hotspot/amd64/AMD64HotSpotLIRGenerator.java	Mon Apr 28 16:07:18 2014 +0200
+++ b/graal/com.oracle.graal.hotspot.amd64/src/com/oracle/graal/hotspot/amd64/AMD64HotSpotLIRGenerator.java	Mon Apr 28 10:14:36 2014 -0700
@@ -548,6 +548,14 @@
         return result;
     }
 
+    public static Register asNarrowReg(Value value) {
+        if (value.getPlatformKind() != NarrowOopStamp.NarrowOop) {
+            throw new InternalError("needed NarrowOop got: " + value.getKind());
+        } else {
+            return asRegister(value);
+        }
+    }
+
     public Value emitAtomicReadAndWrite(Value address, Value newValue) {
         PlatformKind kind = newValue.getPlatformKind();
         Kind memKind = getMemoryKind(kind);
@@ -570,6 +578,11 @@
         }
 
         @Override
+        protected void verify() {
+            assert y instanceof Constant || y.getPlatformKind() == NarrowOopStamp.NarrowOop;
+        }
+
+        @Override
         public void emitCode(CompilationResultBuilder crb, AMD64MacroAssembler masm) {
             if (state != null) {
                 crb.recordImplicitException(masm.position(), state);
@@ -589,7 +602,7 @@
                     masm.cmpl(x.toAddress(), 0xdeaddead);
                 }
             } else {
-                masm.cmpl(asRegister(y), x.toAddress());
+                masm.cmpl(asNarrowReg(y), x.toAddress());
             }
         }
     }

--- a/graal/com.oracle.graal.hotspot.amd64/src/com/oracle/graal/hotspot/amd64/AMD64HotSpotNodeLIRBuilder.java	Mon Apr 28 16:07:18 2014 +0200
+++ b/graal/com.oracle.graal.hotspot.amd64/src/com/oracle/graal/hotspot/amd64/AMD64HotSpotNodeLIRBuilder.java	Mon Apr 28 10:14:36 2014 -0700
@@ -65,26 +65,33 @@
         return result;
     }
 
-    private void emitCompareCompressedMemory(IfNode ifNode, ValueNode value, Access access, CompareNode compare) {
+    private void emitCompareCompressedMemory(IfNode ifNode, ValueNode valueNode, Access access, CompareNode compare) {
+        Value value;
+        // This works by embedding the compressed form for constants, so force a constant instead of
+        // respecting what operand() would return.
+        if (valueNode.isConstant()) {
+            value = valueNode.asConstant();
+        } else {
+            value = gen.load(operand(valueNode));
+        }
+        AMD64AddressValue address = makeAddress(access);
+
         Condition cond = compare.condition();
-        LabelRef trueLabel = getLIRBlock(ifNode.trueSuccessor());
-        LabelRef falseLabel = getLIRBlock(ifNode.falseSuccessor());
-        double trueLabelProbability = ifNode.probability(ifNode.trueSuccessor());
         Value left;
         Value right;
         if (access == filterCompression(compare.x())) {
-            if (value.isConstant()) {
-                left = value.asConstant();
-            } else {
-                left = gen.loadNonConst(operand(value));
-            }
-            right = makeAddress(access);
+            left = value;
+            right = address;
         } else {
             assert access == filterCompression(compare.y());
-            left = makeAddress(access);
-            right = gen.loadNonConst(operand(value));
+            left = address;
+            right = value;
             cond = cond.mirror();
         }
+
+        LabelRef trueLabel = getLIRBlock(ifNode.trueSuccessor());
+        LabelRef falseLabel = getLIRBlock(ifNode.falseSuccessor());
+        double trueLabelProbability = ifNode.probability(ifNode.trueSuccessor());
         getGen().emitCompareBranchMemoryCompressed(left, right, cond, trueLabel, falseLabel, trueLabelProbability, getState(access));
     }