svn commit: r351738 - /db/derby/code/trunk/java/engine/org/apache/derby/impl/services/bytecode/BCMethod.java

[dj...@apache.org]

Author: djd
Date: Fri Dec  2 06:40:59 2005
New Revision: 351738

URL: http://svn.apache.org/viewcvs?rev=351738&view=rev
Log:
DERBY-740 Optimize the cast method to not generate checkcast instructions when
the cast class name exactly matches the current type of the top word on the stack.

Modified:
    db/derby/code/trunk/java/engine/org/apache/derby/impl/services/bytecode/BCMethod.java

Modified: db/derby/code/trunk/java/engine/org/apache/derby/impl/services/bytecode/BCMethod.java
URL: http://svn.apache.org/viewcvs/db/derby/code/trunk/java/engine/org/apache/derby/impl/services/bytecode/BCMethod.java?rev=351738&r1=351737&r2=351738&view=diff
==============================================================================
--- db/derby/code/trunk/java/engine/org/apache/derby/impl/services/bytecode/BCMethod.java (original)
+++ db/derby/code/trunk/java/engine/org/apache/derby/impl/services/bytecode/BCMethod.java Fri Dec  2 06:40:59 2005
@@ -629,10 +629,33 @@
 	}
 
 	public void cast(String className) {
-		Type ct = cb.factory.type(className);
-		Type tbc = popStack();
-
+		
+		// Perform a simple optimization to not
+		// insert a checkcast when the classname
+		// of the cast exactly matches the type name
+		// currently on the stack.
+		// This can reduce the amount of generated code.
+		// This compiler/class generator does not load
+		// classes to check relationships or any other
+		// information. Thus other optimizations where a cast
+		// is not required are not implemented.
+		Type tbc = stackTypes[stackTypeOffset - 1];
+		
 		short sourceType = tbc.vmType();
+		
+		if (sourceType == BCExpr.vm_reference)
+		{
+			// Simple optimize step
+			if (className.equals(tbc.javaName()))
+			{
+				// do nothing, exact matching type
+				return;
+			}
+		}
+		
+		Type ct = cb.factory.type(className);
+		popStack();
+		
 		short targetType = ct.vmType();
 
 		if (SanityManager.DEBUG) {