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-rw-r--r--generic/tclExecute.c16
1 files changed, 15 insertions, 1 deletions
diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index 79b03b9..b0a94fe 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -11,7 +11,7 @@
* See the file "license.terms" for information on usage and redistribution
* of this file, and for a DISCLAIMER OF ALL WARRANTIES.
*
- * RCS: @(#) $Id: tclExecute.c,v 1.94.2.7 2004/07/03 22:13:10 msofer Exp $
+ * RCS: @(#) $Id: tclExecute.c,v 1.94.2.8 2004/09/10 15:30:02 msofer Exp $
*/
#include "tclInt.h"
@@ -1264,6 +1264,20 @@ TclExecuteByteCode(interp, codePtr)
int totalLen = 0;
/*
+ * Peephole optimisation for appending an empty string.
+ * This enables replacing 'K $x [set x{}]' by '$x[set x{}]'
+ * for fastest execution.
+ */
+
+ if (opnd == 2) {
+ Tcl_GetStringFromObj(stackPtr[stackTop], &length);
+ if (length == 0) {
+ /* Just drop the top item from the stack */
+ NEXT_INST_F(2, 1, 0);
+ }
+ }
+
+ /*
* Concatenate strings (with no separators) from the top
* opnd items on the stack starting with the deepest item.
* First, determine how many characters are needed.