[Python-checkins] python/dist/src/Python compile.c,2.322,2.323

[rhettinger at users.sourceforge.net]

Update of /cvsroot/python/python/dist/src/Python
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv32534

Modified Files:
	compile.c 
Log Message:
Simplify chains of conditional jumps.
(Suggested by Neal Norwitz.)



Index: compile.c
===================================================================
RCS file: /cvsroot/python/python/dist/src/Python/compile.c,v
retrieving revision 2.322
retrieving revision 2.323
diff -u -d -r2.322 -r2.323
--- compile.c	24 Aug 2004 04:34:16 -0000	2.322
+++ compile.c	25 Aug 2004 03:18:29 -0000	2.323
@@ -550,11 +550,34 @@
 			}
 			break;
 
+		/* Simplify conditional jump to conditional jump where the
+		   result of the first test implies the success of a similar
+		   test or the failure of the opposite test.
+		   Arises in code like:
+		        "a and b or c"
+			"a and b and c"
+		   x:JUMP_IF_FALSE y   y:JUMP_IF_FALSE z  -->  x:JUMP_IF_FALSE z
+		   x:JUMP_IF_FALSE y   y:JUMP_IF_FALSE z  -->  x:JUMP_IF_FALSE y+3 
+		*/
+		case JUMP_IF_FALSE:
+		case JUMP_IF_TRUE:
+			tgt = GETJUMPTGT(codestr, i);
+			j = codestr[tgt];
+			if (j == JUMP_IF_FALSE  ||  j == JUMP_IF_TRUE) {
+				if (j == opcode) {
+					tgttgt = GETJUMPTGT(codestr, tgt) - i - 3;
+					SETARG(codestr, i, tgttgt);
+				} else {
+					tgt -= i;
+					SETARG(codestr, i, tgt);
+				}
+				break;
+			}
+			/* Intentional fallthrough */  
+
 		/* Replace jumps to unconditional jumps */
 		case FOR_ITER:
 		case JUMP_FORWARD:
-		case JUMP_IF_FALSE:
-		case JUMP_IF_TRUE:
 		case JUMP_ABSOLUTE:
 		case CONTINUE_LOOP:
 		case SETUP_LOOP: