[Mono-bugs] [Bug 61641][Wis] Changed - [PATCH] Suboptimal register allocation with `if' statements

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Changed by lupus@ximian.com.

http://bugzilla.ximian.com/show_bug.cgi?id=61641

--- shadow/61641	2004-07-19 16:30:19.000000000 -0400
+++ shadow/61641.tmp.14912	2005-03-21 05:06:08.000000000 -0500
@@ -671,6 +671,23 @@
 
     - MCS was able to allocate 10% more variables to registers
     - Zipmark got a 10% performance increase on -O=deadce,loop
 
 We should do more evaluation of the new ordering for liveness, but I
 think the initial results are promising.       
+
+------- Additional Comments From lupus@ximian.com  2005-03-21 05:06 -------
+The patch is buggy.
+Var liveness can't be encoded using the IL order of
+basic blocks since it may happen that two vars
+appear non overlapping when instead the control flow
+makes them overlapping. It's trivial to make a test case:
+        use x many times;
+        branch L1;
+L2:     
+        use x many times;
+        ret;
+L1:     
+        use y many times;
+        branch L2;
+If x and y get allocated to the same register you get corruption.        
+