--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/GraalCompiler/src/com/sun/c1x/doc/LoopPeeling.txt	Wed Apr 27 11:50:44 2011 +0200
@@ -0,0 +1,43 @@
+Remaining Issues in the Loop Peeling optimization (September/18/09)
+===================================================================
+
+Known Problems:
+Currently loop peeling is not working when the loop has exception
+blocks. The algorithm has to be updated to handle these cases.
+
+Limitations:
+The algorithm performs loop peeling only on innermost loops. However,
+this is not a limitation. If one wants to peel the outermost loop(s),
+after peeling the innermost loop, an additional pass is necessary
+to update the blocks of the outermost loop, since after peeling
+the innermost loop, newer blocks are added to the CFG.
+
+Current status as of 09/18/2009
+After running using hir configuration, with optimization level 3, the
+following test cases produce wrong results:
+(4 fails)
+233: jtt/except/Catch_Loop01.java: (4) failed with unexpected com.sun.c1x.ci.CiBailout (expected -170)
+234: jtt/except/Catch_Loop02.java: (4) failed with unexpected com.sun.c1x.ci.CiBailout (expected -170)
+245: jtt/except/Catch_StackOverflowError_03.java: (0) failed with unexpected com.sun.c1x.ci.CiBailout (expected 0)
+272: jtt/hotpath/HP_array04.java: (80) failed with unexpected java.lang.AssertionError (expected 15645)
+
+All of them are related the known problem aforementioned.
+All the tests have the innermost loops peeled, and produce right results.
+
+Future Work:
+1- Add more loop tests to jtt. New tests should run the loop 0, 1, 2 or more iterations.
+
+2- Peel loops with exception blocks. 
+
+3- Currently, all innermost loops are peeled. Should we add logic to filter out some loops from loop peeling?
+
+4- Improve the way instructions are cloned. Now the algorithm visits the blocks in BFS order, which
+might produce errors depending on the order the blocks are visited.
+
+5- After inserting new phi instructions at exit blocks, we need to iterate over the remaining CFG to update instructions
+that may use the new phi. The way it's done now might me inefficient if the block has more than one exit node, since
+we can iterate over the same block more than once. This needs to be improved.
+
+5- For performance reasons, improve the way loops are represented, for example, to use a bitmap to represent the loop blocks.
+
+