[llvm] r375380 - [IndVars] Add a todo to reflect a further oppurtunity identified in D69009

[Philip Reames via llvm-commits]

Author: reames
Date: Sun Oct 20 16:44:01 2019
New Revision: 375380

URL: http://llvm.org/viewvc/llvm-project?rev=375380&view=rev
Log:
[IndVars] Add a todo to reflect a further oppurtunity identified in D69009

Nikita pointed out an oppurtunity, might as well document it in the code.


Modified:
    llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp

Modified: llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp?rev=375380&r1=375379&r2=375380&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/IndVarSimplify.cpp Sun Oct 20 16:44:01 2019
@@ -2794,6 +2794,13 @@ bool IndVarSimplify::optimizeLoopExits(L
       Changed = true;
       continue;
     }
+
+    // TODO: There might be another oppurtunity to leverage SCEV's reasoning
+    // here.  If we kept track of the min of dominanting exits so far, we could
+    // discharge exits with EC >= MDEC. This is less powerful than the existing
+    // transform (since later exits aren't considered), but potentially more
+    // powerful for any case where SCEV can prove a >=u b, but neither a == b
+    // or a >u b.  Such a case is not currently known.
   }
   return Changed;
 }