[llvm-commits] [llvm] r50563 - /llvm/branches/Apple/Tak/lib/Transforms/Scalar/LoopIndexSplit.cpp

[Bill Wendling]

Author: void
Date: Thu May  1 19:41:12 2008
New Revision: 50563

URL: http://llvm.org/viewvc/llvm-project?rev=50563&view=rev
Log:
Don't split the loop index if it's not "diamond" shaped. The result could be
code that's much less efficient and have bugs.

Modified:
    llvm/branches/Apple/Tak/lib/Transforms/Scalar/LoopIndexSplit.cpp

Modified: llvm/branches/Apple/Tak/lib/Transforms/Scalar/LoopIndexSplit.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/branches/Apple/Tak/lib/Transforms/Scalar/LoopIndexSplit.cpp?rev=50563&r1=50562&r2=50563&view=diff

==============================================================================
--- llvm/branches/Apple/Tak/lib/Transforms/Scalar/LoopIndexSplit.cpp (original)
+++ llvm/branches/Apple/Tak/lib/Transforms/Scalar/LoopIndexSplit.cpp Thu May  1 19:41:12 2008
@@ -1124,6 +1124,11 @@
   BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
   BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
 
+  // If split block does not dominate the latch then this is not a diamond.
+  // Such loop may not benefit from index split.
+  if (!DT->dominates(SplitCondBlock, Latch))
+    return false;
+
   // Finally this split condition is safe only if merge point for
   // split condition branch is loop latch. This check along with previous
   // check, to ensure that exit condition is in either loop latch or header,