[llvm-commits] [llvm] r103034 - /llvm/trunk/lib/Transforms/Scalar/GVN.cpp

[Bob Wilson]

Author: bwilson
Date: Tue May  4 15:03:21 2010
New Revision: 103034

URL: http://llvm.org/viewvc/llvm-project?rev=103034&view=rev
Log:
Defer adding critical edges to the "toSplit" list until after checking for
indirect branches in all the predecessors.  This avoids unnecessarily
splitting edges in cases where load PRE is not possible anyway.
Thanks to Jakub Staszak for pointing this out.

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

Modified: llvm/trunk/lib/Transforms/Scalar/GVN.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVN.cpp?rev=103034&r1=103033&r2=103034&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/GVN.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/GVN.cpp Tue May  4 15:03:21 2010
@@ -1584,7 +1584,7 @@
   for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
     FullyAvailableBlocks[UnavailableBlocks[i]] = false;
 
-  bool NeedToSplitEdges = false;
+  SmallVector<std::pair<TerminatorInst*, unsigned>, 4> NeedToSplit;
   for (pred_iterator PI = pred_begin(LoadBB), E = pred_end(LoadBB);
        PI != E; ++PI) {
     BasicBlock *Pred = *PI;
@@ -1600,12 +1600,13 @@
         return false;
       }
       unsigned SuccNum = GetSuccessorNumber(Pred, LoadBB);
-      toSplit.push_back(std::make_pair(Pred->getTerminator(), SuccNum));
-      NeedToSplitEdges = true;
+      NeedToSplit.push_back(std::make_pair(Pred->getTerminator(), SuccNum));
     }
   }
-  if (NeedToSplitEdges)
+  if (!NeedToSplit.empty()) {
+    toSplit.append(NeedToSplit.size(), NeedToSplit.front());
     return false;
+  }
 
   // Decide whether PRE is profitable for this load.
   unsigned NumUnavailablePreds = PredLoads.size();