When GVN needs to split critical edges for load PRE, check all of the

predecessors before returning.  Otherwise, if multiple predecessor edges need
splitting, we only get one of them per iteration.  This makes a small but
measurable compile time improvement with -enable-full-load-pre.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97521 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp
index a7cc9049cdd15a4f5e9c2df386ccf1cba7608f10..a4c071602491a5412b5dd42ee1f384c15aeb19a6 100644 (file)
--- a/lib/Transforms/Scalar/GVN.cpp
+++ b/lib/Transforms/Scalar/GVN.cpp
@@ -1580,6 +1580,7 @@ bool GVN::processNonLocalLoad(LoadInst *LI,
   for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i)
     FullyAvailableBlocks[UnavailableBlocks[i]] = false;
 
+  bool NeedToSplitEdges = false;
   for (pred_iterator PI = pred_begin(LoadBB), E = pred_end(LoadBB);
        PI != E; ++PI) {
     BasicBlock *Pred = *PI;
@@ -1596,9 +1597,11 @@ bool GVN::processNonLocalLoad(LoadInst *LI,
       }
       unsigned SuccNum = GetSuccessorNumber(Pred, LoadBB);
       toSplit.push_back(std::make_pair(Pred->getTerminator(), SuccNum));
-      return false;
+      NeedToSplitEdges = true;
     }
   }
+  if (NeedToSplitEdges)
+    return false;
 
   // Decide whether PRE is profitable for this load.
   unsigned NumUnavailablePreds = PredLoads.size();