Compute the loop nest depth of each CfgNode and weight Variables by it.

src/IceCfgNode.cpp

Index: src/IceCfgNode.cpp
diff --git a/src/IceCfgNode.cpp b/src/IceCfgNode.cpp
index f0fae92af6de29990c3fd0fb42e16d76460dc83b..03c75bd50d3490d54da3ebe227cd24627f1bcf08 100644
--- a/src/IceCfgNode.cpp
+++ b/src/IceCfgNode.cpp
@@ -218,6 +218,11 @@ void CfgNode::deletePhis() {
 // not contain duplicates.
 CfgNode *CfgNode::splitIncomingEdge(CfgNode *Pred, SizeT EdgeIndex) {
   CfgNode *NewNode = Func->makeNode();
+  // Depth is the minimum as it works if both are the same, but if one is
+  // outside the loop and the other is inside, the new node should be placed
+  // outside and not be executed multiple times within the loop.
+  NewNode->setLoopNestDepth(
+      std::min(getLoopNestDepth(), Pred->getLoopNestDepth()));
   if (BuildDefs::dump())
     NewNode->setName("split_" + Pred->getName() + "_" + getName() + "_" +
                      std::to_string(EdgeIndex));
@@ -1179,9 +1184,12 @@ void CfgNode::dump(Cfg *Func) const {
   Func->setCurrentNode(this);
   Ostream &Str = Func->getContext()->getStrDump();
   Liveness *Liveness = Func->getLiveness();
-  if (Func->isVerbose(IceV_Instructions)) {
-    Str << getName() << ":\n";
-  }
+  if (Func->isVerbose(IceV_Instructions))
+    Str << getName() << ":";
+  // Dump the loop nest depth
+  if (Func->isVerbose(IceV_Loop))
+    Str << " // LoopNestDepth = " << getLoopNestDepth();
+  Str << "\n";

[Jim Stichnoth, 2015/09/03 23:23:30]

Whoops.  This "\n" should only be dumped if verbose is Instructions or Loop. 
Either add some more logic for that, or go back to your previous version.

EDIT: I have to say that the CHECK lines in the test look particularly icky with
the "//", so I would suggest just going back to your previous version.

[ascull, 2015/09/04 00:23:51]

Done.

   // Dump list of predecessor nodes.
   if (Func->isVerbose(IceV_Preds) && !InEdges.empty()) {
     Str << "    // preds = ";