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

src/IceCfgNode.cpp

 //===- subzero/src/IceCfgNode.cpp - Basic block (node) implementation -----===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 200 matching lines @@
 // Splits the edge from Pred to this node by creating a new node and
 // hooking up the in and out edges appropriately.  (The EdgeIndex
 // parameter is only used to make the new node's name unique when
 // there are multiple edges between the same pair of nodes.)  The new
 // node's instruction list is initialized to the empty list, with no
 // terminator instruction. There must not be multiple edges from Pred
 // to this node so all Inst::getTerminatorEdges implementations must
 // 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));
   // The new node is added to the end of the node list, and will later
   // need to be sorted into a reasonable topological order.
   NewNode->setNeedsPlacement(true);
   // Repoint Pred's out-edge.
   bool Found = false;
   for (CfgNode *&I : Pred->OutEdges) {
     if (I == this) {
@@ skipping 941 matching lines @@
   assert(!Helper.isInBundleLockRegion());
   assert(!Retrying);
 }
 
 void CfgNode::dump(Cfg *Func) const {
   if (!BuildDefs::dump())
     return;
   Func->setCurrentNode(this);
   Ostream &Str = Func->getContext()->getStrDump();
   Liveness *Liveness = Func->getLiveness();
-  if (Func->isVerbose(IceV_Instructions)) {
+  if (Func->isVerbose(IceV_Instructions) || Func->isVerbose(IceV_Loop))

[Jim Stichnoth, 2015/09/03 21:35:09]

I think it would be better to leave this line the way it was.

Instead, I would do something like this:

  if (Func->isVerbose(IceV_Instructions))
    Str << getName() << ":";
  // Dump the loop nest depth
  if (Func->isVerbose(IceV_Loop))
    Str << "    // LoopNestDepth = " << getLoopNestDepth();
  Str << "\n";

Then you'd have the label name and loop depth on the same line for easier
processing.  The test would have to be changed of course.

[ascull, 2015/09/03 22:47:12]

Done.

     Str << getName() << ":\n";
-  }
+  // Dump the loop nest depth
+  if (Func->isVerbose(IceV_Loop))
+    Str << "    // LoopNestDepth = " << getLoopNestDepth() << "\n";
   // Dump list of predecessor nodes.
   if (Func->isVerbose(IceV_Preds) && !InEdges.empty()) {
     Str << "    // preds = ";
     bool First = true;
     for (CfgNode *I : InEdges) {
       if (!First)
         Str << ", ";
       First = false;
       Str << "%" << I->getName();
     }
@@ skipping 82 matching lines @@
   InstIntrinsicCall *Inst = InstIntrinsicCall::create(
       Func, 5, Func->makeVariable(IceType_i64), RMWI64Name, Info->Info);
   Inst->addArg(AtomicRMWOp);
   Inst->addArg(Counter);
   Inst->addArg(One);
   Inst->addArg(OrderAcquireRelease);
   Insts.push_front(Inst);
 }
 
 } // end of namespace Ice