Changes from review:

- Move DisableScheduling flag into TargetOption.h
- Move SDNodeOrdering into its own header file. Give it a minimal interface that
  doesn't conflate construction with storage.
- Move assigning the ordering into the SelectionDAGBuilder.

This isn't used yet, so there should be no functional changes.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91727 91177308-0d34-0410-b5e6-96231b3b80d8

8 files changed, 144 insertions, 193 deletions

diff --git a/include/llvm/CodeGen/SDNodeOrdering.h b/include/llvm/CodeGen/SDNodeOrdering.h
new file mode 100644
index 0000000..07dd1a7
--- /dev/null
+++ b/include/llvm/CodeGen/SDNodeOrdering.h
@@ -0,0 +1,55 @@
+//===-- llvm/CodeGen/SDNodeOrdering.h - SDNode Ordering ---------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares the SDNodeOrdering class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_SDNODEORDERING_H
+#define LLVM_CODEGEN_SDNODEORDERING_H
+
+#include "llvm/ADT/DenseMap.h"
+
+namespace llvm {
+
+/// SDNodeOrdering - Maps a unique (monotonically increasing) value to each
+/// SDNode that roughly corresponds to the ordering of the original LLVM
+/// instruction. This is used for turning off scheduling, because we'll forgo
+/// the normal scheduling algorithms and output the instructions according to
+/// this ordering.
+class SDNodeOrdering {
+  DenseMap<const SDNode*, unsigned> OrderMap;
+
+  void operator=(const SDNodeOrdering&);   // Do not implement.
+  SDNodeOrdering(const SDNodeOrdering&);   // Do not implement.
+public:
+  SDNodeOrdering() {}
+
+  void add(const SDNode *Node, unsigned O) {
+    assert(O && "Invalid ordering!");
+    OrderMap[Node] = O;
+  }
+  void remove(const SDNode *Node) {
+    DenseMap<const SDNode*, unsigned>::iterator Itr = OrderMap.find(Node);
+    if (Itr != OrderMap.end())
+      OrderMap.erase(Itr);
+  }
+  void clear() {
+    OrderMap.clear();
+  }
+  unsigned getOrder(const SDNode *Node) {
+    unsigned Order = OrderMap[Node];
+    assert(Order && "Node isn't in ordering map!");
+    return Order;
+  }
+};
+
+} // end llvm namespace
+
+#endif
diff --git a/include/llvm/CodeGen/SelectionDAG.h b/include/llvm/CodeGen/SelectionDAG.h
index c09c634..a6fd75f 100644
--- a/include/llvm/CodeGen/SelectionDAG.h
+++ b/include/llvm/CodeGen/SelectionDAG.h
@@ -29,12 +29,13 @@
 namespace llvm {
 
 class AliasAnalysis;
-class TargetLowering;
-class MachineModuleInfo;
 class DwarfWriter;
-class MachineFunction;
-class MachineConstantPoolValue;
 class FunctionLoweringInfo;
+class MachineConstantPoolValue;
+class MachineFunction;
+class MachineModuleInfo;
+class SDNodeOrdering;
+class TargetLowering;
 
 template<> struct ilist_traits<SDNode> : public ilist_default_traits<SDNode> {
 private:
@@ -110,45 +111,9 @@ class SelectionDAG {
   /// SelectionDAG.
   BumpPtrAllocator Allocator;
 
-  /// NodeOrdering - Assigns a "line number" value to each SDNode that
-  /// corresponds to the "line number" of the original LLVM instruction. This
-  /// used for turning off scheduling, because we'll forgo the normal scheduling
-  /// algorithm and output the instructions according to this ordering.
-  class NodeOrdering {
-    /// LineNo - The line of the instruction the node corresponds to. A value of
-    /// `0' means it's not assigned.
-    unsigned LineNo;
-    std::map<const SDNode*, unsigned> Order;
-
-    void operator=(const NodeOrdering&); // Do not implement.
-    NodeOrdering(const NodeOrdering&);   // Do not implement.
-  public:
-    NodeOrdering() : LineNo(0) {}
-
-    void add(const SDNode *Node) {
-      assert(LineNo && "Invalid line number!");
-      Order[Node] = LineNo;
-    }
-    void remove(const SDNode *Node) {
-      std::map<const SDNode*, unsigned>::iterator Itr = Order.find(Node);
-      if (Itr != Order.end())
-        Order.erase(Itr);
-    }
-    void clear() {
-      Order.clear();
-      LineNo = 1;
-    }
-    unsigned getLineNo(const SDNode *Node) {
-      unsigned LN = Order[Node];
-      assert(LN && "Node isn't in ordering map!");
-      return LN;
-    }
-    void newInst() {
-      ++LineNo;
-    }
-
-    void dump() const;
-  } *Ordering;
+  /// SDNodeOrdering - The ordering of the SDNodes. It roughly corresponds to
+  /// the ordering of the original LLVM instructions.
+  SDNodeOrdering *Ordering;
 
   /// VerifyNode - Sanity check the given node.  Aborts if it is invalid.
   void VerifyNode(SDNode *N);
@@ -242,13 +207,6 @@ public:
     return Root = N;
   }
 
-  /// NewInst - Tell the ordering object that we're processing a new
-  /// instruction.
-  void NewInst() {
-    if (Ordering)
-      Ordering->newInst();
-  }
-
   /// Combine - This iterates over the nodes in the SelectionDAG, folding
   /// certain types of nodes together, or eliminating superfluous nodes.  The
   /// Level argument controls whether Combine is allowed to produce nodes and
@@ -873,6 +831,9 @@ public:
     }
   }
 
+  /// AssignOrdering - Assign an order to the SDNode.
+  void AssignOrdering(SDNode *SD, unsigned Order);
+
   void dump() const;
 
   /// CreateStackTemporary - Create a stack temporary, suitable for holding the
diff --git a/include/llvm/Target/TargetOptions.h b/include/llvm/Target/TargetOptions.h
index 8d52dad..b43450d 100644
--- a/include/llvm/Target/TargetOptions.h
+++ b/include/llvm/Target/TargetOptions.h
@@ -141,6 +141,11 @@ namespace llvm {
   /// wth earlier copy coalescing.
   extern bool StrongPHIElim;
 
+  /// DisableScheduling - This flag disables instruction scheduling. In
+  /// particular, it assigns an ordering to the SDNodes, which the scheduler
+  /// uses instead of its normal heuristics to perform scheduling.
+  extern bool DisableScheduling;
+
 } // End llvm namespace
 
 #endif
diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
index b2ee8bb..d53de34 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
@@ -20,16 +20,10 @@
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetSubtarget.h"
-#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 using namespace llvm;
 
-cl::opt<bool>
-DisableInstScheduling("disable-inst-scheduling",
-                      cl::init(false),
-                      cl::desc("Disable instruction scheduling"));
-
 ScheduleDAGSDNodes::ScheduleDAGSDNodes(MachineFunction &mf)
   : ScheduleDAG(mf) {
 }
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index da55e6b..1f82791 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -25,6 +25,7 @@
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/PseudoSourceValue.h"
+#include "llvm/CodeGen/SDNodeOrdering.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetData.h"
 #include "llvm/Target/TargetFrameInfo.h"
@@ -48,8 +49,6 @@
 #include <cmath>
 using namespace llvm;
 
-extern cl::opt<bool> DisableInstScheduling;
-
 /// makeVTList - Return an instance of the SDVTList struct initialized with the
 /// specified members.
 static SDVTList makeVTList(const EVT *VTs, unsigned NumVTs) {
@@ -554,9 +553,6 @@ void SelectionDAG::RemoveDeadNodes(SmallVectorImpl<SDNode *> &DeadNodes,
     }
 
     DeallocateNode(N);
-
-    // Remove the ordering of this node.
-    if (Ordering) Ordering->remove(N);
   }
 }
 
@@ -582,9 +578,6 @@ void SelectionDAG::DeleteNodeNotInCSEMaps(SDNode *N) {
   N->DropOperands();
 
   DeallocateNode(N);
-
-  // Remove the ordering of this node.
-  if (Ordering) Ordering->remove(N);
 }
 
 void SelectionDAG::DeallocateNode(SDNode *N) {
@@ -703,7 +696,6 @@ SDNode *SelectionDAG::FindModifiedNodeSlot(SDNode *N, SDValue Op,
   AddNodeIDNode(ID, N->getOpcode(), N->getVTList(), Ops, 1);
   AddNodeIDCustom(ID, N);
   SDNode *Node = CSEMap.FindNodeOrInsertPos(ID, InsertPos);
-  if (Ordering) Ordering->remove(Node);
   return Node;
 }
 
@@ -722,7 +714,6 @@ SDNode *SelectionDAG::FindModifiedNodeSlot(SDNode *N,
   AddNodeIDNode(ID, N->getOpcode(), N->getVTList(), Ops, 2);
   AddNodeIDCustom(ID, N);
   SDNode *Node = CSEMap.FindNodeOrInsertPos(ID, InsertPos);
-  if (Ordering) Ordering->remove(Node);
   return Node;
 }
 
@@ -741,7 +732,6 @@ SDNode *SelectionDAG::FindModifiedNodeSlot(SDNode *N,
   AddNodeIDNode(ID, N->getOpcode(), N->getVTList(), Ops, NumOps);
   AddNodeIDCustom(ID, N);
   SDNode *Node = CSEMap.FindNodeOrInsertPos(ID, InsertPos);
-  if (Ordering) Ordering->remove(Node);
   return Node;
 }
 
@@ -798,10 +788,8 @@ SelectionDAG::SelectionDAG(TargetLowering &tli, FunctionLoweringInfo &fli)
               getVTList(MVT::Other)),
     Root(getEntryNode()), Ordering(0) {
   AllNodes.push_back(&EntryNode);
-  if (DisableInstScheduling) {
-    Ordering = new NodeOrdering();
-    Ordering->add(&EntryNode);
-  }
+  if (DisableScheduling)
+    Ordering = new SDNodeOrdering();
 }
 
 void SelectionDAG::init(MachineFunction &mf, MachineModuleInfo *mmi,
@@ -840,10 +828,8 @@ void SelectionDAG::clear() {
   EntryNode.UseList = 0;
   AllNodes.push_back(&EntryNode);
   Root = getEntryNode();
-  if (DisableInstScheduling) {
-    Ordering = new NodeOrdering();
-    Ordering->add(&EntryNode);
-  }
+  if (DisableScheduling)
+    Ordering = new SDNodeOrdering();
 }
 
 SDValue SelectionDAG::getSExtOrTrunc(SDValue Op, DebugLoc DL, EVT VT) {
@@ -904,17 +890,15 @@ SDValue SelectionDAG::getConstant(const ConstantInt &Val, EVT VT, bool isT) {
   ID.AddPointer(&Val);
   void *IP = 0;
   SDNode *N = NULL;
-  if ((N = CSEMap.FindNodeOrInsertPos(ID, IP))) {
-    if (Ordering) Ordering->add(N);
+  if ((N = CSEMap.FindNodeOrInsertPos(ID, IP)))
     if (!VT.isVector())
       return SDValue(N, 0);
-  }
+
   if (!N) {
     N = NodeAllocator.Allocate<ConstantSDNode>();
     new (N) ConstantSDNode(isT, &Val, EltVT);
     CSEMap.InsertNode(N, IP);
     AllNodes.push_back(N);
-    if (Ordering) Ordering->add(N);
   }
 
   SDValue Result(N, 0);
@@ -951,17 +935,15 @@ SDValue SelectionDAG::getConstantFP(const ConstantFP& V, EVT VT, bool isTarget){
   ID.AddPointer(&V);
   void *IP = 0;
   SDNode *N = NULL;
-  if ((N = CSEMap.FindNodeOrInsertPos(ID, IP))) {
-    if (Ordering) Ordering->add(N);
+  if ((N = CSEMap.FindNodeOrInsertPos(ID, IP)))
     if (!VT.isVector())
       return SDValue(N, 0);
-  }
+
   if (!N) {
     N = NodeAllocator.Allocate<ConstantFPSDNode>();
     new (N) ConstantFPSDNode(isTarget, &V, EltVT);
     CSEMap.InsertNode(N, IP);
     AllNodes.push_back(N);
-    if (Ordering) Ordering->add(N);
   }
 
   SDValue Result(N, 0);
@@ -1016,15 +998,13 @@ SDValue SelectionDAG::getGlobalAddress(const GlobalValue *GV,
   ID.AddInteger(Offset);
   ID.AddInteger(TargetFlags);
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<GlobalAddressSDNode>();
   new (N) GlobalAddressSDNode(Opc, GV, VT, Offset, TargetFlags);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1034,15 +1014,13 @@ SDValue SelectionDAG::getFrameIndex(int FI, EVT VT, bool isTarget) {
   AddNodeIDNode(ID, Opc, getVTList(VT), 0, 0);
   ID.AddInteger(FI);
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<FrameIndexSDNode>();
   new (N) FrameIndexSDNode(FI, VT, isTarget);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1056,15 +1034,13 @@ SDValue SelectionDAG::getJumpTable(int JTI, EVT VT, bool isTarget,
   ID.AddInteger(JTI);
   ID.AddInteger(TargetFlags);
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<JumpTableSDNode>();
   new (N) JumpTableSDNode(JTI, VT, isTarget, TargetFlags);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1084,15 +1060,13 @@ SDValue SelectionDAG::getConstantPool(Constant *C, EVT VT,
   ID.AddPointer(C);
   ID.AddInteger(TargetFlags);
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<ConstantPoolSDNode>();
   new (N) ConstantPoolSDNode(isTarget, C, VT, Offset, Alignment, TargetFlags);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1113,15 +1087,13 @@ SDValue SelectionDAG::getConstantPool(MachineConstantPoolValue *C, EVT VT,
   C->AddSelectionDAGCSEId(ID);
   ID.AddInteger(TargetFlags);
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<ConstantPoolSDNode>();
   new (N) ConstantPoolSDNode(isTarget, C, VT, Offset, Alignment, TargetFlags);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1130,15 +1102,13 @@ SDValue SelectionDAG::getBasicBlock(MachineBasicBlock *MBB) {
   AddNodeIDNode(ID, ISD::BasicBlock, getVTList(MVT::Other), 0, 0);
   ID.AddPointer(MBB);
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<BasicBlockSDNode>();
   new (N) BasicBlockSDNode(MBB);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1154,7 +1124,6 @@ SDValue SelectionDAG::getValueType(EVT VT) {
   N = NodeAllocator.Allocate<VTSDNode>();
   new (N) VTSDNode(VT);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1164,7 +1133,6 @@ SDValue SelectionDAG::getExternalSymbol(const char *Sym, EVT VT) {
   N = NodeAllocator.Allocate<ExternalSymbolSDNode>();
   new (N) ExternalSymbolSDNode(false, Sym, 0, VT);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1177,7 +1145,6 @@ SDValue SelectionDAG::getTargetExternalSymbol(const char *Sym, EVT VT,
   N = NodeAllocator.Allocate<ExternalSymbolSDNode>();
   new (N) ExternalSymbolSDNode(true, Sym, TargetFlags, VT);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1190,8 +1157,8 @@ SDValue SelectionDAG::getCondCode(ISD::CondCode Cond) {
     new (N) CondCodeSDNode(Cond);
     CondCodeNodes[Cond] = N;
     AllNodes.push_back(N);
-    if (Ordering) Ordering->add(N);
   }
+
   return SDValue(CondCodeNodes[Cond], 0);
 }
 
@@ -1283,10 +1250,8 @@ SDValue SelectionDAG::getVectorShuffle(EVT VT, DebugLoc dl, SDValue N1,
     ID.AddInteger(MaskVec[i]);
 
   void* IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
 
   // Allocate the mask array for the node out of the BumpPtrAllocator, since
   // SDNode doesn't have access to it.  This memory will be "leaked" when
@@ -1298,7 +1263,6 @@ SDValue SelectionDAG::getVectorShuffle(EVT VT, DebugLoc dl, SDValue N1,
   new (N) ShuffleVectorSDNode(VT, dl, N1, N2, MaskAlloc);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1316,15 +1280,13 @@ SDValue SelectionDAG::getConvertRndSat(EVT VT, DebugLoc dl,
   SDValue Ops[] = { Val, DTy, STy, Rnd, Sat };
   AddNodeIDNode(ID, ISD::CONVERT_RNDSAT, getVTList(VT), &Ops[0], 5);
   void* IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   CvtRndSatSDNode *N = NodeAllocator.Allocate<CvtRndSatSDNode>();
   new (N) CvtRndSatSDNode(VT, dl, Ops, 5, Code);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1333,15 +1295,13 @@ SDValue SelectionDAG::getRegister(unsigned RegNo, EVT VT) {
   AddNodeIDNode(ID, ISD::Register, getVTList(VT), 0, 0);
   ID.AddInteger(RegNo);
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<RegisterSDNode>();
   new (N) RegisterSDNode(RegNo, VT);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1353,15 +1313,13 @@ SDValue SelectionDAG::getLabel(unsigned Opcode, DebugLoc dl,
   AddNodeIDNode(ID, Opcode, getVTList(MVT::Other), &Ops[0], 1);
   ID.AddInteger(LabelID);
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<LabelSDNode>();
   new (N) LabelSDNode(Opcode, dl, Root, LabelID);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1375,15 +1333,13 @@ SDValue SelectionDAG::getBlockAddress(BlockAddress *BA, EVT VT,
   ID.AddPointer(BA);
   ID.AddInteger(TargetFlags);
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<BlockAddressSDNode>();
   new (N) BlockAddressSDNode(Opc, VT, BA, TargetFlags);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -1396,16 +1352,13 @@ SDValue SelectionDAG::getSrcValue(const Value *V) {
   ID.AddPointer(V);
 
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
 
   SDNode *N = NodeAllocator.Allocate<SrcValueSDNode>();
   new (N) SrcValueSDNode(V);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -2316,16 +2269,14 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, EVT VT) {
   FoldingSetNodeID ID;
   AddNodeIDNode(ID, Opcode, getVTList(VT), 0, 0);
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<SDNode>();
   new (N) SDNode(Opcode, DL, getVTList(VT));
   CSEMap.InsertNode(N, IP);
 
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
 #ifndef NDEBUG
   VerifyNode(N);
 #endif
@@ -2549,10 +2500,9 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL,
     SDValue Ops[1] = { Operand };
     AddNodeIDNode(ID, Opcode, VTs, Ops, 1);
     void *IP = 0;
-    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-      if (Ordering) Ordering->add(E);
+    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
       return SDValue(E, 0);
-    }
+
     N = NodeAllocator.Allocate<UnarySDNode>();
     new (N) UnarySDNode(Opcode, DL, VTs, Operand);
     CSEMap.InsertNode(N, IP);
@@ -2562,7 +2512,6 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL,
   }
 
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
 #ifndef NDEBUG
   VerifyNode(N);
 #endif
@@ -2970,10 +2919,9 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, EVT VT,
     FoldingSetNodeID ID;
     AddNodeIDNode(ID, Opcode, VTs, Ops, 2);
     void *IP = 0;
-    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-      if (Ordering) Ordering->add(E);
+    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
       return SDValue(E, 0);
-    }
+
     N = NodeAllocator.Allocate<BinarySDNode>();
     new (N) BinarySDNode(Opcode, DL, VTs, N1, N2);
     CSEMap.InsertNode(N, IP);
@@ -2983,7 +2931,6 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, EVT VT,
   }
 
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
 #ifndef NDEBUG
   VerifyNode(N);
 #endif
@@ -3050,10 +2997,9 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, EVT VT,
     FoldingSetNodeID ID;
     AddNodeIDNode(ID, Opcode, VTs, Ops, 3);
     void *IP = 0;
-    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-      if (Ordering) Ordering->add(E);
+    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
       return SDValue(E, 0);
-    }
+
     N = NodeAllocator.Allocate<TernarySDNode>();
     new (N) TernarySDNode(Opcode, DL, VTs, N1, N2, N3);
     CSEMap.InsertNode(N, IP);
@@ -3063,7 +3009,6 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, EVT VT,
   }
 
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
 #ifndef NDEBUG
   VerifyNode(N);
 #endif
@@ -3659,14 +3604,12 @@ SDValue SelectionDAG::getAtomic(unsigned Opcode, DebugLoc dl, EVT MemVT,
   void* IP = 0;
   if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
     cast<AtomicSDNode>(E)->refineAlignment(MMO);
-    if (Ordering) Ordering->add(E);
     return SDValue(E, 0);
   }
   SDNode* N = NodeAllocator.Allocate<AtomicSDNode>();
   new (N) AtomicSDNode(Opcode, dl, VTs, MemVT, Chain, Ptr, Cmp, Swp, MMO);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -3724,14 +3667,12 @@ SDValue SelectionDAG::getAtomic(unsigned Opcode, DebugLoc dl, EVT MemVT,
   void* IP = 0;
   if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
     cast<AtomicSDNode>(E)->refineAlignment(MMO);
-    if (Ordering) Ordering->add(E);
     return SDValue(E, 0);
   }
   SDNode* N = NodeAllocator.Allocate<AtomicSDNode>();
   new (N) AtomicSDNode(Opcode, dl, VTs, MemVT, Chain, Ptr, Val, MMO);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -3804,7 +3745,6 @@ SelectionDAG::getMemIntrinsicNode(unsigned Opcode, DebugLoc dl, SDVTList VTList,
     void *IP = 0;
     if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
       cast<MemIntrinsicSDNode>(E)->refineAlignment(MMO);
-      if (Ordering) Ordering->add(E);
       return SDValue(E, 0);
     }
 
@@ -3816,7 +3756,6 @@ SelectionDAG::getMemIntrinsicNode(unsigned Opcode, DebugLoc dl, SDVTList VTList,
     new (N) MemIntrinsicSDNode(Opcode, dl, VTList, Ops, NumOps, MemVT, MMO);
   }
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -3881,14 +3820,12 @@ SelectionDAG::getLoad(ISD::MemIndexedMode AM, DebugLoc dl,
   void *IP = 0;
   if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
     cast<LoadSDNode>(E)->refineAlignment(MMO);
-    if (Ordering) Ordering->add(E);
     return SDValue(E, 0);
   }
   SDNode *N = NodeAllocator.Allocate<LoadSDNode>();
   new (N) LoadSDNode(Ops, dl, VTs, AM, ExtType, MemVT, MMO);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -3959,14 +3896,12 @@ SDValue SelectionDAG::getStore(SDValue Chain, DebugLoc dl, SDValue Val,
   void *IP = 0;
   if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
     cast<StoreSDNode>(E)->refineAlignment(MMO);
-    if (Ordering) Ordering->add(E);
     return SDValue(E, 0);
   }
   SDNode *N = NodeAllocator.Allocate<StoreSDNode>();
   new (N) StoreSDNode(Ops, dl, VTs, ISD::UNINDEXED, false, VT, MMO);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -4021,14 +3956,12 @@ SDValue SelectionDAG::getTruncStore(SDValue Chain, DebugLoc dl, SDValue Val,
   void *IP = 0;
   if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
     cast<StoreSDNode>(E)->refineAlignment(MMO);
-    if (Ordering) Ordering->add(E);
     return SDValue(E, 0);
   }
   SDNode *N = NodeAllocator.Allocate<StoreSDNode>();
   new (N) StoreSDNode(Ops, dl, VTs, ISD::UNINDEXED, true, SVT, MMO);
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -4045,17 +3978,15 @@ SelectionDAG::getIndexedStore(SDValue OrigStore, DebugLoc dl, SDValue Base,
   ID.AddInteger(ST->getMemoryVT().getRawBits());
   ID.AddInteger(ST->getRawSubclassData());
   void *IP = 0;
-  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-    if (Ordering) Ordering->add(E);
+  if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
     return SDValue(E, 0);
-  }
+
   SDNode *N = NodeAllocator.Allocate<StoreSDNode>();
   new (N) StoreSDNode(Ops, dl, VTs, AM,
                       ST->isTruncatingStore(), ST->getMemoryVT(),
                       ST->getMemOperand());
   CSEMap.InsertNode(N, IP);
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
   return SDValue(N, 0);
 }
 
@@ -4121,10 +4052,8 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, EVT VT,
     AddNodeIDNode(ID, Opcode, VTs, Ops, NumOps);
     void *IP = 0;
 
-    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-      if (Ordering) Ordering->add(E);
+    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
       return SDValue(E, 0);
-    }
 
     N = NodeAllocator.Allocate<SDNode>();
     new (N) SDNode(Opcode, DL, VTs, Ops, NumOps);
@@ -4135,7 +4064,6 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, EVT VT,
   }
 
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
 #ifndef NDEBUG
   VerifyNode(N);
 #endif
@@ -4191,10 +4119,9 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, SDVTList VTList,
     FoldingSetNodeID ID;
     AddNodeIDNode(ID, Opcode, VTList, Ops, NumOps);
     void *IP = 0;
-    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-      if (Ordering) Ordering->add(E);
+    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
       return SDValue(E, 0);
-    }
+
     if (NumOps == 1) {
       N = NodeAllocator.Allocate<UnarySDNode>();
       new (N) UnarySDNode(Opcode, DL, VTList, Ops[0]);
@@ -4225,7 +4152,6 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, SDVTList VTList,
     }
   }
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
 #ifndef NDEBUG
   VerifyNode(N);
 #endif
@@ -4688,10 +4614,8 @@ SDNode *SelectionDAG::MorphNodeTo(SDNode *N, unsigned Opc,
   if (VTs.VTs[VTs.NumVTs-1] != MVT::Flag) {
     FoldingSetNodeID ID;
     AddNodeIDNode(ID, Opc, VTs, Ops, NumOps);
-    if (SDNode *ON = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-      if (Ordering) Ordering->add(ON);
+    if (SDNode *ON = CSEMap.FindNodeOrInsertPos(ID, IP))
       return ON;
-    }
   }
 
   if (!RemoveNodeFromCSEMaps(N))
@@ -4755,7 +4679,6 @@ SDNode *SelectionDAG::MorphNodeTo(SDNode *N, unsigned Opc,
 
   if (IP)
     CSEMap.InsertNode(N, IP);   // Memoize the new node.
-  if (Ordering) Ordering->add(N);
   return N;
 }
 
@@ -4894,10 +4817,8 @@ SelectionDAG::getMachineNode(unsigned Opcode, DebugLoc DL, SDVTList VTs,
     FoldingSetNodeID ID;
     AddNodeIDNode(ID, ~Opcode, VTs, Ops, NumOps);
     IP = 0;
-    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-      if (Ordering) Ordering->add(E);
+    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
       return cast<MachineSDNode>(E);
-    }
   }
 
   // Allocate a new MachineSDNode.
@@ -4919,7 +4840,6 @@ SelectionDAG::getMachineNode(unsigned Opcode, DebugLoc DL, SDVTList VTs,
     CSEMap.InsertNode(N, IP);
 
   AllNodes.push_back(N);
-  if (Ordering) Ordering->add(N);
 #ifndef NDEBUG
   VerifyNode(N);
 #endif
@@ -4956,10 +4876,8 @@ SDNode *SelectionDAG::getNodeIfExists(unsigned Opcode, SDVTList VTList,
     FoldingSetNodeID ID;
     AddNodeIDNode(ID, Opcode, VTList, Ops, NumOps);
     void *IP = 0;
-    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP)) {
-      if (Ordering) Ordering->add(E);
+    if (SDNode *E = CSEMap.FindNodeOrInsertPos(ID, IP))
       return E;
-    }
   }
   return NULL;
 }
@@ -5291,6 +5209,12 @@ unsigned SelectionDAG::AssignTopologicalOrder() {
   return DAGSize;
 }
 
+/// AssignOrdering - Assign an order to the SDNode.
+void SelectionDAG::AssignOrdering(SDNode *SD, unsigned Order) {
+  assert(SD && "Trying to assign an order to a null node!");
+  if (Ordering)
+    Ordering->add(SD, Order);
+}
 
 
 //===----------------------------------------------------------------------===//
@@ -6126,9 +6050,6 @@ void SelectionDAG::dump() const {
   errs() << "\n\n";
 }
 
-void SelectionDAG::NodeOrdering::dump() const {
-}
-
 void SDNode::printr(raw_ostream &OS, const SelectionDAG *G) const {
   print_types(OS, G);
   print_details(OS, G);
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 0775485..be0d6af 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -583,8 +583,10 @@ void SelectionDAGBuilder::visit(Instruction &I) {
 }
 
 void SelectionDAGBuilder::visit(unsigned Opcode, User &I) {
-  // Tell the DAG that we're processing a new instruction.
-  DAG.NewInst();
+  // We're processing a new instruction.
+  ++SDNodeOrder;
+
+  SDNode *PrevNode = DAG.getRoot().getNode();
 
   // Note: this doesn't use InstVisitor, because it has to work with
   // ConstantExpr's in addition to instructions.
@@ -592,9 +594,12 @@ void SelectionDAGBuilder::visit(unsigned Opcode, User &I) {
   default: llvm_unreachable("Unknown instruction type encountered!");
     // Build the switch statement using the Instruction.def file.
 #define HANDLE_INST(NUM, OPCODE, CLASS) \
-  case Instruction::OPCODE:return visit##OPCODE((CLASS&)I);
+  case Instruction::OPCODE: visit##OPCODE((CLASS&)I); break;
 #include "llvm/Instruction.def"
   }
+
+  if (DisableScheduling && DAG.getRoot().getNode() != PrevNode)
+    DAG.AssignOrdering(DAG.getRoot().getNode(), SDNodeOrder);
 }
 
 SDValue SelectionDAGBuilder::getValue(const Value *V) {
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 244f9b5..b653c96 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -104,6 +104,10 @@ class SelectionDAGBuilder {
   /// instructions.
   SmallVector<SDValue, 8> PendingExports;
 
+  /// SDNodeOrder - A unique monotonically increasing number used to order the
+  /// SDNodes we create.
+  unsigned SDNodeOrder;
+
   /// Case - A struct to record the Value for a switch case, and the
   /// case's target basic block.
   struct Case {
@@ -300,7 +304,7 @@ public:
   SelectionDAGBuilder(SelectionDAG &dag, TargetLowering &tli,
                       FunctionLoweringInfo &funcinfo,
                       CodeGenOpt::Level ol)
-    : CurDebugLoc(DebugLoc::getUnknownLoc()), 
+    : CurDebugLoc(DebugLoc::getUnknownLoc()), SDNodeOrder(0),
       TLI(tli), DAG(dag), FuncInfo(funcinfo), OptLevel(ol),
       HasTailCall(false),
       Context(dag.getContext()) {
diff --git a/lib/Target/TargetMachine.cpp b/lib/Target/TargetMachine.cpp
index fec59b5..46bc9a3 100644
--- a/lib/Target/TargetMachine.cpp
+++ b/lib/Target/TargetMachine.cpp
@@ -46,6 +46,7 @@ namespace llvm {
   bool DisableJumpTables;
   bool StrongPHIElim;
   bool AsmVerbosityDefault(false);
+  bool DisableScheduling;
 }
 
 static cl::opt<bool, true>
@@ -197,6 +198,11 @@ EnableStrongPHIElim(cl::Hidden, "strong-phi-elim",
   cl::desc("Use strong PHI elimination."),
   cl::location(StrongPHIElim),
   cl::init(false));
+static cl::opt<bool, true>
+DisableInstScheduling("disable-scheduling",
+  cl::desc("Disable instruction scheduling"),
+  cl::location(DisableScheduling),
+  cl::init(false));
 
 //---------------------------------------------------------------------------
 // TargetMachine Class