1 files changed, 136 insertions, 0 deletions
diff --git a/include/llvm/CodeGen/DAGISelHeader.h b/include/llvm/CodeGen/DAGISelHeader.h
new file mode 100644
index 0000000..b2acbc1
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+++ b/include/llvm/CodeGen/DAGISelHeader.h
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+//==-llvm/CodeGen/DAGISelHeader.h - Common DAG ISel definitions  -*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides definitions of the common, target-independent methods and 
+// data, which is used by SelectionDAG-based instruction selectors.
+//
+// *** NOTE: This file is #included into the middle of the target
+// instruction selector class.  These functions are really methods.
+// This is a little awkward, but it allows this code to be shared
+// by all the targets while still being able to call into
+// target-specific code without using a virtual function call.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_DAGISEL_HEADER_H
+#define LLVM_CODEGEN_DAGISEL_HEADER_H
+
+/// ISelPosition - Node iterator marking the current position of
+/// instruction selection as it procedes through the topologically-sorted
+/// node list.
+SelectionDAG::allnodes_iterator ISelPosition;
+
+/// IsChainCompatible - Returns true if Chain is Op or Chain does
+/// not reach Op.
+static bool IsChainCompatible(SDNode *Chain, SDNode *Op) {
+  if (Chain->getOpcode() == ISD::EntryToken)
+    return true;
+  if (Chain->getOpcode() == ISD::TokenFactor)
+    return false;
+  if (Chain->getNumOperands() > 0) {
+    SDValue C0 = Chain->getOperand(0);
+    if (C0.getValueType() == MVT::Other)
+      return C0.getNode() != Op && IsChainCompatible(C0.getNode(), Op);
+  }
+  return true;
+}
+
+/// ISelUpdater - helper class to handle updates of the 
+/// instruciton selection graph.
+class VISIBILITY_HIDDEN ISelUpdater : public SelectionDAG::DAGUpdateListener {
+  SelectionDAG::allnodes_iterator &ISelPosition;
+public:
+  explicit ISelUpdater(SelectionDAG::allnodes_iterator &isp)
+    : ISelPosition(isp) {}
+  
+  /// NodeDeleted - Handle nodes deleted from the graph. If the
+  /// node being deleted is the current ISelPosition node, update
+  /// ISelPosition.
+  ///
+  virtual void NodeDeleted(SDNode *N, SDNode *E) {
+    if (ISelPosition == SelectionDAG::allnodes_iterator(N))
+      ++ISelPosition;
+  }
+
+  /// NodeUpdated - Ignore updates for now.
+  virtual void NodeUpdated(SDNode *N) {}
+};
+
+/// ReplaceUses - replace all uses of the old node F with the use
+/// of the new node T.
+void ReplaceUses(SDValue F, SDValue T) DISABLE_INLINE {
+  ISelUpdater ISU(ISelPosition);
+  CurDAG->ReplaceAllUsesOfValueWith(F, T, &ISU);
+}
+
+/// ReplaceUses - replace all uses of the old nodes F with the use
+/// of the new nodes T.
+void ReplaceUses(const SDValue *F, const SDValue *T,
+                 unsigned Num) DISABLE_INLINE {
+  ISelUpdater ISU(ISelPosition);
+  CurDAG->ReplaceAllUsesOfValuesWith(F, T, Num, &ISU);
+}
+
+/// ReplaceUses - replace all uses of the old node F with the use
+/// of the new node T.
+void ReplaceUses(SDNode *F, SDNode *T) DISABLE_INLINE {
+  ISelUpdater ISU(ISelPosition);
+  CurDAG->ReplaceAllUsesWith(F, T, &ISU);
+}
+
+/// SelectRoot - Top level entry to DAG instruction selector.
+/// Selects instructions starting at the root of the current DAG.
+void SelectRoot(SelectionDAG &DAG) {
+  SelectRootInit();
+
+  // Create a dummy node (which is not added to allnodes), that adds
+  // a reference to the root node, preventing it from being deleted,
+  // and tracking any changes of the root.
+  HandleSDNode Dummy(CurDAG->getRoot());
+  ISelPosition = next(SelectionDAG::allnodes_iterator(CurDAG->getRoot().getNode()));
+
+  // The AllNodes list is now topological-sorted. Visit the
+  // nodes by starting at the end of the list (the root of the
+  // graph) and preceding back toward the beginning (the entry
+  // node).
+  while (ISelPosition != CurDAG->allnodes_begin()) {
+    SDNode *Node = --ISelPosition;
+    // Skip dead nodes. DAGCombiner is expected to eliminate all dead nodes,
+    // but there are currently some corner cases that it misses. Also, this
+    // makes it theoretically possible to disable the DAGCombiner.
+    if (Node->use_empty())
+      continue;
+#if 0
+    DAG.setSubgraphColor(Node, "red");
+#endif
+    SDNode *ResNode = Select(SDValue(Node, 0));
+    // If node should not be replaced, 
+    // continue with the next one.
+    if (ResNode == Node)
+      continue;
+    // Replace node.
+    if (ResNode) {
+#if 0
+      DAG.setSubgraphColor(ResNode, "yellow");
+      DAG.setSubgraphColor(ResNode, "black");
+#endif
+      ReplaceUses(Node, ResNode);
+    }
+    // If after the replacement this node is not used any more,
+    // remove this dead node.
+    if (Node->use_empty()) { // Don't delete EntryToken, etc.
+      ISelUpdater ISU(ISelPosition);
+      CurDAG->RemoveDeadNode(Node, &ISU);
+    }
+  }
+
+  CurDAG->setRoot(Dummy.getValue());
+}
+
+#endif /* LLVM_CODEGEN_DAGISEL_HEADER_H */