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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;
/// 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.
DISABLE_INLINE void ReplaceUses(SDValue F, SDValue T) {
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.
DISABLE_INLINE void ReplaceUses(const SDValue *F, const SDValue *T,
unsigned Num) {
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.
DISABLE_INLINE void ReplaceUses(SDNode *F, SDNode *T) {
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 = SelectionDAG::allnodes_iterator(CurDAG->getRoot().getNode());
++ISelPosition;
// 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;
SDNode *ResNode = Select(Node);
// If node should not be replaced, continue with the next one.
if (ResNode == Node)
continue;
// Replace node.
if (ResNode)
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 */
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