1 //==-llvm/CodeGen/DAGISelHeader.h - Common DAG ISel definitions -*- C++ -*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file provides definitions of the common, target-independent methods and
11 // data, which is used by SelectionDAG-based instruction selectors.
13 // *** NOTE: This file is #included into the middle of the target
14 // instruction selector class. These functions are really methods.
15 // This is a little awkward, but it allows this code to be shared
16 // by all the targets while still being able to call into
17 // target-specific code without using a virtual function call.
19 //===----------------------------------------------------------------------===//
21 #ifndef LLVM_CODEGEN_DAGISEL_HEADER_H
22 #define LLVM_CODEGEN_DAGISEL_HEADER_H
24 /// ISelPosition - Node iterator marking the current position of
25 /// instruction selection as it procedes through the topologically-sorted
27 SelectionDAG::allnodes_iterator ISelPosition;
29 /// IsChainCompatible - Returns true if Chain is Op or Chain does
31 static bool IsChainCompatible(SDNode *Chain, SDNode *Op) {
32 if (Chain->getOpcode() == ISD::EntryToken)
34 if (Chain->getOpcode() == ISD::TokenFactor)
36 if (Chain->getNumOperands() > 0) {
37 SDValue C0 = Chain->getOperand(0);
38 if (C0.getValueType() == MVT::Other)
39 return C0.getNode() != Op && IsChainCompatible(C0.getNode(), Op);
44 /// ISelUpdater - helper class to handle updates of the
45 /// instruciton selection graph.
46 class VISIBILITY_HIDDEN ISelUpdater : public SelectionDAG::DAGUpdateListener {
47 SelectionDAG::allnodes_iterator &ISelPosition;
49 explicit ISelUpdater(SelectionDAG::allnodes_iterator &isp)
50 : ISelPosition(isp) {}
52 /// NodeDeleted - Handle nodes deleted from the graph. If the
53 /// node being deleted is the current ISelPosition node, update
56 virtual void NodeDeleted(SDNode *N, SDNode *E) {
57 if (ISelPosition == SelectionDAG::allnodes_iterator(N))
61 /// NodeUpdated - Ignore updates for now.
62 virtual void NodeUpdated(SDNode *N) {}
65 /// ReplaceUses - replace all uses of the old node F with the use
66 /// of the new node T.
67 void ReplaceUses(SDValue F, SDValue T) DISABLE_INLINE {
68 ISelUpdater ISU(ISelPosition);
69 CurDAG->ReplaceAllUsesOfValueWith(F, T, &ISU);
72 /// ReplaceUses - replace all uses of the old nodes F with the use
73 /// of the new nodes T.
74 void ReplaceUses(const SDValue *F, const SDValue *T,
75 unsigned Num) DISABLE_INLINE {
76 ISelUpdater ISU(ISelPosition);
77 CurDAG->ReplaceAllUsesOfValuesWith(F, T, Num, &ISU);
80 /// ReplaceUses - replace all uses of the old node F with the use
81 /// of the new node T.
82 void ReplaceUses(SDNode *F, SDNode *T) DISABLE_INLINE {
83 ISelUpdater ISU(ISelPosition);
84 CurDAG->ReplaceAllUsesWith(F, T, &ISU);
87 /// SelectRoot - Top level entry to DAG instruction selector.
88 /// Selects instructions starting at the root of the current DAG.
89 void SelectRoot(SelectionDAG &DAG) {
92 // Create a dummy node (which is not added to allnodes), that adds
93 // a reference to the root node, preventing it from being deleted,
94 // and tracking any changes of the root.
95 HandleSDNode Dummy(CurDAG->getRoot());
96 ISelPosition = next(SelectionDAG::allnodes_iterator(CurDAG->getRoot().getNode()));
98 // The AllNodes list is now topological-sorted. Visit the
99 // nodes by starting at the end of the list (the root of the
100 // graph) and preceding back toward the beginning (the entry
102 while (ISelPosition != CurDAG->allnodes_begin()) {
103 SDNode *Node = --ISelPosition;
104 // Skip dead nodes. DAGCombiner is expected to eliminate all dead nodes,
105 // but there are currently some corner cases that it misses. Also, this
106 // makes it theoretically possible to disable the DAGCombiner.
107 if (Node->use_empty())
110 DAG.setSubgraphColor(Node, "red");
112 SDNode *ResNode = Select(SDValue(Node, 0));
113 // If node should not be replaced,
114 // continue with the next one.
120 DAG.setSubgraphColor(ResNode, "yellow");
121 DAG.setSubgraphColor(ResNode, "black");
123 ReplaceUses(Node, ResNode);
125 // If after the replacement this node is not used any more,
126 // remove this dead node.
127 if (Node->use_empty()) { // Don't delete EntryToken, etc.
128 ISelUpdater ISU(ISelPosition);
129 CurDAG->RemoveDeadNode(Node, &ISU);
133 CurDAG->setRoot(Dummy.getValue());
136 #endif /* LLVM_CODEGEN_DAGISEL_HEADER_H */