1 //===-- ScheduleDAG.cpp - Implement a trivial DAG scheduler ---------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Chris Lattner and is distributed under the
6 // University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This implements a simple code linearizer for DAGs. This is not a very good
11 // way to emit code, but gets working code quickly.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "sched"
16 #include "llvm/CodeGen/SelectionDAGISel.h"
17 #include "llvm/CodeGen/SelectionDAG.h"
18 #include "llvm/Target/TargetMachine.h"
19 #include "llvm/Target/TargetInstrInfo.h"
25 MachineBasicBlock *BB;
26 const TargetMachine &TM;
27 const TargetInstrInfo &TII;
29 std::map<SDNode *, unsigned> EmittedOps;
31 SimpleSched(SelectionDAG &D, MachineBasicBlock *bb)
32 : DAG(D), BB(bb), TM(D.getTarget()), TII(*TM.getInstrInfo()) {
33 assert(&TII && "Target doesn't provide instr info?");
41 unsigned Emit(SDOperand Op);
45 unsigned SimpleSched::Emit(SDOperand Op) {
46 // Check to see if we have already emitted this. If so, return the value
47 // already emitted. Note that if a node has a single use it cannot be
48 // revisited, so don't bother putting it in the map.
50 if (Op.Val->hasOneUse()) {
51 OpSlot = 0; // No reuse possible.
53 std::map<SDNode *, unsigned>::iterator OpI = EmittedOps.lower_bound(Op.Val);
54 if (OpI != EmittedOps.end() && OpI->first == Op.Val)
55 return OpI->second + Op.ResNo;
56 OpSlot = &EmittedOps.insert(OpI, std::make_pair(Op.Val, 0))->second;
59 unsigned ResultReg = 0;
60 if (Op.isTargetOpcode()) {
61 unsigned Opc = Op.getTargetOpcode();
62 const TargetInstrDescriptor &II = TII.get(Opc);
64 // Target nodes have any register or immediate operands before any chain
65 // nodes. Check that the DAG matches the TD files's expectation of #
67 assert((unsigned(II.numOperands) == Op.getNumOperands() ||
68 // It could be some number of operands followed by a token chain.
69 (unsigned(II.numOperands)+1 == Op.getNumOperands() &&
70 Op.getOperand(II.numOperands).getValueType() == MVT::Other)) &&
71 "#operands for dag node doesn't match .td file!");
73 // Create the new machine instruction.
74 MachineInstr *MI = new MachineInstr(Opc, II.numOperands, true, true);
76 // Add result register values for things that are defined by this
78 assert(Op.Val->getNumValues() == 1 &&
79 Op.getValue(0).getValueType() == MVT::Other &&
80 "Return values not implemented yet");
82 // Emit all of the operands of this instruction, adding them to the
83 // instruction as appropriate.
84 for (unsigned i = 0, e = Op.getNumOperands(); i != e; ++i) {
85 if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(i))) {
86 MI->addZeroExtImm64Operand(C->getValue());
87 } else if (RegisterSDNode*R =dyn_cast<RegisterSDNode>(Op.getOperand(i))) {
88 MI->addRegOperand(R->getReg(), MachineOperand::Use);
90 unsigned R = Emit(Op.getOperand(i));
91 // Add an operand, unless this corresponds to a chain node.
92 if (Op.getOperand(i).getValueType() != MVT::Other)
93 MI->addRegOperand(R, MachineOperand::Use);
97 // Now that we have emitted all operands, emit this instruction itself.
98 BB->insert(BB->end(), MI);
100 switch (Op.getOpcode()) {
102 "This target-independent node should have been selected!");
103 case ISD::EntryToken: break;
107 if (OpSlot) *OpSlot = ResultReg;
108 return ResultReg+Op.ResNo;
112 /// Pick a safe ordering and emit instructions for each target node in the
114 void SelectionDAGISel::ScheduleAndEmitDAG(SelectionDAG &SD) {
115 SimpleSched(SD, BB).Run();