mirror of
https://github.com/c64scene-ar/llvm-6502.git
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The Cost field is removed. It was only being used in a very limited way, to indicate when the scheduler should attempt to protect a live register, and it isn't really needed to do that. If we ever want the scheduler to start inserting copies in non-prohibitive situations, we'll have to rethink some things anyway. A Latency field is added. Instead of giving each node a single fixed latency, each edge can have its own latency. This will eventually be used to model various micro-architecture properties more accurately. The PointerIntPair class and an internal union are now used, which reduce the overall size. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60806 91177308-0d34-0410-b5e6-96231b3b80d8
478 lines
15 KiB
C++
478 lines
15 KiB
C++
//===---- ScheduleDAG.cpp - Implement the ScheduleDAG class ---------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This implements the ScheduleDAG class, which is a base class used by
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// scheduling implementation classes.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "pre-RA-sched"
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#include "llvm/CodeGen/ScheduleDAG.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include "llvm/Support/Debug.h"
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#include <climits>
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using namespace llvm;
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ScheduleDAG::ScheduleDAG(SelectionDAG *dag, MachineBasicBlock *bb,
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const TargetMachine &tm)
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: DAG(dag), BB(bb), TM(tm), MRI(BB->getParent()->getRegInfo()) {
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TII = TM.getInstrInfo();
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MF = BB->getParent();
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TRI = TM.getRegisterInfo();
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TLI = TM.getTargetLowering();
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ConstPool = MF->getConstantPool();
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}
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ScheduleDAG::~ScheduleDAG() {}
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/// CalculateDepths - compute depths using algorithms for the longest
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/// paths in the DAG
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void ScheduleDAG::CalculateDepths() {
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unsigned DAGSize = SUnits.size();
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std::vector<SUnit*> WorkList;
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WorkList.reserve(DAGSize);
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// Initialize the data structures
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for (unsigned i = 0, e = DAGSize; i != e; ++i) {
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SUnit *SU = &SUnits[i];
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unsigned Degree = SU->Preds.size();
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// Temporarily use the Depth field as scratch space for the degree count.
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SU->Depth = Degree;
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// Is it a node without dependencies?
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if (Degree == 0) {
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assert(SU->Preds.empty() && "SUnit should have no predecessors");
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// Collect leaf nodes
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WorkList.push_back(SU);
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}
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}
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// Process nodes in the topological order
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while (!WorkList.empty()) {
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SUnit *SU = WorkList.back();
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WorkList.pop_back();
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unsigned SUDepth = 0;
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// Use dynamic programming:
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// When current node is being processed, all of its dependencies
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// are already processed.
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// So, just iterate over all predecessors and take the longest path
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for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
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I != E; ++I) {
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unsigned PredDepth = I->getSUnit()->Depth;
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if (PredDepth+1 > SUDepth) {
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SUDepth = PredDepth + 1;
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}
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}
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SU->Depth = SUDepth;
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// Update degrees of all nodes depending on current SUnit
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for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
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I != E; ++I) {
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SUnit *SU = I->getSUnit();
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if (!--SU->Depth)
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// If all dependencies of the node are processed already,
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// then the longest path for the node can be computed now
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WorkList.push_back(SU);
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}
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}
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}
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/// CalculateHeights - compute heights using algorithms for the longest
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/// paths in the DAG
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void ScheduleDAG::CalculateHeights() {
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unsigned DAGSize = SUnits.size();
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std::vector<SUnit*> WorkList;
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WorkList.reserve(DAGSize);
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// Initialize the data structures
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for (unsigned i = 0, e = DAGSize; i != e; ++i) {
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SUnit *SU = &SUnits[i];
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unsigned Degree = SU->Succs.size();
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// Temporarily use the Height field as scratch space for the degree count.
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SU->Height = Degree;
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// Is it a node without dependencies?
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if (Degree == 0) {
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assert(SU->Succs.empty() && "Something wrong");
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assert(WorkList.empty() && "Should be empty");
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// Collect leaf nodes
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WorkList.push_back(SU);
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}
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}
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// Process nodes in the topological order
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while (!WorkList.empty()) {
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SUnit *SU = WorkList.back();
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WorkList.pop_back();
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unsigned SUHeight = 0;
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// Use dynamic programming:
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// When current node is being processed, all of its dependencies
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// are already processed.
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// So, just iterate over all successors and take the longest path
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for (SUnit::const_succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
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I != E; ++I) {
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unsigned SuccHeight = I->getSUnit()->Height;
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if (SuccHeight+1 > SUHeight) {
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SUHeight = SuccHeight + 1;
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}
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}
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SU->Height = SUHeight;
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// Update degrees of all nodes depending on current SUnit
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for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
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I != E; ++I) {
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SUnit *SU = I->getSUnit();
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if (!--SU->Height)
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// If all dependencies of the node are processed already,
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// then the longest path for the node can be computed now
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WorkList.push_back(SU);
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}
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}
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}
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/// dump - dump the schedule.
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void ScheduleDAG::dumpSchedule() const {
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for (unsigned i = 0, e = Sequence.size(); i != e; i++) {
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if (SUnit *SU = Sequence[i])
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SU->dump(this);
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else
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cerr << "**** NOOP ****\n";
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}
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}
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/// Run - perform scheduling.
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///
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void ScheduleDAG::Run() {
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Schedule();
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DOUT << "*** Final schedule ***\n";
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DEBUG(dumpSchedule());
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DOUT << "\n";
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}
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/// SUnit - Scheduling unit. It's an wrapper around either a single SDNode or
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/// a group of nodes flagged together.
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void SUnit::dump(const ScheduleDAG *G) const {
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cerr << "SU(" << NodeNum << "): ";
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G->dumpNode(this);
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}
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void SUnit::dumpAll(const ScheduleDAG *G) const {
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dump(G);
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cerr << " # preds left : " << NumPredsLeft << "\n";
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cerr << " # succs left : " << NumSuccsLeft << "\n";
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cerr << " Latency : " << Latency << "\n";
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cerr << " Depth : " << Depth << "\n";
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cerr << " Height : " << Height << "\n";
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if (Preds.size() != 0) {
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cerr << " Predecessors:\n";
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for (SUnit::const_succ_iterator I = Preds.begin(), E = Preds.end();
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I != E; ++I) {
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cerr << " ";
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switch (I->getKind()) {
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case SDep::Data: cerr << "val "; break;
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case SDep::Anti: cerr << "anti"; break;
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case SDep::Output: cerr << "out "; break;
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case SDep::Order: cerr << "ch "; break;
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}
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cerr << "#";
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cerr << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
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if (I->isArtificial())
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cerr << " *";
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cerr << "\n";
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}
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}
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if (Succs.size() != 0) {
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cerr << " Successors:\n";
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for (SUnit::const_succ_iterator I = Succs.begin(), E = Succs.end();
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I != E; ++I) {
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cerr << " ";
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switch (I->getKind()) {
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case SDep::Data: cerr << "val "; break;
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case SDep::Anti: cerr << "anti"; break;
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case SDep::Output: cerr << "out "; break;
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case SDep::Order: cerr << "ch "; break;
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}
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cerr << "#";
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cerr << I->getSUnit() << " - SU(" << I->getSUnit()->NodeNum << ")";
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if (I->isArtificial())
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cerr << " *";
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cerr << "\n";
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}
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}
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cerr << "\n";
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}
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#ifndef NDEBUG
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/// VerifySchedule - Verify that all SUnits were scheduled and that
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/// their state is consistent.
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///
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void ScheduleDAG::VerifySchedule(bool isBottomUp) {
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bool AnyNotSched = false;
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unsigned DeadNodes = 0;
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unsigned Noops = 0;
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for (unsigned i = 0, e = SUnits.size(); i != e; ++i) {
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if (!SUnits[i].isScheduled) {
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if (SUnits[i].NumPreds == 0 && SUnits[i].NumSuccs == 0) {
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++DeadNodes;
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continue;
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}
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if (!AnyNotSched)
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cerr << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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cerr << "has not been scheduled!\n";
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AnyNotSched = true;
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}
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if (SUnits[i].isScheduled && SUnits[i].Cycle > (unsigned)INT_MAX) {
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if (!AnyNotSched)
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cerr << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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cerr << "has an unexpected Cycle value!\n";
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AnyNotSched = true;
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}
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if (isBottomUp) {
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if (SUnits[i].NumSuccsLeft != 0) {
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if (!AnyNotSched)
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cerr << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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cerr << "has successors left!\n";
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AnyNotSched = true;
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}
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} else {
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if (SUnits[i].NumPredsLeft != 0) {
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if (!AnyNotSched)
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cerr << "*** Scheduling failed! ***\n";
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SUnits[i].dump(this);
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cerr << "has predecessors left!\n";
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AnyNotSched = true;
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}
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}
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}
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for (unsigned i = 0, e = Sequence.size(); i != e; ++i)
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if (!Sequence[i])
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++Noops;
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assert(!AnyNotSched);
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assert(Sequence.size() + DeadNodes - Noops == SUnits.size() &&
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"The number of nodes scheduled doesn't match the expected number!");
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}
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#endif
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/// InitDAGTopologicalSorting - create the initial topological
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/// ordering from the DAG to be scheduled.
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///
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/// The idea of the algorithm is taken from
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/// "Online algorithms for managing the topological order of
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/// a directed acyclic graph" by David J. Pearce and Paul H.J. Kelly
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/// This is the MNR algorithm, which was first introduced by
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/// A. Marchetti-Spaccamela, U. Nanni and H. Rohnert in
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/// "Maintaining a topological order under edge insertions".
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///
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/// Short description of the algorithm:
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///
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/// Topological ordering, ord, of a DAG maps each node to a topological
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/// index so that for all edges X->Y it is the case that ord(X) < ord(Y).
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///
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/// This means that if there is a path from the node X to the node Z,
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/// then ord(X) < ord(Z).
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///
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/// This property can be used to check for reachability of nodes:
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/// if Z is reachable from X, then an insertion of the edge Z->X would
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/// create a cycle.
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///
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/// The algorithm first computes a topological ordering for the DAG by
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/// initializing the Index2Node and Node2Index arrays and then tries to keep
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/// the ordering up-to-date after edge insertions by reordering the DAG.
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///
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/// On insertion of the edge X->Y, the algorithm first marks by calling DFS
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/// the nodes reachable from Y, and then shifts them using Shift to lie
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/// immediately after X in Index2Node.
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void ScheduleDAGTopologicalSort::InitDAGTopologicalSorting() {
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unsigned DAGSize = SUnits.size();
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std::vector<SUnit*> WorkList;
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WorkList.reserve(DAGSize);
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Index2Node.resize(DAGSize);
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Node2Index.resize(DAGSize);
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// Initialize the data structures.
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for (unsigned i = 0, e = DAGSize; i != e; ++i) {
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SUnit *SU = &SUnits[i];
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int NodeNum = SU->NodeNum;
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unsigned Degree = SU->Succs.size();
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// Temporarily use the Node2Index array as scratch space for degree counts.
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Node2Index[NodeNum] = Degree;
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// Is it a node without dependencies?
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if (Degree == 0) {
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assert(SU->Succs.empty() && "SUnit should have no successors");
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// Collect leaf nodes.
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WorkList.push_back(SU);
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}
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}
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int Id = DAGSize;
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while (!WorkList.empty()) {
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SUnit *SU = WorkList.back();
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WorkList.pop_back();
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Allocate(SU->NodeNum, --Id);
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for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
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I != E; ++I) {
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SUnit *SU = I->getSUnit();
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if (!--Node2Index[SU->NodeNum])
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// If all dependencies of the node are processed already,
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// then the node can be computed now.
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WorkList.push_back(SU);
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}
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}
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Visited.resize(DAGSize);
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#ifndef NDEBUG
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// Check correctness of the ordering
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for (unsigned i = 0, e = DAGSize; i != e; ++i) {
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SUnit *SU = &SUnits[i];
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for (SUnit::const_pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
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I != E; ++I) {
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assert(Node2Index[SU->NodeNum] > Node2Index[I->getSUnit()->NodeNum] &&
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"Wrong topological sorting");
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}
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}
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#endif
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}
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/// AddPred - Updates the topological ordering to accomodate an edge
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/// to be added from SUnit X to SUnit Y.
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void ScheduleDAGTopologicalSort::AddPred(SUnit *Y, SUnit *X) {
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int UpperBound, LowerBound;
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LowerBound = Node2Index[Y->NodeNum];
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UpperBound = Node2Index[X->NodeNum];
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bool HasLoop = false;
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// Is Ord(X) < Ord(Y) ?
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if (LowerBound < UpperBound) {
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// Update the topological order.
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Visited.reset();
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DFS(Y, UpperBound, HasLoop);
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assert(!HasLoop && "Inserted edge creates a loop!");
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// Recompute topological indexes.
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Shift(Visited, LowerBound, UpperBound);
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}
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}
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/// RemovePred - Updates the topological ordering to accomodate an
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/// an edge to be removed from the specified node N from the predecessors
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/// of the current node M.
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void ScheduleDAGTopologicalSort::RemovePred(SUnit *M, SUnit *N) {
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// InitDAGTopologicalSorting();
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}
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/// DFS - Make a DFS traversal to mark all nodes reachable from SU and mark
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/// all nodes affected by the edge insertion. These nodes will later get new
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/// topological indexes by means of the Shift method.
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void ScheduleDAGTopologicalSort::DFS(const SUnit *SU, int UpperBound,
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bool& HasLoop) {
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std::vector<const SUnit*> WorkList;
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WorkList.reserve(SUnits.size());
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WorkList.push_back(SU);
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while (!WorkList.empty()) {
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SU = WorkList.back();
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WorkList.pop_back();
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Visited.set(SU->NodeNum);
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for (int I = SU->Succs.size()-1; I >= 0; --I) {
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int s = SU->Succs[I].getSUnit()->NodeNum;
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if (Node2Index[s] == UpperBound) {
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HasLoop = true;
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return;
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}
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// Visit successors if not already and in affected region.
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if (!Visited.test(s) && Node2Index[s] < UpperBound) {
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WorkList.push_back(SU->Succs[I].getSUnit());
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}
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}
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}
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}
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/// Shift - Renumber the nodes so that the topological ordering is
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/// preserved.
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void ScheduleDAGTopologicalSort::Shift(BitVector& Visited, int LowerBound,
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int UpperBound) {
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std::vector<int> L;
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int shift = 0;
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int i;
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for (i = LowerBound; i <= UpperBound; ++i) {
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// w is node at topological index i.
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int w = Index2Node[i];
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if (Visited.test(w)) {
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// Unmark.
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Visited.reset(w);
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L.push_back(w);
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shift = shift + 1;
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} else {
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Allocate(w, i - shift);
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}
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}
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for (unsigned j = 0; j < L.size(); ++j) {
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Allocate(L[j], i - shift);
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i = i + 1;
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}
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}
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/// WillCreateCycle - Returns true if adding an edge from SU to TargetSU will
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/// create a cycle.
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bool ScheduleDAGTopologicalSort::WillCreateCycle(SUnit *SU, SUnit *TargetSU) {
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if (IsReachable(TargetSU, SU))
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return true;
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for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
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I != E; ++I)
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if (I->isAssignedRegDep() &&
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IsReachable(TargetSU, I->getSUnit()))
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return true;
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return false;
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}
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/// IsReachable - Checks if SU is reachable from TargetSU.
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bool ScheduleDAGTopologicalSort::IsReachable(const SUnit *SU,
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const SUnit *TargetSU) {
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// If insertion of the edge SU->TargetSU would create a cycle
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// then there is a path from TargetSU to SU.
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int UpperBound, LowerBound;
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LowerBound = Node2Index[TargetSU->NodeNum];
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UpperBound = Node2Index[SU->NodeNum];
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bool HasLoop = false;
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// Is Ord(TargetSU) < Ord(SU) ?
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if (LowerBound < UpperBound) {
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Visited.reset();
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// There may be a path from TargetSU to SU. Check for it.
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DFS(TargetSU, UpperBound, HasLoop);
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}
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return HasLoop;
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}
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/// Allocate - assign the topological index to the node n.
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void ScheduleDAGTopologicalSort::Allocate(int n, int index) {
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Node2Index[n] = index;
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Index2Node[index] = n;
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}
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ScheduleDAGTopologicalSort::ScheduleDAGTopologicalSort(
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std::vector<SUnit> &sunits)
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: SUnits(sunits) {}
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