BFDRELoop.cc

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/**
 * @file BFDRELoop.cc
 *
 * Definition of BFDRELoop class
 *
 * Performs a dead-result elimination of a loop-bypassed move.
 * The move which is eliminated from the loop body is still left
 * in the epilog, to have correct value for the register after
 * the loop.
 *
 * @author Heikki Kultala 2014-2020(heikki.kultala-no.spam-tuni.fi)
 * @note rating: red
 */
 
#include "BFDRELoop.hh"
#include "DataDependenceGraph.hh"
#include "BF2Scheduler.hh"
#include "MoveNodeDuplicator.hh"
#include "SimpleResourceManager.hh"
#include "Machine.hh"
 
bool BFDRELoop::operator()() {
    if (!sched_.killDeadResults() || targetMachine().alwaysWriteResults()) {
        return false;
    }
 
    if (srcCycle_ < ii()) {
#ifdef DEBUG_BUBBLEFISH_SCHEDULER
        std::cerr << "\t\t\t\tCannot loop-dre due too early result cycle"
                  << std::endl;
#endif
        return false;
    }
 
    if (!dreAllowed()) {
        return false;
    }
 
    // Create a copy to prolog.
    auto a = duplicator().duplicateMoveNode(mn_, true, true);
    prologMN_ = a.first;
    createdPrologCopy_ = a.second;
 
    int prologCycle = BF2Scheduler::PROLOG_CYCLE_BIAS + srcCycle_;
    if (prologRM()->canAssign(prologCycle, *prologMN_)) {
        prologRM()->assign(prologCycle, *prologMN_);
#ifdef DEBUG_BUBBLEFISH_SCHEDULER
        std::cerr << "\t\t\t\tAssigned loop-bypassed dead result to"
                  << " epilog, cycle:" << prologCycle << std::endl;
#endif
        // TODO: where to add to the epilog DDG?
        createdEdges_ = ddg().copyDepsOver(mn_, true, false);
        ddg().dropNode(mn_);
        sched_.nodeKilled(mn_);
        return true;
    } else {
#ifdef DEBUG_BUBBLEFISH_SCHEDULER
        std::cerr << "\t\t\t\tProlog cycle assign fail for loop-dre: "
                  << prologMN_->toString()
                  << " prolog cycle: " << prologCycle << std::endl;
#endif
        if (createdPrologCopy_) {
            duplicator().disposeMoveNode(prologMN_);
        }
        return false;
    }
}
 
void BFDRELoop::undoOnlyMe() {
    assert(prologRM()!=NULL);
    assert(&mn_ != NULL);
    assert(prologMN_->isScheduled());
    prologRM()->unassign(*prologMN_);
    prologMoves_.erase(&mn_);
    if (createdPrologCopy_) {
        duplicator().disposeMoveNode(prologMN_);
    }
 
 
    BFKillNode::undoOnlyMe();
}
 
bool BFDRELoop::dreAllowed() {
    DataDependenceGraph::EdgeSet edges = ddg().outEdges(mn_);
    for (auto edge: edges) {
        if (edge->edgeReason() == DataDependenceEdge::EDGE_OPERATION) {
            return false;
        }
        if ((edge->edgeReason() == DataDependenceEdge::EDGE_REGISTER ||
             edge->edgeReason() ==DataDependenceEdge::EDGE_RA) &&
            edge->dependenceType() == DataDependenceEdge::DEP_RAW) {
            return false;
        }
    }
    return true;
}