BFPostpassLoopDRE.cc

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/**
 * @file BFPostpassLoopDRE.cc
 *
 * Definition of BFPostpassLoopDRE 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.
 *
 * This class is called in the postpass-bypass phase.
 *
 * @author Heikki Kultala 2014-2020(heikki.kultala-no.spam-tuni.fi)
 * @note rating: red
 */
 
#include "BFPostpassLoopDRE.hh"
 
#include "BF2Scheduler.hh"
#include "DataDependenceGraph.hh"
 
#include "BFPostpassDRE.hh"
#include "BFUnscheduleMove.hh"
 
#include "MoveNodeDuplicator.hh"
#include "SimpleResourceManager.hh"
 
 
bool
BFPostpassLoopDRE::operator()() {
    if (!sched_.killDeadResults()) {
        return false;
    }
 
    if (!dreAllowed()) {
        return false;
    }
 
    // Create a copy to prolog.
    prologMN_ = duplicator().getMoveNode(mn_);
    if (prologMN_ == NULL) {
        return false;
    }
 
    int prologCycle = BF2Scheduler::PROLOG_CYCLE_BIAS + srcCycle_;
    if (prologRM()->canAssign(prologCycle, *prologMN_)) {
        prologRM()->assign(prologCycle, *prologMN_);
 
        // then remove
        ddg().copyDepsOver(mn_, true, false);
        ddg().dropNode(mn_);
        sched_.nodeKilled(mn_);
        return true;
#ifdef DEBUG_BUBBLEFISH_SCHEDULER
    } else {
        std::cerr << "\t\t\t\tProlog cycle assign fail for loop-dre: "
                  << prologMN_->toString()
                  << " prolog cycle: " << prologCycle << std::endl;
#endif
    }
    return false;
}
 
bool BFPostpassLoopDRE::dreAllowed() {
    DataDependenceGraph::EdgeSet edges = ddg().outEdges(mn_);
    for (auto edge: edges) {
        if (edge->edgeReason() == DataDependenceEdge::EDGE_OPERATION) {
#ifdef DEBUG_BUBBLEFISH_SCHEDULER
            std::cerr << "DRE not allowed due op edge: "
                      << edge->toString()  << std::endl;
#endif
            return false;
        }
        if ((edge->edgeReason() == DataDependenceEdge::EDGE_REGISTER ||
             edge->edgeReason() ==DataDependenceEdge::EDGE_RA) &&
            edge->dependenceType() == DataDependenceEdge::DEP_RAW) {
#ifdef DEBUG_BUBBLEFISH_SCHEDULER
            std::cerr << "DRE not allowed due edge: "
                      << edge->toString()  << std::endl;
#endif
            return false;
        }
    }
    return true;
}
 
void BFPostpassLoopDRE::undoOnlyMe() {
    ddg().restoreNodeFromParent(mn_);
    sched_.nodeResurrected(mn_);
    prologRM()->unassign(*prologMN_);
}