BFRemoveGuardsFromSuccs.cc

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/**
 * @file BFRemoveGuardsFromSuccs.cc
 *
 * Definition of BFRemoveGuardsFromSuccs class
 *
 * When scheduling a move wihch writes a guard, check for the uses of the
 * guard and try to remove those guad uses to allows scheduling this guard write
 * later. Calls BFRemoveGuardFromSucc.
 *
 * @author Heikki Kultala 2014-2020(heikki.kultala-no.spam-tuni.fi)
 * @note rating: red
 */
 
#include "BFRemoveGuardsFromSuccs.hh"
#include "BFRemoveGuardFromSucc.hh"
#include "DataDependenceGraph.hh"
#include "Move.hh"
#include <list>
#include "SimpleResourceManager.hh"
 
bool BFRemoveGuardsFromSuccs::operator()() {
 
    DataDependenceGraph::EdgeSet outEdges = ddg().outEdges(guardWrite_);
 
//    std::list<BFRemoveGuardFromSucc*> guardRemoves;
    std::list<MoveNode*> guardRemoveNodes;
 
    for (auto e: outEdges) {
        if (e->guardUse() &&
            e->dependenceType() == DataDependenceEdge::DEP_RAW) {
            MoveNode& head = ddg().headNode(*e);
            if (head.move().isUnconditional()) {
                std::cerr << "guard edge to uncond move?" << head.toString()
                          << std::endl;
                continue;
            }
            if (head.isScheduled()) {
                // this is not in critical path.
                int cycle = head.cycle();
                if (cycle > maxLC_ + head.guardLatency()) {
                    continue;
                } else {
                    if (canBeSpeculated(head)) {
                        guardRemoveNodes.push_back(&head);
                    } else {
                        maxLC_ = std::min(
                            maxLC_, head.cycle() - head.guardLatency());
                        continue;
                    }
                }
            }
        }
    }
 
    for (auto i: guardRemoveNodes) {
        MoveNode& mn = *i;
        if (mn.cycle() - mn.guardLatency() <  maxLC_) {
            runPostChild(new BFRemoveGuardFromSucc(sched_, mn));
        }
    }
    if (postChildren_.empty()) {
        return false;
    }
 
    // if could not improve schedule, return everything back the way it was
    int ddglc = ddg().latestCycle(guardWrite_, ii(), false, false);
    int rmlc = rm().latestCycle(ddglc, guardWrite_);
    if (rmlc <= oldLC_) {
        undo();
        return false;
    }
 
    return true;
}