BFMergeAndKeepUser.cc

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/**
 * @file BFMergeAndKeepUser.cc
 *
 * Definition of scheduler operation which performs a bypass, including the
 * ddg updates.
 *
 * @author Heikki Kultala 2020 (hkultala-no.spam-tuni.fi)
 * @note rating: red
 */
 
#include "BFMergeAndKeepUser.hh"
#include "BFConnectNodes.hh"
#include "BFRemoveEdge.hh"
#include "ProgramOperation.hh"
#include "DataDependenceEdge.hh"
#include "DataDependenceGraph.hh"
#include "Move.hh"
#include "Terminal.hh"
#include "MoveNodeDuplicator.hh"
 
#include "BFUpdateMoveOnBypass.hh"
 
bool
BFMergeAndKeepUser::updateEdges(
    MoveNode* src, MoveNode* dst, bool loopBypass, bool pre) {
 
    bool sourceIsRegToItselfCopy = false;
 
    if (src != nullptr && dst != nullptr &&
        ddg().rootGraph()->hasNode(*dst) &
        ddg().rootGraph()->hasNode(*src)) {
        bool removedRawEdge = false;
        auto edges = ddg().rootGraph()->connectingEdges(*src, *dst);
        for (auto e: edges) {
            if (e->isRAW()) {
                removedRawEdge = true;
                runChild(new BFRemoveEdge(sched_, *src, *dst, *e), pre);
                reg_ = e->data();
            }
        }
        if (!removedRawEdge) {
            undo();
            return false;
        }
 
        TTAProgram::Move& sm = src->move();
        sourceIsRegToItselfCopy = sm.source().equals(sm.destination());
 
        // if we are bypassing from a register-to-register copy, we'll have to
        // copy incoming raw edges also in rootgraph level to preserve inter-bb
        // -dependencies.
        for (int i = 0; i < ddg().rootGraphInDegree(*src); i++) {
            DataDependenceEdge& edge = ddg().rootGraphInEdge(*src,i);
 
            // skip antidependencies due bypassed register.. these are no more
            if (edge.edgeReason() == DataDependenceEdge::EDGE_REGISTER &&
                edge.data() == reg_) {
                if (edge.dependenceType() == DataDependenceEdge::DEP_WAW ||
                    edge.dependenceType() == DataDependenceEdge::DEP_WAR) {
                    continue;
                }
            }
 
            // do not copy guard use edges - the user already ahs them.
            // copying them leads to exponential increase in guard ege counts.
            if (edge.guardUse()) {
                continue;
            }
 
            // copy other edges.
            MoveNode& source = ddg().rootGraph()->tailNode(edge);
            DataDependenceEdge* newEdge =
                new DataDependenceEdge(edge, loopBypass);
            runChild(new BFConnectNodes(sched_, source, *dst, newEdge), pre);
        }
 
        if (src->isSourceVariable() || src->isSourceRA()) {
            // if bypassing reg-to-reg this copy anti edges resulting from the
            // read of the other register.
            for (int i = 0; i < ddg().rootGraphOutDegree(*src); i++) {
                DataDependenceEdge& edge = ddg().rootGraphOutEdge(*src,i);
                if ((edge.edgeReason() == DataDependenceEdge::EDGE_REGISTER||
                     edge.edgeReason() == DataDependenceEdge::EDGE_RA) &&
                    edge.dependenceType() == DataDependenceEdge::DEP_WAR &&
                    !edge.tailPseudo()) {
 
                    MoveNode& target = ddg().rootGraph()->headNode(edge);
 
                    if (!(static_cast<DataDependenceGraph*>(ddg().rootGraph()))
                        ->exclusingGuards(*dst, target) &&
                        dst != &target) {
 
                        DataDependenceEdge* newEdge =
                            new DataDependenceEdge(edge, loopBypass);
                        // TODO: loop here!
                        runChild(new BFConnectNodes(
                                     sched_, *dst, target, newEdge), pre);
                    }
                }
            }
        }
    }
 
 
    if (dst != nullptr && ddg().rootGraph()->hasNode(*dst)) {
        // fix WAR antidependencies to WaW
        for (int i = 0; i < ddg().rootGraphOutDegree(*dst); i++) {
            DataDependenceEdge& edge = ddg().rootGraphOutEdge(*dst,i);
            if (edge.edgeReason() == DataDependenceEdge::EDGE_REGISTER &&
                edge.dependenceType() == DataDependenceEdge::DEP_WAR &&
                edge.data() == reg_) {
                // if stupid reg to itself copy, keep to in edges..
                if (!sourceIsRegToItselfCopy) {
                    runChild(
                        new BFRemoveEdge(
                            sched_, *dst,
                            ddg().rootGraph()->headNode(edge), edge), pre);
                   i--; // don't skip one edge here!
                }
            }
        }
    }
    return true;
}
 
bool
BFMergeAndKeepUser::operator()() {
 
 
    if (!ddg().mergeAndKeepAllowed(src_, dst_)) {
        if (!force_) {
            return false;
        }
    }
 
    bool loopBypass = ddg().isLoopBypass(src_, dst_);
 
    // Cannot bypass over multiple loop iterations. even with force flag.
    if (loopBypass) {
        for (int i = 0; i < ddg().inDegree(src_); i++) {
            DataDependenceEdge& edge = ddg().inEdge(src_,i);
            if (!edge.isFalseDep() && edge.isBackEdge()) {
                return false;
            }
        }
    }
    runPreChild(new BFUpdateMoveOnBypass(sched_, src_, dst_));
 
    if (!updateEdges(&src_, &dst_, loopBypass, true)) {
        return false;
    }
 
 
    if (ii() && updatePrologMove_) {
        MoveNode* prologMove = duplicator().getMoveNode(dst_);
        if (prologMove != nullptr) {
            auto prologSrcMove =
                duplicator().duplicateMoveNode(src_,true, false);
            duplicatedSrc_ = prologSrcMove.second;
 
            runPostChild(
                new BFUpdateMoveOnBypass(
                    sched_, *prologSrcMove.first, *prologMove));
 
            updateEdges(
                prologSrcMove.first, prologMove, loopBypass, false);
 
        }
    }
    return true;
 
}
 
void BFMergeAndKeepUser::undoOnlyMe() {
    if (duplicatedSrc_) {
        duplicator().disposeMoveNode(duplicator().getMoveNode(src_));
    }
}