示例#1
0
/**************************************************************************************
 *
 * Corresponding to the live definition pushes, pop the stack as we finish a sub-paths
 * of the graph originating from the block. Refer SSA renaming for any additional info.
 * "curSsaName" tracks the currently live definitions.
 */
void Compiler::optBlockCopyPropPopStacks(BasicBlock* block, LclNumToGenTreePtrStack* curSsaName)
{
    for (GenTreePtr stmt = block->bbTreeList; stmt; stmt = stmt->gtNext)
    {
        for (GenTreePtr tree = stmt->gtStmt.gtStmtList; tree; tree = tree->gtNext)
        {
            if (!tree->IsLocal())
            {
                continue;
            }
            unsigned lclNum = tree->gtLclVarCommon.gtLclNum;
            if (fgExcludeFromSsa(lclNum))
            {
                continue;
            }
            if (tree->gtFlags & GTF_VAR_DEF)
            {
                GenTreePtrStack* stack = nullptr;
                curSsaName->Lookup(lclNum, &stack);
                stack->Pop();
                if (stack->Height() == 0)
                {
                    curSsaName->Remove(lclNum);
                }
            }
        }
    }
}
示例#2
0
/**************************************************************************************
 *
 * Perform copy propagation on a given tree as we walk the graph and if it is a local
 * variable, then look up all currently live definitions and check if any of those
 * definitions share the same value number. If so, then we can make the replacement.
 *
 */
void Compiler::optCopyProp(BasicBlock* block, GenTreePtr stmt, GenTreePtr tree, LclNumToGenTreePtrStack* curSsaName)
{
    // TODO-Review: EH successor/predecessor iteration seems broken.
    if (block->bbCatchTyp == BBCT_FINALLY || block->bbCatchTyp == BBCT_FAULT)
    {
        return;
    }

    // If not local nothing to do.
    if (!tree->IsLocal())
    {
        return;
    }
    if (tree->OperGet() == GT_PHI_ARG || tree->OperGet() == GT_LCL_FLD)
    {
        return;
    }

    // Propagate only on uses.
    if (tree->gtFlags & GTF_VAR_DEF)
    {
        return;
    }
    unsigned lclNum = tree->AsLclVarCommon()->GetLclNum();

    // Skip address exposed variables.
    if (fgExcludeFromSsa(lclNum))
    {
        return;
    }

    assert(tree->gtVNPair.GetConservative() != ValueNumStore::NoVN);

    for (LclNumToGenTreePtrStack::KeyIterator iter = curSsaName->Begin(); !iter.Equal(curSsaName->End()); ++iter)
    {
        unsigned newLclNum = iter.Get();

        GenTreePtr op = iter.GetValue()->Index(0);

        // Nothing to do if same.
        if (lclNum == newLclNum)
        {
            continue;
        }

        // Skip variables with assignments embedded in the statement (i.e., with a comma). Because we
        // are not currently updating their SSA names as live in the copy-prop pass of the stmt.
        if (VarSetOps::IsMember(this, optCopyPropKillSet, lvaTable[newLclNum].lvVarIndex))
        {
            continue;
        }

        if (op->gtFlags & GTF_VAR_CAST)
        {
            continue;
        }
        if (gsShadowVarInfo != nullptr && lvaTable[newLclNum].lvIsParam &&
            gsShadowVarInfo[newLclNum].shadowCopy == lclNum)
        {
            continue;
        }
        ValueNum opVN = GetUseAsgDefVNOrTreeVN(op);
        if (opVN == ValueNumStore::NoVN)
        {
            continue;
        }
        if (op->TypeGet() != tree->TypeGet())
        {
            continue;
        }
        if (opVN != tree->gtVNPair.GetConservative())
        {
            continue;
        }
        if (optCopyProp_LclVarScore(&lvaTable[lclNum], &lvaTable[newLclNum], true) <= 0)
        {
            continue;
        }
        // Check whether the newLclNum is live before being substituted. Otherwise, we could end
        // up in a situation where there must've been a phi node that got pruned because the variable
        // is not live anymore. For example,
        //  if
        //     x0 = 1
        //  else
        //     x1 = 2
        //  print(c) <-- x is not live here. Let's say 'c' shares the value number with "x0."
        //
        // If we simply substituted 'c' with "x0", we would be wrong. Ideally, there would be a phi
        // node x2 = phi(x0, x1) which can then be used to substitute 'c' with. But because of pruning
        // there would be no such phi node. To solve this we'll check if 'x' is live, before replacing
        // 'c' with 'x.'
        if (!lvaTable[newLclNum].lvVerTypeInfo.IsThisPtr())
        {
            if (lvaTable[newLclNum].lvAddrExposed)
            {
                continue;
            }

            // We compute liveness only on tracked variables. So skip untracked locals.
            if (!lvaTable[newLclNum].lvTracked)
            {
                continue;
            }

            // Because of this dependence on live variable analysis, CopyProp phase is immediately
            // after Liveness, SSA and VN.
            if (!VarSetOps::IsMember(this, compCurLife, lvaTable[newLclNum].lvVarIndex))
            {
                continue;
            }
        }
        unsigned newSsaNum = SsaConfig::RESERVED_SSA_NUM;
        if (op->gtFlags & GTF_VAR_DEF)
        {
            newSsaNum = GetSsaNumForLocalVarDef(op);
        }
        else // parameters, this pointer etc.
        {
            newSsaNum = op->AsLclVarCommon()->GetSsaNum();
        }

        if (newSsaNum == SsaConfig::RESERVED_SSA_NUM)
        {
            continue;
        }

#ifdef DEBUG
        if (verbose)
        {
            JITDUMP("VN based copy assertion for ");
            printTreeID(tree);
            printf(" V%02d @%08X by ", lclNum, tree->GetVN(VNK_Conservative));
            printTreeID(op);
            printf(" V%02d @%08X.\n", newLclNum, op->GetVN(VNK_Conservative));
            gtDispTree(tree, nullptr, nullptr, true);
        }
#endif

        lvaTable[lclNum].decRefCnts(block->getBBWeight(this), this);
        lvaTable[newLclNum].incRefCnts(block->getBBWeight(this), this);
        tree->gtLclVarCommon.SetLclNum(newLclNum);
        tree->AsLclVarCommon()->SetSsaNum(newSsaNum);
#ifdef DEBUG
        if (verbose)
        {
            printf("copy propagated to:\n");
            gtDispTree(tree, nullptr, nullptr, true);
        }
#endif
        break;
    }
    return;
}
示例#3
0
/**************************************************************************************
 *
 * Helper to check if tree is a local that participates in SSA numbering.
 */
bool Compiler::optIsSsaLocal(GenTreePtr tree)
{
    return tree->IsLocal() && !fgExcludeFromSsa(tree->AsLclVarCommon()->GetLclNum());
}
示例#4
0
bool RangeCheck::IsMonotonicallyIncreasing(GenTreePtr expr, SearchPath* path)
{
    JITDUMP("[RangeCheck::IsMonotonicallyIncreasing] %p\n", dspPtr(expr));
    if (path->Lookup(expr))
    {
        return true;
    }

    // Add hashtable entry for expr.
    path->Set(expr, NULL);

    // Remove hashtable entry for expr when we exit the present scope.
    auto code = [&] { path->Remove(expr); };
    jitstd::utility::scoped_code<decltype(code)> finally(code);

    // If the rhs expr is constant, then it is not part of the dependency
    // loop which has to increase monotonically.
    ValueNum vn = expr->gtVNPair.GetConservative();
    if (m_pCompiler->vnStore->IsVNConstant(vn))
    {
        return true;
    }
    // If the rhs expr is local, then try to find the def of the local.
    else if (expr->IsLocal())
    {
        Location* loc = GetDef(expr);
        if (loc == nullptr)
        {
            return false;
        }
        GenTreePtr asg = loc->parent;
        assert(asg->OperKind() & GTK_ASGOP);
        switch (asg->OperGet())
        {
        case GT_ASG:
            return IsMonotonicallyIncreasing(asg->gtGetOp2(), path);

        case GT_ASG_ADD:
            return IsBinOpMonotonicallyIncreasing(asg->gtGetOp1(), asg->gtGetOp2(), GT_ADD, path);
        }
        JITDUMP("Unknown local definition type\n");
        return false;
    }
    else if (expr->OperGet() == GT_ADD)
    {
        return IsBinOpMonotonicallyIncreasing(expr->gtGetOp1(), expr->gtGetOp2(), GT_ADD, path);
    }
    else if (expr->OperGet() == GT_PHI)
    {
        for (GenTreeArgList* args = expr->gtOp.gtOp1->AsArgList();
                args != nullptr; args = args->Rest())
        {
            // If the arg is already in the path, skip.
            if (path->Lookup(args->Current()))
            {
                continue;
            }
            if (!IsMonotonicallyIncreasing(args->Current(), path))
            {
                JITDUMP("Phi argument not monotonic\n");
                return false;
            }
        }
        return true;
    }
    JITDUMP("Unknown tree type\n");
    return false;
}