C++ (Cpp) GenTree::CastFromType Examples

Example #1

File: decomposelongs.cpp Project: joperezr/coreclr

//------------------------------------------------------------------------
// DecomposeCast: Decompose GT_CAST.
//
// Arguments:
//    use - the LIR::Use object for the def that needs to be decomposed.
//
// Return Value:
//    The next node to process.
//
GenTree* DecomposeLongs::DecomposeCast(LIR::Use& use)
{
    assert(use.IsInitialized());
    assert(use.Def()->OperGet() == GT_CAST);

    GenTree* cast     = use.Def()->AsCast();
    GenTree* loResult = nullptr;
    GenTree* hiResult = nullptr;

    var_types srcType = cast->CastFromType();
    var_types dstType = cast->CastToType();

    if ((cast->gtFlags & GTF_UNSIGNED) != 0)
    {
        srcType = genUnsignedType(srcType);
    }

    if (varTypeIsLong(srcType))
    {
        if (cast->gtOverflow() && (varTypeIsUnsigned(srcType) != varTypeIsUnsigned(dstType)))
        {
            GenTree* srcOp = cast->gtGetOp1();
            noway_assert(srcOp->OperGet() == GT_LONG);
            GenTree* loSrcOp = srcOp->gtGetOp1();
            GenTree* hiSrcOp = srcOp->gtGetOp2();

            //
            // When casting between long types an overflow check is needed only if the types
            // have different signedness. In both cases (long->ulong and ulong->long) we only
            // need to check if the high part is negative or not. Use the existing cast node
            // to perform a int->uint cast of the high part to take advantage of the overflow
            // check provided by codegen.
            //

            loResult = loSrcOp;

            hiResult                       = cast;
            hiResult->gtType               = TYP_INT;
            hiResult->AsCast()->gtCastType = TYP_UINT;
            hiResult->gtFlags &= ~GTF_UNSIGNED;
            hiResult->gtOp.gtOp1 = hiSrcOp;

            Range().Remove(cast);
            Range().Remove(srcOp);
            Range().InsertAfter(hiSrcOp, hiResult);
        }
        else
        {
            NYI("Unimplemented long->long no-op cast decomposition");
        }
    }
    else if (varTypeIsIntegralOrI(srcType))
    {
        if (cast->gtOverflow() && !varTypeIsUnsigned(srcType) && varTypeIsUnsigned(dstType))
        {
            //
            // An overflow check is needed only when casting from a signed type to ulong.
            // Change the cast type to uint to take advantage of the overflow check provided
            // by codegen and then zero extend the resulting uint to ulong.
            //

            loResult                       = cast;
            loResult->AsCast()->gtCastType = TYP_UINT;
            loResult->gtType               = TYP_INT;

            hiResult = m_compiler->gtNewZeroConNode(TYP_INT);

            Range().InsertAfter(loResult, hiResult);
        }
        else
        {
            if (varTypeIsUnsigned(srcType))
            {
                loResult = cast->gtGetOp1();
                hiResult = m_compiler->gtNewZeroConNode(TYP_INT);

                Range().Remove(cast);
                Range().InsertAfter(loResult, hiResult);
            }
            else
            {
                LIR::Use src(Range(), &(cast->gtOp.gtOp1), cast);
                unsigned lclNum = src.ReplaceWithLclVar(m_compiler, m_blockWeight);

                loResult = src.Def();

                GenTree* loCopy  = m_compiler->gtNewLclvNode(lclNum, TYP_INT);
                GenTree* shiftBy = m_compiler->gtNewIconNode(31, TYP_INT);
                hiResult         = m_compiler->gtNewOperNode(GT_RSH, TYP_INT, loCopy, shiftBy);

                Range().Remove(cast);
                Range().InsertAfter(loResult, loCopy, shiftBy, hiResult);
                m_compiler->lvaIncRefCnts(loCopy);
            }
        }
    }
    else
    {
        NYI("Unimplemented cast decomposition");
    }

    return FinalizeDecomposition(use, loResult, hiResult);
}