verilator/src/V3Slice.cpp

// -*- mode: C++; c-file-style: "cc-mode" -*-
//*************************************************************************
// DESCRIPTION: Verilator: Parse module/signal name references
//
// Code available from: http://www.veripool.org/verilator
//
//*************************************************************************
//
// Copyright 2003-2019 by Wilson Snyder.  This program is free software; you can
// redistribute it and/or modify it under the terms of either the GNU
// Lesser General Public License Version 3 or the Perl Artistic License
// Version 2.0.
//
// Verilator is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
//*************************************************************************
// Slice TRANSFORMATIONS:
//      Top-down traversal (SliceVisitor):
//        NODEASSIGN
//          ARRAYSEL
//            Compare the dimensions to the Var to check for implicit slices.
//            Using ->length() calculate the number of clones needed.
//          VARREF
//            Check the dimensions of the Var for an implicit slice.
//            Replace with ArraySel nodes if needed.
//          SEL, EXTEND
//            We might be assigning a 1-D packed array to a 2-D packed array,
//            this is unsupported.
//          SliceCloneVisitor (called if this node is a slice):
//            NODEASSIGN
//              Clone and iterate the clone:
//                ARRAYSEL
//                  Modify bitp() for the new value and set ->length(1)
//
// TODO: This code was written before SLICESEL was a type it might be
// simplified to look primarily for SLICESELs.
//*************************************************************************

#include "config_build.h"
#include "verilatedos.h"

#include "V3Global.h"
#include "V3Slice.h"
#include "V3Ast.h"

#include <cstdarg>

//*************************************************************************

class SliceVisitor : public AstNVisitor {
    // NODE STATE
    // Cleared on netlist
    //  AstNodeAssign::user1()      -> bool.  True if find is complete
    //  AstNodeUniop::user1()       -> bool.  True if find is complete
    //  AstArraySel::user1p()       -> AstVarRef. The VarRef that the final ArraySel points to
    AstUser1InUse       m_inuser1;

    // STATE
    AstNode*            m_assignp;      // Assignment we are under
    bool                m_assignError;  // True if the current assign already has an error

    // METHODS
    VL_DEBUG_FUNC;  // Declare debug()

    AstNode* cloneAndSel(AstNode* nodep, int elements, int offset) {
        // Insert an ArraySel, except for a few special cases
        AstUnpackArrayDType* arrayp = VN_CAST(nodep->dtypep()->skipRefp(), UnpackArrayDType);
        if (!arrayp) {  // V3Width should have complained, but...
            if (!m_assignError) {
                nodep->v3error(nodep->prettyTypeName()
                               <<" is not an unpacked array, but is in an unpacked array context");
            }
            m_assignError = true;
            return nodep->cloneTree(false);  // Likely will cause downstream errors
        }
        if (arrayp->rangep()->elementsConst() != elements) {
            if (!m_assignError) nodep->v3error("Slices of arrays in assignments have different unpacked dimensions, "
                                               <<elements<<" versus "
                                               <<arrayp->rangep()->elementsConst());
            m_assignError = true;
            elements = 1; offset = 0;
        }
        AstNode* newp;
        if (AstInitArray* initp = VN_CAST(nodep, InitArray)) {
            UINFO(9,"  cloneInitArray("<<elements<<","<<offset<<") "<<nodep<<endl);
            AstNode* itemp = initp->initsp();
            int leOffset = !arrayp->rangep()->littleEndian()
                ? arrayp->rangep()->elementsConst()-1-offset : offset;
            for (int pos = 0; itemp && pos < leOffset; ++pos) {
                itemp = itemp->nextp();
            }
            if (!itemp) {
                nodep->v3error("Array initialization has too few elements, need element "<<offset);
                itemp = initp->initsp();
            }
            newp = itemp->cloneTree(false);
        }
        else if (AstNodeCond* snodep = VN_CAST(nodep, NodeCond)) {
            UINFO(9,"  cloneCond("<<elements<<","<<offset<<") "<<nodep<<endl);
            return snodep->cloneType(snodep->condp()->cloneTree(false),
                                     cloneAndSel(snodep->expr1p(), elements, offset),
                                     cloneAndSel(snodep->expr2p(), elements, offset));
        }
        else if (AstSliceSel* snodep = VN_CAST(nodep, SliceSel)) {
            UINFO(9,"  cloneSliceSel("<<elements<<","<<offset<<") "<<nodep<<endl);
            int leOffset = (snodep->declRange().lo()
                            + (!snodep->declRange().littleEndian()
                               ? snodep->declRange().elements()-1-offset : offset));
            newp = new AstArraySel(nodep->fileline(), snodep->fromp()->cloneTree(false), leOffset);
        }
        else if (VN_IS(nodep, ArraySel)
                 || VN_IS(nodep, NodeVarRef)
                 || VN_IS(nodep, NodeSel)) {
            UINFO(9,"  cloneSel("<<elements<<","<<offset<<") "<<nodep<<endl);
            int leOffset = !arrayp->rangep()->littleEndian()
                ? arrayp->rangep()->elementsConst()-1-offset : offset;
            newp = new AstArraySel(nodep->fileline(), nodep->cloneTree(false), leOffset);
        }
        else {
            if (!m_assignError) nodep->v3error(nodep->prettyTypeName()<<" unexpected in assignment to unpacked array");
            m_assignError = true;
            newp = nodep->cloneTree(false);  // Likely will cause downstream errors
        }
        return newp;
    }

    virtual void visit(AstNodeAssign* nodep) {
        // Called recursively on newly created assignments
        if (!nodep->user1()
            && !VN_IS(nodep, AssignAlias)) {
            nodep->user1(true);
            m_assignError = false;
            if (debug()>=9) { cout<<endl; nodep->dumpTree(cout, " Deslice-In: "); }
            AstNodeDType* dtp = nodep->lhsp()->dtypep()->skipRefp();
            if (AstUnpackArrayDType* arrayp = VN_CAST(dtp, UnpackArrayDType)) {
                // Left and right could have different msb/lsbs/endianness, but #elements is common
                // and all variables are realigned to start at zero
                // Assign of a little endian'ed slice to a big endian one must reverse the elements
                AstNode* newlistp = NULL;
                int elements = arrayp->rangep()->elementsConst();
                for (int offset = 0; offset < elements; ++offset) {
                    AstNode* newp = nodep->cloneType  // AstNodeAssign
                        (cloneAndSel(nodep->lhsp(), elements, offset),
                         cloneAndSel(nodep->rhsp(), elements, offset));
                    if (debug()>=9) { newp->dumpTree(cout, "-new "); }
                    newlistp = AstNode::addNextNull(newlistp, newp);
                }
                if (debug()>=9) { cout<<endl; nodep->dumpTree(cout, " Deslice-Dn: "); }
                nodep->replaceWith(newlistp); nodep->deleteTree(); VL_DANGLING(nodep);
                // Normal edit iterator will now iterate on all of the expansion assignments
                // This will potentially call this function again to resolve next level of slicing
                return;
            }
            m_assignp = nodep;
            iterateChildren(nodep);
            m_assignp = NULL;
        }
    }

    virtual void visit(AstInitArray* nodep) {
        UASSERT_OBJ(!m_assignp, nodep,
                    "Array initialization should have been removed earlier");
    }

    void expandBiOp(AstNodeBiop* nodep) {
        if (!nodep->user1()) {
            nodep->user1(true);
            // If it's an unpacked array, blow it up into comparing each element
            AstNodeDType* fromDtp = nodep->lhsp()->dtypep()->skipRefp();
            UINFO(9, "  Bi-Eq/Neq expansion "<<nodep<<endl);
            if (AstUnpackArrayDType* adtypep = VN_CAST(fromDtp, UnpackArrayDType)) {
                AstNodeBiop* logp = NULL;
                for (int index = 0; index < adtypep->rangep()->elementsConst(); ++index) {
                    // EQ(a,b) -> LOGAND(EQ(ARRAYSEL(a,0), ARRAYSEL(b,0)), ...[1])
                    AstNodeBiop* clonep
                        = VN_CAST(nodep->cloneType
                                  (new AstArraySel(nodep->fileline(),
                                                   nodep->lhsp()->cloneTree(false),
                                                   index),
                                   new AstArraySel(nodep->fileline(),
                                                   nodep->rhsp()->cloneTree(false),
                                                   index)),
                                  NodeBiop);
                    if (!logp) logp = clonep;
                    else {
                        switch (nodep->type()) {
                        case AstType::atEq:  // FALLTHRU
                        case AstType::atEqCase:
                            logp = new AstLogAnd(nodep->fileline(), logp, clonep);
                            break;
                        case AstType::atNeq:  // FALLTHRU
                        case AstType::atNeqCase:
                            logp = new AstLogOr(nodep->fileline(), logp, clonep);
                            break;
                        default:
                            nodep->v3fatalSrc("Unknown node type processing array slice");
                            break;
                        }
                    }
                }
                UASSERT_OBJ(logp, nodep, "Unpacked array with empty indices range");
                nodep->replaceWith(logp);
                pushDeletep(nodep); VL_DANGLING(nodep);
                nodep = logp;
            }
            iterateChildren(nodep);
        }
    }
    virtual void visit(AstEq* nodep) {
        expandBiOp(nodep);
    }
    virtual void visit(AstNeq* nodep) {
        expandBiOp(nodep);
    }
    virtual void visit(AstEqCase* nodep) {
        expandBiOp(nodep);
    }
    virtual void visit(AstNeqCase* nodep) {
        expandBiOp(nodep);
    }

    virtual void visit(AstNode* nodep) {
        // Default: Just iterate
        iterateChildren(nodep);
    }

public:
    // CONSTUCTORS
    explicit SliceVisitor(AstNetlist* nodep) {
        m_assignp = NULL;
        m_assignError = false;
        iterate(nodep);
    }
    virtual ~SliceVisitor() {}
};

//######################################################################
// Link class functions

void V3Slice::sliceAll(AstNetlist* nodep) {
    UINFO(2,__FUNCTION__<<": "<<endl);
    {
        SliceVisitor visitor(nodep);
    }  // Destruct before checking
    V3Global::dumpCheckGlobalTree("slice", 0, v3Global.opt.dumpTreeLevel(__FILE__) >= 3);
}