verilator/src/V3DepthBlock.cpp

// -*- mode: C++; c-file-style: "cc-mode" -*-
//*************************************************************************
// DESCRIPTION: Verilator: Prevent very deep expressions
//
// Code available from: https://verilator.org
//
//*************************************************************************
//
// Copyright 2003-2020 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.
// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
//
//*************************************************************************
// V3DepthBlock's Transformations:
//
// Each module:
//      For each deep block, create cfunc including that block.
//
//*************************************************************************

#include "config_build.h"
#include "verilatedos.h"

#include "V3Global.h"
#include "V3DepthBlock.h"
#include "V3Ast.h"
#include "V3EmitCBase.h"

#include <algorithm>

//######################################################################

class DepthBlockVisitor : public AstNVisitor {
private:
    // NODE STATE

    // STATE
    AstNodeModule* m_modp = nullptr;  // Current module
    AstCFunc* m_cfuncp = nullptr;  // Current function
    int m_depth = 0;  // How deep in an expression
    int m_deepNum = 0;  // How many functions made

    // METHODS
    VL_DEBUG_FUNC;  // Declare debug()

    AstCFunc* createDeepFunc(AstNode* nodep) {
        AstNRelinker relinkHandle;
        nodep->unlinkFrBack(&relinkHandle);
        // Create function
        string name = m_cfuncp->name() + "__deep" + cvtToStr(++m_deepNum);
        AstCFunc* funcp = new AstCFunc(nodep->fileline(), name, nullptr);
        funcp->argTypes(EmitCBaseVisitor::symClassVar());
        funcp->symProlog(true);
        funcp->slow(m_cfuncp->slow());
        funcp->addStmtsp(nodep);
        m_modp->addStmtp(funcp);
        // Call it at the point where the body was removed from
        AstCCall* callp = new AstCCall(nodep->fileline(), funcp);
        callp->argTypes("vlSymsp");
        UINFO(6, "      New " << callp << endl);
        //
        relinkHandle.relink(callp);
        return funcp;
    }

    // VISITORS
    virtual void visit(AstNodeModule* nodep) override {
        UINFO(4, " MOD   " << nodep << endl);
        VL_RESTORER(m_modp);
        {
            m_modp = nodep;
            m_deepNum = 0;
            iterateChildren(nodep);
        }
    }
    virtual void visit(AstCFunc* nodep) override {
        // We recurse into this.
        VL_RESTORER(m_depth);
        VL_RESTORER(m_cfuncp);
        {
            m_depth = 0;
            m_cfuncp = nodep;
            iterateChildren(nodep);
        }
    }
    void visitStmt(AstNodeStmt* nodep) {
        m_depth++;
        if (m_depth > v3Global.opt.compLimitBlocks()
            && !VN_IS(nodep, NodeCCall)) {  // Already done
            UINFO(4, "DeepBlocks " << m_depth << " " << nodep << endl);
            AstNode* backp = nodep->backp();  // Only for debug
            if (debug() >= 9) backp->dumpTree(cout, "-   pre : ");
            AstCFunc* funcp = createDeepFunc(nodep);
            iterate(funcp);
            if (debug() >= 9) backp->dumpTree(cout, "-   post: ");
            if (debug() >= 9) funcp->dumpTree(cout, "-   func: ");
        } else {
            iterateChildren(nodep);
        }
        m_depth--;
    }
    virtual void visit(AstNodeStmt* nodep) override {
        if (!nodep->isStatement()) {
            iterateChildren(nodep);
        } else {
            visitStmt(nodep);
        }
    }

    virtual void visit(AstNodeMath*) override {}  // Accelerate
    //--------------------
    virtual void visit(AstVar*) override {}  // Don't hit varrefs under vars
    virtual void visit(AstNode* nodep) override { iterateChildren(nodep); }

public:
    // CONSTRUCTORS
    explicit DepthBlockVisitor(AstNetlist* nodep) { iterate(nodep); }
    virtual ~DepthBlockVisitor() override {}
};

//######################################################################
// DepthBlock class functions

void V3DepthBlock::depthBlockAll(AstNetlist* nodep) {
    UINFO(2, __FUNCTION__ << ": " << endl);
    { DepthBlockVisitor visitor(nodep); }  // Destruct before checking
    V3Global::dumpCheckGlobalTree("deepblock", 0, v3Global.opt.dumpTreeLevel(__FILE__) >= 3);
}