verilator/src/V3Localize.cpp

//*************************************************************************
// DESCRIPTION: Verilator: Convert BLOCKTEMPs to local variables
//
// Code available from: http://www.veripool.org/verilator
//
// AUTHORS: Wilson Snyder with Paul Wasson, Duane Gabli
//
//*************************************************************************
//
// Copyright 2003-2009 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.
//
//*************************************************************************
// LOCALIZE TRANSFORMATIONS:
//	All modules:
//	    VAR(BLOCKTEMP...
//	       if only referenced in a CFUNC, make it local to that CFUNC
//	    VAR(others
//	       if non-public, set before used, and in signle CFUNC, make it local
//
//*************************************************************************

#include "config_build.h"
#include "verilatedos.h"
#include <cstdio>
#include <cstdarg>
#include <unistd.h>
#include <vector>

#include "V3Global.h"
#include "V3Localize.h"
#include "V3Stats.h"
#include "V3Ast.h"

//######################################################################
// Localize base class

class LocalizeBaseVisitor : public AstNVisitor {
protected:
    // NODE STATE
    // Cleared on entire tree
    //  AstVar::user1p()	-> CFunc which references the variable
    //  AstVar::user2()		-> VarFlags.  Flag state
    //  AstVar::user4()		-> AstVarRef*.  First place signal set; must be first assignment

    // METHODS
    static int debug() {
	static int level = -1;
	if (VL_UNLIKELY(level < 0)) level = v3Global.opt.debugSrcLevel(__FILE__);
	return level;
    }

    // TYPES
    union VarFlags {
	// Per-variable flags
	// Used in user()'s so initializes to all zeros
	struct {
	    int m_notOpt:1;	// NOT optimizable
	    int m_notStd:1;	// NOT optimizable if a non-blocktemp signal
	    int m_stdFuncAsn:1;	// Found simple assignment
	    int m_done:1;	// Removed
	};
	uint32_t m_flags;
	VarFlags(AstNode* nodep) { m_flags = nodep->user2(); }
	void setNodeFlags(AstNode* nodep) { nodep->user2(m_flags); }
    };
};

//######################################################################
// Localize class functions

class LocalizeDehierVisitor : public LocalizeBaseVisitor {
private:
    // NODE STATE/TYPES
    // See above

    // METHODS
    virtual void visit(AstVarRef* nodep, AstNUser*) {
	VarFlags flags (nodep->varp());
	if (flags.m_done) {
	    nodep->hiername("");	// Remove thisp->
	    nodep->hierThis(true);
	}
    }
    virtual void visit(AstNode* nodep, AstNUser*) {
	nodep->iterateChildren(*this);
    }
public:
    // CONSTRUCTORS
    LocalizeDehierVisitor(AstNetlist* nodep) {
	nodep->accept(*this);
    }
    virtual ~LocalizeDehierVisitor() {}
};

//######################################################################
// Localize class functions

class LocalizeVisitor : public LocalizeBaseVisitor {
private:
    // NODE STATE/TYPES
    // See above
    AstUser1InUse	m_inuser1;
    AstUser2InUse	m_inuser2;
    AstUser4InUse	m_inuser4;

    // STATE
    V3Double0	m_statLocVars;	// Statistic tracking
    AstCFunc*	m_cfuncp;	// Current active function
    vector<AstVar*> m_varps;	// List of variables to consider for deletion

    // METHODS
    void clearOptimizable(AstVar* nodep, const char* reason) {
	UINFO(4,"       NoOpt "<<reason<<" "<<nodep<<endl);
	VarFlags flags (nodep);
	flags.m_notOpt = true;
	flags.setNodeFlags(nodep);
    }
    void clearStdOptimizable(AstVar* nodep, const char* reason) {
	UINFO(4,"       NoStd "<<reason<<" "<<nodep<<endl);
	VarFlags flags (nodep);
	flags.m_notStd = true;
	flags.setNodeFlags(nodep);
    }
    void moveVars() {
	for (vector<AstVar*>::iterator it = m_varps.begin(); it != m_varps.end(); ++it) {
	    AstVar* nodep = *it;
	    if (nodep->initp()) clearOptimizable(nodep,"HasInitValue");
	    if (!VarFlags(nodep).m_stdFuncAsn) clearStdOptimizable(nodep,"NoStdAssign");
	    VarFlags flags (nodep);
	    if ((nodep->isMovableToBlock() // Blocktemp
		 || !flags.m_notStd)	// Or used only in block
		&& !flags.m_notOpt	// Optimizable
		&& nodep->user1p()) {	// Single cfunc
		// We don't need to test for tracing; it would be in the tracefunc if it was needed
		UINFO(4,"  ModVar->BlkVar "<<nodep<<endl);
		m_statLocVars++;
		AstCFunc* newfuncp = nodep->user1p()->castNode()->castCFunc();
		nodep->unlinkFrBack();
		newfuncp->addInitsp(nodep);
		// Done
		flags.m_done = true;
		flags.setNodeFlags(nodep);
	    } else {
		clearOptimizable(nodep, "NotDone");
	    }
	}
	m_varps.clear();
    }

    // VISITORS
    virtual void visit(AstNetlist* nodep, AstNUser*) {
	nodep->iterateChildren(*this);
	moveVars();
    }
    virtual void visit(AstCFunc* nodep, AstNUser*) {
	UINFO(4,"  CFUNC "<<nodep<<endl);
	m_cfuncp = nodep;
	searchFuncStmts(nodep->argsp());
	searchFuncStmts(nodep->initsp());
	searchFuncStmts(nodep->stmtsp());
	searchFuncStmts(nodep->finalsp());
	nodep->iterateChildren(*this);
	m_cfuncp = NULL;
    }
    void searchFuncStmts(AstNode* nodep) {
	// Search for basic assignments to allow moving non-blocktemps
	// For now we only find simple assignments not under any other statement.
	// This could be more complicated; allow always-set under both branches of a IF.
	// If so, check for ArrayRef's and such, as they aren't acceptable.
	for (; nodep; nodep=nodep->nextp()) {
	    if (nodep->castNodeAssign()) {
		if (AstVarRef* varrefp = nodep->castNodeAssign()->lhsp()->castVarRef()) {
		    if (!varrefp->lvalue()) varrefp->v3fatalSrc("LHS assignment not lvalue");
		    if (!varrefp->varp()->user4p()) {
			UINFO(4,"      FuncAsn "<<varrefp<<endl);
			varrefp->varp()->user4p(varrefp);
			VarFlags flags (varrefp->varp());
			flags.m_stdFuncAsn = true;
			flags.setNodeFlags(varrefp->varp());
		    }
		}
	    }
	}
    }

    virtual void visit(AstVar* nodep, AstNUser*) {
	if (!nodep->isSigPublic()
	    && !nodep->isPrimaryIO()
	    && !m_cfuncp) {	// Not already inside a function
	    UINFO(4,"    BLKVAR "<<nodep<<endl);
	    m_varps.push_back(nodep);
	}
	// No iterate; Don't want varrefs under it
    }
    virtual void visit(AstVarRef* nodep, AstNUser*) {
	if (!VarFlags(nodep->varp()).m_notOpt) {
	    if (!m_cfuncp) {	// Not in function, can't optimize
		clearOptimizable(nodep->varp(), "BVnofunc");
	    }
	    else {
		// If we're scoping down to it, it isn't really in the same block
		if (!nodep->hierThis()) clearOptimizable(nodep->varp(),"HierRef");
		// Allow a variable to appear in only a single function
		AstNode* oldfunc = nodep->varp()->user1p()->castNode();
		if (!oldfunc) {
		    UINFO(4,"      BVnewref "<<nodep<<endl);
		    nodep->varp()->user1p(m_cfuncp); // Remember where it was used
		} else if (m_cfuncp == oldfunc) {
		    // Same usage
		} else {
		    // Used in multiple functions
		    clearOptimizable(nodep->varp(),"BVmultiF");
		}
		// First varref in function must be assignment found earlier
		AstVarRef* firstasn = (AstVarRef*)(nodep->varp()->user4p());
		if (firstasn && nodep!=firstasn) {
		    clearStdOptimizable(nodep->varp(),"notFirstAsn");
		    nodep->varp()->user4p(NULL);
		}
	    }
	}
	// No iterate; Don't want varrefs under it
    }
    virtual void visit(AstNode* nodep, AstNUser*) {
	nodep->iterateChildren(*this);
    }
public:
    // CONSTRUCTORS
    LocalizeVisitor(AstNetlist* nodep) {
	m_cfuncp = NULL;
	nodep->accept(*this);
    }
    virtual ~LocalizeVisitor() {
	V3Stats::addStat("Optimizations, Vars localized", m_statLocVars);
    }
};

//######################################################################
// Localize class functions

void V3Localize::localizeAll(AstNetlist* nodep) {
    UINFO(2,__FUNCTION__<<": "<<endl);
    LocalizeVisitor visitor (nodep);
    // Fix up hiernames
    LocalizeDehierVisitor dvisitor (nodep);
}