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https://github.com/verilator/verilator.git
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405 lines
14 KiB
C++
405 lines
14 KiB
C++
// -*- mode: C++; c-file-style: "cc-mode" -*-
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//*************************************************************************
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// DESCRIPTION: Verilator: Check for unused/undriven signals
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//
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// Code available from: http://www.veripool.org/verilator
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//
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//*************************************************************************
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//
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// Copyright 2004-2018 by Wilson Snyder. This program is free software; you can
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// redistribute it and/or modify it under the terms of either the GNU
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// Lesser General Public License Version 3 or the Perl Artistic License
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// Version 2.0.
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//
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// Verilator is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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//*************************************************************************
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// V3Undriven's Transformations:
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//
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// Netlist:
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// Make vector for all variables
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// SEL(VARREF(...))) mark only some bits as used/driven
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// else VARREF(...) mark all bits as used/driven
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// Report unused/undriven nets
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//
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//*************************************************************************
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#include "config_build.h"
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#include "verilatedos.h"
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#include <cstdio>
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#include <cstdarg>
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#include <unistd.h>
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#include <algorithm>
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#include <vector>
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#include "V3Global.h"
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#include "V3String.h"
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#include "V3Undriven.h"
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#include "V3Ast.h"
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//######################################################################
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// Class for every variable we may process
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class UndrivenVarEntry {
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// MEMBERS
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AstVar* m_varp; // Variable this tracks
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bool m_usedWhole; // True if whole vector used
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bool m_drivenWhole; // True if whole vector driven
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std::vector<bool> m_flags; // Used/Driven on each subbit
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enum { FLAG_USED = 0, FLAG_DRIVEN = 1, FLAGS_PER_BIT = 2 };
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VL_DEBUG_FUNC; // Declare debug()
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public:
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// CONSTRUCTORS
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explicit UndrivenVarEntry(AstVar* varp) { // Construction for when a var is used
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UINFO(9, "create "<<varp<<endl);
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m_varp = varp;
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m_usedWhole = false;
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m_drivenWhole = false;
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m_flags.resize(varp->width()*FLAGS_PER_BIT);
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for (int i=0; i<varp->width()*FLAGS_PER_BIT; i++) {
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m_flags[i] = false;
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}
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}
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~UndrivenVarEntry() {}
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private:
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// METHODS
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inline bool bitNumOk(int bit) const { return bit>=0 && (bit*FLAGS_PER_BIT < (int)m_flags.size()); }
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inline bool usedFlag(int bit) const { return m_usedWhole || m_flags[bit*FLAGS_PER_BIT + FLAG_USED]; }
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inline bool drivenFlag(int bit) const { return m_drivenWhole || m_flags[bit*FLAGS_PER_BIT + FLAG_DRIVEN]; }
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enum BitNamesWhich { BN_UNUSED, BN_UNDRIVEN, BN_BOTH };
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string bitNames(BitNamesWhich which) {
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string bits="";
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bool prev = false;
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int msb = 0;
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// bit==-1 loops below; we do one extra iteration so end with prev=false
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for (int bit=(m_flags.size()/FLAGS_PER_BIT)-1; bit >= -1; --bit) {
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if (bit>=0
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&& ((which == BN_UNUSED && !usedFlag(bit) && drivenFlag(bit))
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|| (which == BN_UNDRIVEN && usedFlag(bit) && !drivenFlag(bit))
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|| (which == BN_BOTH && !usedFlag(bit) && !drivenFlag(bit)))) {
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if (!prev) { prev=true; msb = bit; }
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} else if (prev) {
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AstBasicDType* bdtypep = m_varp->basicp();
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int lsb = bit+1;
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if (bits != "") bits += ",";
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if (lsb==msb) {
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bits += cvtToStr(lsb+bdtypep->lsb());
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} else {
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if (bdtypep->littleEndian()) {
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bits += cvtToStr(lsb+bdtypep->lsb())+":"+cvtToStr(msb+bdtypep->lsb());
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} else {
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bits += cvtToStr(msb+bdtypep->lsb())+":"+cvtToStr(lsb+bdtypep->lsb());
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}
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}
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prev = false;
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}
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}
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return "["+bits+"]";
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}
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public:
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void usedWhole() {
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UINFO(9, "set u[*] "<<m_varp->name()<<endl);
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m_usedWhole = true;
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}
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void drivenWhole() {
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UINFO(9, "set d[*] "<<m_varp->name()<<endl);
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m_drivenWhole = true;
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}
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void usedBit(int bit, int width) {
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UINFO(9, "set u["<<(bit+width-1)<<":"<<bit<<"] "<<m_varp->name()<<endl);
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for (int i=0; i<width; i++) {
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if (bitNumOk(bit+i)) {
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m_flags[(bit+i)*FLAGS_PER_BIT + FLAG_USED] = true;
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}
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}
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}
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void drivenBit(int bit, int width) {
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UINFO(9, "set d["<<(bit+width-1)<<":"<<bit<<"] "<<m_varp->name()<<endl);
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for (int i=0; i<width; i++) {
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if (bitNumOk(bit+i)) {
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m_flags[(bit+i)*FLAGS_PER_BIT + FLAG_DRIVEN] = true;
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}
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}
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}
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bool isUsedNotDrivenBit(int bit, int width) const {
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for (int i=0; i<width; i++) {
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if (bitNumOk(bit+i)
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&& (m_usedWhole || m_flags[(bit+i)*FLAGS_PER_BIT + FLAG_USED])
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&& !(m_drivenWhole || m_flags[(bit+i)*FLAGS_PER_BIT + FLAG_DRIVEN])) return true;
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}
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return false;
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}
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bool isUsedNotDrivenAny() const {
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return isUsedNotDrivenBit(0, m_flags.size()/FLAGS_PER_BIT);
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}
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bool unusedMatch(AstVar* nodep) {
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string regexp = v3Global.opt.unusedRegexp();
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if (regexp == "") return false;
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string prettyName = nodep->prettyName();
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return VString::wildmatch(prettyName.c_str(), regexp.c_str());
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}
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void reportViolations() {
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// Combine bits into overall state
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AstVar* nodep = m_varp;
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if (!nodep->isParam() && !nodep->isGenVar()) {
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bool allU=true;
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bool allD=true;
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bool anyU=m_usedWhole;
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bool anyD=m_drivenWhole;
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bool anyUnotD=false;
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bool anyDnotU=false;
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bool anynotDU=false;
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for (unsigned bit=0; bit<m_flags.size()/FLAGS_PER_BIT; bit++) {
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bool used = usedFlag(bit);
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bool driv = drivenFlag(bit);
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allU &= used;
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anyU |= used;
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allD &= driv;
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anyD |= driv;
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anyUnotD |= used && !driv;
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anyDnotU |= !used && driv;
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anynotDU |= !used && !driv;
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}
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if (allU) m_usedWhole = true;
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if (allD) m_drivenWhole = true;
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// Test results
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if (nodep->isIfaceRef()) {
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// For interface top level we don't do any tracking
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// Ideally we'd report unused instance cells, but presumably a signal inside one
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// would get reported as unused
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} else if (allU && allD) {
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// It's fine
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} else if (!anyD && !anyU) {
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// UNDRIVEN is considered more serious - as is more likely a bug,
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// thus undriven+unused bits get UNUSED warnings, as they're not as buggy.
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if (!unusedMatch(nodep)) {
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nodep->v3warn(UNUSED, "Signal is not driven, nor used: "<<nodep->prettyName());
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nodep->fileline()->modifyWarnOff(V3ErrorCode::UNUSED, true); // Warn only once
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}
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} else if (allD && !anyU) {
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if (!unusedMatch(nodep)) {
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nodep->v3warn(UNUSED, "Signal is not used: "<<nodep->prettyName());
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nodep->fileline()->modifyWarnOff(V3ErrorCode::UNUSED, true); // Warn only once
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}
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} else if (!anyD && allU) {
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nodep->v3warn(UNDRIVEN, "Signal is not driven: "<<nodep->prettyName());
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nodep->fileline()->modifyWarnOff(V3ErrorCode::UNDRIVEN, true); // Warn only once
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} else {
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// Bits have different dispositions
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bool setU=false; bool setD=false;
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if (anynotDU && !unusedMatch(nodep)) {
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nodep->v3warn(UNUSED, "Bits of signal are not driven, nor used: "<<nodep->prettyName()
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<<bitNames(BN_BOTH));
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setU=true;
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}
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if (anyDnotU && !unusedMatch(nodep)) {
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nodep->v3warn(UNUSED, "Bits of signal are not used: "<<nodep->prettyName()
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<<bitNames(BN_UNUSED));
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setU=true;
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}
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if (anyUnotD) {
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nodep->v3warn(UNDRIVEN, "Bits of signal are not driven: "<<nodep->prettyName()
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<<bitNames(BN_UNDRIVEN));
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setD=true;
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}
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if (setU) nodep->fileline()->modifyWarnOff(V3ErrorCode::UNUSED, true); // Warn only once
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if (setD) nodep->fileline()->modifyWarnOff(V3ErrorCode::UNDRIVEN, true); // Warn only once
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}
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}
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}
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};
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//######################################################################
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// Undriven state, as a visitor of each AstNode
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class UndrivenVisitor : public AstNVisitor {
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private:
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// NODE STATE
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// Netlist:
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// AstVar::user1p -> UndrivenVar* for usage var, 0=not set yet
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AstUser1InUse m_inuser1;
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// Each always:
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// AstNode::user2p -> UndrivenVar* for usage var, 0=not set yet
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AstUser2InUse m_inuser2;
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// STATE
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std::vector<UndrivenVarEntry*> m_entryps[3]; // Nodes to delete when we are finished
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bool m_inBBox; // In black box; mark as driven+used
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AstNodeFTask* m_taskp; // Current task
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AstAlways* m_alwaysp; // Current always if combo, otherwise NULL
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// METHODS
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VL_DEBUG_FUNC; // Declare debug()
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UndrivenVarEntry* getEntryp(AstVar* nodep, int which_user) {
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if (!(which_user==1 ? nodep->user1p() : nodep->user2p())) {
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UndrivenVarEntry* entryp = new UndrivenVarEntry(nodep);
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//UINFO(9," Associate u="<<which_user<<" "<<(void*)this<<" "<<nodep->name()<<endl);
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m_entryps[which_user].push_back(entryp);
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if (which_user==1) nodep->user1p(entryp);
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else if (which_user==2) nodep->user2p(entryp);
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else nodep->v3fatalSrc("Bad case");
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return entryp;
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} else {
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UndrivenVarEntry* entryp = (UndrivenVarEntry*)(which_user==1 ? nodep->user1p() : nodep->user2p());
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return entryp;
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}
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}
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void warnAlwCombOrder(AstNodeVarRef* nodep) {
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AstVar* varp = nodep->varp();
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if (!varp->isParam() && !varp->isGenVar() && !varp->isUsedLoopIdx()
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&& !m_inBBox // We may have falsely considered a SysIgnore as a driver
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&& !VN_IS(nodep, VarXRef) // Xrefs might point at two different instances
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&& !varp->fileline()->warnIsOff(V3ErrorCode::ALWCOMBORDER)) { // Warn only once per variable
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nodep->v3warn(ALWCOMBORDER, "Always_comb variable driven after use: "<<nodep->prettyName());
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varp->fileline()->modifyWarnOff(V3ErrorCode::ALWCOMBORDER, true); // Complain just once for any usage
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}
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}
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// VISITORS
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virtual void visit(AstVar* nodep) {
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for (int usr=1; usr<(m_alwaysp?3:2); ++usr) {
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// For assigns and non-combo always, do just usr==1, to look for module-wide undriven etc
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// For non-combo always, run both usr==1 for above, and also usr==2 for always-only checks
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UndrivenVarEntry* entryp = getEntryp(nodep, usr);
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if (nodep->isInput()
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|| nodep->isSigPublic() || nodep->isSigUserRWPublic()
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|| (m_taskp && (m_taskp->dpiImport() || m_taskp->dpiExport()))) {
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entryp->drivenWhole();
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}
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if (nodep->isOutput()
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|| nodep->isSigPublic() || nodep->isSigUserRWPublic()
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|| nodep->isSigUserRdPublic()
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|| (m_taskp && (m_taskp->dpiImport() || m_taskp->dpiExport()))) {
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entryp->usedWhole();
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}
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}
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// Discover variables used in bit definitions, etc
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iterateChildren(nodep);
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}
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virtual void visit(AstArraySel* nodep) {
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// Arrays are rarely constant assigned, so for now we punt and do all entries
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iterateChildren(nodep);
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}
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virtual void visit(AstSliceSel* nodep) {
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// Arrays are rarely constant assigned, so for now we punt and do all entries
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iterateChildren(nodep);
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}
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virtual void visit(AstSel* nodep) {
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AstNodeVarRef* varrefp = VN_CAST(nodep->fromp(), NodeVarRef);
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AstConst* constp = VN_CAST(nodep->lsbp(), Const);
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if (varrefp && constp && !constp->num().isFourState()) {
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for (int usr=1; usr<(m_alwaysp?3:2); ++usr) {
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UndrivenVarEntry* entryp = getEntryp(varrefp->varp(), usr);
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int lsb = constp->toUInt();
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if (m_inBBox || varrefp->lvalue()) {
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// Don't warn if already driven earlier as "a=0; if(a) a=1;" is fine.
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if (usr==2 && m_alwaysp && entryp->isUsedNotDrivenBit(lsb, nodep->width())) {
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UINFO(9," Select. Entryp="<<(void*)entryp<<endl);
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warnAlwCombOrder(varrefp);
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}
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entryp->drivenBit(lsb, nodep->width());
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}
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if (m_inBBox || !varrefp->lvalue()) entryp->usedBit(lsb, nodep->width());
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}
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} else {
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// else other varrefs handled as unknown mess in AstVarRef
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iterateChildren(nodep);
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}
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}
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virtual void visit(AstNodeVarRef* nodep) {
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// Any variable
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for (int usr=1; usr<(m_alwaysp?3:2); ++usr) {
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UndrivenVarEntry* entryp = getEntryp(nodep->varp(), usr);
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bool fdrv = nodep->lvalue() && nodep->varp()->attrFileDescr(); // FD's are also being read from
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if (m_inBBox || nodep->lvalue()) {
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if (usr==2 && m_alwaysp && entryp->isUsedNotDrivenAny()) {
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UINFO(9," Full bus. Entryp="<<(void*)entryp<<endl);
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warnAlwCombOrder(nodep);
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}
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entryp->drivenWhole();
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}
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if (m_inBBox || !nodep->lvalue() || fdrv) entryp->usedWhole();
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}
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}
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// Don't know what black boxed calls do, assume in+out
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virtual void visit(AstSysIgnore* nodep) {
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bool prevMark = m_inBBox;
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m_inBBox = true;
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iterateChildren(nodep);
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m_inBBox = prevMark;
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}
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virtual void visit(AstAlways* nodep) {
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AstAlways* prevAlwp = m_alwaysp;
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{
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AstNode::user2ClearTree();
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if (nodep->keyword() == VAlwaysKwd::ALWAYS_COMB) UINFO(9," "<<nodep<<endl);
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if (nodep->keyword() == VAlwaysKwd::ALWAYS_COMB) m_alwaysp = nodep;
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else m_alwaysp = NULL;
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iterateChildren(nodep);
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if (nodep->keyword() == VAlwaysKwd::ALWAYS_COMB) UINFO(9," Done "<<nodep<<endl);
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}
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m_alwaysp = prevAlwp;
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}
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virtual void visit(AstNodeFTask* nodep) {
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AstNodeFTask* prevTaskp = m_taskp;
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m_taskp = nodep;
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iterateChildren(nodep);
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m_taskp = prevTaskp;
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}
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// Until we support tables, primitives will have undriven and unused I/Os
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virtual void visit(AstPrimitive* nodep) {}
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// Coverage artifacts etc shouldn't count as a sink
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virtual void visit(AstCoverDecl* nodep) {}
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virtual void visit(AstCoverInc* nodep) {}
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virtual void visit(AstCoverToggle* nodep) {}
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virtual void visit(AstTraceDecl* nodep) {}
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virtual void visit(AstTraceInc* nodep) {}
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// iterate
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virtual void visit(AstConst* nodep) {}
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virtual void visit(AstNode* nodep) {
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iterateChildren(nodep);
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}
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public:
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// CONSTUCTORS
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explicit UndrivenVisitor(AstNetlist* nodep) {
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m_inBBox = false;
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m_taskp = NULL;
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m_alwaysp = NULL;
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iterate(nodep);
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}
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virtual ~UndrivenVisitor() {
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for (std::vector<UndrivenVarEntry*>::iterator it = m_entryps[1].begin(); it != m_entryps[1].end(); ++it) {
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(*it)->reportViolations();
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}
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for (int usr=1; usr<3; ++usr) {
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for (std::vector<UndrivenVarEntry*>::iterator it = m_entryps[usr].begin(); it != m_entryps[usr].end(); ++it) {
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delete (*it);
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}
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}
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}
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};
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//######################################################################
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// Undriven class functions
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void V3Undriven::undrivenAll(AstNetlist* nodep) {
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UINFO(2,__FUNCTION__<<": "<<endl);
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UndrivenVisitor visitor (nodep);
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}
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