verilator/src/V3Unknown.cpp

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// -*- mode: C++; c-file-style: "cc-mode" -*-
//*************************************************************************
// DESCRIPTION: Verilator: Add Unknown assigns
//
// Code available from: http://www.veripool.org/verilator
//
//*************************************************************************
//
// Copyright 2003-2018 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.
//
//*************************************************************************
// V3Unknown's Transformations:
//
// Each module:
// TBD: Eliminate tristates by adding __in, __inen, __en wires in parallel
// Need __en in changed list if a signal is on the LHS of a assign
// Constants:
// RHS, Replace 5'bx_1_x with a module global we init to a random value
// CONST(5'bx_1_x) -> VARREF(_{numberedtemp})
// -> VAR(_{numberedtemp})
// -> INITIAL(VARREF(_{numberedtemp}), OR(5'bx_1_x,AND(random,5'b0_1_x))
// OPTIMIZE: Must not collapse this initial back into the equation.
//
//*************************************************************************
#include "config_build.h"
#include "verilatedos.h"
#include <cstdio>
#include <cstdarg>
#include <unistd.h>
#include <algorithm>
#include "V3Global.h"
#include "V3Unknown.h"
#include "V3Ast.h"
#include "V3Const.h"
#include "V3Stats.h"
//######################################################################
class UnknownVisitor : public AstNVisitor {
private:
// NODE STATE
// Cleared on Netlist
// AstSel::user() -> bool. Set true if already processed
// AstArraySel::user() -> bool. Set true if already processed
// AstNode::user2p() -> AstIf* Inserted if assignment for conditional
AstUser1InUse m_inuser1;
AstUser2InUse m_inuser2;
// STATE
AstNodeModule* m_modp; // Current module
bool m_constXCvt; // Convert X's
V3Double0 m_statUnkVars; // Statistic tracking
AstAssignW* m_assignwp; // Current assignment
AstAssignDly* m_assigndlyp; // Current assignment
// METHODS
static int debug() {
static int level = -1;
if (VL_UNLIKELY(level < 0)) level = v3Global.opt.debugSrcLevel(__FILE__);
return level;
}
void replaceBoundLvalue(AstNode* nodep, AstNode* condp) {
// Spec says a out-of-range LHS SEL results in a NOP.
// This is a PITA. We could:
// 1. IF(...) around an ASSIGN,
// but that would break a "foo[TOO_BIG]=$fopen(...)".
// 2. Hack to extend the size of the output structure
// by one bit, and write to that temporary, but never read it.
// That makes there be two widths() and is likely a bug farm.
// 3. Make a special SEL to choose between the real lvalue
// and a temporary NOP register.
// 4. Assign to a temp, then IF that assignment.
// This is suspected to be nicest to later optimizations.
// 4 seems best but breaks later optimizations. 3 was tried,
// but makes a mess in the emitter as lvalue switching is needed. So 4.
// SEL(...) -> temp
// if (COND(LTE(bit<=maxlsb))) ASSIGN(SEL(...)),temp)
if (m_assignwp) {
// Wire assigns must become always statements to deal with insertion
// of multiple statements. Perhaps someday make all wassigns into always's?
UINFO(5," IM_WireRep "<<m_assignwp<<endl);
m_assignwp->convertToAlways(); pushDeletep(m_assignwp); m_assignwp=NULL;
}
bool needDly = (m_assigndlyp != NULL);
if (m_assigndlyp) {
// Delayed assignments become normal assignments,
// then the temp created becomes the delayed assignment
AstNode* newp = new AstAssign(m_assigndlyp->fileline(),
m_assigndlyp->lhsp()->unlinkFrBackWithNext(),
m_assigndlyp->rhsp()->unlinkFrBackWithNext());
m_assigndlyp->replaceWith(newp); pushDeletep(m_assigndlyp); m_assigndlyp=NULL;
}
AstNode* prep = nodep;
// Scan back to put the condlvalue above all selects (IE top of the lvalue)
while (prep->backp()->castNodeSel()
|| prep->backp()->castSel()) {
prep=prep->backp();
}
FileLine* fl = nodep->fileline();
VL_DANGLING(nodep); // Zap it so we don't use it by mistake - use prep
// Already exists; rather than IF(a,... IF(b... optimize to IF(a&&b,
// Saves us teaching V3Const how to optimize, and it won't be needed again.
if (AstIf* ifp = prep->user2p()->castIf()) {
if (needDly) prep->v3fatalSrc("Should have already converted to non-delay");
AstNRelinker replaceHandle;
AstNode* earliercondp = ifp->condp()->unlinkFrBack(&replaceHandle);
AstNode* newp = new AstLogAnd (condp->fileline(),
condp,
earliercondp);
UINFO(4, "Edit BOUNDLVALUE "<<newp<<endl);
replaceHandle.relink(newp);
}
else {
string name = ((string)"__Vlvbound"+cvtToStr(m_modp->varNumGetInc()));
AstVar* varp = new AstVar(fl, AstVarType::MODULETEMP, name,
prep->dtypep());
m_modp->addStmtp(varp);
AstNode* abovep = prep->backp(); // Grab above point before lose it w/ next replace
prep->replaceWith(new AstVarRef(fl, varp, true));
AstNode* newp = new AstIf(fl, condp,
(needDly
? static_cast<AstNode*>
(new AstAssignDly(fl, prep,
new AstVarRef(fl, varp, false)))
: static_cast<AstNode*>
(new AstAssign (fl, prep,
new AstVarRef(fl, varp, false)))),
NULL);
if (debug()>=9) newp->dumpTree(cout," _new: ");
abovep->addNextStmt(newp,abovep);
prep->user2p(newp); // Save so we may LogAnd it next time
}
}
// VISITORS
virtual void visit(AstNodeModule* nodep) {
UINFO(4," MOD "<<nodep<<endl);
m_modp = nodep;
m_constXCvt = true;
nodep->iterateChildren(*this);
m_modp = NULL;
}
virtual void visit(AstAssignDly* nodep) {
m_assigndlyp = nodep;
nodep->iterateChildren(*this); VL_DANGLING(nodep); // May delete nodep.
m_assigndlyp = NULL;
}
virtual void visit(AstAssignW* nodep) {
m_assignwp = nodep;
nodep->iterateChildren(*this); VL_DANGLING(nodep); // May delete nodep.
m_assignwp = NULL;
}
virtual void visit(AstCaseItem* nodep) {
m_constXCvt = false; // Avoid losing the X's in casex
nodep->condsp()->iterateAndNext(*this);
m_constXCvt = true;
nodep->bodysp()->iterateAndNext(*this);
}
virtual void visit(AstNodeDType* nodep) {
m_constXCvt = false; // Avoid losing the X's in casex
nodep->iterateChildren(*this);
m_constXCvt = true;
}
void visitEqNeqCase(AstNodeBiop* nodep) {
UINFO(4," N/EQCASE->EQ "<<nodep<<endl);
V3Const::constifyEdit(nodep->lhsp()); // lhsp may change
V3Const::constifyEdit(nodep->rhsp()); // rhsp may change
if (nodep->lhsp()->castConst() && nodep->rhsp()->castConst()) {
// Both sides are constant, node can be constant
V3Const::constifyEdit(nodep); VL_DANGLING(nodep);
return;
} else {
AstNode* lhsp = nodep->lhsp()->unlinkFrBack();
AstNode* rhsp = nodep->rhsp()->unlinkFrBack();
AstNode* newp;
// If we got ==1'bx it can never be true (but 1'bx==1'bx can be!)
if (((lhsp->castConst() && lhsp->castConst()->num().isFourState())
|| (rhsp->castConst() && rhsp->castConst()->num().isFourState()))) {
V3Number num (nodep->fileline(), 1, (nodep->castEqCase()?0:1));
newp = new AstConst (nodep->fileline(), num);
lhsp->deleteTree(); VL_DANGLING(lhsp);
rhsp->deleteTree(); VL_DANGLING(rhsp);
} else {
if (nodep->castEqCase())
newp = new AstEq (nodep->fileline(), lhsp, rhsp);
else newp = new AstNeq (nodep->fileline(), lhsp, rhsp);
}
nodep->replaceWith(newp);
nodep->deleteTree(); VL_DANGLING(nodep);
// Iterate tree now that we may have gotten rid of Xs
newp->iterateChildren(*this);
}
}
void visitEqNeqWild(AstNodeBiop* nodep) {
UINFO(4," N/EQWILD->EQ "<<nodep<<endl);
V3Const::constifyEdit(nodep->lhsp()); // lhsp may change
V3Const::constifyEdit(nodep->rhsp()); // rhsp may change
if (nodep->lhsp()->castConst() && nodep->rhsp()->castConst()) {
// Both sides are constant, node can be constant
V3Const::constifyEdit(nodep); VL_DANGLING(nodep);
return;
} else {
AstNode* lhsp = nodep->lhsp()->unlinkFrBack();
AstNode* rhsp = nodep->rhsp()->unlinkFrBack();
AstNode* newp;
if (!rhsp->castConst()) {
nodep->v3error("Unsupported: RHS of ==? or !=? must be constant to be synthesizable"); // Says spec.
// Replace with anything that won't cause more errors
newp = new AstEq (nodep->fileline(), lhsp, rhsp);
} else {
// X or Z's become mask, ala case statements.
V3Number nummask (rhsp->fileline(), rhsp->width());
nummask.opBitsNonX(rhsp->castConst()->num());
V3Number numval (rhsp->fileline(), rhsp->width());
numval.opBitsOne (rhsp->castConst()->num());
AstNode* and1p = new AstAnd(nodep->fileline(), lhsp,
new AstConst(nodep->fileline(), nummask));
AstNode* and2p = new AstConst(nodep->fileline(), numval);
if (nodep->castEqWild())
newp = new AstEq (nodep->fileline(), and1p, and2p);
else newp = new AstNeq (nodep->fileline(), and1p, and2p);
rhsp->deleteTree(); VL_DANGLING(rhsp);
}
nodep->replaceWith(newp);
nodep->deleteTree(); VL_DANGLING(nodep);
// Iterate tree now that we may have gotten rid of the compare
newp->iterateChildren(*this);
}
}
virtual void visit(AstEqCase* nodep) {
visitEqNeqCase(nodep);
}
virtual void visit(AstNeqCase* nodep) {
visitEqNeqCase(nodep);
}
virtual void visit(AstEqWild* nodep) {
visitEqNeqWild(nodep);
}
virtual void visit(AstNeqWild* nodep) {
visitEqNeqWild(nodep);
}
virtual void visit(AstIsUnknown* nodep) {
nodep->iterateChildren(*this);
// Ahh, we're two state, so this is easy
UINFO(4," ISUNKNOWN->0 "<<nodep<<endl);
V3Number zero (nodep->fileline(), 1, 0);
AstConst* newp = new AstConst (nodep->fileline(), zero);
nodep->replaceWith(newp);
nodep->deleteTree(); VL_DANGLING(nodep);
}
virtual void visit(AstConst* nodep) {
if (m_constXCvt
&& nodep->num().isFourState()) {
UINFO(4," CONST4 "<<nodep<<endl);
if (debug()>=9) nodep->dumpTree(cout," Const_old: ");
// CONST(num) -> VARREF(newvarp)
// -> VAR(newvarp)
// -> INITIAL(VARREF(newvarp, OR(num_No_Xs,AND(random,num_1s_Where_X))
V3Number numb1 (nodep->fileline(), nodep->width());
numb1.opBitsOne(nodep->num());
V3Number numbx (nodep->fileline(), nodep->width());
numbx.opBitsXZ(nodep->num());
if (v3Global.opt.xAssign()!="unique") {
// All X bits just become 0; fastest simulation, but not nice
V3Number numnew (nodep->fileline(), numb1.width());
if (v3Global.opt.xAssign()=="1") {
numnew.opOr(numb1, numbx);
} else {
numnew.opAssign(numb1);
}
AstConst* newp = new AstConst(nodep->fileline(), numnew);
nodep->replaceWith(newp);
nodep->deleteTree(); VL_DANGLING(nodep);
UINFO(4," -> "<<newp<<endl);
} else {
// Make a Vxrand variable
// We use the special XTEMP type so it doesn't break pure functions
if (!m_modp) nodep->v3fatalSrc("X number not under module");
string newvarname = ((string)"__Vxrand"
+cvtToStr(m_modp->varNumGetInc()));
AstVar* newvarp
= new AstVar (nodep->fileline(), AstVarType::XTEMP, newvarname,
VFlagLogicPacked(), nodep->width());
++m_statUnkVars;
AstNRelinker replaceHandle;
nodep->unlinkFrBack(&replaceHandle);
AstNodeVarRef* newref1p = new AstVarRef(nodep->fileline(), newvarp, false);
replaceHandle.relink(newref1p); // Replace const with varref
AstInitial* newinitp
= new AstInitial(
nodep->fileline(),
new AstAssign(
nodep->fileline(),
new AstVarRef(nodep->fileline(), newvarp, true),
new AstOr(nodep->fileline(),
new AstConst(nodep->fileline(),numb1),
new AstAnd(nodep->fileline(),
new AstConst(nodep->fileline(),numbx),
new AstRand(nodep->fileline(),
nodep->dtypep(), true)))));
// Add inits in front of other statement.
// In the future, we should stuff the initp into the module's constructor.
AstNode* afterp = m_modp->stmtsp()->unlinkFrBackWithNext();
m_modp->addStmtp(newvarp);
m_modp->addStmtp(newinitp);
m_modp->addStmtp(afterp);
if (debug()>=9) newref1p->dumpTree(cout," _new: ");
if (debug()>=9) newvarp->dumpTree(cout," _new: ");
if (debug()>=9) newinitp->dumpTree(cout," _new: ");
nodep->deleteTree(); VL_DANGLING(nodep);
}
}
}
virtual void visit(AstSel* nodep) {
nodep->iterateChildren(*this);
if (!nodep->user1SetOnce()) {
// Guard against reading/writing past end of bit vector array
AstNode* basefromp = AstArraySel::baseFromp(nodep);
bool lvalue = false;
if (AstNodeVarRef* varrefp = basefromp->castNodeVarRef()) {
lvalue = varrefp->lvalue();
}
// Find range of dtype we are selecting from
// Similar code in V3Const::warnSelect
int maxmsb = nodep->fromp()->dtypep()->width()-1;
if (debug()>=9) nodep->dumpTree(cout,"sel_old: ");
V3Number maxmsbnum (nodep->fileline(), nodep->lsbp()->width(), maxmsb);
// If (maxmsb >= selected), we're in bound
AstNode* condp = new AstGte (nodep->fileline(),
new AstConst(nodep->fileline(), maxmsbnum),
nodep->lsbp()->cloneTree(false));
// See if the condition is constant true (e.g. always in bound due to constant select)
// Note below has null backp(); the Edit function knows how to deal with that.
condp = V3Const::constifyEdit(condp);
if (condp->isOne()) {
// We don't need to add a conditional; we know the existing expression is ok
condp->deleteTree();
}
else if (!lvalue) {
// SEL(...) -> COND(LTE(bit<=maxmsb), ARRAYSEL(...), {width{1'bx}})
AstNRelinker replaceHandle;
nodep->unlinkFrBack(&replaceHandle);
V3Number xnum (nodep->fileline(), nodep->width());
xnum.setAllBitsX();
AstNode* newp = new AstCondBound (nodep->fileline(),
condp,
nodep,
new AstConst(nodep->fileline(), xnum));
if (debug()>=9) newp->dumpTree(cout," _new: ");
// Link in conditional
replaceHandle.relink(newp);
// Added X's, tristate them too
newp->accept(*this);
}
else { // lvalue
replaceBoundLvalue(nodep, condp);
}
}
}
// visit(AstSliceSel) not needed as its bounds are constant and checked
// in V3Width.
virtual void visit(AstArraySel* nodep) {
nodep->iterateChildren(*this);
if (!nodep->user1SetOnce()) {
if (debug()==9) nodep->dumpTree(cout,"-in: ");
// Guard against reading/writing past end of arrays
AstNode* basefromp = AstArraySel::baseFromp(nodep->fromp());
bool lvalue = false;
if (AstNodeVarRef* varrefp = basefromp->castNodeVarRef()) {
lvalue = varrefp->lvalue();
} else if (basefromp->castConst()) {
// If it's a PARAMETER[bit], then basefromp may be a constant instead of a varrefp
} else {
nodep->v3fatalSrc("No VarRef or Const under ArraySel");
}
// Find range of dtype we are selecting from
int declElements = -1;
AstNodeDType* dtypep = nodep->fromp()->dtypep()->skipRefp();
if (!dtypep) nodep->v3fatalSrc("Select of non-selectable type");
if (AstNodeArrayDType* adtypep = dtypep->castNodeArrayDType()) {
declElements = adtypep->elementsConst();
} else {
nodep->v3error("Select from non-array "<<dtypep->prettyTypeName());
}
if (debug()>=9) nodep->dumpTree(cout,"arraysel_old: ");
V3Number widthnum (nodep->fileline(), nodep->bitp()->width(), declElements-1);
// See if the condition is constant true
AstNode* condp = new AstGte (nodep->fileline(),
new AstConst(nodep->fileline(), widthnum),
nodep->bitp()->cloneTree(false));
// Note below has null backp(); the Edit function knows how to deal with that.
condp = V3Const::constifyEdit(condp);
if (condp->isOne()) {
// We don't need to add a conditional; we know the existing expression is ok
condp->deleteTree();
}
else if (!lvalue
&& !nodep->backp()->castArraySel()) { // Too complicated and slow if mid-multidimension
// ARRAYSEL(...) -> COND(LT(bit<maxbit), ARRAYSEL(...), {width{1'bx}})
AstNRelinker replaceHandle;
nodep->unlinkFrBack(&replaceHandle);
V3Number xnum (nodep->fileline(), nodep->width());
if (nodep->isString()) {
xnum = V3Number(V3Number::String(), nodep->fileline(), "");
} else {
xnum.setAllBitsX();
}
AstNode* newp = new AstCondBound (nodep->fileline(),
condp,
nodep,
new AstConst(nodep->fileline(), xnum));
if (debug()>=9) newp->dumpTree(cout," _new: ");
// Link in conditional, can blow away temp xor
replaceHandle.relink(newp);
// Added X's, tristate them too
newp->accept(*this);
}
else if (!lvalue) { // Mid-multidimension read, just use zero
// ARRAYSEL(...) -> ARRAYSEL(COND(LT(bit<maxbit), bit, 0))
AstNRelinker replaceHandle;
AstNode* bitp = nodep->bitp()->unlinkFrBack(&replaceHandle);
V3Number zeronum (nodep->fileline(), bitp->width(), 0);
AstNode* newp = new AstCondBound (bitp->fileline(),
condp,
bitp,
new AstConst(bitp->fileline(), zeronum));
// Added X's, tristate them too
if (debug()>=9) newp->dumpTree(cout," _new: ");
replaceHandle.relink(newp);
newp->accept(*this);
}
else { // lvalue
replaceBoundLvalue(nodep, condp);
}
}
}
//--------------------
// Default: Just iterate
virtual void visit(AstNode* nodep) {
nodep->iterateChildren(*this);
}
public:
// CONSTUCTORS
explicit UnknownVisitor(AstNetlist* nodep) {
m_modp = NULL;
m_assigndlyp = NULL;
m_assignwp = NULL;
m_constXCvt = false;
nodep->accept(*this);
}
virtual ~UnknownVisitor() {
V3Stats::addStat("Unknowns, variables created", m_statUnkVars);
}
};
//######################################################################
// Unknown class functions
void V3Unknown::unknownAll(AstNetlist* nodep) {
UINFO(2,__FUNCTION__<<": "<<endl);
{
UnknownVisitor visitor (nodep);
} // Destruct before checking
V3Global::dumpCheckGlobalTree("unknown", 0, v3Global.opt.dumpTreeLevel(__FILE__) >= 3);
}