verilator/src/V3Delayed.cpp
2021-01-01 10:29:54 -05:00

517 lines
24 KiB
C++

// -*- mode: C++; c-file-style: "cc-mode" -*-
//*************************************************************************
// DESCRIPTION: Verilator: Add temporaries, such as for delayed nodes
//
// Code available from: https://verilator.org
//
//*************************************************************************
//
// Copyright 2003-2021 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
//
//*************************************************************************
// V3Delayed's Transformations:
//
// Each module:
// Replace ASSIGNDLY var, exp
// With ASSIGNDLY newvar, exp
// At top of block: VAR newvar
// At bottom of block: ASSIGNW var newvar
// Need _x_dly = x at top of active if "x" is not always set
// For now we'll say it's set if at top of block (not under IF, etc)
// Need x = _x_dly at bottom of active if "x" is never referenced on LHS
// in the active, and above rule applies too.
// (If so, use x on LHS, not _x_dly.)
//
// If a signal is set in multiple always blocks, we need a dly read & set with
// multiple clock sensitivities. We have 3 options:
// 1. When detected, make a new ACTIVE and move earlier created delayed assignment there
// 2. Form unique ACTIVE for every multiple clocked assignment
// 3. Predetect signals from multiple always blocks and do #2 on them
// Since all 3 require a top activation cleanup, we do #2 which is easiest.
//
// ASSIGNDLY (BITSEL(ARRAYSEL (VARREF(v), bits), selbits), rhs)
// -> VAR __Vdlyvset_x
// VAR __Vdlyvval_x
// VAR __Vdlyvdim_x
// VAR __Vdlyvlsb_x
// ASSIGNW (__Vdlyvset_x,0)
// ...
// ASSIGNW (VARREF(__Vdlyvval_x), rhs)
// ASSIGNW (__Vdlyvdim_x, dimension_number)
// ASSIGNW (__Vdlyvset_x, 1)
// ...
// ASSIGNW (BITSEL(ARRAYSEL(VARREF(x), __Vdlyvdim_x), __Vdlyvlsb_x), __Vdlyvval_x)
//
//*************************************************************************
#include "config_build.h"
#include "verilatedos.h"
#include "V3Global.h"
#include "V3Delayed.h"
#include "V3Ast.h"
#include "V3Stats.h"
#include <algorithm>
#include <deque>
#include <map>
//######################################################################
// Delayed state, as a visitor of each AstNode
class DelayedVisitor final : public AstNVisitor {
private:
// NODE STATE
// Cleared each module:
// AstVarScope::user1p() -> AstVarScope*. Points to temp var created.
// AstVarScope::user2p() -> AstActive*. Points to activity block of signal
// (valid when AstVarScope::user1p is valid)
// AstVarScope::user4p() -> AstAlwaysPost*. Post block for this variable
// AstVarScope::user5p() -> AstVarRef*. Last blocking or non-blocking reference
// AstVar::user2() -> bool. Set true if already made warning
// AstVarRef::user2() -> bool. Set true if already processed
// AstVarRef::user5() -> bool. Set true if was blocking reference
// AstAlwaysPost::user2() -> ActActive*. Points to activity block of signal
// (valid when AstAlwaysPost::user4p is valid)
// AstAlwaysPost::user4() -> AstIf*. Last IF (__Vdlyvset__) created under this AlwaysPost
// Cleared each scope/active:
// AstAssignDly::user3() -> AstVarScope*. __Vdlyvset__ created for this assign
// AstAlwaysPost::user3() -> AstVarScope*. __Vdlyvset__ last referenced in IF
AstUser1InUse m_inuser1;
AstUser2InUse m_inuser2;
AstUser3InUse m_inuser3;
AstUser4InUse m_inuser4;
AstUser5InUse m_inuser5;
// STATE
AstActive* m_activep = nullptr; // Current activate
AstCFunc* m_cfuncp = nullptr; // Current public C Function
AstAssignDly* m_nextDlyp = nullptr; // Next delayed assignment in a list of assignments
bool m_inDly = false; // True in delayed assignments
bool m_inLoop = false; // True in for loops
bool m_inInitial = false; // True in initial blocks
typedef std::map<const std::pair<AstNodeModule*, string>, AstVar*> VarMap;
VarMap m_modVarMap; // Table of new var names created under module
VDouble0 m_statSharedSet; // Statistic tracking
typedef std::unordered_map<const AstVarScope*, int> ScopeVecMap;
ScopeVecMap m_scopeVecMap; // Next var number for each scope
// METHODS
VL_DEBUG_FUNC; // Declare debug()
void markVarUsage(AstNodeVarRef* nodep, bool blocking) {
if (blocking) nodep->user5(true);
AstVarScope* vscp = nodep->varScopep();
// UINFO(4, " MVU " << blocking << " " << nodep << endl);
AstNode* lastrefp = vscp->user5p();
if (!lastrefp) {
vscp->user5p(nodep);
} else {
bool last_was_blocking = lastrefp->user5();
if (last_was_blocking != blocking) {
AstNode* nonblockingp = blocking ? nodep : lastrefp;
AstNode* blockingp = blocking ? lastrefp : nodep;
vscp->v3warn(
BLKANDNBLK,
"Unsupported: Blocked and non-blocking assignments to same variable: "
<< vscp->varp()->prettyNameQ() << '\n'
<< vscp->warnContextPrimary() << '\n'
<< blockingp->warnOther() << "... Location of blocking assignment\n"
<< blockingp->warnContextSecondary() << '\n'
<< nonblockingp->warnOther() << "... Location of nonblocking assignment\n"
<< nonblockingp->warnContextSecondary());
}
}
}
AstVarScope* createVarSc(AstVarScope* oldvarscp, const string& name,
int width /*0==fromoldvar*/, AstNodeDType* newdtypep) {
// Because we've already scoped it, we may need to add both the AstVar and the AstVarScope
UASSERT_OBJ(oldvarscp->scopep(), oldvarscp, "Var unscoped");
AstVar* varp;
AstNodeModule* addmodp = oldvarscp->scopep()->modp();
// We need a new AstVar, but only one for all scopes, to match the new AstVarScope
const auto it = m_modVarMap.find(make_pair(addmodp, name));
if (it != m_modVarMap.end()) {
// Created module's AstVar earlier under some other scope
varp = it->second;
} else {
if (newdtypep) {
varp = new AstVar(oldvarscp->fileline(), AstVarType::BLOCKTEMP, name, newdtypep);
} else if (width == 0) {
varp = new AstVar(oldvarscp->fileline(), AstVarType::BLOCKTEMP, name,
oldvarscp->varp());
varp->dtypeFrom(oldvarscp);
} else { // Used for vset and dimensions, so can zero init
varp = new AstVar(oldvarscp->fileline(), AstVarType::BLOCKTEMP, name,
VFlagBitPacked(), width);
}
addmodp->addStmtp(varp);
m_modVarMap.emplace(make_pair(addmodp, name), varp);
}
AstVarScope* varscp = new AstVarScope(oldvarscp->fileline(), oldvarscp->scopep(), varp);
oldvarscp->scopep()->addVarp(varscp);
return varscp;
}
AstActive* createActivePost(AstVarRef* varrefp) {
AstActive* newactp
= new AstActive(varrefp->fileline(), "sequentdly", m_activep->sensesp());
// Was addNext(), but addNextHere() avoids a linear search.
m_activep->addNextHere(newactp);
return newactp;
}
void checkActivePost(AstVarRef* varrefp, AstActive* oldactivep) {
// Check for MULTIDRIVEN, and if so make new sentree that joins old & new sentree
UASSERT_OBJ(oldactivep, varrefp, "<= old dly assignment not put under sensitivity block");
if (oldactivep->sensesp() != m_activep->sensesp()) {
if (!varrefp->varp()->fileline()->warnIsOff(V3ErrorCode::MULTIDRIVEN)
&& !varrefp->varp()->user2()) {
varrefp->varp()->v3warn(
MULTIDRIVEN,
"Signal has multiple driving blocks with different clocking: "
<< varrefp->varp()->prettyNameQ() << '\n'
<< varrefp->warnOther() << "... Location of first driving block\n"
<< varrefp->warnContextPrimary() << '\n'
<< oldactivep->warnOther() << "... Location of other driving block\n"
<< oldactivep->warnContextSecondary());
varrefp->varp()->user2(true);
}
UINFO(4, "AssignDupDlyVar: " << varrefp << endl);
UINFO(4, " Act: " << m_activep << endl);
UINFO(4, " Act: " << oldactivep << endl);
// Make a new sensitivity list, which is the combination of both blocks
AstSenItem* sena = m_activep->sensesp()->sensesp()->cloneTree(true);
AstSenItem* senb = oldactivep->sensesp()->sensesp()->cloneTree(true);
AstSenTree* treep = new AstSenTree(m_activep->fileline(), sena);
if (senb) treep->addSensesp(senb);
if (AstSenTree* storep = oldactivep->sensesStorep()) {
storep->unlinkFrBack();
pushDeletep(storep);
}
oldactivep->sensesStorep(treep);
oldactivep->sensesp(treep);
}
}
AstNode* createDlyArray(AstAssignDly* nodep, AstNode* lhsp) {
// Create delayed assignment
// See top of this file for transformation
// Return the new LHS for the assignment, Null = unlink
// Find selects
AstNode* newlhsp = nullptr; // nullptr = unlink old assign
AstSel* bitselp = nullptr;
AstArraySel* arrayselp = nullptr;
if (VN_IS(lhsp, Sel)) {
bitselp = VN_CAST(lhsp, Sel);
arrayselp = VN_CAST(bitselp->fromp(), ArraySel);
} else {
arrayselp = VN_CAST(lhsp, ArraySel);
}
UASSERT_OBJ(arrayselp, nodep, "No arraysel under bitsel?");
UASSERT_OBJ(!VN_IS(arrayselp->dtypep()->skipRefp(), UnpackArrayDType), nodep,
"ArraySel with unpacked arrays should have been removed in V3Slice");
UINFO(4, "AssignDlyArray: " << nodep << endl);
//
//=== Dimensions: __Vdlyvdim__
std::deque<AstNode*> dimvalp; // Assignment value for each dimension of assignment
AstNode* dimselp = arrayselp;
for (; VN_IS(dimselp, ArraySel); dimselp = VN_CAST(dimselp, ArraySel)->fromp()) {
AstNode* valp = VN_CAST(dimselp, ArraySel)->bitp()->unlinkFrBack();
dimvalp.push_front(valp);
}
AstVarRef* varrefp = VN_CAST(dimselp, VarRef);
UASSERT_OBJ(varrefp, nodep, "No var underneath arraysels");
UASSERT_OBJ(varrefp->varScopep(), varrefp, "Var didn't get varscoped in V3Scope.cpp");
varrefp->unlinkFrBack();
AstVar* oldvarp = varrefp->varp();
int modVecNum = m_scopeVecMap[varrefp->varScopep()]++;
//
std::deque<AstNode*> dimreadps; // Read value for each dimension of assignment
for (unsigned dimension = 0; dimension < dimvalp.size(); dimension++) {
AstNode* dimp = dimvalp[dimension];
if (VN_IS(dimp, Const)) { // bit = const, can just use it
dimreadps.push_front(dimp);
} else {
string bitvarname = (string("__Vdlyvdim") + cvtToStr(dimension) + "__"
+ oldvarp->shortName() + "__v" + cvtToStr(modVecNum));
AstVarScope* bitvscp
= createVarSc(varrefp->varScopep(), bitvarname, dimp->width(), nullptr);
AstAssign* bitassignp = new AstAssign(
nodep->fileline(), new AstVarRef(nodep->fileline(), bitvscp, VAccess::WRITE),
dimp);
nodep->addNextHere(bitassignp);
dimreadps.push_front(new AstVarRef(nodep->fileline(), bitvscp, VAccess::READ));
}
}
//
//=== Bitselect: __Vdlyvlsb__
AstNode* bitreadp = nullptr; // Code to read Vdlyvlsb
if (bitselp) {
AstNode* lsbvaluep = bitselp->lsbp()->unlinkFrBack();
if (VN_IS(bitselp->fromp(), Const)) {
// vlsb = constant, can just push constant into where we use it
bitreadp = lsbvaluep;
} else {
string bitvarname = (string("__Vdlyvlsb__") + oldvarp->shortName() + "__v"
+ cvtToStr(modVecNum));
AstVarScope* bitvscp
= createVarSc(varrefp->varScopep(), bitvarname, lsbvaluep->width(), nullptr);
AstAssign* bitassignp = new AstAssign(
nodep->fileline(), new AstVarRef(nodep->fileline(), bitvscp, VAccess::WRITE),
lsbvaluep);
nodep->addNextHere(bitassignp);
bitreadp = new AstVarRef(nodep->fileline(), bitvscp, VAccess::READ);
}
}
//
//=== Value: __Vdlyvval__
AstNode* valreadp; // Code to read Vdlyvval
if (VN_IS(nodep->rhsp(), Const)) {
// vval = constant, can just push constant into where we use it
valreadp = nodep->rhsp()->unlinkFrBack();
} else {
string valvarname
= (string("__Vdlyvval__") + oldvarp->shortName() + "__v" + cvtToStr(modVecNum));
AstVarScope* valvscp
= createVarSc(varrefp->varScopep(), valvarname, 0, nodep->rhsp()->dtypep());
newlhsp = new AstVarRef(nodep->fileline(), valvscp, VAccess::WRITE);
valreadp = new AstVarRef(nodep->fileline(), valvscp, VAccess::READ);
}
//
//=== Setting/not setting boolean: __Vdlyvset__
AstVarScope* setvscp;
AstAssignPre* setinitp = nullptr;
if (nodep->user3p()) {
// Simplistic optimization. If the previous statement in same scope was also a =>,
// then we told this nodep->user3 we can use its Vdlyvset rather than making a new one.
// This is good for code like:
// for (i=0; i<5; i++) vector[i] <= something;
setvscp = VN_CAST(nodep->user3p(), VarScope);
++m_statSharedSet;
} else { // Create new one
string setvarname
= (string("__Vdlyvset__") + oldvarp->shortName() + "__v" + cvtToStr(modVecNum));
setvscp = createVarSc(varrefp->varScopep(), setvarname, 1, nullptr);
setinitp = new AstAssignPre(nodep->fileline(),
new AstVarRef(nodep->fileline(), setvscp, VAccess::WRITE),
new AstConst(nodep->fileline(), 0));
AstAssign* setassignp = new AstAssign(
nodep->fileline(), new AstVarRef(nodep->fileline(), setvscp, VAccess::WRITE),
new AstConst(nodep->fileline(), AstConst::BitTrue()));
nodep->addNextHere(setassignp);
}
if (m_nextDlyp) { // Tell next assigndly it can share the variable
m_nextDlyp->user3p(setvscp);
}
//
// Create ALWAYSPOST for delayed variable
// We add all logic to the same block if it's for the same memory
// This ensures that multiple assignments to the same memory will result
// in correctly ordered code - the last assignment must be last.
// It also has the nice side effect of assisting cache locality.
AstNode* selectsp = varrefp;
for (int dimension = int(dimreadps.size()) - 1; dimension >= 0; --dimension) {
selectsp = new AstArraySel(nodep->fileline(), selectsp, dimreadps[dimension]);
}
if (bitselp) {
selectsp = new AstSel(nodep->fileline(), selectsp, bitreadp,
bitselp->widthp()->cloneTree(false));
}
// Build "IF (changeit) ...
UINFO(9, " For " << setvscp << endl);
UINFO(9, " & " << varrefp << endl);
AstAlwaysPost* finalp = VN_CAST(varrefp->varScopep()->user4p(), AlwaysPost);
if (finalp) {
AstActive* oldactivep = VN_CAST(finalp->user2p(), Active);
checkActivePost(varrefp, oldactivep);
if (setinitp) oldactivep->addStmtsp(setinitp);
} else { // first time we've dealt with this memory
finalp = new AstAlwaysPost(nodep->fileline(), nullptr /*sens*/, nullptr /*body*/);
UINFO(9, " Created " << finalp << endl);
AstActive* newactp = createActivePost(varrefp);
newactp->addStmtsp(finalp);
varrefp->varScopep()->user4p(finalp);
finalp->user2p(newactp);
if (setinitp) newactp->addStmtsp(setinitp);
}
AstIf* postLogicp;
if (finalp->user3p() == setvscp) {
// Optimize as above; if sharing Vdlyvset *ON SAME VARIABLE*,
// we can share the IF statement too
postLogicp = VN_CAST(finalp->user4p(), If);
UASSERT_OBJ(postLogicp, nodep,
"Delayed assignment misoptimized; prev var found w/o associated IF");
} else {
postLogicp = new AstIf(nodep->fileline(),
new AstVarRef(nodep->fileline(), setvscp, VAccess::READ),
nullptr, nullptr);
UINFO(9, " Created " << postLogicp << endl);
finalp->addBodysp(postLogicp);
finalp->user3p(setvscp); // Remember IF's vset variable
finalp->user4p(postLogicp); // and the associated IF, as we may be able to reuse it
}
postLogicp->addIfsp(new AstAssign(nodep->fileline(), selectsp, valreadp));
return newlhsp;
}
// VISITORS
virtual void visit(AstNetlist* nodep) override {
// VV***** We reset all userp() on the netlist
m_modVarMap.clear();
iterateChildren(nodep);
}
virtual void visit(AstScope* nodep) override {
UINFO(4, " MOD " << nodep << endl);
AstNode::user3ClearTree();
iterateChildren(nodep);
}
virtual void visit(AstCFunc* nodep) override {
VL_RESTORER(m_cfuncp);
{
m_cfuncp = nodep;
iterateChildren(nodep);
}
}
virtual void visit(AstActive* nodep) override {
m_activep = nodep;
VL_RESTORER(m_inInitial);
{
m_inInitial = nodep->hasInitial();
// Two sets to same variable in different actives must use different vars.
AstNode::user3ClearTree();
iterateChildren(nodep);
}
}
virtual void visit(AstAssignDly* nodep) override {
m_inDly = true;
m_nextDlyp
= VN_CAST(nodep->nextp(), AssignDly); // Next assignment in same block, maybe nullptr.
if (m_cfuncp) {
nodep->v3warn(E_UNSUPPORTED,
"Unsupported: Delayed assignment inside public function/task");
}
if (VN_IS(nodep->lhsp(), ArraySel)
|| (VN_IS(nodep->lhsp(), Sel)
&& VN_IS(VN_CAST(nodep->lhsp(), Sel)->fromp(), ArraySel))) {
AstNode* lhsp = nodep->lhsp()->unlinkFrBack();
AstNode* newlhsp = createDlyArray(nodep, lhsp);
if (m_inLoop) {
nodep->v3warn(BLKLOOPINIT, "Unsupported: Delayed assignment to array inside for "
"loops (non-delayed is ok - see docs)");
}
AstBasicDType* basicp = lhsp->dtypep()->basicp();
if (basicp && basicp->isEventValue()) {
nodep->v3warn(E_UNSUPPORTED, "Unsupported: event arrays");
}
if (newlhsp) {
nodep->lhsp(newlhsp);
} else {
VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
}
VL_DO_DANGLING(pushDeletep(lhsp), lhsp);
} else {
iterateChildren(nodep);
}
m_inDly = false;
m_nextDlyp = nullptr;
}
virtual void visit(AstVarRef* nodep) override {
if (!nodep->user2Inc()) { // Not done yet
if (m_inDly && nodep->access().isWriteOrRW()) {
UINFO(4, "AssignDlyVar: " << nodep << endl);
markVarUsage(nodep, true);
UASSERT_OBJ(m_activep, nodep, "<= not under sensitivity block");
UASSERT_OBJ(!nodep->access().isRW(), nodep, "<= on read+write method");
if (!m_activep->hasClocked()) {
nodep->v3error("Internal: Blocking <= assignment in non-clocked block, should "
"have converted in V3Active");
}
AstVarScope* oldvscp = nodep->varScopep();
UASSERT_OBJ(oldvscp, nodep, "Var didn't get varscoped in V3Scope.cpp");
AstVarScope* dlyvscp = VN_CAST(oldvscp->user1p(), VarScope);
if (dlyvscp) { // Multiple use of delayed variable
AstActive* oldactivep = VN_CAST(dlyvscp->user2p(), Active);
checkActivePost(nodep, oldactivep);
}
if (!dlyvscp) { // First use of this delayed variable
string newvarname = (string("__Vdly__") + nodep->varp()->shortName());
dlyvscp = createVarSc(oldvscp, newvarname, 0, nullptr);
AstNodeAssign* prep;
AstBasicDType* basicp = oldvscp->dtypep()->basicp();
if (basicp && basicp->isEventValue()) {
// Events go to zero on next timestep unless reactivated
prep = new AstAssignPre(
nodep->fileline(),
new AstVarRef(nodep->fileline(), dlyvscp, VAccess::WRITE),
new AstConst(nodep->fileline(), AstConst::BitFalse()));
} else {
prep = new AstAssignPre(
nodep->fileline(),
new AstVarRef(nodep->fileline(), dlyvscp, VAccess::WRITE),
new AstVarRef(nodep->fileline(), oldvscp, VAccess::READ));
}
AstNodeAssign* postp = new AstAssignPost(
nodep->fileline(),
new AstVarRef(nodep->fileline(), oldvscp, VAccess::WRITE),
new AstVarRef(nodep->fileline(), dlyvscp, VAccess::READ));
postp->lhsp()->user2(true); // Don't detect this assignment
oldvscp->user1p(dlyvscp); // So we can find it later
// Make new ACTIVE with identical sensitivity tree
AstActive* newactp = createActivePost(nodep);
dlyvscp->user2p(newactp);
newactp->addStmtsp(prep); // Add to FRONT of statements
newactp->addStmtsp(postp);
}
AstVarRef* newrefp = new AstVarRef(nodep->fileline(), dlyvscp, VAccess::WRITE);
newrefp->user2(true); // No reason to do it again
nodep->replaceWith(newrefp);
VL_DO_DANGLING(pushDeletep(nodep), nodep);
} else if (!m_inDly && nodep->access().isWriteOrRW()) {
// UINFO(9, "NBA " << nodep << endl);
if (!m_inInitial) {
UINFO(4, "AssignNDlyVar: " << nodep << endl);
markVarUsage(nodep, false);
}
}
}
}
virtual void visit(AstNodeFor* nodep) override { // LCOV_EXCL_LINE
nodep->v3fatalSrc(
"For statements should have been converted to while statements in V3Begin");
}
virtual void visit(AstWhile* nodep) override {
VL_RESTORER(m_inLoop);
{
m_inLoop = true;
iterateChildren(nodep);
}
}
//--------------------
virtual void visit(AstNode* nodep) override { iterateChildren(nodep); }
public:
// CONSTRUCTORS
explicit DelayedVisitor(AstNetlist* nodep) { iterate(nodep); }
virtual ~DelayedVisitor() override {
V3Stats::addStat("Optimizations, Delayed shared-sets", m_statSharedSet);
}
};
//######################################################################
// Delayed class functions
void V3Delayed::delayedAll(AstNetlist* nodep) {
UINFO(2, __FUNCTION__ << ": " << endl);
{ DelayedVisitor visitor(nodep); } // Destruct before checking
V3Global::dumpCheckGlobalTree("delayed", 0, v3Global.opt.dumpTreeLevel(__FILE__) >= 3);
}