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split input nets with high fanout

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This commit is contained in:
Alain Dargelas 2025-03-03 15:06:02 -08:00
parent a1ad385702
commit d5d58349fd
1 changed files with 74 additions and 51 deletions
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125
passes/silimate/annotate_cell_fanout.cc
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@ -98,7 +98,7 @@ bool isSigSpecUsedIn(SigSpec &haystack, SigMap &sigmap, SigSpec &needle)
}
// Remove a buffer and fix the fanout connections to use the buffer's input
void removeBuffer(Module *module, SigMap &sigmap, std::set<Cell *>& fanoutcells, Cell *buffer, bool debug)
void removeBuffer(Module *module, SigMap &sigmap, std::set<Cell *> &fanoutcells, Cell *buffer, bool debug)
{
if (debug)
std::cout << "Buffer with fanout 1: " << buffer->name.c_str() << std::endl;
@ -154,7 +154,8 @@ void removeBuffer(Module *module, SigMap &sigmap, std::set<Cell *>& fanoutcells,
module->remove({bufferOutSig.as_wire()});
}
RTLIL::SigSpec getCellOutputSigSpec(Cell* cell, SigMap& sigmap) {
RTLIL::SigSpec getCellOutputSigSpec(Cell *cell, SigMap &sigmap)
{
RTLIL::SigSpec cellOutSig;
for (auto &conn : cell->connections()) {
IdString portName = conn.first;
@ -168,14 +169,14 @@ RTLIL::SigSpec getCellOutputSigSpec(Cell* cell, SigMap& sigmap) {
}
// Get new output signal for a given signal, used all datastructures with change to buffer
SigSpec updateToBuffer(std::map<SigSpec, int>& bufferIndexes, std::map<RTLIL::SigSpec,
std::vector<std::tuple<RTLIL::SigSpec, Cell *>>>& buffer_outputs,
dict<RTLIL::SigSpec, std::set<Cell *>> &sig2CellsInFanout,
std::map<Cell *, int>& bufferActualFanout, int max_output_per_buffer, Cell* cell, SigSpec sigToReplace, bool debug)
SigSpec updateToBuffer(std::map<SigSpec, int> &bufferIndexes,
std::map<RTLIL::SigSpec, std::vector<std::tuple<RTLIL::SigSpec, Cell *>>> &buffer_outputs,
dict<RTLIL::SigSpec, std::set<Cell *>> &sig2CellsInFanout, std::map<Cell *, int> &bufferActualFanout,
int max_output_per_buffer, Cell *cell, SigSpec sigToReplace, bool debug)
{
if (debug)
std::cout << " CHUNK, indexCurrentBuffer: " << bufferIndexes[sigToReplace] << " buffer_outputs " << buffer_outputs[sigToReplace].size()
<< std::endl;
std::cout << " CHUNK, indexCurrentBuffer: " << bufferIndexes[sigToReplace] << " buffer_outputs "
<< buffer_outputs[sigToReplace].size() << std::endl;
// Retrieve the buffer information for that cell's chunk
std::vector<std::tuple<RTLIL::SigSpec, Cell *>> &buf_info_vec = buffer_outputs[sigToReplace];
// Retrieve which buffer is getting filled
@ -288,8 +289,8 @@ void fixfanout(RTLIL::Design *design, RTLIL::Module *module, SigMap &sigmap, dic
std::cout << " IS A CHUNK" << std::endl;
if (buffer_outputs.find(actual) != buffer_outputs.end()) {
// Input is one of the cell's outputs, its a match
SigSpec newSig = updateToBuffer(bufferIndexes, buffer_outputs, sig2CellsInFanout,
bufferActualFanout, max_output_per_buffer, fanoutcell, actual, debug);
SigSpec newSig = updateToBuffer(bufferIndexes, buffer_outputs, sig2CellsInFanout, bufferActualFanout,
max_output_per_buffer, fanoutcell, actual, debug);
// Override the fanout cell's input with the buffer output
fanoutcell->setPort(portName, newSig);
}
@ -302,8 +303,9 @@ void fixfanout(RTLIL::Design *design, RTLIL::Module *module, SigMap &sigmap, dic
std::vector<RTLIL::SigChunk> newChunks;
for (SigChunk chunk : actual.chunks()) {
if (buffer_outputs.find(chunk) != buffer_outputs.end()) {
SigSpec newSig = updateToBuffer(bufferIndexes, buffer_outputs, sig2CellsInFanout,
bufferActualFanout, max_output_per_buffer, fanoutcell, chunk, debug);
SigSpec newSig =
updateToBuffer(bufferIndexes, buffer_outputs, sig2CellsInFanout, bufferActualFanout,
max_output_per_buffer, fanoutcell, chunk, debug);
// Append the buffer's output in the chunk vector
newChunks.push_back(newSig.as_chunk());
} else {
@ -332,7 +334,8 @@ void fixfanout(RTLIL::Design *design, RTLIL::Module *module, SigMap &sigmap, dic
}
}
void calculateFanout(RTLIL::Module *module, SigMap &sigmap, dict<RTLIL::SigSpec, std::set<Cell *>> &sig2CellsInFanout, dict<Cell *, int> &cellFanout)
void calculateFanout(RTLIL::Module *module, SigMap &sigmap, dict<RTLIL::SigSpec, std::set<Cell *>> &sig2CellsInFanout, dict<Cell *, int> &cellFanout,
dict<SigSpec, int> &sigFanout)
{
// Precompute cell output sigspec to cell map
dict<RTLIL::SigSpec, std::set<Cell *>> sig2CellsInFanin;
@ -343,7 +346,6 @@ void calculateFanout(RTLIL::Module *module, SigMap &sigmap, dict<RTLIL::SigSpec,
lhs2rhs_rhs2lhs(module, sigmap, rhsSig2LhsSig, lhsSig2RhsSig);
// Accumulate fanout from cell connections
dict<RTLIL::SigSpec, int> sigFanout;
for (auto itrSig : sig2CellsInFanout) {
SigSpec sigspec = itrSig.first;
std::set<Cell *> &cells = itrSig.second;
@ -400,10 +402,41 @@ std::string substringuntil(const std::string &str, char delimiter)
}
}
void splitNet(Design *design, std::set<std::string> &netsToSplitS, RTLIL::SigSpec &sigToSplit, bool formalFriendly, bool inputsToo = false)
{
Wire *parentWire = getParentWire(sigToSplit);
if (!parentWire)
return;
std::string parent = parentWire->name.c_str();
if (parent == "") {
return;
}
parent = substringuntil(parent, '[');
if (netsToSplitS.find(parent) == netsToSplitS.end()) {
netsToSplitS.insert(parent);
// Splitnets has to be invoke with individual nets. Sending a bunch of nets as selection,
// selects more than required (bug in selection/splitnets).
std::cout << "splitnets -ports_only w:" << parent << std::endl;
Pass::call(design, "splitnets w:" + parent); // Wire
if (!formalFriendly) {
// Formal verification does not like ports to be split.
// This option will prevent some buffering to happen on high fanout input/output ports,
// but it will make formal happy.
if (inputsToo) {
std::cout << "splitnets -ports_only x:" << parent << std::endl;
Pass::call(design, "splitnets -ports_only x:" + parent); // Input/Output port
} else {
std::cout << "splitnets -ports_only o:" << parent << std::endl;
Pass::call(design, "splitnets -ports_only o:" + parent); // Output port
}
}
}
}
struct AnnotateCellFanout : public ScriptPass {
AnnotateCellFanout() : ScriptPass("annotate_cell_fanout", "Annotate the cell fanout on the cell") {}
void script() override {}
void help() override
void help() override
{
log("\n");
log(" annotate_cell_fanout [options] [selection]\n");
@ -453,53 +486,41 @@ struct AnnotateCellFanout : public ScriptPass {
}
for (auto module : design->selected_modules()) {
bool fixedFanout = false;
{
// Split output nets of cells with high fanout
// Calculate fanout
SigMap sigmap(module);
dict<Cell *, int> cellFanout;
dict<SigSpec, int> sigFanout;
dict<RTLIL::SigSpec, std::set<Cell *>> sig2CellsInFanout;
calculateFanout(module, sigmap, sig2CellsInFanout, cellFanout);
calculateFanout(module, sigmap, sig2CellsInFanout, cellFanout, sigFanout);
std::vector<Cell *> cellsToFixFanout;
std::set<std::string> netsToSplitS;
// Split output nets of cells with high fanout
for (auto itrCell : cellFanout) {
Cell *cell = itrCell.first;
int fanout = itrCell.second;
if (limit > 0 && (fanout > limit)) {
cellsToFixFanout.push_back(cell);
RTLIL::SigSpec cellOutSig = getCellOutputSigSpec(cell, sigmap);
splitNet(design, netsToSplitS, cellOutSig, formalFriendly);
}
}
std::set<std::string> netsToSplitS;
std::string netsToSplit;
std::string portsToSplit;
for (Cell *cell : cellsToFixFanout) {
RTLIL::SigSpec cellOutSig;
for (auto &conn : cell->connections()) {
IdString portName = conn.first;
RTLIL::SigSpec actual = conn.second;
if (cell->output(portName)) {
cellOutSig = sigmap(actual);
break;
// Split module input nets with high fanout
std::set<Wire *> wiresToSplit;
for (Wire *wire : module->wires()) {
if (wire->port_input) {
SigSpec inp = sigmap(wire);
int fanout = sigFanout[inp];
std::cout << "Input" << wire->name.c_str() << " fanout: " << fanout << std::endl;
if (limit > 0 && (fanout > limit)) {
wiresToSplit.insert(wire);
}
}
std::string parent = getParentWire(cellOutSig)->name.c_str();
parent = substringuntil(parent, '[');
if (netsToSplitS.find(parent) == netsToSplitS.end()) {
netsToSplit += std::string(" w:") + parent; // Wire
portsToSplit += std::string(" o:") + parent; // Output port
netsToSplitS.insert(parent);
// Splitnets has to be invoke with individual nets, sending a bunch of nets as selection
// selects more than required (bug in selection/splitnets).
std::string splitnets = std::string("splitnets ") + netsToSplit;
Pass::call(design, splitnets);
splitnets = std::string("splitnets -ports_only ") + portsToSplit;
if (!formalFriendly)
// Formal verification does not like ports to be split.
// This will prevent some buffering to happen on output ports used also internally in high
// fanout, but it will make formal happy.
Pass::call(design, splitnets);
netsToSplit = "";
portsToSplit = "";
}
}
for (Wire *wire : wiresToSplit) {
SigSpec inp = sigmap(wire);
splitNet(design, netsToSplitS, inp, formalFriendly, true);
}
}
@ -507,8 +528,9 @@ struct AnnotateCellFanout : public ScriptPass {
// Fix high fanout
SigMap sigmap(module);
dict<Cell *, int> cellFanout;
dict<SigSpec, int> sigFanout;
dict<RTLIL::SigSpec, std::set<Cell *>> sig2CellsInFanout;
calculateFanout(module, sigmap, sig2CellsInFanout, cellFanout);
calculateFanout(module, sigmap, sig2CellsInFanout, cellFanout, sigFanout);
for (auto itrCell : cellFanout) {
Cell *cell = itrCell.first;
@ -527,8 +549,9 @@ struct AnnotateCellFanout : public ScriptPass {
// If Fanout got fixed, recalculate and annotate final fanout
SigMap sigmap(module);
dict<Cell *, int> cellFanout;
dict<SigSpec, int> sigFanout;
dict<RTLIL::SigSpec, std::set<Cell *>> sig2CellsInFanout;
calculateFanout(module, sigmap, sig2CellsInFanout, cellFanout);
calculateFanout(module, sigmap, sig2CellsInFanout, cellFanout, sigFanout);
for (auto itrCell : cellFanout) {
Cell *cell = itrCell.first;
int fanout = itrCell.second;