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Merge pull request #2134 from whitequark/cxxrtl-opt-debug
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cxxrtl: introduce -Og optimization level
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@whitequark
whitequark committed Jun 10, 2020
2 parents b2a0f49 + 5467fe5 commit 8f1a320
Showing 1 changed file with 105 additions and 52 deletions.
157 changes: 105 additions & 52 deletions backends/cxxrtl/cxxrtl_backend.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -527,12 +527,15 @@ struct CxxrtlWorker {
std::ostream *impl_f = nullptr;
std::ostream *intf_f = nullptr;

bool elide_internal = false;
bool elide_public = false;
bool run_flatten = false;
bool run_proc = false;

bool unbuffer_internal = false;
bool unbuffer_public = false;
bool localize_internal = false;
bool localize_public = false;
bool run_proc_flatten = false;
bool max_opt_level = false;
bool elide_internal = false;
bool elide_public = false;

bool debug_info = false;

Expand All @@ -547,6 +550,7 @@ struct CxxrtlWorker {
dict<const RTLIL::Cell*, pool<const RTLIL::Cell*>> transparent_for;
dict<const RTLIL::Wire*, FlowGraph::Node> elided_wires;
dict<const RTLIL::Module*, std::vector<FlowGraph::Node>> schedule;
pool<const RTLIL::Wire*> unbuffered_wires;
pool<const RTLIL::Wire*> localized_wires;
dict<const RTLIL::Wire*, const RTLIL::Wire*> debug_alias_wires;
dict<const RTLIL::Wire*, RTLIL::Const> debug_const_wires;
Expand Down Expand Up @@ -786,7 +790,8 @@ struct CxxrtlWorker {
dump_const(chunk.data, chunk.width, chunk.offset);
return false;
} else {
if (!is_lhs && elided_wires.count(chunk.wire)) {
if (elided_wires.count(chunk.wire)) {
log_assert(!is_lhs);
const FlowGraph::Node &node = elided_wires[chunk.wire];
switch (node.type) {
case FlowGraph::Node::Type::CONNECT:
Expand All @@ -799,7 +804,7 @@ struct CxxrtlWorker {
default:
log_assert(false);
}
} else if (localized_wires[chunk.wire] || is_input_wire(chunk.wire)) {
} else if (unbuffered_wires[chunk.wire] || is_input_wire(chunk.wire)) {
f << mangle(chunk.wire);
} else {
f << mangle(chunk.wire) << (is_lhs ? ".next" : ".curr");
Expand Down Expand Up @@ -1434,13 +1439,13 @@ struct CxxrtlWorker {
{
if (elided_wires.count(wire))
return;
if (localized_wires.count(wire) != is_local_context)
return;

if (is_local_context) {
dump_attrs(wire);
f << indent << "value<" << wire->width << "> " << mangle(wire) << ";\n";
} else {
if (unbuffered_wires[wire]) {
if (localized_wires[wire] == is_local_context) {
dump_attrs(wire);
f << indent << "value<" << wire->width << "> " << mangle(wire) << ";\n";
}
} else if (!is_local_context) {
std::string width;
if (wire->module->has_attribute(ID(cxxrtl_blackbox)) && wire->has_attribute(ID(cxxrtl_width))) {
width = wire->get_string_attribute(ID(cxxrtl_width));
Expand Down Expand Up @@ -1590,7 +1595,7 @@ struct CxxrtlWorker {
inc_indent();
f << indent << "bool changed = false;\n";
for (auto wire : module->wires()) {
if (elided_wires.count(wire) || localized_wires.count(wire))
if (elided_wires.count(wire) || unbuffered_wires.count(wire))
continue;
if (is_input_wire(wire)) {
if (edge_wires[wire])
Expand Down Expand Up @@ -1619,6 +1624,7 @@ struct CxxrtlWorker {

void dump_debug_info_method(RTLIL::Module *module)
{
size_t count_public_wires = 0;
size_t count_const_wires = 0;
size_t count_alias_wires = 0;
size_t count_member_wires = 0;
Expand All @@ -1628,6 +1634,7 @@ struct CxxrtlWorker {
for (auto wire : module->wires()) {
if (wire->name[0] != '\\')
continue;
count_public_wires++;
if (debug_const_wires.count(wire)) {
// Wire tied to a constant
f << indent << "static const value<" << wire->width << "> const_" << mangle(wire) << " = ";
Expand Down Expand Up @@ -1665,11 +1672,12 @@ struct CxxrtlWorker {
}
dec_indent();

log_debug("Debug information statistics for module %s:\n", log_id(module));
log_debug(" Const wires: %zu\n", count_const_wires);
log_debug(" Alias wires: %zu\n", count_alias_wires);
log_debug(" Member wires: %zu\n", count_member_wires);
log_debug(" Other wires: %zu (no debug information)\n", count_skipped_wires);
log_debug("Debug information statistics for module `%s':\n", log_id(module));
log_debug(" Public wires: %zu, of which:\n", count_public_wires);
log_debug(" Const wires: %zu\n", count_const_wires);
log_debug(" Alias wires: %zu\n", count_alias_wires);
log_debug(" Member wires: %zu\n", count_member_wires);
log_debug(" Other wires: %zu (no debug information)\n", count_skipped_wires);
}

void dump_metadata_map(const dict<RTLIL::IdString, RTLIL::Const> &metadata_map)
Expand Down Expand Up @@ -1949,7 +1957,7 @@ struct CxxrtlWorker {
void analyze_design(RTLIL::Design *design)
{
bool has_feedback_arcs = false;
bool has_buffered_wires = false;
bool has_buffered_comb_wires = false;

for (auto module : design->modules()) {
if (!design->selected_module(module))
Expand Down Expand Up @@ -2145,17 +2153,19 @@ struct CxxrtlWorker {
log("Module `%s' contains feedback arcs through wires:\n", log_id(module));
for (auto wire : feedback_wires)
log(" %s\n", log_id(wire));
log("\n");
}

for (auto wire : module->wires()) {
if (feedback_wires[wire]) continue;
if (wire->port_id != 0) continue;
if (wire->get_bool_attribute(ID::keep)) continue;
if (wire->name.begins_with("$") && !localize_internal) continue;
if (wire->name.begins_with("\\") && !localize_public) continue;
if (wire->name.begins_with("$") && !unbuffer_internal) continue;
if (wire->name.begins_with("\\") && !unbuffer_public) continue;
if (edge_wires[wire]) continue;
if (flow.wire_sync_defs.count(wire) > 0) continue;
unbuffered_wires.insert(wire);
if (wire->name.begins_with("$") && !localize_internal) continue;
if (wire->name.begins_with("\\") && !localize_public) continue;
localized_wires.insert(wire);
}

Expand All @@ -2165,22 +2175,19 @@ struct CxxrtlWorker {
// it is possible that a design with no feedback arcs would end up with doubly buffered wires in such cases
// as a wire with multiple drivers where one of them is combinatorial and the other is synchronous. Such designs
// also require more than one delta cycle to converge.
pool<const RTLIL::Wire*> buffered_wires;
pool<const RTLIL::Wire*> buffered_comb_wires;
for (auto wire : module->wires()) {
if (flow.wire_comb_defs[wire].size() > 0 && !elided_wires.count(wire) && !localized_wires[wire]) {
if (!feedback_wires[wire])
buffered_wires.insert(wire);
}
if (flow.wire_comb_defs[wire].size() > 0 && !unbuffered_wires[wire] && !feedback_wires[wire])
buffered_comb_wires.insert(wire);
}
if (!buffered_wires.empty()) {
has_buffered_wires = true;
if (!buffered_comb_wires.empty()) {
has_buffered_comb_wires = true;
log("Module `%s' contains buffered combinatorial wires:\n", log_id(module));
for (auto wire : buffered_wires)
for (auto wire : buffered_comb_wires)
log(" %s\n", log_id(wire));
log("\n");
}

eval_converges[module] = feedback_wires.empty() && buffered_wires.empty();
eval_converges[module] = feedback_wires.empty() && buffered_comb_wires.empty();

if (debug_info) {
// Find wires that alias other wires or are tied to a constant; debug information can be enriched with these
Expand All @@ -2191,7 +2198,7 @@ struct CxxrtlWorker {
for (auto wire : module->wires()) {
if (wire->name[0] != '\\')
continue;
if (!localized_wires[wire])
if (!unbuffered_wires[wire])
continue;
const RTLIL::Wire *wire_it = wire;
while (1) {
Expand All @@ -2204,7 +2211,7 @@ struct CxxrtlWorker {
RTLIL::SigSpec rhs_sig = node->connect.second;
if (rhs_sig.is_wire()) {
RTLIL::Wire *rhs_wire = rhs_sig.as_wire();
if (localized_wires[rhs_wire]) {
if (unbuffered_wires[rhs_wire]) {
wire_it = rhs_wire; // maybe an alias
} else {
debug_alias_wires[wire] = rhs_wire; // is an alias
Expand All @@ -2220,18 +2227,20 @@ struct CxxrtlWorker {
}
}
}
if (has_feedback_arcs || has_buffered_wires) {
if (has_feedback_arcs || has_buffered_comb_wires) {
// Although both non-feedback buffered combinatorial wires and apparent feedback wires may be eliminated
// by optimizing the design, if after `proc; flatten` there are any feedback wires remaining, it is very
// likely that these feedback wires are indicative of a true logic loop, so they get emphasized in the message.
const char *why_pessimistic = nullptr;
if (has_feedback_arcs)
why_pessimistic = "feedback wires";
else if (has_buffered_wires)
else if (has_buffered_comb_wires)
why_pessimistic = "buffered combinatorial wires";
log_warning("Design contains %s, which require delta cycles during evaluation.\n", why_pessimistic);
if (!max_opt_level)
log("Increasing the optimization level may eliminate %s from the design.\n", why_pessimistic);
if (!run_flatten)
log("Flattening may eliminate %s from the design.\n", why_pessimistic);
if (!run_proc)
log("Converting processes to netlists may eliminate %s from the design.\n", why_pessimistic);
}
}

Expand Down Expand Up @@ -2266,10 +2275,13 @@ struct CxxrtlWorker {
bool has_sync_init, has_packed_mem;
log_push();
check_design(design, has_sync_init, has_packed_mem);
if (run_proc_flatten) {
Pass::call(design, "proc");
if (run_flatten) {
Pass::call(design, "flatten");
did_anything = true;
}
if (run_proc) {
Pass::call(design, "proc");
did_anything = true;
} else if (has_sync_init) {
// We're only interested in proc_init, but it depends on proc_prune and proc_clean, so call those
// in case they weren't already. (This allows `yosys foo.v -o foo.cc` to work.)
Expand All @@ -2294,7 +2306,8 @@ struct CxxrtlWorker {
};

struct CxxrtlBackend : public Backend {
static const int DEFAULT_OPT_LEVEL = 5;
static const int DEFAULT_OPT_LEVEL = 6;
static const int OPT_LEVEL_DEBUG = 4;
static const int DEFAULT_DEBUG_LEVEL = 1;

CxxrtlBackend() : Backend("cxxrtl", "convert design to C++ RTL simulation") { }
Expand Down Expand Up @@ -2466,6 +2479,17 @@ struct CxxrtlBackend : public Backend {
log(" place the generated code into namespace <ns-name>. if not specified,\n");
log(" \"cxxrtl_design\" is used.\n");
log("\n");
log(" -noflatten\n");
log(" don't flatten the design. fully flattened designs can evaluate within\n");
log(" one delta cycle if they have no combinatorial feedback.\n");
log(" note that the debug interface and waveform dumps use full hierarchical\n");
log(" names for all wires even in flattened designs.\n");
log("\n");
log(" -noproc\n");
log(" don't convert processes to netlists. in most designs, converting\n");
log(" processes significantly improves evaluation performance at the cost of\n");
log(" slight increase in compilation time.\n");
log("\n");
log(" -O <level>\n");
log(" set the optimization level. the default is -O%d. higher optimization\n", DEFAULT_OPT_LEVEL);
log(" levels dramatically decrease compile and run time, and highest level\n");
Expand All @@ -2475,19 +2499,26 @@ struct CxxrtlBackend : public Backend {
log(" no optimization.\n");
log("\n");
log(" -O1\n");
log(" elide internal wires if possible.\n");
log(" localize internal wires if possible.\n");
log("\n");
log(" -O2\n");
log(" like -O1, and localize internal wires if possible.\n");
log(" like -O1, and unbuffer internal wires if possible.\n");
log("\n");
log(" -O3\n");
log(" like -O2, and elide public wires not marked (*keep*) if possible.\n");
log(" like -O2, and elide internal wires if possible.\n");
log("\n");
log(" -O4\n");
log(" like -O3, and localize public wires not marked (*keep*) if possible.\n");
log(" like -O3, and unbuffer public wires not marked (*keep*) if possible.\n");
log("\n");
log(" -O5\n");
log(" like -O4, and run `proc; flatten` first.\n");
log(" like -O4, and localize public wires not marked (*keep*) if possible.\n");
log("\n");
log(" -O6\n");
log(" like -O5, and elide public wires not marked (*keep*) if possible.\n");
log("\n");
log(" -Og\n");
log(" highest optimization level that provides debug information for all\n");
log(" public wires. currently, alias for -O%d.\n", OPT_LEVEL_DEBUG);
log("\n");
log(" -g <level>\n");
log(" set the debug level. the default is -g%d. higher debug levels provide\n", DEFAULT_DEBUG_LEVEL);
Expand All @@ -2504,6 +2535,8 @@ struct CxxrtlBackend : public Backend {

void execute(std::ostream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
{
bool noflatten = false;
bool noproc = false;
int opt_level = DEFAULT_OPT_LEVEL;
int debug_level = DEFAULT_DEBUG_LEVEL;
CxxrtlWorker worker;
Expand All @@ -2513,6 +2546,23 @@ struct CxxrtlBackend : public Backend {
size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++)
{
if (args[argidx] == "-noflatten") {
noflatten = true;
continue;
}
if (args[argidx] == "-noproc") {
noproc = true;
continue;
}
if (args[argidx] == "-Og") {
opt_level = OPT_LEVEL_DEBUG;
continue;
}
if (args[argidx] == "-O" && argidx+1 < args.size() && args[argidx+1] == "g") {
argidx++;
opt_level = OPT_LEVEL_DEBUG;
continue;
}
if (args[argidx] == "-O" && argidx+1 < args.size()) {
opt_level = std::stoi(args[++argidx]);
continue;
Expand Down Expand Up @@ -2541,30 +2591,33 @@ struct CxxrtlBackend : public Backend {
}
extra_args(f, filename, args, argidx);

worker.run_flatten = !noflatten;
worker.run_proc = !noproc;
switch (opt_level) {
// the highest level here must match DEFAULT_OPT_LEVEL
case 6:
worker.elide_public = true;
YS_FALLTHROUGH
case 5:
worker.max_opt_level = true;
worker.run_proc_flatten = true;
worker.localize_public = true;
YS_FALLTHROUGH
case 4:
worker.localize_public = true;
worker.unbuffer_public = true;
YS_FALLTHROUGH
case 3:
worker.elide_public = true;
worker.elide_internal = true;
YS_FALLTHROUGH
case 2:
worker.localize_internal = true;
YS_FALLTHROUGH
case 1:
worker.elide_internal = true;
worker.unbuffer_internal = true;
YS_FALLTHROUGH
case 0:
break;
default:
log_cmd_error("Invalid optimization level %d.\n", opt_level);
}

switch (debug_level) {
// the highest level here must match DEFAULT_DEBUG_LEVEL
case 1:
Expand Down

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