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cxxrtl: run hierarchy -auto-top if no top module is present.

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In most cases, a CXXRTL simulation would use a top module, either
because this module serves as an entry point to the CXXRTL C API,
or because the outputs of a top module are unbuffered, improving
performance. Taking this into account, the CXXRTL backend now runs
`hierarchy -auto-top` if there is no top module. For the few cases
where this behavior is unwanted, it now accepts a `-nohierarchy`
option.

Fixes #2373.
This commit is contained in:
whitequark 2020-11-02 19:18:56 +00:00
parent d9af3cadf8
commit 65083e9520
1 changed files with 26 additions and 7 deletions
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33
backends/cxxrtl/cxxrtl_backend.cc
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@ -527,6 +527,7 @@ struct CxxrtlWorker {
std::ostream *impl_f = nullptr;
std::ostream *intf_f = nullptr;
bool run_hierarchy = false;
bool run_flatten = false;
bool run_proc = false;
@ -2329,9 +2330,9 @@ struct CxxrtlWorker {
}
}
void check_design(RTLIL::Design *design, bool &has_sync_init, bool &has_packed_mem)
void check_design(RTLIL::Design *design, bool &has_top, bool &has_sync_init, bool &has_packed_mem)
{
has_sync_init = has_packed_mem = false;
has_sync_init = has_packed_mem = has_top = false;
for (auto module : design->modules()) {
if (module->get_blackbox_attribute() && !module->has_attribute(ID(cxxrtl_blackbox)))
@ -2343,6 +2344,9 @@ struct CxxrtlWorker {
if (!design->selected_module(module))
continue;
if (module->get_bool_attribute(ID::top))
has_top = true;
for (auto proc : module->processes)
for (auto sync : proc.second->syncs)
if (sync->type == RTLIL::STi)
@ -2358,9 +2362,13 @@ struct CxxrtlWorker {
void prepare_design(RTLIL::Design *design)
{
bool did_anything = false;
bool has_sync_init, has_packed_mem;
bool has_top, has_sync_init, has_packed_mem;
log_push();
check_design(design, has_sync_init, has_packed_mem);
check_design(design, has_top, has_sync_init, has_packed_mem);
if (run_hierarchy && !has_top) {
Pass::call(design, "hierarchy -auto-top");
did_anything = true;
}
if (run_flatten) {
Pass::call(design, "flatten");
did_anything = true;
@ -2381,9 +2389,9 @@ struct CxxrtlWorker {
did_anything = true;
}
// Recheck the design if it was modified.
if (has_sync_init || has_packed_mem)
check_design(design, has_sync_init, has_packed_mem);
log_assert(!(has_sync_init || has_packed_mem));
if (did_anything)
check_design(design, has_top, has_sync_init, has_packed_mem);
log_assert(has_top && !has_sync_init && !has_packed_mem);
log_pop();
if (did_anything)
log_spacer();
@ -2565,6 +2573,11 @@ 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(" -nohierarchy\n");
log(" use design hierarchy as-is. in most designs, a top module should be\n");
log(" present as it is exposed through the C API and has unbuffered outputs\n");
log(" for improved performance; it will be determined automatically if absent.\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");
@ -2621,6 +2634,7 @@ struct CxxrtlBackend : public Backend {
void execute(std::ostream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design) override
{
bool nohierarchy = false;
bool noflatten = false;
bool noproc = false;
int opt_level = DEFAULT_OPT_LEVEL;
@ -2632,6 +2646,10 @@ struct CxxrtlBackend : public Backend {
size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++)
{
if (args[argidx] == "-nohierarchy") {
nohierarchy = true;
continue;
}
if (args[argidx] == "-noflatten") {
noflatten = true;
continue;
@ -2677,6 +2695,7 @@ struct CxxrtlBackend : public Backend {
}
extra_args(f, filename, args, argidx);
worker.run_hierarchy = !nohierarchy;
worker.run_flatten = !noflatten;
worker.run_proc = !noproc;
switch (opt_level) {