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Merge the two autoidx hashtables into one

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When something calls `IdString::c_str()` on an autoidx ID, we need to cache the
full string in a thread-safe way. If we need to allocate an entry in some data
structure to do that, it's difficult to do in a thread-safe no-performance-hazard way.
So instead, store the cached string pointer in the same hashtable as the prefix
pointer.
This commit is contained in:
Robert O'Callahan 2025-11-25 00:47:11 +00:00
parent 8f0ecce53f
commit 948001f39f
2 changed files with 28 additions and 27 deletions
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36
kernel/rtlil.h
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@ -134,6 +134,13 @@ struct RTLIL::IdString
std::string_view str_view() const { return {buf, static_cast<size_t>(size)}; }
};
struct AutoidxStorage {
// Append the negated (i.e. positive) ID to this string to get
// the real string. The prefix strings must live forever.
const std::string *prefix;
// Cache of the full string, or nullptr if not cached yet.
char *full_str;
};
// the global id string cache
@ -147,12 +154,9 @@ struct RTLIL::IdString
static std::vector<Storage> global_id_storage_;
// Lookup table for non-autoidx IDs
static std::unordered_map<std::string_view, int> global_id_index_;
// Shared prefix string storage for autoidx IDs, which have negative
// indices. Append the negated (i.e. positive) ID to this string to get
// the real string. The prefix strings must live forever.
static std::unordered_map<int, const std::string*> global_autoidx_id_prefix_storage_;
// Explicit string storage for autoidx IDs
static std::unordered_map<int, char*> global_autoidx_id_storage_;
// Storage for autoidx IDs, which have negative indices, i.e. all entries in this
// map have negative keys.
static std::unordered_map<int, AutoidxStorage> global_autoidx_id_storage_;
// All (index, refcount) pairs in this map have refcount > 0.
static std::unordered_map<int, int> global_refcount_storage_;
static std::vector<int> global_free_idx_list_;
@ -205,7 +209,7 @@ struct RTLIL::IdString
static IdString new_autoidx_with_prefix(const std::string *prefix) {
log_assert(!Multithreading::active());
int index = -(autoidx++);
global_autoidx_id_prefix_storage_.insert({index, prefix});
global_autoidx_id_storage_.insert({index, {prefix, nullptr}});
return from_index(index);
}
@ -238,16 +242,16 @@ struct RTLIL::IdString
inline const char *c_str() const {
if (index_ >= 0)
return global_id_storage_.at(index_).buf;
auto it = global_autoidx_id_storage_.find(index_);
if (it != global_autoidx_id_storage_.end())
return it->second;
const std::string &prefix = *global_autoidx_id_prefix_storage_.at(index_);
AutoidxStorage &s = global_autoidx_id_storage_.at(index_);
if (s.full_str != nullptr)
return s.full_str;
const std::string &prefix = *s.prefix;
std::string suffix = std::to_string(-index_);
char *c = new char[prefix.size() + suffix.size() + 1];
memcpy(c, prefix.data(), prefix.size());
memcpy(c + prefix.size(), suffix.c_str(), suffix.size() + 1);
global_autoidx_id_storage_.insert(it, {index_, c});
s.full_str = c;
return c;
}
@ -262,7 +266,7 @@ struct RTLIL::IdString
*out += global_id_storage_.at(index_).str_view();
return;
}
*out += *global_autoidx_id_prefix_storage_.at(index_);
*out += *global_autoidx_id_storage_.at(index_).prefix;
*out += std::to_string(-index_);
}
@ -348,7 +352,7 @@ struct RTLIL::IdString
if (index_ >= 0) {
return const_iterator(global_id_storage_.at(index_));
}
return const_iterator(global_autoidx_id_prefix_storage_.at(index_), -index_);
return const_iterator(global_autoidx_id_storage_.at(index_).prefix, -index_);
}
const_iterator end() const {
return const_iterator();
@ -358,7 +362,7 @@ struct RTLIL::IdString
if (index_ >= 0) {
return Substrings(global_id_storage_.at(index_));
}
return Substrings(global_autoidx_id_prefix_storage_.at(index_), -index_);
return Substrings(global_autoidx_id_storage_.at(index_).prefix, -index_);
}
inline bool lt_by_name(const IdString &rhs) const {
@ -411,7 +415,7 @@ struct RTLIL::IdString
#endif
return *(storage.buf + i);
}
const std::string &id_start = *global_autoidx_id_prefix_storage_.at(index_);
const std::string &id_start = *global_autoidx_id_storage_.at(index_).prefix;
if (i < id_start.size())
return id_start[i];
i -= id_start.size();