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Stop using mutable in Const.

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Now that we only call `bitvectorize()` in non-const methods, we can move the casting-away-const to only happen
in `bitvectorize()`, which is deprecated so only some plugins (maybe) are using it.

This means `const` `Const` methods don't change the underlying data, which means
they'll be safe to use from multiple threads if/when we want to do that.
This commit is contained in:
Robert O'Callahan 2025-08-29 05:56:19 +00:00
parent a515055be4
commit cd370bf6d1
2 changed files with 34 additions and 20 deletions
Download patch file Download diff file Expand all files Collapse all files

32
kernel/rtlil.cc
View file

@ -204,12 +204,22 @@ const pool<IdString> &RTLIL::builtin_ff_cell_types() {
#define check(condition) log_assert(condition && "malformed Const union")
Const::bitvectype& Const::get_bits() const {
const Const::bitvectype& Const::get_bits() const {
check(is_bits());
return *get_if_bits();
}
std::string& Const::get_str() const {
const std::string& Const::get_str() const {
check(is_str());
return *get_if_str();
}
Const::bitvectype& Const::get_bits() {
check(is_bits());
return *get_if_bits();
}
std::string& Const::get_str() {
check(is_str());
return *get_if_str();
}
@ -395,7 +405,7 @@ bool RTLIL::Const::as_bool() const
return false;
}
bitvectype& bv = get_bits();
const bitvectype& bv = get_bits();
for (size_t i = 0; i < bv.size(); i++)
if (bv[i] == State::S1)
return true;
@ -542,7 +552,7 @@ std::string RTLIL::Const::decode_string() const
if (auto str = get_if_str())
return *str;
bitvectype& bv = get_bits();
const bitvectype& bv = get_bits();
const int n = GetSize(bv);
const int n_over_8 = n / 8;
std::string s;
@ -590,7 +600,7 @@ bool RTLIL::Const::empty() const {
}
}
void RTLIL::Const::bitvectorize_internal() const {
void RTLIL::Const::bitvectorize_internal() {
if (tag == backing_tag::bits)
return;
@ -641,7 +651,7 @@ bool RTLIL::Const::is_fully_zero() const
return true;
}
bitvectype& bv = get_bits();
const bitvectype& bv = get_bits();
for (const auto &bit : bv)
if (bit != RTLIL::State::S0)
@ -661,7 +671,7 @@ bool RTLIL::Const::is_fully_ones() const
return true;
}
bitvectype& bv = get_bits();
const bitvectype& bv = get_bits();
for (const auto &bit : bv)
if (bit != RTLIL::State::S1)
return false;
@ -676,7 +686,7 @@ bool RTLIL::Const::is_fully_def() const
if (is_str())
return true;
bitvectype& bv = get_bits();
const bitvectype& bv = get_bits();
for (const auto &bit : bv)
if (bit != RTLIL::State::S0 && bit != RTLIL::State::S1)
return false;
@ -691,7 +701,7 @@ bool RTLIL::Const::is_fully_undef() const
if (auto str = get_if_str())
return str->empty();
bitvectype& bv = get_bits();
const bitvectype& bv = get_bits();
for (const auto &bit : bv)
if (bit != RTLIL::State::Sx && bit != RTLIL::State::Sz)
return false;
@ -706,7 +716,7 @@ bool RTLIL::Const::is_fully_undef_x_only() const
if (auto str = get_if_str())
return str->empty();
bitvectype& bv = get_bits();
const bitvectype& bv = get_bits();
for (const auto &bit : bv)
if (bit != RTLIL::State::Sx)
return false;
@ -742,7 +752,7 @@ Hasher RTLIL::Const::hash_into(Hasher h) const
// If the bits are all 0/1, hash packed bits using the string hash.
// Otherwise hash the leading packed bits with the rest of the bits individually.
bitvectype &bv = get_bits();
const bitvectype &bv = get_bits();
int size = GetSize(bv);
std::string packed;
int packed_size = (size + 7) >> 3;

22
kernel/rtlil.h
View file

@ -723,23 +723,27 @@ private:
using bitvectype = std::vector<RTLIL::State>;
enum class backing_tag: bool { bits, string };
// Do not access the union or tag even in Const methods unless necessary
mutable backing_tag tag;
backing_tag tag;
union {
mutable bitvectype bits_;
mutable std::string str_;
bitvectype bits_;
std::string str_;
};
// Use these private utilities instead
bool is_bits() const { return tag == backing_tag::bits; }
bool is_str() const { return tag == backing_tag::string; }
bitvectype* get_if_bits() const { return is_bits() ? &bits_ : NULL; }
std::string* get_if_str() const { return is_str() ? &str_ : NULL; }
bitvectype* get_if_bits() { return is_bits() ? &bits_ : NULL; }
std::string* get_if_str() { return is_str() ? &str_ : NULL; }
const bitvectype* get_if_bits() const { return is_bits() ? &bits_ : NULL; }
const std::string* get_if_str() const { return is_str() ? &str_ : NULL; }
bitvectype& get_bits() const;
std::string& get_str() const;
bitvectype& get_bits();
std::string& get_str();
const bitvectype& get_bits() const;
const std::string& get_str() const;
std::vector<RTLIL::State>& bits_internal();
void bitvectorize_internal() const;
void bitvectorize_internal();
public:
Const() : flags(RTLIL::CONST_FLAG_NONE), tag(backing_tag::bits), bits_(std::vector<RTLIL::State>()) {}
@ -772,7 +776,7 @@ public:
[[deprecated("Don't use direct access to the internal std::vector<State>, that's an implementation detail.")]]
std::vector<RTLIL::State>& bits() { return bits_internal(); }
[[deprecated("Don't call bitvectorize() directly, it's an implementation detail.")]]
void bitvectorize() const { bitvectorize_internal(); }
void bitvectorize() const { const_cast<Const*>(this)->bitvectorize_internal(); }
bool as_bool() const;