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[analysis] Let Flat lattice take multiple types #8052

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Merged
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Nov 15, 2025
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[analysis] Let Flat lattice take multiple types #8052

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68 changes: 47 additions & 21 deletions src/analysis/lattices/flat.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,13 +17,15 @@
#ifndef wasm_analysis_lattices_flat_h
#define wasm_analysis_lattices_flat_h

#include <tuple>
#include <type_traits>
#include <variant>

#if __cplusplus >= 202002L
#include <concepts>
#endif

#include "../lattice.h"
#include "analysis/lattice.h"
#include "support/utilities.h"

namespace wasm::analysis {
Expand All @@ -33,27 +35,48 @@ namespace wasm::analysis {
template<typename T>
concept Flattenable = std::copyable<T> && std::equality_comparable<T>;

// Given a type T, Flat<T> is the lattice where none of the values of T are
// comparable except with themselves, but they are all greater than a common
// bottom element not in T and less than a common top element also not in T.
template<Flattenable T>
// Given types Ts..., Flat<T...> is the lattice where none of the values of any
// T are comparable except with themselves, but they are all greater than a
// common bottom element and less than a common top element.
template<Flattenable T, Flattenable... Ts>
#else
template<typename T>
template<typename T, typename... Ts>
#endif
struct Flat {
private:
struct Bot {};
struct Top {};
struct Bot : std::monostate {};
struct Top : std::monostate {};

template<std::size_t I>
using TI = std::tuple_element_t<I, std::tuple<T, Ts...>>;

public:
struct Element : std::variant<Bot, T, Top> {
struct Element : std::variant<T, Ts..., Bot, Top> {
bool isBottom() const noexcept { return std::get_if<Bot>(this); }
bool isTop() const noexcept { return std::get_if<Top>(this); }
const T* getVal() const noexcept { return std::get_if<T>(this); }
T* getVal() noexcept { return std::get_if<T>(this); }
template<typename U = T> const U* getVal() const noexcept {
return std::get_if<U>(this);
}
template<typename U = T> U* getVal() noexcept {
return std::get_if<U>(this);
}
template<std::size_t I> const TI<I>* getVal() const noexcept {
return std::get_if<I>(this);
}
template<std::size_t I> TI<I>* getVal() noexcept {
return std::get_if<I>(this);
}
bool operator==(const Element& other) const noexcept {
return ((isBottom() && other.isBottom()) || (isTop() && other.isTop()) ||
(getVal() && other.getVal() && *getVal() == *other.getVal()));
return this->index() == other.index() &&
std::visit(
[](const auto& a, const auto& b) {
if constexpr (std::is_same_v<decltype(a), decltype(b)>) {
return a == b;
}
return false;
},
*this,
other);
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@kripken kripken Nov 14, 2025

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I can guess at what this line does, but where in the docs is it described? I can't seem to find that (the variant of visit with two objects after the lambda)

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@tlively tlively Nov 15, 2025

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std::visit is fun because it can take an arbitrary number of std::variant arguments as long as the visitor functions can take that same number of parameters. See the Variants&&... values variadic parameter given in https://en.cppreference.com/w/cpp/utility/variant/visit2.html.

}
bool operator!=(const Element& other) const noexcept {
return !(*this == other);
Expand All @@ -62,18 +85,21 @@ struct Flat {

Element getBottom() const noexcept { return Element{Bot{}}; }
Element getTop() const noexcept { return Element{Top{}}; }
Element get(T&& val) const noexcept { return Element{std::move(val)}; }
template<typename U> Element get(U&& val) const noexcept {
return Element{std::move(val)};
}

LatticeComparison compare(const Element& a, const Element& b) const noexcept {
if (a.index() < b.index()) {
return LESS;
} else if (a.index() > b.index()) {
return GREATER;
} else if (auto pA = a.getVal(); pA && *pA != *b.getVal()) {
return NO_RELATION;
} else {
if (a == b) {
return EQUAL;
}
if (a.isTop() || b.isBottom()) {
return GREATER;
}
if (a.isBottom() || b.isTop()) {
return LESS;
}
return NO_RELATION;
}

bool join(Element& joinee, const Element& joiner) const noexcept {
Expand Down
36 changes: 26 additions & 10 deletions test/gtest/lattices.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -348,6 +348,22 @@ TEST(FlatLattice, Join) {
flat, flat.getBottom(), flat.get(0), flat.get(1), flat.getTop());
}

TEST(FlatLattice, MultipleTypes) {
analysis::Flat<int, std::string> flat;
testDiamondJoin(
flat, flat.getBottom(), flat.get(0), flat.get("foo"), flat.getTop());

auto stringElem = flat.get("foo");

EXPECT_EQ(stringElem.getVal<0>(), nullptr);
ASSERT_NE(stringElem.getVal<1>(), nullptr);
EXPECT_EQ(*stringElem.getVal<1>(), std::string("foo"));

EXPECT_EQ(stringElem.getVal<int>(), nullptr);
ASSERT_NE(stringElem.getVal<std::string>(), nullptr);
EXPECT_EQ(*stringElem.getVal<std::string>(), std::string("foo"));
}

TEST(LiftLattice, GetBottom) {
analysis::Lift lift{analysis::Bool{}};
EXPECT_TRUE(lift.getBottom().isBottom());
Expand Down Expand Up @@ -711,19 +727,19 @@ TEST(StackLattice, Compare) {
auto& flat = stack.lattice;
testDiamondCompare(stack,
{},
{flat.get(0)},
{flat.get(0), flat.get(1)},
{flat.get(0), flat.getTop()});
{flat.get(0u)},
{flat.get(0u), flat.get(1u)},
{flat.get(0u), flat.getTop()});
}

TEST(StackLattice, Join) {
analysis::Stack stack{analysis::Flat<uint32_t>{}};
auto& flat = stack.lattice;
testDiamondJoin(stack,
{},
{flat.get(0)},
{flat.get(0), flat.get(1)},
{flat.get(0), flat.getTop()});
{flat.get(0u)},
{flat.get(0u), flat.get(1u)},
{flat.get(0u), flat.getTop()});
}

using OddEvenInt = analysis::Flat<uint32_t>;
Expand Down Expand Up @@ -815,10 +831,10 @@ TEST(AbstractionLattice, Join) {
#define JOIN(a, b, c) expectJoin(__FILE__, __LINE__, a, b, c)

auto bot = abstraction.getBottom();
auto one = OddEvenAbstraction::Element(OddEvenInt{}.get(1));
auto two = OddEvenAbstraction::Element(OddEvenInt{}.get(2));
auto three = OddEvenAbstraction::Element(OddEvenInt{}.get(3));
auto four = OddEvenAbstraction::Element(OddEvenInt{}.get(4));
auto one = OddEvenAbstraction::Element(OddEvenInt{}.get(1u));
auto two = OddEvenAbstraction::Element(OddEvenInt{}.get(2u));
auto three = OddEvenAbstraction::Element(OddEvenInt{}.get(3u));
auto four = OddEvenAbstraction::Element(OddEvenInt{}.get(4u));
auto even = OddEvenAbstraction::Element(OddEvenBool{}.get(true));
auto odd = OddEvenAbstraction::Element(OddEvenBool{}.get(false));
auto top = OddEvenAbstraction::Element(OddEvenBool{}.getTop());
Expand Down
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