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Merged
merged 13 commits into from
Apr 23, 2025
Merged

Update evaluateCastCheck for exact types #7541

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dda5f7b
Propagate exactness when combining GUFA possible contents
tlively Apr 22, 2025
a51e2da
Use exactness to optimize GUFA cone depth
tlively Apr 22, 2025
a868b6f
[NFC] Simplify Array2Struct type replacement
tlively Apr 22, 2025
44b9b60
Merge branch 'main' into gufa-exact-cone
tlively Apr 22, 2025
0f68de3
Merge branch 'gufa-exact-cone' into array2struct-simplify
tlively Apr 22, 2025
dcf2ef1
Move exact type handling to cone creation
tlively Apr 22, 2025
ba2488a
Merge branch 'gufa-exact-cone' into array2struct-simplify
tlively Apr 22, 2025
229b3e7
Revert GUFA cone optimization
tlively Apr 23, 2025
0ffc664
Update evaluateCastCheck for exact types
tlively Apr 23, 2025
5f9bdda
simplify comment
tlively Apr 23, 2025
b97feb7
Merge branch 'main' into cast-check-tests
tlively Apr 23, 2025
82feeea
comments
tlively Apr 23, 2025
eef2504
Merge branch 'main' into cast-check-tests
tlively Apr 23, 2025
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18 changes: 16 additions & 2 deletions src/ir/gc-type-utils.h
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Original file line number Diff line number Diff line change
Expand Up @@ -104,7 +104,21 @@ inline EvaluationResult evaluateCastCheck(Type refType, Type castType) {
}

auto castHeapType = castType.getHeapType();
auto refIsHeapSubType = HeapType::isSubType(refHeapType, castHeapType);

// Check whether a value of type `a` is known to also have type `b`, assuming
// it is non-null.
auto isHeapSubtype = [](Type a, Type b) {
// If the heap type of `a` has no subtypes, then we know its value must be
// exactly `a`.
// TODO: Use information from a subtypes analysis, if available.
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Suggested change
// TODO: Use information from a subtypes analysis, if available.
// Infer if a must be exact: if it has no subtypes, then it must be.
// TODO: Use information from a subtypes analysis, if available.

if (!a.getHeapType().isBasic() && !a.getHeapType().isOpen()) {
a = a.with(Exact);
}
// Ignore nullability.
return Type::isSubType(a.with(NonNullable), b.with(NonNullable));
};
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I'm still not following this comment+code. If a is a user-defined heap type, why does it matter if it is open or not?

E.g. I would expect isHeapSubtype(child, parent) to return true regardless of the openness of child, since child "also has type" parent. Or do I not understand what "also has type" means?

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The "heap type" being checked here includes exactness, which is why we are actually comparing types and selectively ignoring nullability.

We're not just comparing the static type of the cast input with the cast target type. Instead, we're comparing the most specific safe approximation of the dynamic type of the cast input we can get with the cast target. If we know the value has dynamic heap type $foo, and $foo is final and cannot have subtypes, then we also know that the value must have dynamic heap type (exact $foo) because it cannot have any other type and still be a $foo.

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Sorry, what is a "dynamic type"?

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The type of the value at runtime.

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Thanks, now I can follow the code here.

I wrote a comment suggestion above.


auto refIsHeapSubType = isHeapSubtype(refType, castType);

if (refIsHeapSubType) {
// The heap type is a subtype. All we need is for nullability to work out as
Expand All @@ -121,7 +135,7 @@ inline EvaluationResult evaluateCastCheck(Type refType, Type castType) {
return SuccessOnlyIfNonNull;
}

auto castIsHeapSubType = HeapType::isSubType(castHeapType, refHeapType);
auto castIsHeapSubType = isHeapSubtype(castType, refType);
bool heapTypesCompatible = refIsHeapSubType || castIsHeapSubType;

if (!heapTypesCompatible || castHeapType.isBottom()) {
Expand Down
3 changes: 2 additions & 1 deletion test/gtest/CMakeLists.txt
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Expand Up @@ -6,7 +6,7 @@ endif()

set(unittest_SOURCES
arena.cpp
source-map.cpp
cast-check.cpp
cfg.cpp
dfa_minimization.cpp
disjoint_sets.cpp
Expand All @@ -18,6 +18,7 @@ set(unittest_SOURCES
possible-contents.cpp
printing.cpp
scc.cpp
source-map.cpp
stringify.cpp
suffix_tree.cpp
topological-sort.cpp
Expand Down
212 changes: 212 additions & 0 deletions test/gtest/cast-check.cpp
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Original file line number Diff line number Diff line change
@@ -0,0 +1,212 @@
/*
* Copyright 2025 WebAssembly Community Group participants
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

#include "ir/gc-type-utils.h"
#include "type-test.h"
#include "wasm-type.h"
#include "gtest/gtest.h"

namespace wasm {

using namespace GCTypeUtils;

class CastCheckTest : public TypeTest {
protected:
HeapType super, sub, subFinal;

void SetUp() override {
TypeBuilder builder(3);
builder[0] = Struct();
builder[0].setOpen();
builder[1] = Struct();
builder[1].subTypeOf(builder[0]).setOpen();
builder[2] = Struct();
builder[2].subTypeOf(builder[0]);

auto built = builder.build();
ASSERT_TRUE(built);

super = (*built)[0];
sub = (*built)[1];
subFinal = (*built)[2];
}
};

TEST_F(CastCheckTest, CastToSelfNonFinal) {
#define EXPECT_CAST( \
srcNullability, srcExactness, castNullability, castExactness, result) \
EXPECT_EQ(evaluateCastCheck(Type(super, srcNullability, srcExactness), \
Type(super, castNullability, castExactness)), \
result);

EXPECT_CAST(Nullable, Inexact, Nullable, Inexact, Success);
EXPECT_CAST(Nullable, Inexact, Nullable, Exact, Unknown);
EXPECT_CAST(Nullable, Inexact, NonNullable, Inexact, SuccessOnlyIfNonNull);
EXPECT_CAST(Nullable, Inexact, NonNullable, Exact, Unknown);
EXPECT_CAST(Nullable, Exact, Nullable, Inexact, Success);
EXPECT_CAST(Nullable, Exact, Nullable, Exact, Success);
EXPECT_CAST(Nullable, Exact, NonNullable, Inexact, SuccessOnlyIfNonNull);
EXPECT_CAST(Nullable, Exact, NonNullable, Exact, SuccessOnlyIfNonNull);
EXPECT_CAST(NonNullable, Inexact, Nullable, Inexact, Success);
EXPECT_CAST(NonNullable, Inexact, Nullable, Exact, Unknown);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Inexact, Success);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Exact, Unknown);
EXPECT_CAST(NonNullable, Exact, Nullable, Inexact, Success);
EXPECT_CAST(NonNullable, Exact, Nullable, Exact, Success);
EXPECT_CAST(NonNullable, Exact, NonNullable, Inexact, Success);
EXPECT_CAST(NonNullable, Exact, NonNullable, Exact, Success);
#undef EXPECT_CAST
}

TEST_F(CastCheckTest, CastToSelfFinal) {
#define EXPECT_CAST( \
srcNullability, srcExactness, castNullability, castExactness, result) \
EXPECT_EQ(evaluateCastCheck(Type(subFinal, srcNullability, srcExactness), \
Type(subFinal, castNullability, castExactness)), \
result);

EXPECT_CAST(Nullable, Inexact, Nullable, Inexact, Success);
EXPECT_CAST(Nullable, Inexact, Nullable, Exact, Success);
EXPECT_CAST(Nullable, Inexact, NonNullable, Inexact, SuccessOnlyIfNonNull);
EXPECT_CAST(Nullable, Inexact, NonNullable, Exact, SuccessOnlyIfNonNull);
EXPECT_CAST(Nullable, Exact, Nullable, Inexact, Success);
EXPECT_CAST(Nullable, Exact, Nullable, Exact, Success);
EXPECT_CAST(Nullable, Exact, NonNullable, Inexact, SuccessOnlyIfNonNull);
EXPECT_CAST(Nullable, Exact, NonNullable, Exact, SuccessOnlyIfNonNull);
EXPECT_CAST(NonNullable, Inexact, Nullable, Inexact, Success);
EXPECT_CAST(NonNullable, Inexact, Nullable, Exact, Success);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Inexact, Success);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Exact, Success);
EXPECT_CAST(NonNullable, Exact, Nullable, Inexact, Success);
EXPECT_CAST(NonNullable, Exact, Nullable, Exact, Success);
EXPECT_CAST(NonNullable, Exact, NonNullable, Inexact, Success);
EXPECT_CAST(NonNullable, Exact, NonNullable, Exact, Success);
#undef EXPECT_CAST
}

TEST_F(CastCheckTest, CastToSuper) {
#define EXPECT_CAST( \
srcNullability, srcExactness, castNullability, castExactness, result) \
EXPECT_EQ(evaluateCastCheck(Type(sub, srcNullability, srcExactness), \
Type(super, castNullability, castExactness)), \
result);

EXPECT_CAST(Nullable, Inexact, Nullable, Inexact, Success);
EXPECT_CAST(Nullable, Inexact, Nullable, Exact, SuccessOnlyIfNull);
EXPECT_CAST(Nullable, Inexact, NonNullable, Inexact, SuccessOnlyIfNonNull);
EXPECT_CAST(Nullable, Inexact, NonNullable, Exact, Failure);
EXPECT_CAST(Nullable, Exact, Nullable, Inexact, Success);
EXPECT_CAST(Nullable, Exact, Nullable, Exact, SuccessOnlyIfNull);
EXPECT_CAST(Nullable, Exact, NonNullable, Inexact, SuccessOnlyIfNonNull);
EXPECT_CAST(Nullable, Exact, NonNullable, Exact, Failure);
EXPECT_CAST(NonNullable, Inexact, Nullable, Inexact, Success);
EXPECT_CAST(NonNullable, Inexact, Nullable, Exact, Failure);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Inexact, Success);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Exact, Failure);
EXPECT_CAST(NonNullable, Exact, Nullable, Inexact, Success);
EXPECT_CAST(NonNullable, Exact, Nullable, Exact, Failure);
EXPECT_CAST(NonNullable, Exact, NonNullable, Inexact, Success);
EXPECT_CAST(NonNullable, Exact, NonNullable, Exact, Failure);
#undef EXPECT_CAST
}

TEST_F(CastCheckTest, CastToSub) {
#define EXPECT_CAST( \
srcNullability, srcExactness, castNullability, castExactness, result) \
EXPECT_EQ(evaluateCastCheck(Type(super, srcNullability, srcExactness), \
Type(sub, castNullability, castExactness)), \
result);

EXPECT_CAST(Nullable, Inexact, Nullable, Inexact, Unknown);
EXPECT_CAST(Nullable, Inexact, Nullable, Exact, Unknown);
EXPECT_CAST(Nullable, Inexact, NonNullable, Inexact, Unknown);
EXPECT_CAST(Nullable, Inexact, NonNullable, Exact, Unknown);
EXPECT_CAST(Nullable, Exact, Nullable, Inexact, SuccessOnlyIfNull);
EXPECT_CAST(Nullable, Exact, Nullable, Exact, SuccessOnlyIfNull);
EXPECT_CAST(Nullable, Exact, NonNullable, Inexact, Failure);
EXPECT_CAST(Nullable, Exact, NonNullable, Exact, Failure);
EXPECT_CAST(NonNullable, Inexact, Nullable, Inexact, Unknown);
EXPECT_CAST(NonNullable, Inexact, Nullable, Exact, Unknown);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Inexact, Unknown);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Exact, Unknown);
EXPECT_CAST(NonNullable, Exact, Nullable, Inexact, Failure);
EXPECT_CAST(NonNullable, Exact, Nullable, Exact, Failure);
EXPECT_CAST(NonNullable, Exact, NonNullable, Inexact, Failure);
EXPECT_CAST(NonNullable, Exact, NonNullable, Exact, Failure);
#undef EXPECT_CAST
}

TEST_F(CastCheckTest, CastToSibling) {
#define EXPECT_CAST( \
srcNullability, srcExactness, castNullability, castExactness, result) \
EXPECT_EQ(evaluateCastCheck(Type(sub, srcNullability, srcExactness), \
Type(subFinal, castNullability, castExactness)), \
result);

EXPECT_CAST(Nullable, Inexact, Nullable, Inexact, SuccessOnlyIfNull);
EXPECT_CAST(Nullable, Inexact, Nullable, Exact, SuccessOnlyIfNull);
EXPECT_CAST(Nullable, Inexact, NonNullable, Inexact, Failure);
EXPECT_CAST(Nullable, Inexact, NonNullable, Exact, Failure);
EXPECT_CAST(Nullable, Exact, Nullable, Inexact, SuccessOnlyIfNull);
EXPECT_CAST(Nullable, Exact, Nullable, Exact, SuccessOnlyIfNull);
EXPECT_CAST(Nullable, Exact, NonNullable, Inexact, Failure);
EXPECT_CAST(Nullable, Exact, NonNullable, Exact, Failure);
EXPECT_CAST(NonNullable, Inexact, Nullable, Inexact, Failure);
EXPECT_CAST(NonNullable, Inexact, Nullable, Exact, Failure);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Inexact, Failure);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Exact, Failure);
EXPECT_CAST(NonNullable, Exact, Nullable, Inexact, Failure);
EXPECT_CAST(NonNullable, Exact, Nullable, Exact, Failure);
EXPECT_CAST(NonNullable, Exact, NonNullable, Inexact, Failure);
EXPECT_CAST(NonNullable, Exact, NonNullable, Exact, Failure);
#undef EXPECT_CAST
}

TEST_F(CastCheckTest, CastToBottom) {
#define EXPECT_CAST(srcNullability, srcExactness, castNullability, result) \
EXPECT_EQ(evaluateCastCheck(Type(super, srcNullability, srcExactness), \
Type(HeapType::none, castNullability, Inexact)), \
result);

EXPECT_CAST(Nullable, Inexact, Nullable, SuccessOnlyIfNull);
EXPECT_CAST(Nullable, Inexact, NonNullable, Failure);
EXPECT_CAST(Nullable, Exact, Nullable, SuccessOnlyIfNull);
EXPECT_CAST(Nullable, Exact, NonNullable, Failure);
EXPECT_CAST(NonNullable, Inexact, Nullable, Failure);
EXPECT_CAST(NonNullable, Inexact, NonNullable, Failure);
EXPECT_CAST(NonNullable, Exact, Nullable, Failure);
EXPECT_CAST(NonNullable, Exact, NonNullable, Failure);
#undef EXPECT_CAST
}

TEST_F(CastCheckTest, CastFromBottom) {
#define EXPECT_CAST(srcNullability, castNullability, castExactness, result) \
EXPECT_EQ(evaluateCastCheck(Type(HeapType::none, srcNullability, Inexact), \
Type(super, castNullability, castExactness)), \
result);

EXPECT_CAST(Nullable, Nullable, Inexact, Success);
EXPECT_CAST(Nullable, Nullable, Exact, Success);
EXPECT_CAST(Nullable, NonNullable, Inexact, Failure);
EXPECT_CAST(Nullable, NonNullable, Exact, Failure);
EXPECT_CAST(NonNullable, Nullable, Inexact, GCTypeUtils::Unreachable);
EXPECT_CAST(NonNullable, Nullable, Exact, GCTypeUtils::Unreachable);
EXPECT_CAST(NonNullable, NonNullable, Inexact, GCTypeUtils::Unreachable);
EXPECT_CAST(NonNullable, NonNullable, Exact, GCTypeUtils::Unreachable);
#undef EXPECT_CAST
}

} // namespace wasm
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