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Merged
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Apr 28, 2025
Merged

Use GLB in PossibleContents::intersect #7550

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35 changes: 6 additions & 29 deletions src/ir/possible-contents.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -182,47 +182,26 @@ void PossibleContents::intersect(const PossibleContents& other) {
auto heapType = type.getHeapType();
auto otherHeapType = otherType.getHeapType();

// If both inputs are nullable then the intersection is nullable as well.
auto nullability =
type.isNullable() && otherType.isNullable() ? Nullable : NonNullable;
// Intersect the types.
auto newType = Type::getGreatestLowerBound(type, otherType);

auto setNoneOrNull = [&]() {
if (nullability == Nullable) {
if (newType.isNullable()) {
value = Literal::makeNull(heapType);
} else {
value = None();
}
};

// If the heap types are not compatible then they are in separate hierarchies
// and there is no intersection, aside from possibly a null of the bottom
// type.
auto isSubType = HeapType::isSubType(heapType, otherHeapType);
auto otherIsSubType = HeapType::isSubType(otherHeapType, heapType);
if (!isSubType && !otherIsSubType) {
if (heapType.getBottom() == otherHeapType.getBottom()) {
setNoneOrNull();
} else {
value = None();
}
if (newType == Type::unreachable || newType.isNull()) {
setNoneOrNull();
return;
}

// The heap types are compatible, so intersect the cones.
auto depthFromRoot = heapType.getDepth();
auto otherDepthFromRoot = otherHeapType.getDepth();

// To compute the new cone, find the new heap type for it, and to compute its
// depth, consider the adjustments to the existing depths that stem from the
// choice of new heap type.
HeapType newHeapType;

if (depthFromRoot < otherDepthFromRoot) {
newHeapType = otherHeapType;
} else {
newHeapType = heapType;
}

// Note the global's information, if we started as a global. In that case, the
// code below will refine our type but we can remain a global, which we will
// accomplish by restoring our global status at the end.
Expand All @@ -231,8 +210,6 @@ void PossibleContents::intersect(const PossibleContents& other) {
globalName = getGlobal();
}

auto newType = Type(newHeapType, nullability);

// By assumption |other| has full depth. Consider the other cone in |this|.
if (hasFullCone()) {
// Both are full cones, so the result is as well.
Expand All @@ -252,7 +229,7 @@ void PossibleContents::intersect(const PossibleContents& other) {
// E.g. if |this| is a cone of depth 10, and |otherHeapType| is an immediate
// subtype of |this|, then the new cone must be of depth 9.
auto newDepth = getCone().depth;
if (newHeapType == otherHeapType) {
if (newType.getHeapType() == otherHeapType) {
assert(depthFromRoot <= otherDepthFromRoot);
auto reduction = otherDepthFromRoot - depthFromRoot;
if (reduction > newDepth) {
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36 changes: 36 additions & 0 deletions test/lit/passes/gufa-cast-all-exact.wast
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Expand Up @@ -138,3 +138,39 @@
)
)
)

(module
;; CHECK: (type $foo (sub (struct (field i32))))
;; NO_CD: (type $foo (sub (struct (field i32))))
(type $foo (sub (struct (field i32))))

;; CHECK: (import "" "" (global $null-exact (ref null (exact $foo))))
;; NO_CD: (import "" "" (global $null-exact (ref null (exact $foo))))
(import "" "" (global $null-exact (ref null (exact $foo))))

;; CHECK: (func $as-non-null (type $1) (result i32)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.as_non_null
;; CHECK-NEXT: (global.get $null-exact)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (unreachable)
;; CHECK-NEXT: )
;; NO_CD: (func $as-non-null (type $1) (result i32)
;; NO_CD-NEXT: (drop
;; NO_CD-NEXT: (ref.as_non_null
;; NO_CD-NEXT: (global.get $null-exact)
;; NO_CD-NEXT: )
;; NO_CD-NEXT: )
;; NO_CD-NEXT: (unreachable)
;; NO_CD-NEXT: )
(func $as-non-null (result i32)
(struct.get $foo 0
;; Regression test for an assertion failure when the intersection here
;; dropped exactness as well as nullness.
(ref.as_non_null
(global.get $null-exact)
)
)
)
)
9 changes: 7 additions & 2 deletions test/lit/passes/gufa-refs.wast
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Expand Up @@ -6069,8 +6069,13 @@
;; CHECK: (func $test-set-bottom (type $2)
;; CHECK-NEXT: (block ;; (replaces unreachable ArraySet we can't emit)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.cast nullref
;; CHECK-NEXT: (global.get $global)
;; CHECK-NEXT: (block (result nullref)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (ref.cast nullref
;; CHECK-NEXT: (global.get $global)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (ref.null none)
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Why did this change? Previously the ref.cast emitted a nullable bottom type, and it should still keep doing so IIUC... the description mentions a change to non-nullable ones, but that's not the case here, so it must be something else?

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This is what I was referring to with non-nullable references because the possible contents in $global is a non-null value, even though its static type is nullable.

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Oh right, the actual value is non-nullable, thanks!

;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
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