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Update J2CLItableMerging to consider custom descriptors #7729

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Update J2CLItableMerging to consider custom descriptors #7729

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63 changes: 41 additions & 22 deletions src/passes/J2CLItableMerging.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -104,20 +104,33 @@ struct J2CLItableMerging : public Pass {
continue;
}

auto type = heapType.getStruct();
if (typeNameInfo.fieldNames.empty() ||
!typeNameInfo.fieldNames[0].equals("vtable")) {
continue;
}
if (typeNameInfo.fieldNames.size() < 1 ||
!typeNameInfo.fieldNames[1].equals("itable")) {
if (typeNameInfo.fieldNames.empty()) {
continue;
}

auto vtabletype = type.fields[0].type.getHeapType();
auto itabletype = type.fields[1].type.getHeapType();
// The vtable may either be the first field or the custom descriptor.
std::optional<HeapType> vtabletype;
std::optional<HeapType> itabletype;
Comment on lines +112 to +113
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If these would be empty, then we'll just continue to the next loop iteration anyway, so I don't see a reason to make them optional.

Suggested change
std::optional<HeapType> vtabletype;
std::optional<HeapType> itabletype;
HeapType vtabletype;
HeapType itabletype;

auto type = heapType.getStruct();
if (auto descriptor = heapType.getDescriptorType()) {
if (!typeNameInfo.fieldNames[0].equals("itable")) {
continue;
}
vtabletype = descriptor;
itabletype = type.fields[0].type.getHeapType();
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You might want to reserve field 0 in the descriptor. Once we have JS interop, the JS prototype will (almost certainly) have to be stored in field 0.

} else {
if (!typeNameInfo.fieldNames[0].equals("vtable")) {
continue;
}
if (!typeNameInfo.fieldNames.count(1) ||
!typeNameInfo.fieldNames[1].equals("itable")) {
Comment on lines +125 to +126
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It seems we should have a similar check before looking up the name of field 0. Also, we can avoid double lookup by doing this:

Suggested change
if (!typeNameInfo.fieldNames.count(1) ||
!typeNameInfo.fieldNames[1].equals("itable")) {
if (auto it = typeNameInfo.fieldNames.find(1);
it == typeNameInfo.fieldNames.end() || it->second.equals("itable")) {

continue;
}
vtabletype = type.fields[0].type.getHeapType();
itabletype = type.fields[1].type.getHeapType();
}

auto structItableSize = itabletype.getStruct().fields.size();
auto structItableSize = itabletype->getStruct().fields.size();

if (itableSize != 0 && itableSize != structItableSize) {
Fatal() << "--merge-j2cl-itables needs to be the first pass to run "
Expand All @@ -128,11 +141,11 @@ struct J2CLItableMerging : public Pass {

// Add a new StructInfo to the list by value so that its memory gets
// reclaimed automatically on exit.
structInfos.push_back(StructInfo{heapType, vtabletype, itabletype});
structInfos.push_back(StructInfo{heapType, *vtabletype, *itabletype});
// Point to the StructInfo just added to the list to be able to look it
// up by its vtable and itable types.
structInfoByVtableType[vtabletype] = &structInfos.back();
structInfoByITableType[itabletype] = &structInfos.back();
structInfoByVtableType[*vtabletype] = &structInfos.back();
structInfoByITableType[*itabletype] = &structInfos.back();
}

// 2. Collect the globals for vtables and itables.
Expand Down Expand Up @@ -275,16 +288,22 @@ struct J2CLItableMerging : public Pass {
}

// This is a struct.get that returns an itable type;
// Change to return the corresponding vtable type.
// Change to return the corresponding vtable type. If the vtable is a
// custom descriptor, change to a ref.get_desc instruction.
Builder builder(*getModule());
replaceCurrent(builder.makeStructGet(
0,
curr->ref,
MemoryOrder::Unordered,
parent.structInfoByITableType[curr->type.getHeapType()]
->javaClass.getStruct()
.fields[0]
.type));

HeapType& javaClass = parent.structInfoByITableType[curr->type.getHeapType()]->javaClass;
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A HeapType is represented as a single number, so no need to take a reference to it unless you're going to mutate it.

Suggested change
HeapType& javaClass = parent.structInfoByITableType[curr->type.getHeapType()]->javaClass;
HeapType javaClass = parent.structInfoByITableType[curr->type.getHeapType()]->javaClass;

if (javaClass.getDescriptorType()) {
replaceCurrent(builder.makeRefGetDesc(curr->ref));
} else {
replaceCurrent(builder.makeStructGet(
0,
curr->ref,
MemoryOrder::Unordered,
javaClass.getStruct()
.fields[0]
.type));
}
}
};

Expand Down
225 changes: 223 additions & 2 deletions test/lit/passes/j2cl-merge-itables.wast
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Original file line number Diff line number Diff line change
Expand Up @@ -100,7 +100,7 @@
(global.get $SubObject.vtable)
(global.get $SubObject.itable)))
(drop
;; The access to vtable field 0 is offset but the itable size and
;; The access to vtable field 0 is offset by the itable size and
;; will be an access to field 1.
(struct.get $SubObject.vtable 0
(struct.get $SubObject $vtable
Expand Down Expand Up @@ -214,7 +214,7 @@
(global.get $SubObject.vtable)
(global.get $SubObject.itable)))
(drop
;; The access to vtable field 0 is offset but the itable size and
;; The access to vtable field 0 is offset by the itable size and
;; will be an access to field 1.
(struct.get $SubObject.vtable 0
(struct.get $SubObject $vtable
Expand All @@ -227,3 +227,224 @@
(local.get $o))))
)
)

;; Custom descriptors - Shared itable instance.
(module
(rec
;; CHECK: (rec
;; CHECK-NEXT: (type $Object (sub (descriptor $Object.vtable (struct (field $itable (ref $Object.itable))))))
(type $Object (sub (descriptor $Object.vtable (struct
(field $itable (ref $Object.itable))))))

;; CHECK: (type $SubObject (sub $Object (descriptor $SubObject.vtable (struct (field $itable (ref $Object.itable))))))
(type $SubObject (sub $Object (descriptor $SubObject.vtable (struct
(field $itable (ref $Object.itable))))))

;; CHECK: (type $function (func))
(type $function (func))

;; The $Object.itable field (a structref) will be added as a field to
;; the beginning of this vtable.
;; CHECK: (type $Object.vtable (sub (describes $Object (struct (field structref)))))
(type $Object.vtable (sub (describes $Object (struct))))

;; The $Object.itable field (a structref) will be added as a field to
;; the beginning of this vtable.
;; CHECK: (type $SubObject.vtable (sub $Object.vtable (describes $SubObject (struct (field structref) (field (ref $function))))))
(type $SubObject.vtable (sub $Object.vtable (describes $SubObject (struct
(field (ref $function))))))

;; CHECK: (type $Object.itable (struct (field structref)))
(type $Object.itable (struct
(field (ref null struct))))
)

;; CHECK: (type $6 (func))

;; CHECK: (global $Object.itable (ref $Object.itable) (struct.new_default $Object.itable))
(global $Object.itable (ref $Object.itable)
(struct.new_default $Object.itable))

;; CHECK: (global $SubObject.itable (ref $Object.itable) (global.get $Object.itable))
(global $SubObject.itable (ref $Object.itable)
(global.get $Object.itable)) ;; uses shared empty itable instance.

;; The initialization for the itable field (null struct) will be added to this
;; vtable instance.
;; CHECK: (global $SubObject.vtable (ref (exact $SubObject.vtable)) (struct.new $SubObject.vtable
;; CHECK-NEXT: (ref.null none)
;; CHECK-NEXT: (ref.func $SubObject.f)
;; CHECK-NEXT: ))
(global $SubObject.vtable (ref (exact $SubObject.vtable))
(struct.new $SubObject.vtable (ref.func $SubObject.f)))


;; The initialization for the itable field (null struct) will be added to this
;; vtable instance.
;; CHECK: (global $Object.vtable (ref (exact $Object.vtable)) (struct.new $Object.vtable
;; CHECK-NEXT: (ref.null none)
;; CHECK-NEXT: ))
(global $Object.vtable (ref (exact $Object.vtable))
(struct.new $Object.vtable))

;; CHECK: (func $SubObject.f (type $function)
;; CHECK-NEXT: )
(func $SubObject.f
(type $function)
)

;; CHECK: (func $usages (type $6)
;; CHECK-NEXT: (local $o (ref null $SubObject))
;; CHECK-NEXT: (local.set $o
;; CHECK-NEXT: (struct.new $SubObject
;; CHECK-NEXT: (global.get $SubObject.itable)
;; CHECK-NEXT: (global.get $SubObject.vtable)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (struct.get $SubObject.vtable 1
;; CHECK-NEXT: (ref.get_desc $SubObject
;; CHECK-NEXT: (local.get $o)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (struct.get $SubObject.vtable 0
;; CHECK-NEXT: (ref.get_desc $SubObject
;; CHECK-NEXT: (local.get $o)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $usages
(local $o (ref null $SubObject))
(local.set $o
(struct.new $SubObject
(global.get $SubObject.itable)
(global.get $SubObject.vtable)))
(drop
;; The access to vtable field 0 is offset by the itable size and
;; will be an access to field 1.
(struct.get $SubObject.vtable 0
(ref.get_desc $SubObject
(local.get $o))))
(drop
;; The access to itable field 0 will be rerouted to be an access to
;; vtable field 0.
(struct.get $Object.itable 0
(struct.get $SubObject $itable
(local.get $o))))
)
)

;; Custom descriptors - Each type has its own itable.
(module
(rec
;; CHECK: (rec
;; CHECK-NEXT: (type $Object (sub (descriptor $Object.vtable (struct (field $itable (ref $Object.itable))))))
(type $Object (sub (descriptor $Object.vtable (struct
(field $itable (ref $Object.itable))))))

;; CHECK: (type $SubObject (sub $Object (descriptor $SubObject.vtable (struct (field $itable (ref $SubObject.itable))))))
(type $SubObject (sub $Object (descriptor $SubObject.vtable (struct
(field $itable (ref $SubObject.itable))))))

;; CHECK: (type $function (func))
(type $function (func))

;; CHECK: (type $Object.itable (sub (struct (field structref))))
(type $Object.itable (sub (struct
(field (ref null struct)))))

;; CHECK: (type $SubObject.itable (sub $Object.itable (struct (field structref))))
(type $SubObject.itable (sub $Object.itable
(struct (field (ref null struct)))))

;; The $Object.itable field (a structref) will be added as a field to
;; the beginning of this vtable.
;; CHECK: (type $Object.vtable (sub (describes $Object (struct (field structref)))))
(type $Object.vtable (sub (describes $Object (struct))))

;; The $SubObject.itable field (a structref) will be added as a field to
;; the beginning of this vtable.
;; CHECK: (type $SubObject.vtable (sub $Object.vtable (describes $SubObject (struct (field structref) (field (ref $function))))))
(type $SubObject.vtable (sub $Object.vtable (describes $SubObject
(struct (field (ref $function))))))
)

;; The initialization for the itable field (null struct) will be added to this
;; vtable instance.
;; CHECK: (type $7 (func))

;; CHECK: (global $SubObject.vtable (ref (exact $SubObject.vtable)) (struct.new $SubObject.vtable
;; CHECK-NEXT: (ref.null none)
;; CHECK-NEXT: (ref.func $SubObject.f)
;; CHECK-NEXT: ))
(global $SubObject.vtable (ref (exact $SubObject.vtable))
(struct.new $SubObject.vtable (ref.func $SubObject.f)))

;; CHECK: (global $SubObject.itable (ref $SubObject.itable) (struct.new_default $SubObject.itable))
(global $SubObject.itable (ref $SubObject.itable)
(struct.new_default $SubObject.itable))

;; The initialization for the itable field (null struct) will be added to this
;; vtable instance.
;; CHECK: (global $Object.vtable (ref (exact $Object.vtable)) (struct.new $Object.vtable
;; CHECK-NEXT: (ref.null none)
;; CHECK-NEXT: ))
(global $Object.vtable (ref (exact $Object.vtable))
(struct.new $Object.vtable))

;; CHECK: (global $Object.itable (ref $Object.itable) (struct.new_default $Object.itable))
(global $Object.itable (ref $Object.itable)
(struct.new_default $Object.itable))

;; CHECK: (func $SubObject.f (type $function)
;; CHECK-NEXT: )
(func $SubObject.f
(type $function)
)

;; CHECK: (func $usages (type $7)
;; CHECK-NEXT: (local $o (ref null $SubObject))
;; CHECK-NEXT: (local.set $o
;; CHECK-NEXT: (struct.new $SubObject
;; CHECK-NEXT: (global.get $SubObject.itable)
;; CHECK-NEXT: (global.get $SubObject.vtable)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (struct.get $SubObject.vtable 1
;; CHECK-NEXT: (ref.get_desc $SubObject
;; CHECK-NEXT: (local.get $o)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (struct.get $SubObject.vtable 0
;; CHECK-NEXT: (ref.get_desc $SubObject
;; CHECK-NEXT: (local.get $o)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $usages
(local $o (ref null $SubObject))
(local.set $o
(struct.new $SubObject
(global.get $SubObject.itable)
(global.get $SubObject.vtable)))
(drop
;; The access to vtable field 0 is offset by the itable size and
;; will be an access to field 1.
(struct.get $SubObject.vtable 0
(ref.get_desc $SubObject
(local.get $o))))
(drop
;; The access to itable field 0 will be rerouted to be an access to
;; vtable field 0.
(struct.get $Object.itable 0
(struct.get $SubObject $itable
(local.get $o))))
)
)
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