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[dart2wasm] Use a separate Wasm struct for every Dart class

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This removes the optimization that would reuse the Wasm struct of the
superclass if no new fields were added in a class. Such reuse
interferes with debugging.

Binaryen performs a similar optimization in its TypeMerging pass. It
seems to be doing a better job with the more precise type information
provided after this change. Benchmarks show a positive trend.

The change uncovered a number of latent bugs in the compiler, which
are also fixed in this CL:
- References to `StackTrace` objects must be typed with the
  representation type of `StackTrace`, rather than its struct type.
- The dynamic call vtable entry and dynamic invocation forwarder
  functions must use `_ListBase` rather than `_List` for their
  parameters, since we sometimes pass growable lists to these
  functions.
- Most covariant parameters must use the top type, since any object
  can be passed into such parameters via class type parameter
  covariance or tear-offs.

The change makes us fail a number of tests with very deep class
hierarchies due to the Wasm subtyping depth limit of 63. The
optimization did not absolve us from this limitation. It just made us
only count classes with newly added fields.

The limitation is not expected to cause any problems for real code.
The maximum subclassing depth that occurs in the Flute benchmark is
11. FWIW, Java has a limit of 60.

The limitation is mentioned along with other limitations in
https://github.com/dart-lang/sdk/issues/53703

Change-Id: Ifaa23d8278989e2549c41696d8913e55ed1e80aa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/324460
Commit-Queue: Aske Simon Christensen <askesc@google.com>
Reviewed-by: Ömer Ağacan <omersa@google.com>
This commit is contained in:
Aske Simon Christensen
2023-10-10 14:35:53 +00:00
committed by Commit Queue
parent eaa308fbef
commit 2cbb5eabca
6 changed files with 54 additions and 53 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/dart2wasm/lib/async.dart
+9 -7
View File
@@ -278,8 +278,8 @@ class _ExceptionHandlerStack {
codeGen.b.catch_(codeGen.translator.exceptionTag);
final stackTraceLocal =
codeGen.addLocal(codeGen.translator.stackTraceInfo.nonNullableType);
final stackTraceLocal = codeGen
.addLocal(codeGen.translator.stackTraceInfo.repr.nonNullableType);
codeGen.b.local_set(stackTraceLocal);
final exceptionLocal =
@@ -573,8 +573,8 @@ class AsyncCodeGenerator extends CodeGenerator {
asyncSuspendStateInfo.nonNullableType, // _AsyncSuspendState
translator.topInfo.nullableType, // Object?, await value
translator.topInfo.nullableType, // Object?, error value
translator
.stackTraceInfo.nullableType // StackTrace?, error stack trace
translator.stackTraceInfo.repr
.nullableType // StackTrace?, error stack trace
], [
// Inner function does not return a value, but it's Dart type is
// `void Function(...)` and all Dart functions return a value, so we
@@ -647,7 +647,7 @@ class AsyncCodeGenerator extends CodeGenerator {
b.local_get(asyncStateLocal);
b.ref_null(translator.topInfo.struct); // await value
b.ref_null(translator.topInfo.struct); // error value
b.ref_null(translator.stackTraceInfo.struct); // stack trace
b.ref_null(translator.stackTraceInfo.repr.struct); // stack trace
b.call(resumeFun);
b.drop(); // drop null
@@ -783,7 +783,8 @@ class AsyncCodeGenerator extends CodeGenerator {
b.catch_(translator.exceptionTag);
final stackTraceLocal = addLocal(translator.stackTraceInfo.nonNullableType);
final stackTraceLocal =
addLocal(translator.stackTraceInfo.repr.nonNullableType);
b.local_set(stackTraceLocal);
final exceptionLocal = addLocal(translator.topInfo.nonNullableType);
@@ -1291,7 +1292,8 @@ class AsyncCodeGenerator extends CodeGenerator {
wrap(node.expression, translator.topInfo.nonNullableType);
b.local_set(exceptionLocal);
final stackTraceLocal = addLocal(translator.stackTraceInfo.nonNullableType);
final stackTraceLocal =
addLocal(translator.stackTraceInfo.repr.nonNullableType);
call(translator.stackTraceCurrent.reference);
b.local_set(stackTraceLocal);
pkg/dart2wasm/lib/class_info.dart
+3 -20
View File
@@ -366,19 +366,8 @@ class ClassInfoCollector {
}
}
// A class can reuse the Wasm struct of the superclass if it doesn't
// declare any Wasm fields of its own. This is the case when three
// conditions are met:
// 1. All type parameters can reuse a type parameter field of the
// superclass.
// 2. The class declares no Dart fields of its own.
// 3. The class is not a special class that contains hidden fields.
bool canReuseSuperStruct =
typeParameterMatch.length == cls.typeParameters.length &&
cls.fields.where((f) => f.isInstanceMember).isEmpty;
w.StructType struct = canReuseSuperStruct
? superInfo.struct
: m.types.defineStruct(cls.name, superType: superInfo.struct);
w.StructType struct =
m.types.defineStruct(cls.name, superType: superInfo.struct);
info = ClassInfo(
cls, _nextClassId++, superInfo.depth + 1, struct, superInfo,
typeParameterMatch: typeParameterMatch);
@@ -447,7 +436,7 @@ class ClassInfoCollector {
// Top - add class id field
info._addField(
w.FieldType(w.NumType.i32, mutable: false), FieldIndex.classId);
} else if (info.struct != superInfo.struct) {
} else {
// Copy fields from superclass
for (w.FieldType fieldType in superInfo.struct.fields) {
info._addField(fieldType);
@@ -476,12 +465,6 @@ class ClassInfoCollector {
info._addField(w.FieldType(wasmType, mutable: !field.isFinal));
}
}
} else {
for (TypeParameter parameter in info.cls!.typeParameters) {
// Reuse supertype type variable
translator.typeParameterIndex[parameter] =
translator.typeParameterIndex[info.typeParameterMatch[parameter]]!;
}
}
}
pkg/dart2wasm/lib/code_generator.dart
+2 -2
View File
@@ -1150,7 +1150,7 @@ class CodeGenerator extends ExpressionVisitor1<w.ValueType, w.ValueType>
// stack after each type test. Also, store the stack trace in a local.
w.Local thrownException = addLocal(translator.topInfo.nonNullableType);
w.Local thrownStackTrace =
addLocal(translator.stackTraceInfo.nonNullableType);
addLocal(translator.stackTraceInfo.repr.nonNullableType);
void emitCatchBlock(Catch catch_, bool emitGuard) {
// For each catch node:
@@ -1864,7 +1864,7 @@ class CodeGenerator extends ExpressionVisitor1<w.ValueType, w.ValueType>
translator.types.makeType(this, typeArguments[elementIdx]);
}, isGrowable: true);
final typeArgsLocal = function.addLocal(
translator.classInfo[translator.fixedLengthListClass]!.nonNullableType);
translator.classInfo[translator.growableListClass]!.nonNullableType);
b.local_set(typeArgsLocal);
// Evaluate positional arguments
pkg/dart2wasm/lib/dispatch_table.dart
+31 -16
View File
@@ -41,6 +41,9 @@ class SelectorInfo {
/// Is this an implicit or explicit setter?
final bool isSetter;
/// Does this method have any tear-off uses?
bool hasTearOffUses = false;
/// Maps class IDs to the selector's member in the class. The member can be
/// abstract.
final Map<int, Reference> targets = {};
@@ -113,28 +116,39 @@ class SelectorInfo {
named = const {};
returns = [function.computeFunctionType(Nullability.nonNullable)];
} else {
DartType typeForParam(VariableDeclaration param, int index) {
if (param.isCovariantByClass) {
// The type argument of a static type is not required to conform
// to the bounds of the type variable. Thus, any object can be
// passed to a parameter that is covariant by class.
return translator.coreTypes.objectNullableRawType;
}
if (param.isCovariantByDeclaration) {
if (hasTearOffUses) {
// The type of a covariant parameter in the runtime function
// type of a tear-off is always `Object?`. Thus, if the method
// has any tear-off uses, any object could be passed into the
// parameter.
return translator.coreTypes.objectNullableRawType;
}
if (!translator.options.omitTypeChecks) {
// A runtime type check of the parameter will be generated.
// The value therefore must be boxed.
ensureBoxed[index] = true;
}
}
return param.type;
}
positional = [
for (VariableDeclaration param in function.positionalParameters)
param.type
for (int i = 0; i < function.positionalParameters.length; i++)
typeForParam(function.positionalParameters[i], 1 + i)
];
named = {
for (VariableDeclaration param in function.namedParameters)
param.name!: param.type
param.name!: typeForParam(param, 1 + nameIndex[param.name!]!)
};
returns = target.isSetter ? const [] : [function.returnType];
// Box parameters that need covariance checks
if (!translator.options.omitTypeChecks) {
for (int i = 0; i < function.positionalParameters.length; i += 1) {
final param = function.positionalParameters[i];
ensureBoxed[1 + i] |=
param.isCovariantByClass || param.isCovariantByDeclaration;
}
for (VariableDeclaration param in function.namedParameters) {
ensureBoxed[1 + nameIndex[param.name!]!] |=
param.isCovariantByClass || param.isCovariantByDeclaration;
}
}
}
}
assert(returns.length <= outputSets.length);
@@ -287,6 +301,7 @@ class DispatchTable {
_selectorMetadata[selectorId].callCount, paramInfo,
isSetter: isSetter));
assert(selector.isSetter == isSetter);
selector.hasTearOffUses |= metadata.hasTearOffUses;
selector.paramInfo.merge(paramInfo);
if (calledDynamically) {
if (isGetter) {
pkg/dart2wasm/lib/sync_star.dart
+1 -1
View File
@@ -241,7 +241,7 @@ class SyncStarCodeGenerator extends CodeGenerator {
m.types.defineFunction([
suspendStateInfo.nonNullableType,
translator.topInfo.nullableType,
translator.stackTraceInfo.nullableType
translator.stackTraceInfo.repr.nullableType
], const [
w.NumType.i32
]),
pkg/dart2wasm/lib/translator.dart
+8 -7
View File
@@ -173,13 +173,13 @@ class Translator with KernelNodes {
w.RefType.def(closureLayouter.closureBaseStruct, nullable: false),
// Type arguments
classInfo[fixedLengthListClass]!.nonNullableType,
classInfo[listBaseClass]!.nonNullableType,
// Positional arguments
classInfo[fixedLengthListClass]!.nonNullableType,
classInfo[listBaseClass]!.nonNullableType,
// Named arguments, represented as array of symbol and object pairs
classInfo[fixedLengthListClass]!.nonNullableType,
classInfo[listBaseClass]!.nonNullableType,
], [
topInfo.nullableType
]);
@@ -191,13 +191,13 @@ class Translator with KernelNodes {
topInfo.nonNullableType,
// Type arguments
classInfo[fixedLengthListClass]!.nonNullableType,
classInfo[listBaseClass]!.nonNullableType,
// Positional arguments
classInfo[fixedLengthListClass]!.nonNullableType,
classInfo[listBaseClass]!.nonNullableType,
// Named arguments, represented as array of symbol and object pairs
classInfo[fixedLengthListClass]!.nonNullableType,
classInfo[listBaseClass]!.nonNullableType,
], [
topInfo.nullableType
]);
@@ -465,7 +465,8 @@ class Translator with KernelNodes {
/// exception tag is used to throw and catch all Dart exceptions.
w.Tag createExceptionTag() {
w.FunctionType tagType = m.types.defineFunction(
[topInfo.nonNullableType, stackTraceInfo.nonNullableType], const []);
[topInfo.nonNullableType, stackTraceInfo.repr.nonNullableType],
const []);
w.Tag tag = m.tags.define(tagType);
return tag;
}