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Avoid memory issues with hoisted variables #4183

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merged 1 commit into from Jul 21, 2021
Merged

Avoid memory issues with hoisted variables #4183

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3 changes: 1 addition & 2 deletions src/ast/nodes/Identifier.ts
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Expand Up @@ -9,7 +9,6 @@ import { HasEffectsContext, InclusionContext } from '../ExecutionContext';
import { NodeEvent } from '../NodeEvents';
import FunctionScope from '../scopes/FunctionScope';
import { EMPTY_PATH, ObjectPath, PathTracker } from '../utils/PathTracker';
import { UNDEFINED_EXPRESSION } from '../values';
import GlobalVariable from '../variables/GlobalVariable';
import LocalVariable from '../variables/LocalVariable';
import Variable from '../variables/Variable';
Expand Down Expand Up @@ -60,7 +59,7 @@ export default class Identifier extends NodeBase implements PatternNode {
variable = this.scope.addDeclaration(this, this.context, init, true);
if (treeshake && treeshake.correctVarValueBeforeDeclaration) {
// Necessary to make sure the init is deoptimized. We cannot call deoptimizePath here.
this.scope.addDeclaration(this, this.context, UNDEFINED_EXPRESSION, true);
variable.markInitializersForDeoptimization();
}
break;
case 'function':
Expand Down
6 changes: 3 additions & 3 deletions src/ast/scopes/BlockScope.ts
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@@ -1,7 +1,6 @@
import { AstContext } from '../../Module';
import Identifier from '../nodes/Identifier';
import { ExpressionEntity } from '../nodes/shared/Expression';
import { UNDEFINED_EXPRESSION } from '../values';
import LocalVariable from '../variables/LocalVariable';
import ChildScope from './ChildScope';

Expand All @@ -13,10 +12,11 @@ export default class BlockScope extends ChildScope {
isHoisted: boolean
): LocalVariable {
if (isHoisted) {
this.parent.addDeclaration(identifier, context, init, isHoisted);
const variable = this.parent.addDeclaration(identifier, context, init, isHoisted);
// Necessary to make sure the init is deoptimized for conditional declarations.
// We cannot call deoptimizePath here.
return this.parent.addDeclaration(identifier, context, UNDEFINED_EXPRESSION, isHoisted);
variable.markInitializersForDeoptimization();
return variable;
} else {
return super.addDeclaration(identifier, context, init, false);
}
Expand Down
19 changes: 12 additions & 7 deletions src/ast/variables/LocalVariable.ts
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Expand Up @@ -21,7 +21,6 @@ import Variable from './Variable';
const MAX_PATH_DEPTH = 7;

export default class LocalVariable extends Variable {
additionalInitializers: ExpressionEntity[] | null = null;
calledFromTryStatement = false;
declarations: (Identifier | ExportDefaultDeclaration)[];
init: ExpressionEntity | null;
Expand All @@ -30,6 +29,7 @@ export default class LocalVariable extends Variable {
// Caching and deoptimization:
// We track deoptimization when we do not return something unknown
protected deoptimizationTracker: PathTracker;
private additionalInitializers: ExpressionEntity[] | null = null;
private expressionsToBeDeoptimized: DeoptimizableEntity[] = [];

constructor(
Expand All @@ -47,13 +47,9 @@ export default class LocalVariable extends Variable {

addDeclaration(identifier: Identifier, init: ExpressionEntity | null): void {
this.declarations.push(identifier);
if (this.additionalInitializers === null) {
this.additionalInitializers = this.init === null ? [] : [this.init];
this.init = UNKNOWN_EXPRESSION;
this.isReassigned = true;
}
const additionalInitializers = this.markInitializersForDeoptimization();
if (init !== null) {
this.additionalInitializers.push(init);
additionalInitializers.push(init);
}
}

Expand Down Expand Up @@ -212,4 +208,13 @@ export default class LocalVariable extends Variable {
markCalledFromTryStatement(): void {
this.calledFromTryStatement = true;
}

markInitializersForDeoptimization(): ExpressionEntity[] {
if (this.additionalInitializers === null) {
this.additionalInitializers = this.init === null ? [] : [this.init];
this.init = UNKNOWN_EXPRESSION;
this.isReassigned = true;
}
return this.additionalInitializers;
}
}
3 changes: 3 additions & 0 deletions test/form/samples/deep-switch-declarations/_config.js
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@@ -0,0 +1,3 @@
module.exports = {
description: 'handles hoisted declarations in deeply nested switch statements'
};
32 changes: 32 additions & 0 deletions test/form/samples/deep-switch-declarations/_expected.js
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@@ -0,0 +1,32 @@
switch(x){ default: var x=1;
switch(x){ default: var x=2;
switch(x){ default: var x=3;
switch(x){ default: var x=4;
switch(x){ default: var x=5;
switch(x){ default: var x=6;
switch(x){ default: var x=7;
switch(x){ default: var x=8;
switch(x){ default: var x=9;
switch(x){ default: var x=10;
switch(x){ default: var x=11;
switch(x){ default: var x=12;
switch(x){ default: var x=13;
switch(x){ default: var x=14;
switch(x){ default: var x=15;
switch(x){ default: var x=16;
switch(x){ default: var x=17;
switch(x){ default: var x=18;
switch(x){ default: var x=19;
switch(x){ default: var x=20;
switch(x){ default: var x=21;
switch(x){ default: var x=22;
switch(x){ default: var x=23;
switch(x){ default: var x=24;
switch(x){ default: var x=25;
switch(x){ default: var x=26;
switch(x){ default: var x=27;
switch(x){ default: var x=28;
switch(x){ default: var x=29;
switch(x){ default: var x=30;
}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}
console.log(x);
32 changes: 32 additions & 0 deletions test/form/samples/deep-switch-declarations/main.js
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@@ -0,0 +1,32 @@
switch(x){ default: var x=1;
switch(x){ default: var x=2;
switch(x){ default: var x=3;
switch(x){ default: var x=4;
switch(x){ default: var x=5;
switch(x){ default: var x=6;
switch(x){ default: var x=7;
switch(x){ default: var x=8;
switch(x){ default: var x=9;
switch(x){ default: var x=10;
switch(x){ default: var x=11;
switch(x){ default: var x=12;
switch(x){ default: var x=13;
switch(x){ default: var x=14;
switch(x){ default: var x=15;
switch(x){ default: var x=16;
switch(x){ default: var x=17;
switch(x){ default: var x=18;
switch(x){ default: var x=19;
switch(x){ default: var x=20;
switch(x){ default: var x=21;
switch(x){ default: var x=22;
switch(x){ default: var x=23;
switch(x){ default: var x=24;
switch(x){ default: var x=25;
switch(x){ default: var x=26;
switch(x){ default: var x=27;
switch(x){ default: var x=28;
switch(x){ default: var x=29;
switch(x){ default: var x=30;
}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}
console.log(x);