fbcc2e874d
Design doc: bit.ly/v8-repl-mode
This CL adds a new REPL mode that can be used via
DebugEvaluate::GlobalREPL. REPL mode only implements re-declaration
of 'let' bindings at the moment. Example:
REPL Input 1: let x = 21;
REPL Input 2: let x = 42;
This would normally throw a SyntaxError, but works in REPL mode.
The implementation is done by:
- Setting a 'repl mode' bit on {Script}, {ScopeInfo}, {ParseInfo}
and script {Scope}.
- Each global let declaration still gets a slot reserved in the
respective {ScriptContext}.
- When a new REPL mode {ScriptContext} is created, name clashes
for let bindings are not reported as errors.
- Declarations, loads and stores for global let in REPL mode are
now "load/store global" instead of accessing their respective
context slot directly. This causes a lookup in the ScriptContextTable
where the found slot for each name is guaranteed to be the same
(the first one).
Bug: chromium:1004193, chromium:1018158
Change-Id: Ia6ab526b9f696400dbb8bfb611a4d43606119a47
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1876061
Commit-Queue: Simon Zünd <szuend@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64793}
33 lines
887 B
JavaScript
33 lines
887 B
JavaScript
// Copyright 2019 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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//
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// Flags: --opt
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Debug = debug.Debug
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const evaluate = Debug.evaluateGlobalREPL;
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const evaluateNonREPL = (source) => Debug.evaluateGlobal(source, false).value();
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// Test that a let declared variable 'x' bound by an optimized function is
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// updated properly.
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evaluate('let x = 42;');
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evaluate('function foo() { return x; }');
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%PrepareFunctionForOptimization(foo);
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foo();
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foo();
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%OptimizeFunctionOnNextCall(foo);
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assertEquals(42, foo());
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assertOptimized(foo);
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evaluate('let x = 21');
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assertEquals(21, foo());
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// Test that we do not throw a 'use before declaration error' and
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// that the optimized code does not load the hole from the wrong
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// script context.
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evaluate('x; let x;');
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assertEquals(undefined, foo());
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