Sigmund Cherem
912005267d
Change-Id: I46be49b2effec3e38a3dc44cd45cfe736f77fa78 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/182680 Commit-Queue: Sigmund Cherem <sigmund@google.com> Reviewed-by: Joshua Litt <joshualitt@google.com> Reviewed-by: Nicholas Shahan <nshahan@google.com> Reviewed-by: Stephen Adams <sra@google.com>
41 lines
1.5 KiB
Dart
41 lines
1.5 KiB
Dart
// Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// @dart = 2.7
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// dart2js regression test where the SSA backend would use the wrong
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// type for an instruction: when doing a speculative type propagation,
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// if an instruction gets analyzed multiple times, we used to save the
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// last inferred type, which could be speculative, instead of the
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// first inferred type, which is the actual, non-speculative, type.
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//
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// Because we are doing speculative type propagation at the very end,
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// before emitting the bailout version, the only place where we might
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// do wrong optimizations is during the codegen. It turns out that the
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// codegen optimizes '==' comparisons on null to '===' in case it knows
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// the receiver cannot be null. So in the following example, the
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// [:e == null:] comparison in [foo] got wrongly generated to a
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// JavaScript identity check (that is, using '==='). But this
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// comparison does not work for undefined, which the DOM sometimes
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// returns.
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import "native_testing.dart";
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var a = 42;
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var b = 0;
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foo(e) {
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// Loop to force a bailout.
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for (int i = 0; i < b; i++) {
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a = e[i]; // Will desire a readable primitive.
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}
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// Our heuristics for '==' on an indexable primitive is that it's
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// more common to do it on string, so we'll want e to be a string.
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return a == e || e == null;
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}
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main() {
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Expect.isTrue(foo(JS('', 'void 0')));
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}
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