fbf351cf21
Refactor-only: This moves declaration of implementation details into the .cc file. No logic changes. Bug: v8:9574 Change-Id: I985ce17138e65f18dbb629b9f6660009e034fbf0 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1786279 Commit-Queue: Jakob Gruber <jgruber@chromium.org> Commit-Queue: Maya Lekova <mslekova@chromium.org> Auto-Submit: Jakob Gruber <jgruber@chromium.org> Reviewed-by: Maya Lekova <mslekova@chromium.org> Cr-Commit-Position: refs/heads/master@{#63562}
58 lines
1.7 KiB
C++
58 lines
1.7 KiB
C++
// Copyright 2016 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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#ifndef V8_COMPILER_STORE_STORE_ELIMINATION_H_
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#define V8_COMPILER_STORE_STORE_ELIMINATION_H_
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#include "src/common/globals.h"
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namespace v8 {
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namespace internal {
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class TickCounter;
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class Zone;
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namespace compiler {
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class JSGraph;
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// Store-store elimination.
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//
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// The aim of this optimization is to detect the following pattern in the
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// effect graph:
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//
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// - StoreField[+24, kRepTagged](263, ...)
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//
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// ... lots of nodes from which the field at offset 24 of the object
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// returned by node #263 cannot be observed ...
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//
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// - StoreField[+24, kRepTagged](263, ...)
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//
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// In such situations, the earlier StoreField cannot be observed, and can be
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// eliminated. This optimization should work for any offset and input node, of
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// course.
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//
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// The optimization also works across splits. It currently does not work for
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// loops, because we tend to put a stack check in loops, and like deopts,
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// stack checks can observe anything.
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// Assumption: every byte of a JS object is only ever accessed through one
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// offset. For instance, byte 15 of a given object may be accessed using a
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// two-byte read at offset 14, or a four-byte read at offset 12, but never
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// both in the same program.
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//
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// This implementation needs all dead nodes removed from the graph, and the
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// graph should be trimmed.
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class StoreStoreElimination final : public AllStatic {
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public:
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static void Run(JSGraph* js_graph, TickCounter* tick_counter,
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Zone* temp_zone);
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};
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} // namespace compiler
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} // namespace internal
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} // namespace v8
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#endif // V8_COMPILER_STORE_STORE_ELIMINATION_H_
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