9a8efd8a4e
Change-Id: I20ed35a7fb5104a9cc66bb54fa8966589c43d7f9 Reviewed-on: https://chromium-review.googlesource.com/507287 Reviewed-by: Andreas Haas <ahaas@chromium.org> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org> Reviewed-by: Daniel Clifford <danno@chromium.org> Reviewed-by: Jakob Gruber <jgruber@chromium.org> Reviewed-by: Marja Hölttä <marja@chromium.org> Reviewed-by: Jochen Eisinger <jochen@chromium.org> Commit-Queue: Wiktor Garbacz <wiktorg@google.com> Cr-Commit-Position: refs/heads/master@{#45458}
92 lines
2.5 KiB
C++
92 lines
2.5 KiB
C++
// Copyright 2017 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_LABEL_H_
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#define V8_LABEL_H_
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#include "src/base/macros.h"
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namespace v8 {
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namespace internal {
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// -----------------------------------------------------------------------------
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// Labels represent pc locations; they are typically jump or call targets.
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// After declaration, a label can be freely used to denote known or (yet)
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// unknown pc location. Assembler::bind() is used to bind a label to the
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// current pc. A label can be bound only once.
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class Label {
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public:
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enum Distance { kNear, kFar };
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INLINE(Label()) {
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Unuse();
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UnuseNear();
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}
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INLINE(~Label()) {
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DCHECK(!is_linked());
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DCHECK(!is_near_linked());
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}
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INLINE(void Unuse()) { pos_ = 0; }
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INLINE(void UnuseNear()) { near_link_pos_ = 0; }
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INLINE(bool is_bound() const) { return pos_ < 0; }
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INLINE(bool is_unused() const) { return pos_ == 0 && near_link_pos_ == 0; }
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INLINE(bool is_linked() const) { return pos_ > 0; }
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INLINE(bool is_near_linked() const) { return near_link_pos_ > 0; }
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// Returns the position of bound or linked labels. Cannot be used
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// for unused labels.
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int pos() const {
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if (pos_ < 0) return -pos_ - 1;
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if (pos_ > 0) return pos_ - 1;
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UNREACHABLE();
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}
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int near_link_pos() const { return near_link_pos_ - 1; }
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private:
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// pos_ encodes both the binding state (via its sign)
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// and the binding position (via its value) of a label.
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//
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// pos_ < 0 bound label, pos() returns the jump target position
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// pos_ == 0 unused label
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// pos_ > 0 linked label, pos() returns the last reference position
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int pos_;
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// Behaves like |pos_| in the "> 0" case, but for near jumps to this label.
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int near_link_pos_;
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void bind_to(int pos) {
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pos_ = -pos - 1;
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DCHECK(is_bound());
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}
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void link_to(int pos, Distance distance = kFar) {
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if (distance == kNear) {
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near_link_pos_ = pos + 1;
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DCHECK(is_near_linked());
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} else {
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pos_ = pos + 1;
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DCHECK(is_linked());
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}
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}
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friend class Assembler;
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friend class Displacement;
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friend class RegExpMacroAssemblerIrregexp;
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#if V8_TARGET_ARCH_ARM64
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// On ARM64, the Assembler keeps track of pointers to Labels to resolve
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// branches to distant targets. Copying labels would confuse the Assembler.
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DISALLOW_COPY_AND_ASSIGN(Label); // NOLINT
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#endif
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};
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} // namespace internal
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} // namespace v8
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#endif // V8_LABEL_H_
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