+
−/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+
− * vim: set ts=8 sts=4 et sw=4 tw=99:
+
− * This Source Code Form is subject to the terms of the Mozilla Public
+
− * License, v. 2.0. If a copy of the MPL was not distributed with this
+
− * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
−
+
−#ifndef jit_ICState_h
+
−#define jit_ICState_h
+
−
+
−#include "jit/JitOptions.h"
+
−
+
−namespace js {
+
−namespace jit {
+
−
+
−// ICState stores information about a Baseline or Ion IC.
+
−class ICState
+
−{
+
−  public:
+
−    // When we attach the maximum number of stubs, we discard all stubs and
+
−    // transition the IC to Megamorphic to attach stubs that are more generic
+
−    // (handle more cases). If we again attach the maximum number of stubs, we
+
−    // transition to Generic and (depending on the IC) will either attach a
+
−    // single stub that handles everything or stop attaching new stubs.
+
−    //
+
−    // We also transition to Generic when we repeatedly fail to attach a stub,
+
−    // to avoid wasting time trying.
+
−    enum class Mode : uint8_t { Specialized = 0, Megamorphic, Generic };
+
−
+
−  private:
+
−    Mode mode_;
+
−
+
−    // Number of optimized stubs currently attached to this IC.
+
−    uint8_t numOptimizedStubs_;
+
−
+
−    // Number of times we failed to attach a stub.
+
−    uint8_t numFailures_;
+
−
+
−    // This is only used for shared Baseline ICs and stored here to save space.
+
−    bool invalid_ : 1;
+
−
+
−    static const size_t MaxOptimizedStubs = 6;
+
−
+
−    void transition(Mode mode) {
+
−        MOZ_ASSERT(mode > mode_);
+
−        mode_ = mode;
+
−        numFailures_ = 0;
+
−    }
+
−
+
−    MOZ_ALWAYS_INLINE size_t maxFailures() const {
+
−        // Allow more failures if we attached stubs.
+
−        static_assert(MaxOptimizedStubs == 6,
+
−                      "numFailures_/maxFailures should fit in uint8_t");
+
−        size_t res = 5 + size_t(40) * numOptimizedStubs_;
+
−        MOZ_ASSERT(res <= UINT8_MAX, "numFailures_ should not overflow");
+
−        return res;
+
−    }
+
−
+
−  public:
+
−    ICState()
+
−      : invalid_(false)
+
−    {
+
−        reset();
+
−    }
+
−
+
−    Mode mode() const { return mode_; }
+
−    size_t numOptimizedStubs() const { return numOptimizedStubs_; }
+
−
+
−    MOZ_ALWAYS_INLINE bool canAttachStub() const {
+
−        MOZ_ASSERT(numOptimizedStubs_ <= MaxOptimizedStubs);
+
−        if (mode_ == Mode::Generic || JitOptions.disableCacheIR)
+
−            return false;
+
−        return true;
+
−    }
+
−
+
−    bool invalid() const { return invalid_; }
+
−    void setInvalid() { invalid_ = true; }
+
−
+
−    // If this returns true, we transitioned to a new mode and the caller
+
−    // should discard all stubs.
+
−    MOZ_MUST_USE MOZ_ALWAYS_INLINE bool maybeTransition() {
+
−        MOZ_ASSERT(numOptimizedStubs_ <= MaxOptimizedStubs);
+
−        if (mode_ == Mode::Generic)
+
−            return false;
+
−        if (numOptimizedStubs_ < MaxOptimizedStubs && numFailures_ < maxFailures())
+
−            return false;
+
−        if (numFailures_ == maxFailures() || mode_ == Mode::Megamorphic) {
+
−            transition(Mode::Generic);
+
−            return true;
+
−        }
+
−        MOZ_ASSERT(mode_ == Mode::Specialized);
+
−        transition(Mode::Megamorphic);
+
−        return true;
+
−    }
+
−    void reset() {
+
−        mode_ = Mode::Specialized;
+
−        numOptimizedStubs_ = 0;
+
−        numFailures_ = 0;
+
−    }
+
−    void trackAttached() {
+
−        // We'd like to assert numOptimizedStubs_ < MaxOptimizedStubs, but
+
−        // since this code is also used for non-CacheIR Baseline stubs, assert
+
−        // < 16 for now. Note that we do have the stronger assert in other
+
−        // methods, because they are only used by CacheIR ICs.
+
−        MOZ_ASSERT(numOptimizedStubs_ < 16);
+
−        numOptimizedStubs_++;
+
−        numFailures_ = 0;
+
−    }
+
−    void trackNotAttached() {
+
−        // Note: we can't assert numFailures_ < maxFailures() because
+
−        // maxFailures() depends on numOptimizedStubs_ and it's possible a
+
−        // GC discarded stubs before we got here.
+
−        numFailures_++;
+
−        MOZ_ASSERT(numFailures_ > 0, "numFailures_ should not overflow");
+
−    }
+
−    void trackUnlinkedStub() {
+
−        MOZ_ASSERT(numOptimizedStubs_ > 0);
+
−        numOptimizedStubs_--;
+
−    }
+
−    void trackUnlinkedAllStubs() {
+
−        numOptimizedStubs_ = 0;
+
−    }
+
−};
+
−
+
−} // namespace jit
+
−} // namespace js
+
−
+
−#endif /* jit_ICState_h */