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// Copyright 2013 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef V8_HYDROGEN_GVN_H_
#define V8_HYDROGEN_GVN_H_
#include "hydrogen.h"
#include "hydrogen-instructions.h"
#include "compiler.h"
#include "zone.h"
namespace v8 {
namespace internal {
// This class extends GVNFlagSet with additional "special" dynamic side effects,
// which can be used to represent side effects that cannot be expressed using
// the GVNFlags of an HInstruction. These special side effects are tracked by a
// SideEffectsTracker (see below).
class SideEffects V8_FINAL {
public:
static const int kNumberOfSpecials = 64 - kNumberOfFlags;
SideEffects() : bits_(0) {
ASSERT(kNumberOfFlags + kNumberOfSpecials == sizeof(bits_) * CHAR_BIT);
}
explicit SideEffects(GVNFlagSet flags) : bits_(flags.ToIntegral()) {}
bool IsEmpty() const { return bits_ == 0; }
bool ContainsFlag(GVNFlag flag) const {
return (bits_ & MaskFlag(flag)) != 0;
}
bool ContainsSpecial(int special) const {
return (bits_ & MaskSpecial(special)) != 0;
}
bool ContainsAnyOf(SideEffects set) const { return (bits_ & set.bits_) != 0; }
void Add(SideEffects set) { bits_ |= set.bits_; }
void AddSpecial(int special) { bits_ |= MaskSpecial(special); }
void AddAllSpecial() { bits_ |= ~static_cast<uint64_t>(0) << kNumberOfFlags; }
void RemoveFlag(GVNFlag flag) { bits_ &= ~MaskFlag(flag); }
void RemoveAll() { bits_ = 0; }
uint64_t ToIntegral() const { return bits_; }
void PrintTo(StringStream* stream) const;
private:
uint64_t MaskFlag(GVNFlag flag) const {
return static_cast<uint64_t>(1) << static_cast<unsigned>(flag);
}
uint64_t MaskSpecial(int special) const {
ASSERT(special >= 0);
ASSERT(special < kNumberOfSpecials);
return static_cast<uint64_t>(1) << static_cast<unsigned>(
special + kNumberOfFlags);
}
uint64_t bits_;
};
// Tracks inobject field loads/stores in a fine grained fashion, and represents
// them using the "special" dynamic side effects of the SideEffects class (see
// above). This way unrelated inobject field stores don't prevent hoisting and
// merging of inobject field loads.
class SideEffectsTracker V8_FINAL BASE_EMBEDDED {
public:
SideEffectsTracker() : num_inobject_fields_(0) {}
SideEffects ComputeChanges(HInstruction* instr);
SideEffects ComputeDependsOn(HInstruction* instr);
void PrintSideEffectsTo(StringStream* stream, SideEffects side_effects) const;
private:
bool ComputeInobjectField(HObjectAccess access, int* index);
HObjectAccess inobject_fields_[SideEffects::kNumberOfSpecials];
int num_inobject_fields_;
};
// Perform common subexpression elimination and loop-invariant code motion.
class HGlobalValueNumberingPhase V8_FINAL : public HPhase {
public:
explicit HGlobalValueNumberingPhase(HGraph* graph);
void Run();
private:
SideEffects CollectSideEffectsOnPathsToDominatedBlock(
HBasicBlock* dominator,
HBasicBlock* dominated);
void AnalyzeGraph();
void ComputeBlockSideEffects();
void LoopInvariantCodeMotion();
void ProcessLoopBlock(HBasicBlock* block,
HBasicBlock* before_loop,
SideEffects loop_kills);
bool AllowCodeMotion();
bool ShouldMove(HInstruction* instr, HBasicBlock* loop_header);
SideEffectsTracker side_effects_tracker_;
bool removed_side_effects_;
// A map of block IDs to their side effects.
ZoneList<SideEffects> block_side_effects_;
// A map of loop header block IDs to their loop's side effects.
ZoneList<SideEffects> loop_side_effects_;
// Used when collecting side effects on paths from dominator to
// dominated.
BitVector visited_on_paths_;
DISALLOW_COPY_AND_ASSIGN(HGlobalValueNumberingPhase);
};
} } // namespace v8::internal
#endif // V8_HYDROGEN_GVN_H_
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