2009-02-27 13:00:32 +00:00
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// Copyright 2008 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#ifndef V8_REGISTER_ALLOCATOR_H_
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#define V8_REGISTER_ALLOCATOR_H_
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#include "macro-assembler.h"
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namespace v8 { namespace internal {
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2009-04-03 12:01:56 +00:00
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// -------------------------------------------------------------------------
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// StaticType
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//
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// StaticType represent the type of an expression or a word at runtime.
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// The types are ordered by knowledge, so that if a value can come about
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// in more than one way, and there are different static types inferred
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// for the different ways, the types can be combined to a type that we
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// are still certain of (possibly just "unknown").
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class StaticType BASE_EMBEDDED {
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public:
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StaticType() : static_type_(UNKNOWN_TYPE) {}
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static StaticType unknown() { return StaticType(); }
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static StaticType smi() { return StaticType(SMI_TYPE); }
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static StaticType jsstring() { return StaticType(STRING_TYPE); }
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static StaticType heap_object() { return StaticType(HEAP_OBJECT_TYPE); }
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// Accessors
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bool is_unknown() { return static_type_ == UNKNOWN_TYPE; }
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bool is_smi() { return static_type_ == SMI_TYPE; }
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bool is_heap_object() { return (static_type_ & HEAP_OBJECT_TYPE) != 0; }
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bool is_jsstring() { return static_type_ == STRING_TYPE; }
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bool operator==(StaticType other) const {
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return static_type_ == other.static_type_;
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}
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// Find the best approximating type for a value.
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// The argument must not be NULL.
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static StaticType TypeOf(Object* object) {
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// Remember to make the most specific tests first. A string is also a heap
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// object, so test for string-ness first.
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if (object->IsSmi()) return smi();
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if (object->IsString()) return jsstring();
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if (object->IsHeapObject()) return heap_object();
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return unknown();
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}
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// Merges two static types to a type that combines the knowledge
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// of both. If there is no way to combine (e.g., being a string *and*
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// being a smi), the resulting type is unknown.
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StaticType merge(StaticType other) {
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StaticType x(
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static_cast<StaticTypeEnum>(static_type_ & other.static_type_));
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return x;
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}
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private:
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enum StaticTypeEnum {
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// Numbers are chosen so that least upper bound of the following
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// partial order is implemented by bitwise "and":
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//
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// string
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// |
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// heap-object smi
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// \ /
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// unknown
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//
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UNKNOWN_TYPE = 0x00,
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SMI_TYPE = 0x01,
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HEAP_OBJECT_TYPE = 0x02,
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STRING_TYPE = 0x04 | HEAP_OBJECT_TYPE
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};
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explicit StaticType(StaticTypeEnum static_type) : static_type_(static_type) {}
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// StaticTypeEnum static_type_;
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byte static_type_;
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};
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2009-02-27 13:00:32 +00:00
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// -------------------------------------------------------------------------
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// Results
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//
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// Results encapsulate the compile-time values manipulated by the code
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// generator. They can represent registers or constants.
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class Result BASE_EMBEDDED {
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public:
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enum Type {
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INVALID,
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REGISTER,
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CONSTANT
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};
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// Construct an invalid result.
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explicit Result(CodeGenerator* cgen)
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: static_type_(),
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type_(INVALID),
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cgen_(cgen) {}
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// Construct a register Result.
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Result(Register reg,
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CodeGenerator* cgen);
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// Construct a register Result with a known static type.
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Result(Register reg,
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CodeGenerator* cgen,
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StaticType static_type);
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// Construct a Result whose value is a compile-time constant.
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Result(Handle<Object> value, CodeGenerator * cgen)
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: static_type_(StaticType::TypeOf(*value)),
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type_(CONSTANT),
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cgen_(cgen) {
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data_.handle_ = value.location();
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}
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// The copy constructor and assignment operators could each create a new
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// register reference.
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Result(const Result& other) {
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other.CopyTo(this);
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}
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Result& operator=(const Result& other) {
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if (this != &other) {
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Unuse();
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other.CopyTo(this);
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}
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return *this;
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}
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2009-03-20 12:58:14 +00:00
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inline ~Result();
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2009-03-20 12:58:14 +00:00
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inline void Unuse();
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StaticType static_type() const { return static_type_; }
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void set_static_type(StaticType static_type) { static_type_ = static_type; }
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Type type() const { return static_cast<Type>(type_); }
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bool is_valid() const { return type() != INVALID; }
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bool is_register() const { return type() == REGISTER; }
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bool is_constant() const { return type() == CONSTANT; }
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Register reg() const {
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ASSERT(type() == REGISTER);
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return data_.reg_;
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}
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Handle<Object> handle() const {
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ASSERT(type() == CONSTANT);
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return Handle<Object>(data_.handle_);
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}
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// Move this result to an arbitrary register. The register is not
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// necessarily spilled from the frame or even singly-referenced outside
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// it.
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void ToRegister();
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// Move this result to a specified register. The register is spilled from
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// the frame, and the register is singly-referenced (by this result)
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// outside the frame.
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void ToRegister(Register reg);
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private:
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StaticType static_type_;
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byte type_;
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union {
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Register reg_;
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Object** handle_;
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} data_;
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CodeGenerator* cgen_;
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void CopyTo(Result* destination) const;
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};
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// -------------------------------------------------------------------------
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// Register file
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//
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// The register file tracks reference counts for the processor registers.
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// It is used by both the register allocator and the virtual frame.
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class RegisterFile BASE_EMBEDDED {
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public:
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RegisterFile() { Reset(); }
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void Reset() {
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for (int i = 0; i < kNumRegisters; i++) {
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ref_counts_[i] = 0;
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}
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}
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// Predicates and accessors for the reference counts. The versions
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// that take a register code rather than a register are for
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// convenience in loops over the register codes.
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bool is_used(int reg_code) const { return ref_counts_[reg_code] > 0; }
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bool is_used(Register reg) const { return is_used(reg.code()); }
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int count(int reg_code) const { return ref_counts_[reg_code]; }
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int count(Register reg) const { return count(reg.code()); }
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// Record a use of a register by incrementing its reference count.
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void Use(Register reg) {
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ref_counts_[reg.code()]++;
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}
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// Record that a register will no longer be used by decrementing its
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// reference count.
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void Unuse(Register reg) {
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ASSERT(!reg.is(no_reg));
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ASSERT(is_used(reg.code()));
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ref_counts_[reg.code()]--;
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}
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// Copy the reference counts from this register file to the other.
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void CopyTo(RegisterFile* other);
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private:
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int ref_counts_[kNumRegisters];
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2009-03-18 10:31:31 +00:00
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// Very fast inlined loop to find a free register.
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// Used in RegisterAllocator::AllocateWithoutSpilling.
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// Returns kNumRegisters if no free register found.
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inline int ScanForFreeRegister() {
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int i = 0;
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for (; i < kNumRegisters ; ++i) {
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if (ref_counts_[i] == 0) break;
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}
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return i;
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}
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2009-02-27 13:00:32 +00:00
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friend class RegisterAllocator;
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};
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// -------------------------------------------------------------------------
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// Register allocator
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//
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class RegisterAllocator BASE_EMBEDDED {
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public:
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explicit RegisterAllocator(CodeGenerator* cgen) : cgen_(cgen) {}
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// A register file with each of the reserved registers counted once.
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static RegisterFile Reserved();
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// Unuse all the reserved registers in a register file.
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static void UnuseReserved(RegisterFile* register_file);
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2009-05-11 13:57:19 +00:00
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// True if the register is reserved by the code generator, false if it
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// can be freely used by the allocator.
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static bool IsReserved(int reg_code);
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static bool IsReserved(Register reg) { return IsReserved(reg); }
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// Predicates and accessors for the registers' reference counts.
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bool is_used(int reg_code) const { return registers_.is_used(reg_code); }
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bool is_used(Register reg) const { return registers_.is_used(reg.code()); }
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int count(int reg_code) const { return registers_.count(reg_code); }
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int count(Register reg) const { return registers_.count(reg.code()); }
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// Explicitly record a reference to a register.
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void Use(Register reg) { registers_.Use(reg); }
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// Explicitly record that a register will no longer be used.
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void Unuse(Register reg) { registers_.Unuse(reg); }
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// Initialize the register allocator for entry to a JS function. On
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// entry, the registers used by the JS calling convention are
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// externally referenced (ie, outside the virtual frame); and the
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// other registers are free.
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void Initialize();
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// Reset the register reference counts to free all non-reserved registers.
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// A frame-external reference is kept to each of the reserved registers.
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void Reset();
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// Allocate a free register and return a register result if possible or
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// fail and return an invalid result.
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Result Allocate();
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// Allocate a specific register if possible, spilling it from the frame if
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// necessary, or else fail and return an invalid result.
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Result Allocate(Register target);
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// Allocate a free register without spilling any from the current frame or
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// fail and return an invalid result.
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Result AllocateWithoutSpilling();
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// Allocate a free byte register without spilling any from the
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// current frame or fail and return an invalid result.
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Result AllocateByteRegisterWithoutSpilling();
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// Copy the internal state to a register file, to be restored later by
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// RestoreFrom.
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void SaveTo(RegisterFile* register_file) {
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registers_.CopyTo(register_file);
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}
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void RestoreFrom(RegisterFile* register_file) {
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register_file->CopyTo(®isters_);
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}
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private:
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CodeGenerator* cgen_;
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RegisterFile registers_;
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};
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} } // namespace v8::internal
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#endif // V8_REGISTER_ALLOCATOR_H_
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