abstractmacroassembler.h

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/*
 * Copyright (C) 2008 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE INC. 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 AbstractMacroAssembler_h
#define AbstractMacroAssembler_h

#include <wtf/Platform.h>

#if ENABLE(ASSEMBLER)

namespace JSC {

template <class AssemblerType>
class AbstractMacroAssembler {
public:
    class Jump;
    class PatchBuffer;
    class CodeLocationLabel;
    class CodeLocationJump;
    class CodeLocationCall;
    class CodeLocationDataLabel32;
    class CodeLocationDataLabelPtr;

    typedef typename AssemblerType::RegisterID RegisterID;
    typedef typename AssemblerType::JmpSrc JmpSrc;
    typedef typename AssemblerType::JmpDst JmpDst;


    // Section 1: MacroAssembler operand types
    //
    // The following types are used as operands to MacroAssembler operations,
    // describing immediate  and memory operands to the instructions to be planted.


    enum Scale {
        TimesOne,
        TimesTwo,
        TimesFour,
        TimesEight,
    };

    // Address:
    //
    // Describes a simple base-offset address.
    struct Address {
        explicit Address(RegisterID base, int32_t offset = 0)
            : base(base)
            , offset(offset)
        {
        }

        RegisterID base;
        int32_t offset;
    };

    // ImplicitAddress:
    //
    // This class is used for explicit 'load' and 'store' operations
    // (as opposed to situations in which a memory operand is provided
    // to a generic operation, such as an integer arithmetic instruction).
    //
    // In the case of a load (or store) operation we want to permit
    // addresses to be implicitly constructed, e.g. the two calls:
    //
    //     load32(Address(addrReg), destReg);
    //     load32(addrReg, destReg);
    //
    // Are equivalent, and the explicit wrapping of the Address in the former
    // is unnecessary.
    struct ImplicitAddress {
        ImplicitAddress(RegisterID base)
            : base(base)
            , offset(0)
        {
        }

        ImplicitAddress(Address address)
            : base(address.base)
            , offset(address.offset)
        {
        }

        RegisterID base;
        int32_t offset;
    };

    // BaseIndex:
    //
    // Describes a complex addressing mode.
    struct BaseIndex {
        BaseIndex(RegisterID base, RegisterID index, Scale scale, int32_t offset = 0)
            : base(base)
            , index(index)
            , scale(scale)
            , offset(offset)
        {
        }

        RegisterID base;
        RegisterID index;
        Scale scale;
        int32_t offset;
    };

    // AbsoluteAddress:
    //
    // Describes an memory operand given by a pointer.  For regular load & store
    // operations an unwrapped void* will be used, rather than using this.
    struct AbsoluteAddress {
        explicit AbsoluteAddress(void* ptr)
            : m_ptr(ptr)
        {
        }

        void* m_ptr;
    };

    // ImmPtr:
    //
    // A pointer sized immediate operand to an instruction - this is wrapped
    // in a class requiring explicit construction in order to differentiate
    // from pointers used as absolute addresses to memory operations
    struct ImmPtr {
        explicit ImmPtr(void* value)
            : m_value(value)
        {
        }

        intptr_t asIntptr()
        {
            return reinterpret_cast<intptr_t>(m_value);
        }

        void* m_value;
    };

    // Imm32:
    //
    // A 32bit immediate operand to an instruction - this is wrapped in a
    // class requiring explicit construction in order to prevent RegisterIDs
    // (which are implemented as an enum) from accidentally being passed as
    // immediate values.
    struct Imm32 {
        explicit Imm32(int32_t value)
            : m_value(value)
        {
        }

#if !PLATFORM(X86_64)
        explicit Imm32(ImmPtr ptr)
            : m_value(ptr.asIntptr())
        {
        }
#endif

        int32_t m_value;
    };


    // Section 2: MacroAssembler code buffer handles
    //
    // The following types are used to reference items in the code buffer
    // during JIT code generation.  For example, the type Jump is used to
    // track the location of a jump instruction so that it may later be
    // linked to a label marking its destination.


    // Label:
    //
    // A Label records a point in the generated instruction stream, typically such that
    // it may be used as a destination for a jump.
    class Label {
        friend class Jump;
        template<class AssemblerType_T>
        friend class AbstractMacroAssembler;
        friend class PatchBuffer;
    public:
        Label()
        {
        }

        Label(AbstractMacroAssembler<AssemblerType>* masm)
            : m_label(masm->m_assembler.label())
        {
        }
        
        bool isUsed() const { return m_label.isUsed(); }
        void used() { m_label.used(); }
    private:
        JmpDst m_label;
    };

    // DataLabelPtr:
    //
    // A DataLabelPtr is used to refer to a location in the code containing a pointer to be
    // patched after the code has been generated.
    class DataLabelPtr {
        template<class AssemblerType_T>
        friend class AbstractMacroAssembler;
        friend class PatchBuffer;
    public:
        DataLabelPtr()
        {
        }

        DataLabelPtr(AbstractMacroAssembler<AssemblerType>* masm)
            : m_label(masm->m_assembler.label())
        {
        }
        
    private:
        JmpDst m_label;
    };

    // DataLabel32:
    //
    // A DataLabelPtr is used to refer to a location in the code containing a pointer to be
    // patched after the code has been generated.
    class DataLabel32 {
        template<class AssemblerType_T>
        friend class AbstractMacroAssembler;
        friend class PatchBuffer;
    public:
        DataLabel32()
        {
        }

        DataLabel32(AbstractMacroAssembler<AssemblerType>* masm)
            : m_label(masm->m_assembler.label())
        {
        }

    private:
        JmpDst m_label;
    };

    // Call:
    //
    // A Call object is a reference to a call instruction that has been planted
    // into the code buffer - it is typically used to link the call, setting the
    // relative offset such that when executed it will call to the desired
    // destination.
    class Call {
        friend class PatchBuffer;
        template<class AssemblerType_T>
        friend class AbstractMacroAssembler;
    public:
        enum Flags {
            None = 0x0,
            Linkable = 0x1,
            Near = 0x2,
            LinkableNear = 0x3,
        };

        Call()
            : m_flags(None)
        {
        }
        
        Call(JmpSrc jmp, Flags flags)
            : m_jmp(jmp)
            , m_flags(flags)
        {
        }

        bool isFlagSet(Flags flag)
        {
            return m_flags & flag;
        }

        static Call fromTailJump(Jump jump)
        {
            return Call(jump.m_jmp, Linkable);
        }

    private:
        JmpSrc m_jmp;
        Flags m_flags;
    };

    // Jump:
    //
    // A jump object is a reference to a jump instruction that has been planted
    // into the code buffer - it is typically used to link the jump, setting the
    // relative offset such that when executed it will jump to the desired
    // destination.
    class Jump {
        friend class PatchBuffer;
        template<class AssemblerType_T>
        friend class AbstractMacroAssembler;
        friend class Call;
    public:
        Jump()
        {
        }
        
        Jump(JmpSrc jmp)    
            : m_jmp(jmp)
        {
        }
        
        void link(AbstractMacroAssembler<AssemblerType>* masm)
        {
            masm->m_assembler.linkJump(m_jmp, masm->m_assembler.label());
        }
        
        void linkTo(Label label, AbstractMacroAssembler<AssemblerType>* masm)
        {
            masm->m_assembler.linkJump(m_jmp, label.m_label);
        }

    private:
        JmpSrc m_jmp;
    };

    // JumpList:
    //
    // A JumpList is a set of Jump objects.
    // All jumps in the set will be linked to the same destination.
    class JumpList {
        friend class PatchBuffer;

    public:
        void link(AbstractMacroAssembler<AssemblerType>* masm)
        {
            size_t size = m_jumps.size();
            for (size_t i = 0; i < size; ++i)
                m_jumps[i].link(masm);
            m_jumps.clear();
        }
        
        void linkTo(Label label, AbstractMacroAssembler<AssemblerType>* masm)
        {
            size_t size = m_jumps.size();
            for (size_t i = 0; i < size; ++i)
                m_jumps[i].linkTo(label, masm);
            m_jumps.clear();
        }
        
        void append(Jump jump)
        {
            m_jumps.append(jump);
        }
        
        void append(JumpList& other)
        {
            m_jumps.append(other.m_jumps.begin(), other.m_jumps.size());
        }

        bool empty()
        {
            return !m_jumps.size();
        }

    private:
        Vector<Jump, 16> m_jumps;
    };


    // Section 3: MacroAssembler JIT instruction stream handles.
    //
    // The MacroAssembler supported facilities to modify a JIT generated
    // instruction stream after it has been generated (relinking calls and
    // jumps, and repatching data values).  The following types are used
    // to store handles into the underlying instruction stream, the type
    // providing semantic information as to what it is that is in the
    // instruction stream at this point, and thus what operations may be
    // performed on it.


    // CodeLocationCommon:
    //
    // Base type for other CodeLocation* types.  A postion in the JIT genertaed
    // instruction stream, without any semantic information.
    class CodeLocationCommon {
    public:
        CodeLocationCommon()
            : m_location(0)
        {
        }

        // In order to avoid the need to store multiple handles into the
        // instructions stream, where the code generation is deterministic
        // and the labels will always be a fixed distance apart, these
        // methods may be used to recover a handle that has nopw been
        // retained, based on a known fixed relative offset from one that has.
        CodeLocationLabel labelAtOffset(int offset);
        CodeLocationJump jumpAtOffset(int offset);
        CodeLocationCall callAtOffset(int offset);
        CodeLocationDataLabelPtr dataLabelPtrAtOffset(int offset);
        CodeLocationDataLabel32 dataLabel32AtOffset(int offset);

        operator bool() { return m_location; }
        void reset() { m_location = 0; }

    protected:
        explicit CodeLocationCommon(void* location)
            : m_location(location)
        {