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 /*

  * Copyright (c) 1997, 2009, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

  * questions.

  *

  */

 // This file contains platform-independent assembler declarations.

 class CodeBuffer;

 class MacroAssembler;

 class AbstractAssembler;

 class Label;

 /**

  * Labels represent destinations for control transfer instructions.  Such

  * instructions can accept a Label as their target argument.  A Label is

  * bound to the current location in the code stream by calling the

  * MacroAssembler's 'bind' method, which in turn calls the Label's 'bind'

  * method.  A Label may be referenced by an instruction before it's bound

  * (i.e., 'forward referenced').  'bind' stores the current code offset

  * in the Label object.

  *

  * If an instruction references a bound Label, the offset field(s) within

  * the instruction are immediately filled in based on the Label's code

  * offset.  If an instruction references an unbound label, that

  * instruction is put on a list of instructions that must be patched

  * (i.e., 'resolved') when the Label is bound.

  *

  * 'bind' will call the platform-specific 'patch_instruction' method to

  * fill in the offset field(s) for each unresolved instruction (if there

  * are any).  'patch_instruction' lives in one of the

  * cpu/<arch>/vm/assembler_<arch>* files.

  *

  * Instead of using a linked list of unresolved instructions, a Label has

  * an array of unresolved instruction code offsets.  _patch_index

  * contains the total number of forward references.  If the Label's array

  * overflows (i.e., _patch_index grows larger than the array size), a

  * GrowableArray is allocated to hold the remaining offsets.  (The cache

  * size is 4 for now, which handles over 99.5% of the cases)

  *

  * Labels may only be used within a single CodeSection.  If you need

  * to create references between code sections, use explicit relocations.

  */

 class Label VALUE_OBJ_CLASS_SPEC {

  private:

   enum { PatchCacheSize = 4 };

   // _loc encodes both the binding state (via its sign)

   // and the binding locator (via its value) of a label.

   //

   // _loc >= 0   bound label, loc() encodes the target (jump) position

   // _loc == -1  unbound label

   int _loc;

   // References to instructions that jump to this unresolved label.

   // These instructions need to be patched when the label is bound

   // using the platform-specific patchInstruction() method.

   //

   // To avoid having to allocate from the C-heap each time, we provide

   // a local cache and use the overflow only if we exceed the local cache

   int _patches[PatchCacheSize];

   int _patch_index;

   GrowableArray<int>* _patch_overflow;

   Label(const Label&) { ShouldNotReachHere(); }

  public:

   /**

    * After binding, be sure 'patch_instructions' is called later to link

    */

   void bind_loc(int loc) {

     assert(loc >= 0, "illegal locator");

     assert(_loc == -1, "already bound");

     _loc = loc;

   }

   void bind_loc(int pos, int sect);  // = bind_loc(locator(pos, sect))

 #ifndef PRODUCT

   // Iterates over all unresolved instructions for printing

   void print_instructions(MacroAssembler* masm) const;

 #endif // PRODUCT

   /**

    * Returns the position of the the Label in the code buffer

    * The position is a 'locator', which encodes both offset and section.

    */

   int loc() const {

     assert(_loc >= 0, "unbound label");

     return _loc;

   }

   int loc_pos() const;   // == locator_pos(loc())

   int loc_sect() const;  // == locator_sect(loc())

   bool is_bound() const    { return _loc >=  0; }

   bool is_unbound() const  { return _loc == -1 && _patch_index > 0; }

   bool is_unused() const   { return _loc == -1 && _patch_index == 0; }

   /**

    * Adds a reference to an unresolved displacement instruction to

    * this unbound label

    *

    * @param cb         the code buffer being patched

    * @param branch_loc the locator of the branch instruction in the code buffer

    */

   void add_patch_at(CodeBuffer* cb, int branch_loc);

   /**

    * Iterate over the list of patches, resolving the instructions

    * Call patch_instruction on each 'branch_loc' value

    */

   void patch_instructions(MacroAssembler* masm);

   void init() {

     _loc = -1;

     _patch_index = 0;

     _patch_overflow = NULL;

   }

   Label() {

     init();

   }

 };

 // A union type for code which has to assemble both constant and

 // non-constant operands, when the distinction cannot be made

 // statically.

 class RegisterOrConstant VALUE_OBJ_CLASS_SPEC {

  private:

   Register _r;

   intptr_t _c;

  public:

   RegisterOrConstant(): _r(noreg), _c(0) {}

   RegisterOrConstant(Register r): _r(r), _c(0) {}

   RegisterOrConstant(intptr_t c): _r(noreg), _c(c) {}

   Register as_register() const { assert(is_register(),""); return _r; }

   intptr_t as_constant() const { assert(is_constant(),""); return _c; }

   Register register_or_noreg() const { return _r; }

   intptr_t constant_or_zero() const  { return _c; }

   bool is_register() const { return _r != noreg; }

   bool is_constant() const { return _r == noreg; }

 };

 // The Abstract Assembler: Pure assembler doing NO optimizations on the

 // instruction level; i.e., what you write is what you get.

 // The Assembler is generating code into a CodeBuffer.

 class AbstractAssembler : public ResourceObj  {

   friend class Label;

  protected:

   CodeSection* _code_section;          // section within the code buffer

   address      _code_begin;            // first byte of code buffer

   address      _code_limit;            // first byte after code buffer

   address      _code_pos;              // current code generation position

   OopRecorder* _oop_recorder;          // support for relocInfo::oop_type

   // Code emission & accessing

   address addr_at(int pos) const       { return _code_begin + pos; }

   // This routine is called with a label is used for an address.

   // Labels and displacements truck in offsets, but target must return a PC.

   address target(Label& L);            // return _code_section->target(L)

   bool is8bit(int x) const             { return -0x80 <= x && x < 0x80; }

   bool isByte(int x) const             { return 0 <= x && x < 0x100; }

   bool isShiftCount(int x) const       { return 0 <= x && x < 32; }

   void emit_byte(int x);  // emit a single byte

   void emit_word(int x);  // emit a 16-bit word (not a wordSize word!)

   void emit_long(jint x); // emit a 32-bit word (not a longSize word!)

   void emit_address(address x); // emit an address (not a longSize word!)

   // Instruction boundaries (required when emitting relocatable values).

   class InstructionMark: public StackObj {

    private:

     AbstractAssembler* _assm;

    public:

     InstructionMark(AbstractAssembler* assm) : _assm(assm) {

       assert(assm->inst_mark() == NULL, "overlapping instructions");

       _assm->set_inst_mark();

     }

     ~InstructionMark() {

       _assm->clear_inst_mark();

     }

   };

   friend class InstructionMark;

   #ifdef ASSERT

   // Make it return true on platforms which need to verify

   // instruction boundaries for some operations.

   inline static bool pd_check_instruction_mark();

   #endif

   // Label functions

   void print(Label& L);

  public:

   // Creation

   AbstractAssembler(CodeBuffer* code);

   // save end pointer back to code buf.

   void sync();

   // ensure buf contains all code (call this before using/copying the code)

   void flush();

   // Accessors

   CodeBuffer*   code() const;          // _code_section->outer()

   CodeSection*  code_section() const   { return _code_section; }

   int           sect() const;          // return _code_section->index()

   address       pc() const             { return _code_pos; }

   int           offset() const         { return _code_pos - _code_begin; }

   int           locator() const;       // CodeBuffer::locator(offset(), sect())

   OopRecorder*  oop_recorder() const   { return _oop_recorder; }

   void      set_oop_recorder(OopRecorder* r) { _oop_recorder = r; }

   address  inst_mark() const;

   void set_inst_mark();

   void clear_inst_mark();

   // Constants in code

   void a_byte(int x);

   void a_long(jint x);

   void relocate(RelocationHolder const& rspec, int format = 0);

   void relocate(   relocInfo::relocType rtype, int format = 0) {

     if (rtype != relocInfo::none)

       relocate(Relocation::spec_simple(rtype), format);

   }

   static int code_fill_byte();         // used to pad out odd-sized code buffers

   // Associate a comment with the current offset.  It will be printed

   // along with the disassembly when printing nmethods.  Currently

   // only supported in the instruction section of the code buffer.

   void block_comment(const char* comment);

   // Label functions

   void bind(Label& L); // binds an unbound label L to the current code position

   // Move to a different section in the same code buffer.

   void set_code_section(CodeSection* cs);

   // Inform assembler when generating stub code and relocation info

   address    start_a_stub(int required_space);

   void       end_a_stub();

   // Ditto for constants.

   address    start_a_const(int required_space, int required_align = sizeof(double));

   void       end_a_const();

   // fp constants support

   address double_constant(jdouble c) {

     address ptr = start_a_const(sizeof(c), sizeof(c));

     if (ptr != NULL) {

       *(jdouble*)ptr = c;

       _code_pos = ptr + sizeof(c);

       end_a_const();

     }

     return ptr;

   }

   address float_constant(jfloat c) {

     address ptr = start_a_const(sizeof(c), sizeof(c));

     if (ptr != NULL) {

       *(jfloat*)ptr = c;

       _code_pos = ptr + sizeof(c);

       end_a_const();

     }

     return ptr;

   }

   address address_constant(address c, RelocationHolder const& rspec) {

     address ptr = start_a_const(sizeof(c), sizeof(c));

     if (ptr != NULL) {

       relocate(rspec);

       *(address*)ptr = c;

       _code_pos = ptr + sizeof(c);

       end_a_const();

     }

     return ptr;

   }

   inline address address_constant(Label& L);

   inline address address_table_constant(GrowableArray<Label*> label);

   // Bootstrapping aid to cope with delayed determination of constants.

   // Returns a static address which will eventually contain the constant.

   // The value zero (NULL) stands instead of a constant which is still uncomputed.

   // Thus, the eventual value of the constant must not be zero.

   // This is fine, since this is designed for embedding object field

   // offsets in code which must be generated before the object class is loaded.

   // Field offsets are never zero, since an object's header (mark word)

   // is located at offset zero.

   RegisterOrConstant delayed_value(int(*value_fn)(), Register tmp, int offset = 0) {

     return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);

   }

   RegisterOrConstant delayed_value(address(*value_fn)(), Register tmp, int offset = 0) {

     return delayed_value_impl(delayed_value_addr(value_fn), tmp, offset);

   }

   virtual RegisterOrConstant delayed_value_impl(intptr_t* delayed_value_addr, Register tmp, int offset) = 0;

   // Last overloading is platform-dependent; look in assembler_<arch>.cpp.

   static intptr_t* delayed_value_addr(int(*constant_fn)());

   static intptr_t* delayed_value_addr(address(*constant_fn)());

   static void update_delayed_values();

   // Bang stack to trigger StackOverflowError at a safe location

   // implementation delegates to machine-specific bang_stack_with_offset

   void generate_stack_overflow_check( int frame_size_in_bytes );

   virtual void bang_stack_with_offset(int offset) = 0;

   /**

    * A platform-dependent method to patch a jump instruction that refers

    * to this label.

    *

    * @param branch the location of the instruction to patch

    * @param masm the assembler which generated the branch

    */

   void pd_patch_instruction(address branch, address target);

 #ifndef PRODUCT

   /**

    * Platform-dependent method of printing an instruction that needs to be

    * patched.

    *

    * @param branch the instruction to be patched in the buffer.

    */

   static void pd_print_patched_instruction(address branch);

 #endif // PRODUCT

 };

 #include "incls/_assembler_pd.hpp.incl"