1 /*

     2  * Copyright 1997-2006 Sun Microsystems, Inc.  All Rights Reserved.

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

     4  *

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

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

     7  * published by the Free Software Foundation.

     8  *

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

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

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

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

    13  * accompanied this code).

    14  *

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

    16  * 2 along with this work; if not, write to the Free Software Foundation,

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

    18  *

    19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    20  * CA 95054 USA or visit www.sun.com if you need additional information or

    21  * have any questions.

    22  *

    23  */

    24 

    25 // This file contains platform-independant assembler declarations.

    26 

    27 class CodeBuffer;

    28 class MacroAssembler;

    29 class AbstractAssembler;

    30 class Label;

    31 

    32 /**

    33  * Labels represent destinations for control transfer instructions.  Such

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

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

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

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

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

    39  * in the Label object.

    40  *

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

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

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

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

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

    46  *

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

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

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

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

    51  *

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

    53  * an array of unresolved instruction code offsets.  _patch_index

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

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

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

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

    58  *

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

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

    61  */

    62 class Label VALUE_OBJ_CLASS_SPEC {

    63  private:

    64   enum { PatchCacheSize = 4 };

    65 

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

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

    68   //

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

    70   // _loc == -1  unbound label

    71   int _loc;

    72 

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

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

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

    76   //

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

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

    79   int _patches[PatchCacheSize];

    80   int _patch_index;

    81   GrowableArray<int>* _patch_overflow;

    82 

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

    84 

    85  public:

    86 

    87   /**

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

    89    */

    90   void bind_loc(int loc) {

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

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

    93     _loc = loc;

    94   }

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

    96 

    97 #ifndef PRODUCT

    98   // Iterates over all unresolved instructions for printing

    99   void print_instructions(MacroAssembler* masm) const;

   100 #endif // PRODUCT

   101 

   102   /**

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

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

   105    */

   106   int loc() const {

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

   108     return _loc;

   109   }

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

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

   112 

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

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

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

   116 

   117   /**

   118    * Adds a reference to an unresolved displacement instruction to

   119    * this unbound label

   120    *

   121    * @param cb         the code buffer being patched

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

   123    */

   124   void add_patch_at(CodeBuffer* cb, int branch_loc);

   125 

   126   /**

   127    * Iterate over the list of patches, resolving the instructions

   128    * Call patch_instruction on each 'branch_loc' value

   129    */

   130   void patch_instructions(MacroAssembler* masm);

   131 

   132   void init() {

   133     _loc = -1;

   134     _patch_index = 0;

   135     _patch_overflow = NULL;

   136   }

   137 

   138   Label() {

   139     init();

   140   }

   141 };

   142 

   143 

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

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

   146 // The Assembler is generating code into a CodeBuffer.

   147 class AbstractAssembler : public ResourceObj  {

   148   friend class Label;

   149 

   150  protected:

   151   CodeSection* _code_section;          // section within the code buffer

   152   address      _code_begin;            // first byte of code buffer

   153   address      _code_limit;            // first byte after code buffer

   154   address      _code_pos;              // current code generation position

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

   156 

   157   // Code emission & accessing

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

   159 

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

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

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

   163 

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

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

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

   167 

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

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

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

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

   172 

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

   174   class InstructionMark: public StackObj {

   175    private:

   176     AbstractAssembler* _assm;

   177 

   178    public:

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

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

   181       _assm->set_inst_mark();

   182     }

   183     ~InstructionMark() {

   184       _assm->clear_inst_mark();

   185     }

   186   };

   187   friend class InstructionMark;

   188   #ifdef ASSERT

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

   190   // instruction boundaries for some operations.

   191   inline static bool pd_check_instruction_mark();

   192   #endif

   193 

   194   // Label functions

   195   void print(Label& L);

   196 

   197  public:

   198 

   199   // Creation

   200   AbstractAssembler(CodeBuffer* code);

   201 

   202   // save end pointer back to code buf.

   203   void sync();

   204 

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

   206   void flush();

   207 

   208   // Accessors

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

   210   CodeSection*  code_section() const   { return _code_section; }

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

   212   address       pc() const             { return _code_pos; }

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

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

   215   OopRecorder*  oop_recorder() const   { return _oop_recorder; }

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

   217 

   218   address  inst_mark() const;

   219   void set_inst_mark();

   220   void clear_inst_mark();

   221 

   222   // Constants in code

   223   void a_byte(int x);

   224   void a_long(jint x);

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

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

   227     if (rtype != relocInfo::none)

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

   229   }

   230 

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

   232 

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

   234   // along with the disassembly when printing nmethods.  Currently

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

   236   void block_comment(const char* comment);

   237 

   238   // Label functions

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

   240 

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

   242   void set_code_section(CodeSection* cs);

   243 

   244   // Inform assembler when generating stub code and relocation info

   245   address    start_a_stub(int required_space);

   246   void       end_a_stub();

   247   // Ditto for constants.

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

   249   void       end_a_const();

   250 

   251   // fp constants support

   252   address double_constant(jdouble c) {

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

   254     if (ptr != NULL) {

   255       *(jdouble*)ptr = c;

   256       _code_pos = ptr + sizeof(c);

   257       end_a_const();

   258     }

   259     return ptr;

   260   }

   261   address float_constant(jfloat c) {

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

   263     if (ptr != NULL) {

   264       *(jfloat*)ptr = c;

   265       _code_pos = ptr + sizeof(c);

   266       end_a_const();

   267     }

   268     return ptr;

   269   }

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

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

   272     if (ptr != NULL) {

   273       relocate(rspec);

   274       *(address*)ptr = c;

   275       _code_pos = ptr + sizeof(c);

   276       end_a_const();

   277     }

   278     return ptr;

   279   }

   280   inline address address_constant(Label& L);

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

   282 

   283   // Bang stack to trigger StackOverflowError at a safe location

   284   // implementation delegates to machine-specific bang_stack_with_offset

   285   void generate_stack_overflow_check( int frame_size_in_bytes );

   286   virtual void bang_stack_with_offset(int offset) = 0;

   287 

   288 

   289   /**

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

   291    * to this label.

   292    *

   293    * @param branch the location of the instruction to patch

   294    * @param masm the assembler which generated the branch

   295    */

   296   void pd_patch_instruction(address branch, address target);

   297 

   298 #ifndef PRODUCT

   299   /**

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

   301    * patched.

   302    *

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

   304    */

   305   static void pd_print_patched_instruction(address branch);

   306 #endif // PRODUCT

   307 };

   308 

   309 #include "incls/_assembler_pd.hpp.incl"