1 /*
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  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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  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  *
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 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
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 24 
 25 #ifndef SHARE_CODE_VTABLESTUBS_HPP
 26 #define SHARE_CODE_VTABLESTUBS_HPP
 27 
 28 #include "asm/macroAssembler.hpp"
 29 #include "code/vmreg.hpp"
 30 #include "memory/allocation.hpp"
 31 
 32 // A VtableStub holds an individual code stub for a pair (vtable index, #args) for either itables or vtables
 33 // There's a one-to-one relationship between a VtableStub and such a pair.
 34 
 35 // A word on VtableStub sizing:
 36 //   Such a vtable/itable stub consists of the instance data
 37 //   and an immediately following CodeBuffer.
 38 //   Unfortunately, the required space for the code buffer varies, depending on
 39 //   the setting of compile time macros (PRODUCT, ASSERT, ...) and of command line
 40 //   parameters. Actual data may have an influence on the size as well.
 41 //
 42 //   A simple approximation for the VtableStub size would be to just take a value
 43 //   "large enough" for all circumstances - a worst case estimate.
 44 //   As there can exist many stubs - and they never go away - we certainly don't
 45 //   want to waste more code cache space than absolutely necessary.
 46 //
 47 //   We need a different approach which, as far as possible, should be independent
 48 //   from or adaptive to code size variations. These variations may be caused by
 49 //   changed compile time or run time switches as well as by changed emitter code.
 50 //
 51 //   Here is the idea:
 52 //   For the first stub we generate, we allocate a "large enough" code buffer.
 53 //   Once all instructions are emitted, we know the actual size of the stub.
 54 //   Remembering that size allows us to allocate a tightly matching code buffer
 55 //   for all subsequent stubs. That covers all "static variance", i.e. all variance
 56 //   that is due to compile time macros, command line parameters, machine capabilities,
 57 //   and other influences which are immutable for the life span of the vm.
 58 //
 59 //   Life isn't always that easy. Code size may depend on actual data, "load constant"
 60 //   being an example for that. All code segments with such "dynamic variance" require
 61 //   additional care. We need to know or estimate the worst case code size for each
 62 //   such segment. With that knowledge, we can maintain a "slop counter" in the
 63 //   platform-specific stub emitters. It accumulates the difference between worst-case
 64 //   and actual code size. When the stub is fully generated, the actual stub size is
 65 //   adjusted (increased) by the slop counter value.
 66 //
 67 //   As a result, we allocate all but the first code buffers with the same, tightly matching size.
 68 //
 69 
 70 // VtableStubs creates the code stubs for compiled calls through vtables.
 71 // There is one stub per (vtable index, args_size) pair, and the stubs are
 72 // never deallocated. They don't need to be GCed because they contain no oops.
 73 class VtableStub;
 74 
 75 class VtableStubs : AllStatic {
 76  public:                                         // N must be public (some compilers need this for _table)
 77   enum {
 78     N    = 256,                                  // size of stub table; must be power of two
 79     mask = N - 1
 80   };
 81 
 82  private:
 83   friend class VtableStub;
 84   static VtableStub* _table[N];                  // table of existing stubs
 85   static int         _number_of_vtable_stubs;    // number of stubs created so far (for statistics)
 86   static int         _vtab_stub_size;            // current size estimate for vtable stub (quasi-constant)
 87   static int         _itab_stub_size;            // current size estimate for itable stub (quasi-constant)
 88 
 89   static VtableStub* create_vtable_stub(int vtable_index, bool caller_is_c1);
 90   static VtableStub* create_itable_stub(int vtable_index, bool caller_is_c1);
 91   static VtableStub* lookup            (bool is_vtable_stub, int vtable_index, bool caller_is_c1);
 92   static void        enter             (bool is_vtable_stub, int vtable_index, bool caller_is_c1, VtableStub* s);
 93   static inline uint hash              (bool is_vtable_stub, int vtable_index, bool caller_is_c1);
 94   static address     find_stub         (bool is_vtable_stub, int vtable_index, bool caller_is_c1);
 95   static void        bookkeeping(MacroAssembler* masm, outputStream* out, VtableStub* s,
 96                                  address npe_addr, address ame_addr,   bool is_vtable_stub,
 97                                  int     index,    int     slop_bytes, int  index_dependent_slop);
 98   static int         code_size_limit(bool is_vtable_stub);
 99   static void        check_and_set_size_limit(bool is_vtable_stub,
100                                               int   code_size,
101                                               int   padding);
102 
103  public:
104   static address     find_vtable_stub(int vtable_index, bool caller_is_c1) { return find_stub(true,  vtable_index, caller_is_c1); }
105   static address     find_itable_stub(int itable_index, bool caller_is_c1) { return find_stub(false, itable_index, caller_is_c1); }
106 
107   static VtableStub* entry_point(address pc);                        // vtable stub entry point for a pc
108   static bool        contains(address pc);                           // is pc within any stub?
109   static VtableStub* stub_containing(address pc);                    // stub containing pc or NULL
110   static int         number_of_vtable_stubs() { return _number_of_vtable_stubs; }
111   static void        initialize();
112   static void        vtable_stub_do(void f(VtableStub*));            // iterates over all vtable stubs
113 };
114 
115 
116 class VtableStub {
117  private:
118   friend class VtableStubs;
119 
120   static address _chunk;             // For allocation
121   static address _chunk_end;         // For allocation
122   static VMReg   _receiver_location; // Where to find receiver
123 
124   VtableStub*    _next;              // Pointer to next entry in hash table
125   const short    _index;             // vtable index
126   short          _ame_offset;        // Where an AbstractMethodError might occur
127   short          _npe_offset;        // Where a NullPointerException might occur
128   bool           _is_vtable_stub;    // True if vtable stub, false, is itable stub
129   bool           _caller_is_c1;      // True if this is for a caller compiled by C1,
130                                      // which doesn't scalarize parameters.
131   /* code follows here */            // The vtableStub code
132 
133   void* operator new(size_t size, int code_size) throw();
134 
135   VtableStub(bool is_vtable_stub, int index, bool caller_is_c1)
136         : _next(NULL), _index(index), _ame_offset(-1), _npe_offset(-1),
137           _is_vtable_stub(is_vtable_stub), _caller_is_c1(caller_is_c1) {}
138   VtableStub* next() const                       { return _next; }
139   int index() const                              { return _index; }
140   static VMReg receiver_location()               { return _receiver_location; }
141   void set_next(VtableStub* n)                   { _next = n; }
142 
143  public:
144   address code_begin() const                     { return (address)(this + 1); }
145   address code_end() const                       { return code_begin() + VtableStubs::code_size_limit(_is_vtable_stub); }
146   address entry_point() const                    { return code_begin(); }
147   static int entry_offset()                      { return sizeof(class VtableStub); }
148 
149   bool matches(bool is_vtable_stub, int index, bool caller_is_c1) const {
150     return _index == index && _is_vtable_stub == is_vtable_stub && _caller_is_c1 == caller_is_c1;
151   }
152   bool contains(address pc) const                { return code_begin() <= pc && pc < code_end(); }
153 
154  private:
155   void set_exception_points(address npe_addr, address ame_addr) {
156     _npe_offset = npe_addr - code_begin();
157     _ame_offset = ame_addr - code_begin();
158     assert(is_abstract_method_error(ame_addr),   "offset must be correct");
159     assert(is_null_pointer_exception(npe_addr),  "offset must be correct");
160     assert(!is_abstract_method_error(npe_addr),  "offset must be correct");
161     assert(!is_null_pointer_exception(ame_addr), "offset must be correct");
162   }
163 
164   // platform-dependent routines
165   static int  pd_code_alignment();
166   // CNC: Removed because vtable stubs are now made with an ideal graph
167   // static bool pd_disregard_arg_size();
168 
169   static void align_chunk() {
170     uintptr_t off = (uintptr_t)( _chunk + sizeof(VtableStub) ) % pd_code_alignment();
171     if (off != 0)  _chunk += pd_code_alignment() - off;
172   }
173 
174  public:
175   // Query
176   bool is_itable_stub()                          { return !_is_vtable_stub; }
177   bool is_vtable_stub()                          { return  _is_vtable_stub; }
178   bool caller_is_c1()                            { return  _caller_is_c1;   }
179   bool is_abstract_method_error(address epc)     { return epc == code_begin()+_ame_offset; }
180   bool is_null_pointer_exception(address epc)    { return epc == code_begin()+_npe_offset; }
181 
182   void print_on(outputStream* st) const;
183   void print() const;
184 
185 };
186 
187 #endif // SHARE_CODE_VTABLESTUBS_HPP