src/hotspot/share/code/vtableStubs.hpp - platform/libcore - Git at Google

 /*
  * Copyright (c) 1997, 2018, 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.
  *
  */

 #ifndef SHARE_VM_CODE_VTABLESTUBS_HPP
 #define SHARE_VM_CODE_VTABLESTUBS_HPP

 #include "asm/macroAssembler.hpp"
 #include "code/vmreg.hpp"
 #include "memory/allocation.hpp"

 // A VtableStub holds an individual code stub for a pair (vtable index, #args) for either itables or vtables
 // There's a one-to-one relationship between a VtableStub and such a pair.

 // A word on VtableStub sizing:
 //   Such a vtable/itable stub consists of the instance data
 //   and an immediately following CodeBuffer.
 //   Unfortunately, the required space for the code buffer varies, depending on
 //   the setting of compile time macros (PRODUCT, ASSERT, ...) and of command line
 //   parameters. Actual data may have an influence on the size as well.
 //
 //   A simple approximation for the VtableStub size would be to just take a value
 //   "large enough" for all circumstances - a worst case estimate.
 //   As there can exist many stubs - and they never go away - we certainly don't
 //   want to waste more code cache space than absolutely necessary.
 //
 //   We need a different approach which, as far as possible, should be independent
 //   from or adaptive to code size variations. These variations may be caused by
 //   changed compile time or run time switches as well as by changed emitter code.
 //
 //   Here is the idea:
 //   For the first stub we generate, we allocate a "large enough" code buffer.
 //   Once all instructions are emitted, we know the actual size of the stub.
 //   Remembering that size allows us to allocate a tightly matching code buffer
 //   for all subsequent stubs. That covers all "static variance", i.e. all variance
 //   that is due to compile time macros, command line parameters, machine capabilities,
 //   and other influences which are immutable for the life span of the vm.
 //
 //   Life isn't always that easy. Code size may depend on actual data, "load constant"
 //   being an example for that. All code segments with such "dynamic variance" require
 //   additional care. We need to know or estimate the worst case code size for each
 //   such segment. With that knowledge, we can maintain a "slop counter" in the
 //   platform-specific stub emitters. It accumulates the difference between worst-case
 //   and actual code size. When the stub is fully generated, the actual stub size is
 //   adjusted (increased) by the slop counter value.
 //
 //   As a result, we allocate all but the first code buffers with the same, tightly matching size.
 //

 // VtableStubs creates the code stubs for compiled calls through vtables.
 // There is one stub per (vtable index, args_size) pair, and the stubs are
 // never deallocated. They don't need to be GCed because they contain no oops.
 class VtableStub;

 class VtableStubs : AllStatic {
  public:                                         // N must be public (some compilers need this for _table)
   enum {
     N    = 256,                                  // size of stub table; must be power of two
     mask = N - 1
   };

  private:
   friend class VtableStub;
   static VtableStub* _table[N];                  // table of existing stubs
   static int         _number_of_vtable_stubs;    // number of stubs created so far (for statistics)
   static int         _vtab_stub_size;            // current size estimate for vtable stub (quasi-constant)
   static int         _itab_stub_size;            // current size estimate for itable stub (quasi-constant)

   static VtableStub* create_vtable_stub(int vtable_index);
   static VtableStub* create_itable_stub(int vtable_index);
   static VtableStub* lookup            (bool is_vtable_stub, int vtable_index);
   static void        enter             (bool is_vtable_stub, int vtable_index, VtableStub* s);
   static inline uint hash              (bool is_vtable_stub, int vtable_index);
   static address     find_stub         (bool is_vtable_stub, int vtable_index);
   static void        bookkeeping(MacroAssembler* masm, outputStream* out, VtableStub* s,
                                  address npe_addr, address ame_addr,   bool is_vtable_stub,
                                  int     index,    int     slop_bytes, int  index_dependent_slop);
   static int         code_size_limit(bool is_vtable_stub);
   static void        check_and_set_size_limit(bool is_vtable_stub,
                                               int   code_size,
                                               int   padding);

  public:
   static address     find_vtable_stub(int vtable_index) { return find_stub(true,  vtable_index); }
   static address     find_itable_stub(int itable_index) { return find_stub(false, itable_index); }

   static VtableStub* entry_point(address pc);                        // vtable stub entry point for a pc
   static bool        contains(address pc);                           // is pc within any stub?
   static VtableStub* stub_containing(address pc);                    // stub containing pc or NULL
   static int         number_of_vtable_stubs() { return _number_of_vtable_stubs; }
   static void        initialize();
   static void        vtable_stub_do(void f(VtableStub*));            // iterates over all vtable stubs
 };


 class VtableStub {
  private:
   friend class VtableStubs;

   static address _chunk;             // For allocation
   static address _chunk_end;         // For allocation
   static VMReg   _receiver_location; // Where to find receiver

   VtableStub*    _next;              // Pointer to next entry in hash table
   const short    _index;             // vtable index
   short          _ame_offset;        // Where an AbstractMethodError might occur
   short          _npe_offset;        // Where a NullPointerException might occur
   bool           _is_vtable_stub;    // True if vtable stub, false, is itable stub
   /* code follows here */            // The vtableStub code

   void* operator new(size_t size, int code_size) throw();

   VtableStub(bool is_vtable_stub, int index)
         : _next(NULL), _is_vtable_stub(is_vtable_stub),
           _index(index), _ame_offset(-1), _npe_offset(-1) {}
   VtableStub* next() const                       { return _next; }
   int index() const                              { return _index; }
   static VMReg receiver_location()               { return _receiver_location; }
   void set_next(VtableStub* n)                   { _next = n; }

  public:
   address code_begin() const                     { return (address)(this + 1); }
   address code_end() const                       { return code_begin() + VtableStubs::code_size_limit(_is_vtable_stub); }
   address entry_point() const                    { return code_begin(); }
   static int entry_offset()                      { return sizeof(class VtableStub); }

   bool matches(bool is_vtable_stub, int index) const {
     return _index == index && _is_vtable_stub == is_vtable_stub;
   }
   bool contains(address pc) const                { return code_begin() <= pc && pc < code_end(); }

  private:
   void set_exception_points(address npe_addr, address ame_addr) {
     _npe_offset = npe_addr - code_begin();
     _ame_offset = ame_addr - code_begin();
     assert(is_abstract_method_error(ame_addr),   "offset must be correct");
     assert(is_null_pointer_exception(npe_addr),  "offset must be correct");
     assert(!is_abstract_method_error(npe_addr),  "offset must be correct");
     assert(!is_null_pointer_exception(ame_addr), "offset must be correct");
   }

   // platform-dependent routines
   static int  pd_code_alignment();
   // CNC: Removed because vtable stubs are now made with an ideal graph
   // static bool pd_disregard_arg_size();

   static void align_chunk() {
     uintptr_t off = (uintptr_t)( _chunk + sizeof(VtableStub) ) % pd_code_alignment();
     if (off != 0)  _chunk += pd_code_alignment() - off;
   }

  public:
   // Query
   bool is_itable_stub()                          { return !_is_vtable_stub; }
   bool is_vtable_stub()                          { return  _is_vtable_stub; }
   bool is_abstract_method_error(address epc)     { return epc == code_begin()+_ame_offset; }
   bool is_null_pointer_exception(address epc)    { return epc == code_begin()+_npe_offset; }

   void print_on(outputStream* st) const;
   void print() const                             { print_on(tty); }

 };

 #endif // SHARE_VM_CODE_VTABLESTUBS_HPP
	/*
	* Copyright (c) 1997, 2018, 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.
	*
	*/

	#ifndef SHARE_VM_CODE_VTABLESTUBS_HPP
	#define SHARE_VM_CODE_VTABLESTUBS_HPP

	#include "asm/macroAssembler.hpp"
	#include "code/vmreg.hpp"
	#include "memory/allocation.hpp"

	// A VtableStub holds an individual code stub for a pair (vtable index, #args) for either itables or vtables
	// There's a one-to-one relationship between a VtableStub and such a pair.

	// A word on VtableStub sizing:
	// Such a vtable/itable stub consists of the instance data
	// and an immediately following CodeBuffer.
	// Unfortunately, the required space for the code buffer varies, depending on
	// the setting of compile time macros (PRODUCT, ASSERT, ...) and of command line
	// parameters. Actual data may have an influence on the size as well.
	//
	// A simple approximation for the VtableStub size would be to just take a value
	// "large enough" for all circumstances - a worst case estimate.
	// As there can exist many stubs - and they never go away - we certainly don't
	// want to waste more code cache space than absolutely necessary.
	//
	// We need a different approach which, as far as possible, should be independent
	// from or adaptive to code size variations. These variations may be caused by
	// changed compile time or run time switches as well as by changed emitter code.
	//
	// Here is the idea:
	// For the first stub we generate, we allocate a "large enough" code buffer.
	// Once all instructions are emitted, we know the actual size of the stub.
	// Remembering that size allows us to allocate a tightly matching code buffer
	// for all subsequent stubs. That covers all "static variance", i.e. all variance
	// that is due to compile time macros, command line parameters, machine capabilities,
	// and other influences which are immutable for the life span of the vm.
	//
	// Life isn't always that easy. Code size may depend on actual data, "load constant"
	// being an example for that. All code segments with such "dynamic variance" require
	// additional care. We need to know or estimate the worst case code size for each
	// such segment. With that knowledge, we can maintain a "slop counter" in the
	// platform-specific stub emitters. It accumulates the difference between worst-case
	// and actual code size. When the stub is fully generated, the actual stub size is
	// adjusted (increased) by the slop counter value.
	//
	// As a result, we allocate all but the first code buffers with the same, tightly matching size.
	//

	// VtableStubs creates the code stubs for compiled calls through vtables.
	// There is one stub per (vtable index, args_size) pair, and the stubs are
	// never deallocated. They don't need to be GCed because they contain no oops.
	class VtableStub;

	class VtableStubs : AllStatic {
	public: // N must be public (some compilers need this for _table)
	enum {
	N = 256, // size of stub table; must be power of two
	mask = N - 1
	};

	private:
	friend class VtableStub;
	static VtableStub* _table[N]; // table of existing stubs
	static int _number_of_vtable_stubs; // number of stubs created so far (for statistics)
	static int _vtab_stub_size; // current size estimate for vtable stub (quasi-constant)
	static int _itab_stub_size; // current size estimate for itable stub (quasi-constant)

	static VtableStub* create_vtable_stub(int vtable_index);
	static VtableStub* create_itable_stub(int vtable_index);
	static VtableStub* lookup (bool is_vtable_stub, int vtable_index);
	static void enter (bool is_vtable_stub, int vtable_index, VtableStub* s);
	static inline uint hash (bool is_vtable_stub, int vtable_index);
	static address find_stub (bool is_vtable_stub, int vtable_index);
	static void bookkeeping(MacroAssembler* masm, outputStream* out, VtableStub* s,
	address npe_addr, address ame_addr, bool is_vtable_stub,
	int index, int slop_bytes, int index_dependent_slop);
	static int code_size_limit(bool is_vtable_stub);
	static void check_and_set_size_limit(bool is_vtable_stub,
	int code_size,
	int padding);

	public:
	static address find_vtable_stub(int vtable_index) { return find_stub(true, vtable_index); }
	static address find_itable_stub(int itable_index) { return find_stub(false, itable_index); }

	static VtableStub* entry_point(address pc); // vtable stub entry point for a pc
	static bool contains(address pc); // is pc within any stub?
	static VtableStub* stub_containing(address pc); // stub containing pc or NULL
	static int number_of_vtable_stubs() { return _number_of_vtable_stubs; }
	static void initialize();
	static void vtable_stub_do(void f(VtableStub*)); // iterates over all vtable stubs
	};


	class VtableStub {
	private:
	friend class VtableStubs;

	static address _chunk; // For allocation
	static address _chunk_end; // For allocation
	static VMReg _receiver_location; // Where to find receiver

	VtableStub* _next; // Pointer to next entry in hash table
	const short _index; // vtable index
	short _ame_offset; // Where an AbstractMethodError might occur
	short _npe_offset; // Where a NullPointerException might occur
	bool _is_vtable_stub; // True if vtable stub, false, is itable stub
	/* code follows here */ // The vtableStub code

	void* operator new(size_t size, int code_size) throw();

	VtableStub(bool is_vtable_stub, int index)
	: _next(NULL), _is_vtable_stub(is_vtable_stub),
	_index(index), _ame_offset(-1), _npe_offset(-1) {}
	VtableStub* next() const { return _next; }
	int index() const { return _index; }
	static VMReg receiver_location() { return _receiver_location; }
	void set_next(VtableStub* n) { _next = n; }

	public:
	address code_begin() const { return (address)(this + 1); }
	address code_end() const { return code_begin() + VtableStubs::code_size_limit(_is_vtable_stub); }
	address entry_point() const { return code_begin(); }
	static int entry_offset() { return sizeof(class VtableStub); }

	bool matches(bool is_vtable_stub, int index) const {
	return _index == index && _is_vtable_stub == is_vtable_stub;
	}
	bool contains(address pc) const { return code_begin() <= pc && pc < code_end(); }

	private:
	void set_exception_points(address npe_addr, address ame_addr) {
	_npe_offset = npe_addr - code_begin();
	_ame_offset = ame_addr - code_begin();
	assert(is_abstract_method_error(ame_addr), "offset must be correct");
	assert(is_null_pointer_exception(npe_addr), "offset must be correct");
	assert(!is_abstract_method_error(npe_addr), "offset must be correct");
	assert(!is_null_pointer_exception(ame_addr), "offset must be correct");
	}

	// platform-dependent routines
	static int pd_code_alignment();
	// CNC: Removed because vtable stubs are now made with an ideal graph
	// static bool pd_disregard_arg_size();

	static void align_chunk() {
	uintptr_t off = (uintptr_t)( _chunk + sizeof(VtableStub) ) % pd_code_alignment();
	if (off != 0) _chunk += pd_code_alignment() - off;
	}

	public:
	// Query
	bool is_itable_stub() { return !_is_vtable_stub; }
	bool is_vtable_stub() { return _is_vtable_stub; }
	bool is_abstract_method_error(address epc) { return epc == code_begin()+_ame_offset; }
	bool is_null_pointer_exception(address epc) { return epc == code_begin()+_npe_offset; }

	void print_on(outputStream* st) const;
	void print() const { print_on(tty); }

	};

	#endif // SHARE_VM_CODE_VTABLESTUBS_HPP