1 /*
   2  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_CODE_LOCATION_HPP
  26 #define SHARE_VM_CODE_LOCATION_HPP
  27 
  28 #include "asm/assembler.hpp"
  29 #include "code/vmreg.hpp"
  30 #include "memory/allocation.hpp"
  31 
  32 // A Location describes a concrete machine variable location
  33 // (such as integer or floating point register or a stack-held
  34 // variable). Used when generating debug-information for nmethods.
  35 //
  36 // Encoding:
  37 //
  38 // bits (use low bits for best compression):
  39 //  Type:   [3..0]
  40 //  Where:  [4]
  41 //  Offset: [31..5]
  42 
  43 class Location {
  44   friend class VMStructs;
  45  public:
  46   enum Where {
  47     on_stack,
  48     in_register
  49   };
  50 
  51   enum Type {
  52     invalid,                    // Invalid location
  53     normal,                     // Ints, floats, double halves
  54     oop,                        // Oop (please GC me!)
  55     int_in_long,                // Integer held in long register
  56     lng,                        // Long held in one register
  57     float_in_dbl,               // Float held in double register
  58     dbl,                        // Double held in one register
  59     addr,                       // JSR return address
  60     narrowoop                   // Narrow Oop (please GC me!)
  61   };
  62 
  63 
  64  private:
  65   enum {
  66     TYPE_MASK    = (juint) 0x0F,
  67     TYPE_SHIFT   = 0,
  68     WHERE_MASK   = (juint) 0x10,
  69     WHERE_SHIFT  = 4,
  70     OFFSET_MASK  = (juint) 0xFFFFFFE0,
  71     OFFSET_SHIFT = 5
  72   };
  73 
  74   juint _value;
  75 
  76   // Create a bit-packed Location
  77   Location(Where where_, Type type_, unsigned offset_) {
  78     set(where_, type_, offset_);
  79     assert( where () == where_ , "" );
  80     assert( type  () == type_  , "" );
  81     assert( offset() == offset_, "" );
  82   }
  83 
  84   inline void set(Where where_, Type type_, unsigned offset_) {
  85     _value = (juint) ((where_  << WHERE_SHIFT) |
  86                       (type_   << TYPE_SHIFT)  |
  87                       ((offset_ << OFFSET_SHIFT) & OFFSET_MASK));
  88   }
  89 
  90  public:
  91 
  92   // Stack location Factory.  Offset is 4-byte aligned; remove low bits
  93   static Location new_stk_loc( Type t, int offset ) { return Location(on_stack,t,offset>>LogBytesPerInt); }
  94   // Register location Factory
  95   static Location new_reg_loc( Type t, VMReg reg ) { return Location(in_register, t, reg->value()); }
  96   // Default constructor
  97   Location() { set(on_stack,invalid,0); }
  98 
  99   // Bit field accessors
 100   Where where()  const { return (Where)       ((_value & WHERE_MASK)  >> WHERE_SHIFT);}
 101   Type  type()   const { return (Type)        ((_value & TYPE_MASK)   >> TYPE_SHIFT); }
 102   unsigned offset() const { return (unsigned) ((_value & OFFSET_MASK) >> OFFSET_SHIFT); }
 103 
 104   // Accessors
 105   bool is_register() const    { return where() == in_register; }
 106   bool is_stack() const       { return where() == on_stack;    }
 107 
 108   int stack_offset() const    { assert(where() == on_stack,    "wrong Where"); return offset()<<LogBytesPerInt; }
 109   int register_number() const { assert(where() == in_register, "wrong Where"); return offset()   ; }
 110 
 111   VMReg reg() const { assert(where() == in_register, "wrong Where"); return VMRegImpl::as_VMReg(offset())   ; }
 112 
 113   // Printing
 114   void print_on(outputStream* st) const;
 115 
 116   // Serialization of debugging information
 117   Location(DebugInfoReadStream* stream);
 118   void write_on(DebugInfoWriteStream* stream);
 119 
 120   // check
 121   static bool legal_offset_in_bytes(int offset_in_bytes);
 122 };
 123 
 124 #endif // SHARE_VM_CODE_LOCATION_HPP