location.hpp revision 1472:c18cbe5936b8 
1/*
2 * Copyright (c) 1997, 2008, 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.
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23 */
24
25// A Location describes a concrete machine variable location
26// (such as integer or floating point register or a stack-held
27// variable). Used when generating debug-information for nmethods.
28//
29// Encoding:
30//
31// bits (use low bits for best compression):
32//  Type:   [3..0]
33//  Where:  [4]
34//  Offset: [31..5]
35
36class Location VALUE_OBJ_CLASS_SPEC {
37  friend class VMStructs;
38 public:
39  enum Where {
40    on_stack,
41    in_register
42  };
43
44  enum Type {
45    invalid,                    // Invalid location
46    normal,                     // Ints, floats, double halves
47    oop,                        // Oop (please GC me!)
48    int_in_long,                // Integer held in long register
49    lng,                        // Long held in one register
50    float_in_dbl,               // Float held in double register
51    dbl,                        // Double held in one register
52    addr,                       // JSR return address
53    narrowoop                   // Narrow Oop (please GC me!)
54  };
55
56
57 private:
58  enum {
59    TYPE_MASK    = (juint) 0x0F,
60    TYPE_SHIFT   = 0,
61    WHERE_MASK   = (juint) 0x10,
62    WHERE_SHIFT  = 4,
63    OFFSET_MASK  = (juint) 0xFFFFFFE0,
64    OFFSET_SHIFT = 5
65  };
66
67  juint _value;
68
69  // Create a bit-packed Location
70  Location(Where where_, Type type_, unsigned offset_) {
71    set(where_, type_, offset_);
72    assert( where () == where_ , "" );
73    assert( type  () == type_  , "" );
74    assert( offset() == offset_, "" );
75  }
76
77  inline void set(Where where_, Type type_, unsigned offset_) {
78    _value = (juint) ((where_  << WHERE_SHIFT) |
79                      (type_   << TYPE_SHIFT)  |
80                      ((offset_ << OFFSET_SHIFT) & OFFSET_MASK));
81  }
82
83 public:
84
85  // Stack location Factory.  Offset is 4-byte aligned; remove low bits
86  static Location new_stk_loc( Type t, int offset ) { return Location(on_stack,t,offset>>LogBytesPerInt); }
87  // Register location Factory
88  static Location new_reg_loc( Type t, VMReg reg ) { return Location(in_register, t, reg->value()); }
89  // Default constructor
90  Location() { set(on_stack,invalid,0); }
91
92  // Bit field accessors
93  Where where()  const { return (Where)       ((_value & WHERE_MASK)  >> WHERE_SHIFT);}
94  Type  type()   const { return (Type)        ((_value & TYPE_MASK)   >> TYPE_SHIFT); }
95  unsigned offset() const { return (unsigned) ((_value & OFFSET_MASK) >> OFFSET_SHIFT); }
96
97  // Accessors
98  bool is_register() const    { return where() == in_register; }
99  bool is_stack() const       { return where() == on_stack;    }
100
101  int stack_offset() const    { assert(where() == on_stack,    "wrong Where"); return offset()<<LogBytesPerInt; }
102  int register_number() const { assert(where() == in_register, "wrong Where"); return offset()   ; }
103
104  VMReg reg() const { assert(where() == in_register, "wrong Where"); return VMRegImpl::as_VMReg(offset())   ; }
105
106  // Printing
107  void print_on(outputStream* st) const;
108
109  // Serialization of debugging information
110  Location(DebugInfoReadStream* stream);
111  void write_on(DebugInfoWriteStream* stream);
112
113  // check
114  static bool legal_offset_in_bytes(int offset_in_bytes);
115};
116