branch.hh revision 7099:1949ba4db2cf 
1/* Copyright (c) 2007-2008 The Florida State University
2 * All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are
6 * met: redistributions of source code must retain the above copyright
7 * notice, this list of conditions and the following disclaimer;
8 * redistributions in binary form must reproduce the above copyright
9 * notice, this list of conditions and the following disclaimer in the
10 * documentation and/or other materials provided with the distribution;
11 * neither the name of the copyright holders nor the names of its
12 * contributors may be used to endorse or promote products derived from
13 * this software without specific prior written permission.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
18 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
19 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
21 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
25 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 * Authors: Stephen Hines
28 */
29#ifndef __ARCH_ARM_INSTS_BRANCH_HH__
30#define __ARCH_ARM_INSTS_BRANCH_HH__
31
32#include "arch/arm/insts/pred_inst.hh"
33
34namespace ArmISA
35{
36/**
37 * Base class for instructions whose disassembly is not purely a
38 * function of the machine instruction (i.e., it depends on the
39 * PC).  This class overrides the disassemble() method to check
40 * the PC and symbol table values before re-using a cached
41 * disassembly string.  This is necessary for branches and jumps,
42 * where the disassembly string includes the target address (which
43 * may depend on the PC and/or symbol table).
44 */
45class PCDependentDisassembly : public PredOp
46{
47  protected:
48    /// Cached program counter from last disassembly
49    mutable Addr cachedPC;
50
51    /// Cached symbol table pointer from last disassembly
52    mutable const SymbolTable *cachedSymtab;
53
54    /// Constructor
55    PCDependentDisassembly(const char *mnem, ExtMachInst _machInst,
56                           OpClass __opClass)
57        : PredOp(mnem, _machInst, __opClass),
58          cachedPC(0), cachedSymtab(0)
59    {
60    }
61
62    const std::string &
63    disassemble(Addr pc, const SymbolTable *symtab) const;
64};
65
66/**
67 * Base class for branches (PC-relative control transfers),
68 * conditional or unconditional.
69 */
70class Branch : public PCDependentDisassembly
71{
72  protected:
73    /// target address (signed) Displacement .
74    int32_t disp;
75
76    /// Constructor.
77    Branch(const char *mnem, ExtMachInst _machInst, OpClass __opClass)
78        : PCDependentDisassembly(mnem, _machInst, __opClass),
79          disp(machInst.offset << 2)
80    {
81        //If Bit 26 is 1 then Sign Extend
82        if ( (disp & 0x02000000) > 0  ) {
83            disp |=  0xFC000000;
84        }
85    }
86
87    Addr branchTarget(Addr branchPC) const;
88
89    std::string
90    generateDisassembly(Addr pc, const SymbolTable *symtab) const;
91};
92
93/**
94 * Base class for branch and exchange instructions on the ARM
95 */
96class BranchExchange : public PredOp
97{
98  protected:
99    /// Constructor
100    BranchExchange(const char *mnem, ExtMachInst _machInst,
101                           OpClass __opClass)
102        : PredOp(mnem, _machInst, __opClass)
103    {
104    }
105
106    std::string
107    generateDisassembly(Addr pc, const SymbolTable *symtab) const;
108};
109
110
111/**
112 * Base class for jumps (register-indirect control transfers).  In
113 * the Arm ISA, these are always unconditional.
114 */
115class Jump : public PCDependentDisassembly
116{
117  protected:
118
119    /// Displacement to target address (signed).
120    int32_t disp;
121
122    uint32_t target;
123
124  public:
125    /// Constructor
126    Jump(const char *mnem, ExtMachInst _machInst, OpClass __opClass)
127        : PCDependentDisassembly(mnem, _machInst, __opClass),
128          disp(machInst.offset << 2)
129    {
130    }
131
132    Addr branchTarget(ThreadContext *tc) const;
133
134    std::string
135    generateDisassembly(Addr pc, const SymbolTable *symtab) const;
136};
137}
138
139#endif //__ARCH_ARM_INSTS_BRANCH_HH__
140