1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ART_COMPILER_DEBUG_DWARF_EXPRESSION_H_
18#define ART_COMPILER_DEBUG_DWARF_EXPRESSION_H_
19
20#include <cstddef>
21#include <cstdint>
22
23#include "debug/dwarf/dwarf_constants.h"
24#include "debug/dwarf/writer.h"
25
26namespace art {
27namespace dwarf {
28
29// Writer for DWARF expressions which are used in .debug_info and .debug_loc sections.
30// See the DWARF specification for the precise meaning of the opcodes.
31// If multiple equivalent encodings are possible, it will choose the most compact one.
32// The writer is not exhaustive - it only implements opcodes we have needed so far.
33class Expression : private Writer<> {
34 public:
35  using Writer<>::data;
36  using Writer<>::size;
37
38  // Push signed integer on the stack.
39  void WriteOpConsts(int32_t value) {
40    if (0 <= value && value < 32) {
41      PushUint8(DW_OP_lit0 + value);
42    } else {
43      PushUint8(DW_OP_consts);
44      PushSleb128(value);
45    }
46  }
47
48  // Push unsigned integer on the stack.
49  void WriteOpConstu(uint32_t value) {
50    if (value < 32) {
51      PushUint8(DW_OP_lit0 + value);
52    } else {
53      PushUint8(DW_OP_constu);
54      PushUleb128(value);
55    }
56  }
57
58  // Variable is stored in given register.
59  void WriteOpReg(uint32_t dwarf_reg_num) {
60    if (dwarf_reg_num < 32) {
61      PushUint8(DW_OP_reg0 + dwarf_reg_num);
62    } else {
63      PushUint8(DW_OP_regx);
64      PushUleb128(dwarf_reg_num);
65    }
66  }
67
68  // Variable is stored on stack.  Also see DW_AT_frame_base.
69  void WriteOpFbreg(int32_t stack_offset) {
70    PushUint8(DW_OP_fbreg);
71    PushSleb128(stack_offset);
72  }
73
74  // The variable is stored in multiple locations (pieces).
75  void WriteOpPiece(uint32_t num_bytes) {
76    PushUint8(DW_OP_piece);
77    PushUleb128(num_bytes);
78  }
79
80  // Loads 32-bit or 64-bit value depending on architecture.
81  void WriteOpDeref() { PushUint8(DW_OP_deref); }
82
83  // Loads value of given byte size.
84  void WriteOpDerefSize(uint8_t num_bytes) {
85    PushUint8(DW_OP_deref_size);
86    PushUint8(num_bytes);
87  }
88
89  // Pop two values and push their sum.
90  void WriteOpPlus() { PushUint8(DW_OP_plus); }
91
92  // Add constant value to value on top of stack.
93  void WriteOpPlusUconst(uint32_t offset) {
94    PushUint8(DW_OP_plus_uconst);
95    PushUleb128(offset);
96  }
97
98  // Negate top of stack.
99  void WriteOpNeg() { PushUint8(DW_OP_neg); }
100
101  // Pop two values and push their bitwise-AND.
102  void WriteOpAnd() { PushUint8(DW_OP_and); }
103
104  // Push stack base pointer as determined from .debug_frame.
105  void WriteOpCallFrameCfa() { PushUint8(DW_OP_call_frame_cfa); }
106
107  // Push address of the variable we are working with.
108  void WriteOpPushObjectAddress() { PushUint8(DW_OP_push_object_address); }
109
110  // Return the top stack as the value of the variable.
111  // Otherwise, the top of stack is the variable's location.
112  void WriteOpStackValue() { PushUint8(DW_OP_stack_value); }
113
114  explicit Expression(std::vector<uint8_t>* buffer) : Writer<>(buffer) {
115    buffer->clear();
116  }
117};
118}  // namespace dwarf
119}  // namespace art
120
121#endif  // ART_COMPILER_DEBUG_DWARF_EXPRESSION_H_
122