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1 /*
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2 * Copyright 1997-2006 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 // This file contains platform-independant assembler declarations.
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26
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27 class CodeBuffer;
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28 class MacroAssembler;
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29 class AbstractAssembler;
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30 class Label;
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31
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32 /**
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33 * Labels represent destinations for control transfer instructions. Such
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34 * instructions can accept a Label as their target argument. A Label is
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35 * bound to the current location in the code stream by calling the
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36 * MacroAssembler's 'bind' method, which in turn calls the Label's 'bind'
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37 * method. A Label may be referenced by an instruction before it's bound
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38 * (i.e., 'forward referenced'). 'bind' stores the current code offset
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39 * in the Label object.
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40 *
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41 * If an instruction references a bound Label, the offset field(s) within
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42 * the instruction are immediately filled in based on the Label's code
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43 * offset. If an instruction references an unbound label, that
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44 * instruction is put on a list of instructions that must be patched
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45 * (i.e., 'resolved') when the Label is bound.
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46 *
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47 * 'bind' will call the platform-specific 'patch_instruction' method to
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48 * fill in the offset field(s) for each unresolved instruction (if there
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49 * are any). 'patch_instruction' lives in one of the
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50 * cpu/<arch>/vm/assembler_<arch>* files.
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51 *
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52 * Instead of using a linked list of unresolved instructions, a Label has
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53 * an array of unresolved instruction code offsets. _patch_index
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54 * contains the total number of forward references. If the Label's array
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55 * overflows (i.e., _patch_index grows larger than the array size), a
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56 * GrowableArray is allocated to hold the remaining offsets. (The cache
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57 * size is 4 for now, which handles over 99.5% of the cases)
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58 *
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59 * Labels may only be used within a single CodeSection. If you need
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60 * to create references between code sections, use explicit relocations.
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61 */
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62 class Label VALUE_OBJ_CLASS_SPEC {
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63 private:
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64 enum { PatchCacheSize = 4 };
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65
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66 // _loc encodes both the binding state (via its sign)
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67 // and the binding locator (via its value) of a label.
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68 //
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69 // _loc >= 0 bound label, loc() encodes the target (jump) position
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70 // _loc == -1 unbound label
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71 int _loc;
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72
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73 // References to instructions that jump to this unresolved label.
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74 // These instructions need to be patched when the label is bound
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75 // using the platform-specific patchInstruction() method.
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76 //
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77 // To avoid having to allocate from the C-heap each time, we provide
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78 // a local cache and use the overflow only if we exceed the local cache
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79 int _patches[PatchCacheSize];
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80 int _patch_index;
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81 GrowableArray<int>* _patch_overflow;
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82
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83 Label(const Label&) { ShouldNotReachHere(); }
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84
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85 public:
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86
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87 /**
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88 * After binding, be sure 'patch_instructions' is called later to link
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89 */
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90 void bind_loc(int loc) {
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91 assert(loc >= 0, "illegal locator");
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92 assert(_loc == -1, "already bound");
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93 _loc = loc;
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94 }
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95 void bind_loc(int pos, int sect); // = bind_loc(locator(pos, sect))
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96
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97 #ifndef PRODUCT
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98 // Iterates over all unresolved instructions for printing
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99 void print_instructions(MacroAssembler* masm) const;
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100 #endif // PRODUCT
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101
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102 /**
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103 * Returns the position of the the Label in the code buffer
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104 * The position is a 'locator', which encodes both offset and section.
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105 */
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106 int loc() const {
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107 assert(_loc >= 0, "unbound label");
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108 return _loc;
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109 }
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110 int loc_pos() const; // == locator_pos(loc())
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111 int loc_sect() const; // == locator_sect(loc())
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112
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113 bool is_bound() const { return _loc >= 0; }
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114 bool is_unbound() const { return _loc == -1 && _patch_index > 0; }
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115 bool is_unused() const { return _loc == -1 && _patch_index == 0; }
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116
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117 /**
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118 * Adds a reference to an unresolved displacement instruction to
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119 * this unbound label
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120 *
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121 * @param cb the code buffer being patched
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122 * @param branch_loc the locator of the branch instruction in the code buffer
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123 */
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124 void add_patch_at(CodeBuffer* cb, int branch_loc);
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125
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126 /**
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127 * Iterate over the list of patches, resolving the instructions
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128 * Call patch_instruction on each 'branch_loc' value
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129 */
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130 void patch_instructions(MacroAssembler* masm);
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131
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132 void init() {
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133 _loc = -1;
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134 _patch_index = 0;
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135 _patch_overflow = NULL;
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136 }
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137
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138 Label() {
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139 init();
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140 }
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141 };
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142
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143
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144 // The Abstract Assembler: Pure assembler doing NO optimizations on the
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145 // instruction level; i.e., what you write is what you get.
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146 // The Assembler is generating code into a CodeBuffer.
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147 class AbstractAssembler : public ResourceObj {
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148 friend class Label;
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149
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150 protected:
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151 CodeSection* _code_section; // section within the code buffer
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152 address _code_begin; // first byte of code buffer
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153 address _code_limit; // first byte after code buffer
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154 address _code_pos; // current code generation position
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155 OopRecorder* _oop_recorder; // support for relocInfo::oop_type
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156
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157 // Code emission & accessing
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158 address addr_at(int pos) const { return _code_begin + pos; }
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159
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160 // This routine is called with a label is used for an address.
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161 // Labels and displacements truck in offsets, but target must return a PC.
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162 address target(Label& L); // return _code_section->target(L)
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163
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164 bool is8bit(int x) const { return -0x80 <= x && x < 0x80; }
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165 bool isByte(int x) const { return 0 <= x && x < 0x100; }
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166 bool isShiftCount(int x) const { return 0 <= x && x < 32; }
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167
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168 void emit_byte(int x); // emit a single byte
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169 void emit_word(int x); // emit a 16-bit word (not a wordSize word!)
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170 void emit_long(jint x); // emit a 32-bit word (not a longSize word!)
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171 void emit_address(address x); // emit an address (not a longSize word!)
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172
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173 // Instruction boundaries (required when emitting relocatable values).
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174 class InstructionMark: public StackObj {
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175 private:
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176 AbstractAssembler* _assm;
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177
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178 public:
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179 InstructionMark(AbstractAssembler* assm) : _assm(assm) {
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180 assert(assm->inst_mark() == NULL, "overlapping instructions");
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181 _assm->set_inst_mark();
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182 }
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183 ~InstructionMark() {
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184 _assm->clear_inst_mark();
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185 }
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186 };
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187 friend class InstructionMark;
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188 #ifdef ASSERT
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189 // Make it return true on platforms which need to verify
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190 // instruction boundaries for some operations.
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191 inline static bool pd_check_instruction_mark();
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192 #endif
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193
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194 // Label functions
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195 void print(Label& L);
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196
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197 public:
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198
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199 // Creation
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200 AbstractAssembler(CodeBuffer* code);
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201
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202 // save end pointer back to code buf.
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203 void sync();
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204
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205 // ensure buf contains all code (call this before using/copying the code)
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206 void flush();
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207
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208 // Accessors
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209 CodeBuffer* code() const; // _code_section->outer()
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210 CodeSection* code_section() const { return _code_section; }
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211 int sect() const; // return _code_section->index()
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212 address pc() const { return _code_pos; }
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213 int offset() const { return _code_pos - _code_begin; }
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214 int locator() const; // CodeBuffer::locator(offset(), sect())
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215 OopRecorder* oop_recorder() const { return _oop_recorder; }
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216 void set_oop_recorder(OopRecorder* r) { _oop_recorder = r; }
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217
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218 address inst_mark() const;
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219 void set_inst_mark();
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220 void clear_inst_mark();
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221
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222 // Constants in code
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223 void a_byte(int x);
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224 void a_long(jint x);
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225 void relocate(RelocationHolder const& rspec, int format = 0);
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226 void relocate( relocInfo::relocType rtype, int format = 0) {
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227 if (rtype != relocInfo::none)
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228 relocate(Relocation::spec_simple(rtype), format);
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229 }
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230
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231 static int code_fill_byte(); // used to pad out odd-sized code buffers
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232
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233 // Associate a comment with the current offset. It will be printed
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234 // along with the disassembly when printing nmethods. Currently
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235 // only supported in the instruction section of the code buffer.
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236 void block_comment(const char* comment);
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237
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238 // Label functions
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239 void bind(Label& L); // binds an unbound label L to the current code position
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240
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241 // Move to a different section in the same code buffer.
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242 void set_code_section(CodeSection* cs);
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243
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244 // Inform assembler when generating stub code and relocation info
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245 address start_a_stub(int required_space);
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246 void end_a_stub();
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247 // Ditto for constants.
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248 address start_a_const(int required_space, int required_align = sizeof(double));
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249 void end_a_const();
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250
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251 // fp constants support
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252 address double_constant(jdouble c) {
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253 address ptr = start_a_const(sizeof(c), sizeof(c));
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254 if (ptr != NULL) {
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255 *(jdouble*)ptr = c;
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256 _code_pos = ptr + sizeof(c);
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257 end_a_const();
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258 }
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259 return ptr;
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260 }
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261 address float_constant(jfloat c) {
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262 address ptr = start_a_const(sizeof(c), sizeof(c));
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263 if (ptr != NULL) {
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264 *(jfloat*)ptr = c;
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265 _code_pos = ptr + sizeof(c);
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266 end_a_const();
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267 }
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268 return ptr;
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269 }
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270 address address_constant(address c, RelocationHolder const& rspec) {
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271 address ptr = start_a_const(sizeof(c), sizeof(c));
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272 if (ptr != NULL) {
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273 relocate(rspec);
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274 *(address*)ptr = c;
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275 _code_pos = ptr + sizeof(c);
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276 end_a_const();
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277 }
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278 return ptr;
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279 }
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280 inline address address_constant(Label& L);
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281 inline address address_table_constant(GrowableArray<Label*> label);
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282
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283 // Bang stack to trigger StackOverflowError at a safe location
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284 // implementation delegates to machine-specific bang_stack_with_offset
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285 void generate_stack_overflow_check( int frame_size_in_bytes );
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286 virtual void bang_stack_with_offset(int offset) = 0;
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287
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288
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289 /**
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290 * A platform-dependent method to patch a jump instruction that refers
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291 * to this label.
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292 *
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293 * @param branch the location of the instruction to patch
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294 * @param masm the assembler which generated the branch
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295 */
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296 void pd_patch_instruction(address branch, address target);
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297
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298 #ifndef PRODUCT
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299 /**
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300 * Platform-dependent method of printing an instruction that needs to be
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301 * patched.
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302 *
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303 * @param branch the instruction to be patched in the buffer.
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304 */
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305 static void pd_print_patched_instruction(address branch);
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306 #endif // PRODUCT
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307 };
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308
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309 #include "incls/_assembler_pd.hpp.incl"
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