branch.isa revision 7720:65d338a8dba4
1// -*- mode:c++ -*- 2 3// Copyright (c) 2007 MIPS Technologies, Inc. 4// All rights reserved. 5// 6// Redistribution and use in source and binary forms, with or without 7// modification, are permitted provided that the following conditions are 8// met: redistributions of source code must retain the above copyright 9// notice, this list of conditions and the following disclaimer; 10// redistributions in binary form must reproduce the above copyright 11// notice, this list of conditions and the following disclaimer in the 12// documentation and/or other materials provided with the distribution; 13// neither the name of the copyright holders nor the names of its 14// contributors may be used to endorse or promote products derived from 15// this software without specific prior written permission. 16// 17// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 18// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 19// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 20// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 21// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 22// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 23// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 27// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28// 29// Authors: Korey Sewell 30 31//////////////////////////////////////////////////////////////////// 32// 33// Control transfer instructions 34// 35 36output header {{ 37 38#include <iostream> 39 using namespace std; 40 41 /** 42 * Base class for instructions whose disassembly is not purely a 43 * function of the machine instruction (i.e., it depends on the 44 * PC). This class overrides the disassemble() method to check 45 * the PC and symbol table values before re-using a cached 46 * disassembly string. This is necessary for branches and jumps, 47 * where the disassembly string includes the target address (which 48 * may depend on the PC and/or symbol table). 49 */ 50 class PCDependentDisassembly : public MipsStaticInst 51 { 52 protected: 53 /// Cached program counter from last disassembly 54 mutable Addr cachedPC; 55 56 /// Cached symbol table pointer from last disassembly 57 mutable const SymbolTable *cachedSymtab; 58 59 /// Constructor 60 PCDependentDisassembly(const char *mnem, MachInst _machInst, 61 OpClass __opClass) 62 : MipsStaticInst(mnem, _machInst, __opClass), 63 cachedPC(0), cachedSymtab(0) 64 { 65 } 66 67 const std::string & 68 disassemble(Addr pc, const SymbolTable *symtab) const; 69 }; 70 71 /** 72 * Base class for branches (PC-relative control transfers), 73 * conditional or unconditional. 74 */ 75 class Branch : public PCDependentDisassembly 76 { 77 protected: 78 /// target address (signed) Displacement . 79 int32_t disp; 80 81 /// Constructor. 82 Branch(const char *mnem, MachInst _machInst, OpClass __opClass) 83 : PCDependentDisassembly(mnem, _machInst, __opClass), 84 disp(OFFSET << 2) 85 { 86 //If Bit 17 is 1 then Sign Extend 87 if ( (disp & 0x00020000) > 0 ) { 88 disp |= 0xFFFE0000; 89 } 90 } 91 92 MipsISA::PCState branchTarget(const MipsISA::PCState &branchPC) const; 93 94 std::string 95 generateDisassembly(Addr pc, const SymbolTable *symtab) const; 96 }; 97 98 /** 99 * Base class for jumps (register-indirect control transfers). In 100 * the Mips ISA, these are always unconditional. 101 */ 102 class Jump : public PCDependentDisassembly 103 { 104 protected: 105 106 /// Displacement to target address (signed). 107 int32_t disp; 108 109 uint32_t target; 110 111 public: 112 /// Constructor 113 Jump(const char *mnem, MachInst _machInst, OpClass __opClass) 114 : PCDependentDisassembly(mnem, _machInst, __opClass), 115 disp(JMPTARG << 2) 116 { 117 } 118 119 MipsISA::PCState branchTarget(ThreadContext *tc) const; 120 121 std::string 122 generateDisassembly(Addr pc, const SymbolTable *symtab) const; 123 }; 124}}; 125 126output decoder {{ 127 MipsISA::PCState 128 Branch::branchTarget(const MipsISA::PCState &branchPC) const 129 { 130 MipsISA::PCState target = branchPC; 131 target.advance(); 132 target.npc(branchPC.pc() + sizeof(MachInst) + disp); 133 target.nnpc(target.npc() + sizeof(MachInst)); 134 return target; 135 } 136 137 MipsISA::PCState 138 Jump::branchTarget(ThreadContext *tc) const 139 { 140 MipsISA::PCState target = tc->pcState(); 141 Addr pc = target.pc(); 142 target.advance(); 143 target.npc((pc & 0xF0000000) | disp); 144 target.nnpc(target.npc() + sizeof(MachInst)); 145 return target; 146 } 147 148 const std::string & 149 PCDependentDisassembly::disassemble(Addr pc, 150 const SymbolTable *symtab) const 151 { 152 if (!cachedDisassembly || 153 pc != cachedPC || symtab != cachedSymtab) 154 { 155 if (cachedDisassembly) 156 delete cachedDisassembly; 157 158 cachedDisassembly = 159 new std::string(generateDisassembly(pc, symtab)); 160 cachedPC = pc; 161 cachedSymtab = symtab; 162 } 163 164 return *cachedDisassembly; 165 } 166 167 std::string 168 Branch::generateDisassembly(Addr pc, const SymbolTable *symtab) const 169 { 170 std::stringstream ss; 171 172 ccprintf(ss, "%-10s ", mnemonic); 173 174 // There's only one register arg (RA), but it could be 175 // either a source (the condition for conditional 176 // branches) or a destination (the link reg for 177 // unconditional branches) 178 if (_numSrcRegs == 1) { 179 printReg(ss, _srcRegIdx[0]); 180 ss << ", "; 181 } else if(_numSrcRegs == 2) { 182 printReg(ss, _srcRegIdx[0]); 183 ss << ", "; 184 printReg(ss, _srcRegIdx[1]); 185 ss << ", "; 186 } 187 188 Addr target = pc + 4 + disp; 189 190 std::string str; 191 if (symtab && symtab->findSymbol(target, str)) 192 ss << str; 193 else 194 ccprintf(ss, "0x%x", target); 195 196 return ss.str(); 197 } 198 199 std::string 200 Jump::generateDisassembly(Addr pc, const SymbolTable *symtab) const 201 { 202 std::stringstream ss; 203 204 ccprintf(ss, "%-10s ", mnemonic); 205 206 if ( strcmp(mnemonic,"jal") == 0 ) { 207 Addr npc = pc + 4; 208 ccprintf(ss,"0x%x",(npc & 0xF0000000) | disp); 209 } else if (_numSrcRegs == 0) { 210 std::string str; 211 if (symtab && symtab->findSymbol(disp, str)) 212 ss << str; 213 else 214 ccprintf(ss, "0x%x", disp); 215 } else if (_numSrcRegs == 1) { 216 printReg(ss, _srcRegIdx[0]); 217 } else if(_numSrcRegs == 2) { 218 printReg(ss, _srcRegIdx[0]); 219 ss << ", "; 220 printReg(ss, _srcRegIdx[1]); 221 } 222 223 return ss.str(); 224 } 225}}; 226 227def format Branch(code, *opt_flags) {{ 228 not_taken_code = '' 229 230 #Build Instruction Flags 231 #Use Link & Likely Flags to Add Link/Condition Code 232 inst_flags = ('IsDirectControl', ) 233 for x in opt_flags: 234 if x == 'Link': 235 code += 'R31 = pc.nnpc();\n' 236 elif x == 'Likely': 237 not_taken_code = 'pc.advance();' 238 inst_flags += ('IsCondDelaySlot', ) 239 else: 240 inst_flags += (x, ) 241 242 #Take into account uncond. branch instruction 243 if 'cond = 1' in code: 244 inst_flags += ('IsUncondControl', ) 245 else: 246 inst_flags += ('IsCondControl', ) 247 248 #Condition code 249 code = ''' 250 bool cond; 251 MipsISA::PCState pc = PCS; 252 %(code)s 253 if (cond) { 254 pc.nnpc(pc.npc() + disp); 255 } else { 256 %(not_taken_code)s 257 } 258 PCS = pc; 259 ''' % { "code" : code, "not_taken_code" : not_taken_code } 260 261 iop = InstObjParams(name, Name, 'Branch', code, inst_flags) 262 header_output = BasicDeclare.subst(iop) 263 decoder_output = BasicConstructor.subst(iop) 264 decode_block = BasicDecode.subst(iop) 265 exec_output = BasicExecute.subst(iop) 266}}; 267 268def format DspBranch(code, *opt_flags) {{ 269 not_taken_code = '' 270 271 #Build Instruction Flags 272 #Use Link & Likely Flags to Add Link/Condition Code 273 inst_flags = ('IsDirectControl', ) 274 for x in opt_flags: 275 if x == 'Link': 276 code += 'R32 = pc.nnpc();' 277 elif x == 'Likely': 278 not_taken_code = 'pc.advance();' 279 inst_flags += ('IsCondDelaySlot', ) 280 else: 281 inst_flags += (x, ) 282 283 #Take into account uncond. branch instruction 284 if 'cond = 1' in code: 285 inst_flags += ('IsUncondControl', ) 286 else: 287 inst_flags += ('IsCondControl', ) 288 289 #Condition code 290 code = ''' 291 MipsISA::PCState pc = PCS; 292 bool cond; 293 uint32_t dspctl = DSPControl; 294 %(code)s 295 if (cond) { 296 pc.nnpc(pc.npc() + disp); 297 } else { 298 %(not_taken_code)s 299 } 300 PCS = pc; 301 ''' % { "code" : code, "not_taken_code" : not_taken_code } 302 303 iop = InstObjParams(name, Name, 'Branch', code, inst_flags) 304 header_output = BasicDeclare.subst(iop) 305 decoder_output = BasicConstructor.subst(iop) 306 decode_block = BasicDecode.subst(iop) 307 exec_output = BasicExecute.subst(iop) 308}}; 309 310def format Jump(code, *opt_flags) {{ 311 #Build Instruction Flags 312 #Use Link Flag to Add Link Code 313 inst_flags = ('IsIndirectControl', 'IsUncondControl') 314 for x in opt_flags: 315 if x == 'Link': 316 code = ''' 317 R31 = pc.nnpc(); 318 ''' + code 319 elif x == 'ClearHazards': 320 code += '/* Code Needed to Clear Execute & Inst Hazards */\n' 321 else: 322 inst_flags += (x, ) 323 324 code = ''' 325 MipsISA::PCState pc = PCS; 326 ''' + code 327 328 iop = InstObjParams(name, Name, 'Jump', code, inst_flags) 329 header_output = BasicDeclare.subst(iop) 330 decoder_output = BasicConstructor.subst(iop) 331 decode_block = BasicDecode.subst(iop) 332 exec_output = BasicExecute.subst(iop) 333}}; 334 335 336 337 338