1 //===-- Thumb2SizeReduction.cpp - Thumb2 code size reduction pass -*- C++ -*-=// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #define DEBUG_TYPE "t2-reduce-size" 11 #include "ARM.h" 12 #include "ARMBaseRegisterInfo.h" 13 #include "ARMBaseInstrInfo.h" 14 #include "ARMSubtarget.h" 15 #include "Thumb2InstrInfo.h" 16 #include "MCTargetDesc/ARMAddressingModes.h" 17 #include "llvm/CodeGen/MachineInstr.h" 18 #include "llvm/CodeGen/MachineInstrBuilder.h" 19 #include "llvm/CodeGen/MachineFunctionPass.h" 20 #include "llvm/Support/CommandLine.h" 21 #include "llvm/Support/Debug.h" 22 #include "llvm/Support/raw_ostream.h" 23 #include "llvm/ADT/DenseMap.h" 24 #include "llvm/ADT/Statistic.h" 25 using namespace llvm; 26 27 STATISTIC(NumNarrows, "Number of 32-bit instrs reduced to 16-bit ones"); 28 STATISTIC(Num2Addrs, "Number of 32-bit instrs reduced to 2addr 16-bit ones"); 29 STATISTIC(NumLdSts, "Number of 32-bit load / store reduced to 16-bit ones"); 30 31 static cl::opt<int> ReduceLimit("t2-reduce-limit", 32 cl::init(-1), cl::Hidden); 33 static cl::opt<int> ReduceLimit2Addr("t2-reduce-limit2", 34 cl::init(-1), cl::Hidden); 35 static cl::opt<int> ReduceLimitLdSt("t2-reduce-limit3", 36 cl::init(-1), cl::Hidden); 37 38 namespace { 39 /// ReduceTable - A static table with information on mapping from wide 40 /// opcodes to narrow 41 struct ReduceEntry { 42 unsigned WideOpc; // Wide opcode 43 unsigned NarrowOpc1; // Narrow opcode to transform to 44 unsigned NarrowOpc2; // Narrow opcode when it's two-address 45 uint8_t Imm1Limit; // Limit of immediate field (bits) 46 uint8_t Imm2Limit; // Limit of immediate field when it's two-address 47 unsigned LowRegs1 : 1; // Only possible if low-registers are used 48 unsigned LowRegs2 : 1; // Only possible if low-registers are used (2addr) 49 unsigned PredCC1 : 2; // 0 - If predicated, cc is on and vice versa. 50 // 1 - No cc field. 51 // 2 - Always set CPSR. 52 unsigned PredCC2 : 2; 53 unsigned PartFlag : 1; // 16-bit instruction does partial flag update 54 unsigned Special : 1; // Needs to be dealt with specially 55 }; 56 57 static const ReduceEntry ReduceTable[] = { 58 // Wide, Narrow1, Narrow2, imm1,imm2, lo1, lo2, P/C, PF, S 59 { ARM::t2ADCrr, 0, ARM::tADC, 0, 0, 0, 1, 0,0, 0,0 }, 60 { ARM::t2ADDri, ARM::tADDi3, ARM::tADDi8, 3, 8, 1, 1, 0,0, 0,1 }, 61 { ARM::t2ADDrr, ARM::tADDrr, ARM::tADDhirr, 0, 0, 1, 0, 0,1, 0,0 }, 62 { ARM::t2ADDSri,ARM::tADDi3, ARM::tADDi8, 3, 8, 1, 1, 2,2, 0,1 }, 63 { ARM::t2ADDSrr,ARM::tADDrr, 0, 0, 0, 1, 0, 2,0, 0,1 }, 64 { ARM::t2ANDrr, 0, ARM::tAND, 0, 0, 0, 1, 0,0, 1,0 }, 65 { ARM::t2ASRri, ARM::tASRri, 0, 5, 0, 1, 0, 0,0, 1,0 }, 66 { ARM::t2ASRrr, 0, ARM::tASRrr, 0, 0, 0, 1, 0,0, 1,0 }, 67 { ARM::t2BICrr, 0, ARM::tBIC, 0, 0, 0, 1, 0,0, 1,0 }, 68 //FIXME: Disable CMN, as CCodes are backwards from compare expectations 69 //{ ARM::t2CMNrr, ARM::tCMN, 0, 0, 0, 1, 0, 2,0, 0,0 }, 70 { ARM::t2CMPri, ARM::tCMPi8, 0, 8, 0, 1, 0, 2,0, 0,0 }, 71 { ARM::t2CMPrr, ARM::tCMPhir, 0, 0, 0, 0, 0, 2,0, 0,1 }, 72 { ARM::t2EORrr, 0, ARM::tEOR, 0, 0, 0, 1, 0,0, 1,0 }, 73 // FIXME: adr.n immediate offset must be multiple of 4. 74 //{ ARM::t2LEApcrelJT,ARM::tLEApcrelJT, 0, 0, 0, 1, 0, 1,0, 0,0 }, 75 { ARM::t2LSLri, ARM::tLSLri, 0, 5, 0, 1, 0, 0,0, 1,0 }, 76 { ARM::t2LSLrr, 0, ARM::tLSLrr, 0, 0, 0, 1, 0,0, 1,0 }, 77 { ARM::t2LSRri, ARM::tLSRri, 0, 5, 0, 1, 0, 0,0, 1,0 }, 78 { ARM::t2LSRrr, 0, ARM::tLSRrr, 0, 0, 0, 1, 0,0, 1,0 }, 79 // FIXME: tMOVi8 and tMVN also partially update CPSR but they are less 80 // likely to cause issue in the loop. As a size / performance workaround, 81 // they are not marked as such. 82 { ARM::t2MOVi, ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 0,0 }, 83 { ARM::t2MOVi16,ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 0,1 }, 84 // FIXME: Do we need the 16-bit 'S' variant? 85 { ARM::t2MOVr,ARM::tMOVr, 0, 0, 0, 0, 0, 1,0, 0,0 }, 86 { ARM::t2MUL, 0, ARM::tMUL, 0, 0, 0, 1, 0,0, 1,0 }, 87 { ARM::t2MVNr, ARM::tMVN, 0, 0, 0, 1, 0, 0,0, 0,0 }, 88 { ARM::t2ORRrr, 0, ARM::tORR, 0, 0, 0, 1, 0,0, 1,0 }, 89 { ARM::t2REV, ARM::tREV, 0, 0, 0, 1, 0, 1,0, 0,0 }, 90 { ARM::t2REV16, ARM::tREV16, 0, 0, 0, 1, 0, 1,0, 0,0 }, 91 { ARM::t2REVSH, ARM::tREVSH, 0, 0, 0, 1, 0, 1,0, 0,0 }, 92 { ARM::t2RORrr, 0, ARM::tROR, 0, 0, 0, 1, 0,0, 1,0 }, 93 { ARM::t2RSBri, ARM::tRSB, 0, 0, 0, 1, 0, 0,0, 0,1 }, 94 { ARM::t2RSBSri,ARM::tRSB, 0, 0, 0, 1, 0, 2,0, 0,1 }, 95 { ARM::t2SBCrr, 0, ARM::tSBC, 0, 0, 0, 1, 0,0, 0,0 }, 96 { ARM::t2SUBri, ARM::tSUBi3, ARM::tSUBi8, 3, 8, 1, 1, 0,0, 0,0 }, 97 { ARM::t2SUBrr, ARM::tSUBrr, 0, 0, 0, 1, 0, 0,0, 0,0 }, 98 { ARM::t2SUBSri,ARM::tSUBi3, ARM::tSUBi8, 3, 8, 1, 1, 2,2, 0,0 }, 99 { ARM::t2SUBSrr,ARM::tSUBrr, 0, 0, 0, 1, 0, 2,0, 0,0 }, 100 { ARM::t2SXTB, ARM::tSXTB, 0, 0, 0, 1, 0, 1,0, 0,1 }, 101 { ARM::t2SXTH, ARM::tSXTH, 0, 0, 0, 1, 0, 1,0, 0,1 }, 102 { ARM::t2TSTrr, ARM::tTST, 0, 0, 0, 1, 0, 2,0, 0,0 }, 103 { ARM::t2UXTB, ARM::tUXTB, 0, 0, 0, 1, 0, 1,0, 0,1 }, 104 { ARM::t2UXTH, ARM::tUXTH, 0, 0, 0, 1, 0, 1,0, 0,1 }, 105 106 // FIXME: Clean this up after splitting each Thumb load / store opcode 107 // into multiple ones. 108 { ARM::t2LDRi12,ARM::tLDRi, ARM::tLDRspi, 5, 8, 1, 0, 0,0, 0,1 }, 109 { ARM::t2LDRs, ARM::tLDRr, 0, 0, 0, 1, 0, 0,0, 0,1 }, 110 { ARM::t2LDRBi12,ARM::tLDRBi, 0, 5, 0, 1, 0, 0,0, 0,1 }, 111 { ARM::t2LDRBs, ARM::tLDRBr, 0, 0, 0, 1, 0, 0,0, 0,1 }, 112 { ARM::t2LDRHi12,ARM::tLDRHi, 0, 5, 0, 1, 0, 0,0, 0,1 }, 113 { ARM::t2LDRHs, ARM::tLDRHr, 0, 0, 0, 1, 0, 0,0, 0,1 }, 114 { ARM::t2LDRSBs,ARM::tLDRSB, 0, 0, 0, 1, 0, 0,0, 0,1 }, 115 { ARM::t2LDRSHs,ARM::tLDRSH, 0, 0, 0, 1, 0, 0,0, 0,1 }, 116 { ARM::t2STRi12,ARM::tSTRi, ARM::tSTRspi, 5, 8, 1, 0, 0,0, 0,1 }, 117 { ARM::t2STRs, ARM::tSTRr, 0, 0, 0, 1, 0, 0,0, 0,1 }, 118 { ARM::t2STRBi12,ARM::tSTRBi, 0, 5, 0, 1, 0, 0,0, 0,1 }, 119 { ARM::t2STRBs, ARM::tSTRBr, 0, 0, 0, 1, 0, 0,0, 0,1 }, 120 { ARM::t2STRHi12,ARM::tSTRHi, 0, 5, 0, 1, 0, 0,0, 0,1 }, 121 { ARM::t2STRHs, ARM::tSTRHr, 0, 0, 0, 1, 0, 0,0, 0,1 }, 122 123 { ARM::t2LDMIA, ARM::tLDMIA, 0, 0, 0, 1, 1, 1,1, 0,1 }, 124 { ARM::t2LDMIA_RET,0, ARM::tPOP_RET, 0, 0, 1, 1, 1,1, 0,1 }, 125 { ARM::t2LDMIA_UPD,ARM::tLDMIA_UPD,ARM::tPOP,0, 0, 1, 1, 1,1, 0,1 }, 126 // ARM::t2STM (with no basereg writeback) has no Thumb1 equivalent 127 { ARM::t2STMIA_UPD,ARM::tSTMIA_UPD, 0, 0, 0, 1, 1, 1,1, 0,1 }, 128 { ARM::t2STMDB_UPD, 0, ARM::tPUSH, 0, 0, 1, 1, 1,1, 0,1 }, 129 }; 130 131 class Thumb2SizeReduce : public MachineFunctionPass { 132 public: 133 static char ID; 134 Thumb2SizeReduce(); 135 136 const Thumb2InstrInfo *TII; 137 const ARMSubtarget *STI; 138 139 virtual bool runOnMachineFunction(MachineFunction &MF); 140 141 virtual const char *getPassName() const { 142 return "Thumb2 instruction size reduction pass"; 143 } 144 145 private: 146 /// ReduceOpcodeMap - Maps wide opcode to index of entry in ReduceTable. 147 DenseMap<unsigned, unsigned> ReduceOpcodeMap; 148 149 bool canAddPseudoFlagDep(MachineInstr *Def, MachineInstr *Use); 150 151 bool VerifyPredAndCC(MachineInstr *MI, const ReduceEntry &Entry, 152 bool is2Addr, ARMCC::CondCodes Pred, 153 bool LiveCPSR, bool &HasCC, bool &CCDead); 154 155 bool ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI, 156 const ReduceEntry &Entry); 157 158 bool ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI, 159 const ReduceEntry &Entry, bool LiveCPSR, 160 MachineInstr *CPSRDef); 161 162 /// ReduceTo2Addr - Reduce a 32-bit instruction to a 16-bit two-address 163 /// instruction. 164 bool ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI, 165 const ReduceEntry &Entry, 166 bool LiveCPSR, MachineInstr *CPSRDef); 167 168 /// ReduceToNarrow - Reduce a 32-bit instruction to a 16-bit 169 /// non-two-address instruction. 170 bool ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI, 171 const ReduceEntry &Entry, 172 bool LiveCPSR, MachineInstr *CPSRDef); 173 174 /// ReduceMBB - Reduce width of instructions in the specified basic block. 175 bool ReduceMBB(MachineBasicBlock &MBB); 176 }; 177 char Thumb2SizeReduce::ID = 0; 178 } 179 180 Thumb2SizeReduce::Thumb2SizeReduce() : MachineFunctionPass(ID) { 181 for (unsigned i = 0, e = array_lengthof(ReduceTable); i != e; ++i) { 182 unsigned FromOpc = ReduceTable[i].WideOpc; 183 if (!ReduceOpcodeMap.insert(std::make_pair(FromOpc, i)).second) 184 assert(false && "Duplicated entries?"); 185 } 186 } 187 188 static bool HasImplicitCPSRDef(const MCInstrDesc &MCID) { 189 for (const unsigned *Regs = MCID.ImplicitDefs; *Regs; ++Regs) 190 if (*Regs == ARM::CPSR) 191 return true; 192 return false; 193 } 194 195 /// canAddPseudoFlagDep - For A9 (and other out-of-order) implementations, 196 /// the 's' 16-bit instruction partially update CPSR. Abort the 197 /// transformation to avoid adding false dependency on last CPSR setting 198 /// instruction which hurts the ability for out-of-order execution engine 199 /// to do register renaming magic. 200 /// This function checks if there is a read-of-write dependency between the 201 /// last instruction that defines the CPSR and the current instruction. If there 202 /// is, then there is no harm done since the instruction cannot be retired 203 /// before the CPSR setting instruction anyway. 204 /// Note, we are not doing full dependency analysis here for the sake of compile 205 /// time. We're not looking for cases like: 206 /// r0 = muls ... 207 /// r1 = add.w r0, ... 208 /// ... 209 /// = mul.w r1 210 /// In this case it would have been ok to narrow the mul.w to muls since there 211 /// are indirect RAW dependency between the muls and the mul.w 212 bool 213 Thumb2SizeReduce::canAddPseudoFlagDep(MachineInstr *Def, MachineInstr *Use) { 214 if (!Def || !STI->avoidCPSRPartialUpdate()) 215 return false; 216 217 SmallSet<unsigned, 2> Defs; 218 for (unsigned i = 0, e = Def->getNumOperands(); i != e; ++i) { 219 const MachineOperand &MO = Def->getOperand(i); 220 if (!MO.isReg() || MO.isUndef() || MO.isUse()) 221 continue; 222 unsigned Reg = MO.getReg(); 223 if (Reg == 0 || Reg == ARM::CPSR) 224 continue; 225 Defs.insert(Reg); 226 } 227 228 for (unsigned i = 0, e = Use->getNumOperands(); i != e; ++i) { 229 const MachineOperand &MO = Use->getOperand(i); 230 if (!MO.isReg() || MO.isUndef() || MO.isDef()) 231 continue; 232 unsigned Reg = MO.getReg(); 233 if (Defs.count(Reg)) 234 return false; 235 } 236 237 // No read-after-write dependency. The narrowing will add false dependency. 238 return true; 239 } 240 241 bool 242 Thumb2SizeReduce::VerifyPredAndCC(MachineInstr *MI, const ReduceEntry &Entry, 243 bool is2Addr, ARMCC::CondCodes Pred, 244 bool LiveCPSR, bool &HasCC, bool &CCDead) { 245 if ((is2Addr && Entry.PredCC2 == 0) || 246 (!is2Addr && Entry.PredCC1 == 0)) { 247 if (Pred == ARMCC::AL) { 248 // Not predicated, must set CPSR. 249 if (!HasCC) { 250 // Original instruction was not setting CPSR, but CPSR is not 251 // currently live anyway. It's ok to set it. The CPSR def is 252 // dead though. 253 if (!LiveCPSR) { 254 HasCC = true; 255 CCDead = true; 256 return true; 257 } 258 return false; 259 } 260 } else { 261 // Predicated, must not set CPSR. 262 if (HasCC) 263 return false; 264 } 265 } else if ((is2Addr && Entry.PredCC2 == 2) || 266 (!is2Addr && Entry.PredCC1 == 2)) { 267 /// Old opcode has an optional def of CPSR. 268 if (HasCC) 269 return true; 270 // If old opcode does not implicitly define CPSR, then it's not ok since 271 // these new opcodes' CPSR def is not meant to be thrown away. e.g. CMP. 272 if (!HasImplicitCPSRDef(MI->getDesc())) 273 return false; 274 HasCC = true; 275 } else { 276 // 16-bit instruction does not set CPSR. 277 if (HasCC) 278 return false; 279 } 280 281 return true; 282 } 283 284 static bool VerifyLowRegs(MachineInstr *MI) { 285 unsigned Opc = MI->getOpcode(); 286 bool isPCOk = (Opc == ARM::t2LDMIA_RET || Opc == ARM::t2LDMIA || 287 Opc == ARM::t2LDMDB || Opc == ARM::t2LDMIA_UPD || 288 Opc == ARM::t2LDMDB_UPD); 289 bool isLROk = (Opc == ARM::t2STMIA_UPD || Opc == ARM::t2STMDB_UPD); 290 bool isSPOk = isPCOk || isLROk; 291 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { 292 const MachineOperand &MO = MI->getOperand(i); 293 if (!MO.isReg() || MO.isImplicit()) 294 continue; 295 unsigned Reg = MO.getReg(); 296 if (Reg == 0 || Reg == ARM::CPSR) 297 continue; 298 if (isPCOk && Reg == ARM::PC) 299 continue; 300 if (isLROk && Reg == ARM::LR) 301 continue; 302 if (Reg == ARM::SP) { 303 if (isSPOk) 304 continue; 305 if (i == 1 && (Opc == ARM::t2LDRi12 || Opc == ARM::t2STRi12)) 306 // Special case for these ldr / str with sp as base register. 307 continue; 308 } 309 if (!isARMLowRegister(Reg)) 310 return false; 311 } 312 return true; 313 } 314 315 bool 316 Thumb2SizeReduce::ReduceLoadStore(MachineBasicBlock &MBB, MachineInstr *MI, 317 const ReduceEntry &Entry) { 318 if (ReduceLimitLdSt != -1 && ((int)NumLdSts >= ReduceLimitLdSt)) 319 return false; 320 321 unsigned Scale = 1; 322 bool HasImmOffset = false; 323 bool HasShift = false; 324 bool HasOffReg = true; 325 bool isLdStMul = false; 326 unsigned Opc = Entry.NarrowOpc1; 327 unsigned OpNum = 3; // First 'rest' of operands. 328 uint8_t ImmLimit = Entry.Imm1Limit; 329 330 switch (Entry.WideOpc) { 331 default: 332 llvm_unreachable("Unexpected Thumb2 load / store opcode!"); 333 case ARM::t2LDRi12: 334 case ARM::t2STRi12: 335 if (MI->getOperand(1).getReg() == ARM::SP) { 336 Opc = Entry.NarrowOpc2; 337 ImmLimit = Entry.Imm2Limit; 338 HasOffReg = false; 339 } 340 341 Scale = 4; 342 HasImmOffset = true; 343 HasOffReg = false; 344 break; 345 case ARM::t2LDRBi12: 346 case ARM::t2STRBi12: 347 HasImmOffset = true; 348 HasOffReg = false; 349 break; 350 case ARM::t2LDRHi12: 351 case ARM::t2STRHi12: 352 Scale = 2; 353 HasImmOffset = true; 354 HasOffReg = false; 355 break; 356 case ARM::t2LDRs: 357 case ARM::t2LDRBs: 358 case ARM::t2LDRHs: 359 case ARM::t2LDRSBs: 360 case ARM::t2LDRSHs: 361 case ARM::t2STRs: 362 case ARM::t2STRBs: 363 case ARM::t2STRHs: 364 HasShift = true; 365 OpNum = 4; 366 break; 367 case ARM::t2LDMIA: 368 case ARM::t2LDMDB: { 369 unsigned BaseReg = MI->getOperand(0).getReg(); 370 if (!isARMLowRegister(BaseReg) || Entry.WideOpc != ARM::t2LDMIA) 371 return false; 372 373 // For the non-writeback version (this one), the base register must be 374 // one of the registers being loaded. 375 bool isOK = false; 376 for (unsigned i = 4; i < MI->getNumOperands(); ++i) { 377 if (MI->getOperand(i).getReg() == BaseReg) { 378 isOK = true; 379 break; 380 } 381 } 382 383 if (!isOK) 384 return false; 385 386 OpNum = 0; 387 isLdStMul = true; 388 break; 389 } 390 case ARM::t2LDMIA_RET: { 391 unsigned BaseReg = MI->getOperand(1).getReg(); 392 if (BaseReg != ARM::SP) 393 return false; 394 Opc = Entry.NarrowOpc2; // tPOP_RET 395 OpNum = 2; 396 isLdStMul = true; 397 break; 398 } 399 case ARM::t2LDMIA_UPD: 400 case ARM::t2LDMDB_UPD: 401 case ARM::t2STMIA_UPD: 402 case ARM::t2STMDB_UPD: { 403 OpNum = 0; 404 405 unsigned BaseReg = MI->getOperand(1).getReg(); 406 if (BaseReg == ARM::SP && 407 (Entry.WideOpc == ARM::t2LDMIA_UPD || 408 Entry.WideOpc == ARM::t2STMDB_UPD)) { 409 Opc = Entry.NarrowOpc2; // tPOP or tPUSH 410 OpNum = 2; 411 } else if (!isARMLowRegister(BaseReg) || 412 (Entry.WideOpc != ARM::t2LDMIA_UPD && 413 Entry.WideOpc != ARM::t2STMIA_UPD)) { 414 return false; 415 } 416 417 isLdStMul = true; 418 break; 419 } 420 } 421 422 unsigned OffsetReg = 0; 423 bool OffsetKill = false; 424 if (HasShift) { 425 OffsetReg = MI->getOperand(2).getReg(); 426 OffsetKill = MI->getOperand(2).isKill(); 427 428 if (MI->getOperand(3).getImm()) 429 // Thumb1 addressing mode doesn't support shift. 430 return false; 431 } 432 433 unsigned OffsetImm = 0; 434 if (HasImmOffset) { 435 OffsetImm = MI->getOperand(2).getImm(); 436 unsigned MaxOffset = ((1 << ImmLimit) - 1) * Scale; 437 438 if ((OffsetImm & (Scale - 1)) || OffsetImm > MaxOffset) 439 // Make sure the immediate field fits. 440 return false; 441 } 442 443 // Add the 16-bit load / store instruction. 444 DebugLoc dl = MI->getDebugLoc(); 445 MachineInstrBuilder MIB = BuildMI(MBB, *MI, dl, TII->get(Opc)); 446 if (!isLdStMul) { 447 MIB.addOperand(MI->getOperand(0)); 448 MIB.addOperand(MI->getOperand(1)); 449 450 if (HasImmOffset) 451 MIB.addImm(OffsetImm / Scale); 452 453 assert((!HasShift || OffsetReg) && "Invalid so_reg load / store address!"); 454 455 if (HasOffReg) 456 MIB.addReg(OffsetReg, getKillRegState(OffsetKill)); 457 } 458 459 // Transfer the rest of operands. 460 for (unsigned e = MI->getNumOperands(); OpNum != e; ++OpNum) 461 MIB.addOperand(MI->getOperand(OpNum)); 462 463 // Transfer memoperands. 464 MIB->setMemRefs(MI->memoperands_begin(), MI->memoperands_end()); 465 466 // Transfer MI flags. 467 MIB.setMIFlags(MI->getFlags()); 468 469 DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " << *MIB); 470 471 MBB.erase(MI); 472 ++NumLdSts; 473 return true; 474 } 475 476 bool 477 Thumb2SizeReduce::ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI, 478 const ReduceEntry &Entry, 479 bool LiveCPSR, MachineInstr *CPSRDef) { 480 unsigned Opc = MI->getOpcode(); 481 if (Opc == ARM::t2ADDri) { 482 // If the source register is SP, try to reduce to tADDrSPi, otherwise 483 // it's a normal reduce. 484 if (MI->getOperand(1).getReg() != ARM::SP) { 485 if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, CPSRDef)) 486 return true; 487 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef); 488 } 489 // Try to reduce to tADDrSPi. 490 unsigned Imm = MI->getOperand(2).getImm(); 491 // The immediate must be in range, the destination register must be a low 492 // reg, the predicate must be "always" and the condition flags must not 493 // be being set. 494 if (Imm & 3 || Imm > 1020) 495 return false; 496 if (!isARMLowRegister(MI->getOperand(0).getReg())) 497 return false; 498 if (MI->getOperand(3).getImm() != ARMCC::AL) 499 return false; 500 const MCInstrDesc &MCID = MI->getDesc(); 501 if (MCID.hasOptionalDef() && 502 MI->getOperand(MCID.getNumOperands()-1).getReg() == ARM::CPSR) 503 return false; 504 505 MachineInstrBuilder MIB = BuildMI(MBB, *MI, MI->getDebugLoc(), 506 TII->get(ARM::tADDrSPi)) 507 .addOperand(MI->getOperand(0)) 508 .addOperand(MI->getOperand(1)) 509 .addImm(Imm / 4); // The tADDrSPi has an implied scale by four. 510 AddDefaultPred(MIB); 511 512 // Transfer MI flags. 513 MIB.setMIFlags(MI->getFlags()); 514 515 DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " <<*MIB); 516 517 MBB.erase(MI); 518 ++NumNarrows; 519 return true; 520 } 521 522 if (Entry.LowRegs1 && !VerifyLowRegs(MI)) 523 return false; 524 525 const MCInstrDesc &MCID = MI->getDesc(); 526 if (MCID.mayLoad() || MCID.mayStore()) 527 return ReduceLoadStore(MBB, MI, Entry); 528 529 switch (Opc) { 530 default: break; 531 case ARM::t2ADDSri: 532 case ARM::t2ADDSrr: { 533 unsigned PredReg = 0; 534 if (getInstrPredicate(MI, PredReg) == ARMCC::AL) { 535 switch (Opc) { 536 default: break; 537 case ARM::t2ADDSri: { 538 if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, CPSRDef)) 539 return true; 540 // fallthrough 541 } 542 case ARM::t2ADDSrr: 543 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef); 544 } 545 } 546 break; 547 } 548 case ARM::t2RSBri: 549 case ARM::t2RSBSri: 550 case ARM::t2SXTB: 551 case ARM::t2SXTH: 552 case ARM::t2UXTB: 553 case ARM::t2UXTH: 554 if (MI->getOperand(2).getImm() == 0) 555 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef); 556 break; 557 case ARM::t2MOVi16: 558 // Can convert only 'pure' immediate operands, not immediates obtained as 559 // globals' addresses. 560 if (MI->getOperand(1).isImm()) 561 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef); 562 break; 563 case ARM::t2CMPrr: { 564 // Try to reduce to the lo-reg only version first. Why there are two 565 // versions of the instruction is a mystery. 566 // It would be nice to just have two entries in the master table that 567 // are prioritized, but the table assumes a unique entry for each 568 // source insn opcode. So for now, we hack a local entry record to use. 569 static const ReduceEntry NarrowEntry = 570 { ARM::t2CMPrr,ARM::tCMPr, 0, 0, 0, 1, 1,2, 0, 0,1 }; 571 if (ReduceToNarrow(MBB, MI, NarrowEntry, LiveCPSR, CPSRDef)) 572 return true; 573 return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef); 574 } 575 } 576 return false; 577 } 578 579 bool 580 Thumb2SizeReduce::ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI, 581 const ReduceEntry &Entry, 582 bool LiveCPSR, MachineInstr *CPSRDef) { 583 584 if (ReduceLimit2Addr != -1 && ((int)Num2Addrs >= ReduceLimit2Addr)) 585 return false; 586 587 unsigned Reg0 = MI->getOperand(0).getReg(); 588 unsigned Reg1 = MI->getOperand(1).getReg(); 589 if (Reg0 != Reg1) { 590 // Try to commute the operands to make it a 2-address instruction. 591 unsigned CommOpIdx1, CommOpIdx2; 592 if (!TII->findCommutedOpIndices(MI, CommOpIdx1, CommOpIdx2) || 593 CommOpIdx1 != 1 || MI->getOperand(CommOpIdx2).getReg() != Reg0) 594 return false; 595 MachineInstr *CommutedMI = TII->commuteInstruction(MI); 596 if (!CommutedMI) 597 return false; 598 } 599 if (Entry.LowRegs2 && !isARMLowRegister(Reg0)) 600 return false; 601 if (Entry.Imm2Limit) { 602 unsigned Imm = MI->getOperand(2).getImm(); 603 unsigned Limit = (1 << Entry.Imm2Limit) - 1; 604 if (Imm > Limit) 605 return false; 606 } else { 607 unsigned Reg2 = MI->getOperand(2).getReg(); 608 if (Entry.LowRegs2 && !isARMLowRegister(Reg2)) 609 return false; 610 } 611 612 // Check if it's possible / necessary to transfer the predicate. 613 const MCInstrDesc &NewMCID = TII->get(Entry.NarrowOpc2); 614 unsigned PredReg = 0; 615 ARMCC::CondCodes Pred = getInstrPredicate(MI, PredReg); 616 bool SkipPred = false; 617 if (Pred != ARMCC::AL) { 618 if (!NewMCID.isPredicable()) 619 // Can't transfer predicate, fail. 620 return false; 621 } else { 622 SkipPred = !NewMCID.isPredicable(); 623 } 624 625 bool HasCC = false; 626 bool CCDead = false; 627 const MCInstrDesc &MCID = MI->getDesc(); 628 if (MCID.hasOptionalDef()) { 629 unsigned NumOps = MCID.getNumOperands(); 630 HasCC = (MI->getOperand(NumOps-1).getReg() == ARM::CPSR); 631 if (HasCC && MI->getOperand(NumOps-1).isDead()) 632 CCDead = true; 633 } 634 if (!VerifyPredAndCC(MI, Entry, true, Pred, LiveCPSR, HasCC, CCDead)) 635 return false; 636 637 // Avoid adding a false dependency on partial flag update by some 16-bit 638 // instructions which has the 's' bit set. 639 if (Entry.PartFlag && NewMCID.hasOptionalDef() && HasCC && 640 canAddPseudoFlagDep(CPSRDef, MI)) 641 return false; 642 643 // Add the 16-bit instruction. 644 DebugLoc dl = MI->getDebugLoc(); 645 MachineInstrBuilder MIB = BuildMI(MBB, *MI, dl, NewMCID); 646 MIB.addOperand(MI->getOperand(0)); 647 if (NewMCID.hasOptionalDef()) { 648 if (HasCC) 649 AddDefaultT1CC(MIB, CCDead); 650 else 651 AddNoT1CC(MIB); 652 } 653 654 // Transfer the rest of operands. 655 unsigned NumOps = MCID.getNumOperands(); 656 for (unsigned i = 1, e = MI->getNumOperands(); i != e; ++i) { 657 if (i < NumOps && MCID.OpInfo[i].isOptionalDef()) 658 continue; 659 if (SkipPred && MCID.OpInfo[i].isPredicate()) 660 continue; 661 MIB.addOperand(MI->getOperand(i)); 662 } 663 664 // Transfer MI flags. 665 MIB.setMIFlags(MI->getFlags()); 666 667 DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " << *MIB); 668 669 MBB.erase(MI); 670 ++Num2Addrs; 671 return true; 672 } 673 674 bool 675 Thumb2SizeReduce::ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI, 676 const ReduceEntry &Entry, 677 bool LiveCPSR, MachineInstr *CPSRDef) { 678 if (ReduceLimit != -1 && ((int)NumNarrows >= ReduceLimit)) 679 return false; 680 681 unsigned Limit = ~0U; 682 if (Entry.Imm1Limit) 683 Limit = (1 << Entry.Imm1Limit) - 1; 684 685 const MCInstrDesc &MCID = MI->getDesc(); 686 for (unsigned i = 0, e = MCID.getNumOperands(); i != e; ++i) { 687 if (MCID.OpInfo[i].isPredicate()) 688 continue; 689 const MachineOperand &MO = MI->getOperand(i); 690 if (MO.isReg()) { 691 unsigned Reg = MO.getReg(); 692 if (!Reg || Reg == ARM::CPSR) 693 continue; 694 if (Entry.LowRegs1 && !isARMLowRegister(Reg)) 695 return false; 696 } else if (MO.isImm() && 697 !MCID.OpInfo[i].isPredicate()) { 698 if (((unsigned)MO.getImm()) > Limit) 699 return false; 700 } 701 } 702 703 // Check if it's possible / necessary to transfer the predicate. 704 const MCInstrDesc &NewMCID = TII->get(Entry.NarrowOpc1); 705 unsigned PredReg = 0; 706 ARMCC::CondCodes Pred = getInstrPredicate(MI, PredReg); 707 bool SkipPred = false; 708 if (Pred != ARMCC::AL) { 709 if (!NewMCID.isPredicable()) 710 // Can't transfer predicate, fail. 711 return false; 712 } else { 713 SkipPred = !NewMCID.isPredicable(); 714 } 715 716 bool HasCC = false; 717 bool CCDead = false; 718 if (MCID.hasOptionalDef()) { 719 unsigned NumOps = MCID.getNumOperands(); 720 HasCC = (MI->getOperand(NumOps-1).getReg() == ARM::CPSR); 721 if (HasCC && MI->getOperand(NumOps-1).isDead()) 722 CCDead = true; 723 } 724 if (!VerifyPredAndCC(MI, Entry, false, Pred, LiveCPSR, HasCC, CCDead)) 725 return false; 726 727 // Avoid adding a false dependency on partial flag update by some 16-bit 728 // instructions which has the 's' bit set. 729 if (Entry.PartFlag && NewMCID.hasOptionalDef() && HasCC && 730 canAddPseudoFlagDep(CPSRDef, MI)) 731 return false; 732 733 // Add the 16-bit instruction. 734 DebugLoc dl = MI->getDebugLoc(); 735 MachineInstrBuilder MIB = BuildMI(MBB, *MI, dl, NewMCID); 736 MIB.addOperand(MI->getOperand(0)); 737 if (NewMCID.hasOptionalDef()) { 738 if (HasCC) 739 AddDefaultT1CC(MIB, CCDead); 740 else 741 AddNoT1CC(MIB); 742 } 743 744 // Transfer the rest of operands. 745 unsigned NumOps = MCID.getNumOperands(); 746 for (unsigned i = 1, e = MI->getNumOperands(); i != e; ++i) { 747 if (i < NumOps && MCID.OpInfo[i].isOptionalDef()) 748 continue; 749 if ((MCID.getOpcode() == ARM::t2RSBSri || 750 MCID.getOpcode() == ARM::t2RSBri || 751 MCID.getOpcode() == ARM::t2SXTB || 752 MCID.getOpcode() == ARM::t2SXTH || 753 MCID.getOpcode() == ARM::t2UXTB || 754 MCID.getOpcode() == ARM::t2UXTH) && i == 2) 755 // Skip the zero immediate operand, it's now implicit. 756 continue; 757 bool isPred = (i < NumOps && MCID.OpInfo[i].isPredicate()); 758 if (SkipPred && isPred) 759 continue; 760 const MachineOperand &MO = MI->getOperand(i); 761 if (MO.isReg() && MO.isImplicit() && MO.getReg() == ARM::CPSR) 762 // Skip implicit def of CPSR. Either it's modeled as an optional 763 // def now or it's already an implicit def on the new instruction. 764 continue; 765 MIB.addOperand(MO); 766 } 767 if (!MCID.isPredicable() && NewMCID.isPredicable()) 768 AddDefaultPred(MIB); 769 770 // Transfer MI flags. 771 MIB.setMIFlags(MI->getFlags()); 772 773 DEBUG(errs() << "Converted 32-bit: " << *MI << " to 16-bit: " << *MIB); 774 775 MBB.erase(MI); 776 ++NumNarrows; 777 return true; 778 } 779 780 static bool UpdateCPSRDef(MachineInstr &MI, bool LiveCPSR, bool &DefCPSR) { 781 bool HasDef = false; 782 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { 783 const MachineOperand &MO = MI.getOperand(i); 784 if (!MO.isReg() || MO.isUndef() || MO.isUse()) 785 continue; 786 if (MO.getReg() != ARM::CPSR) 787 continue; 788 789 DefCPSR = true; 790 if (!MO.isDead()) 791 HasDef = true; 792 } 793 794 return HasDef || LiveCPSR; 795 } 796 797 static bool UpdateCPSRUse(MachineInstr &MI, bool LiveCPSR) { 798 for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { 799 const MachineOperand &MO = MI.getOperand(i); 800 if (!MO.isReg() || MO.isUndef() || MO.isDef()) 801 continue; 802 if (MO.getReg() != ARM::CPSR) 803 continue; 804 assert(LiveCPSR && "CPSR liveness tracking is wrong!"); 805 if (MO.isKill()) { 806 LiveCPSR = false; 807 break; 808 } 809 } 810 811 return LiveCPSR; 812 } 813 814 bool Thumb2SizeReduce::ReduceMBB(MachineBasicBlock &MBB) { 815 bool Modified = false; 816 817 // Yes, CPSR could be livein. 818 bool LiveCPSR = MBB.isLiveIn(ARM::CPSR); 819 MachineInstr *CPSRDef = 0; 820 821 MachineBasicBlock::iterator MII = MBB.begin(), E = MBB.end(); 822 MachineBasicBlock::iterator NextMII; 823 for (; MII != E; MII = NextMII) { 824 NextMII = llvm::next(MII); 825 826 MachineInstr *MI = &*MII; 827 LiveCPSR = UpdateCPSRUse(*MI, LiveCPSR); 828 829 unsigned Opcode = MI->getOpcode(); 830 DenseMap<unsigned, unsigned>::iterator OPI = ReduceOpcodeMap.find(Opcode); 831 if (OPI != ReduceOpcodeMap.end()) { 832 const ReduceEntry &Entry = ReduceTable[OPI->second]; 833 // Ignore "special" cases for now. 834 if (Entry.Special) { 835 if (ReduceSpecial(MBB, MI, Entry, LiveCPSR, CPSRDef)) { 836 Modified = true; 837 MachineBasicBlock::iterator I = prior(NextMII); 838 MI = &*I; 839 } 840 goto ProcessNext; 841 } 842 843 // Try to transform to a 16-bit two-address instruction. 844 if (Entry.NarrowOpc2 && 845 ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, CPSRDef)) { 846 Modified = true; 847 MachineBasicBlock::iterator I = prior(NextMII); 848 MI = &*I; 849 goto ProcessNext; 850 } 851 852 // Try to transform to a 16-bit non-two-address instruction. 853 if (Entry.NarrowOpc1 && 854 ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef)) { 855 Modified = true; 856 MachineBasicBlock::iterator I = prior(NextMII); 857 MI = &*I; 858 } 859 } 860 861 ProcessNext: 862 bool DefCPSR = false; 863 LiveCPSR = UpdateCPSRDef(*MI, LiveCPSR, DefCPSR); 864 if (MI->getDesc().isCall()) 865 // Calls don't really set CPSR. 866 CPSRDef = 0; 867 else if (DefCPSR) 868 // This is the last CPSR defining instruction. 869 CPSRDef = MI; 870 } 871 872 return Modified; 873 } 874 875 bool Thumb2SizeReduce::runOnMachineFunction(MachineFunction &MF) { 876 const TargetMachine &TM = MF.getTarget(); 877 TII = static_cast<const Thumb2InstrInfo*>(TM.getInstrInfo()); 878 STI = &TM.getSubtarget<ARMSubtarget>(); 879 880 bool Modified = false; 881 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) 882 Modified |= ReduceMBB(*I); 883 return Modified; 884 } 885 886 /// createThumb2SizeReductionPass - Returns an instance of the Thumb2 size 887 /// reduction pass. 888 FunctionPass *llvm::createThumb2SizeReductionPass() { 889 return new Thumb2SizeReduce(); 890 } 891
