X86FloatingPoint.cpp revision f2e49d4c1a8839f30e8ca9617139d63db173fa80
1//===-- FloatingPoint.cpp - Floating point Reg -> Stack converter ---------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the pass which converts floating point instructions from 11// virtual registers into register stack instructions. 12// 13//===----------------------------------------------------------------------===// 14 15#define DEBUG_TYPE "fp" 16#include "X86.h" 17#include "X86InstrInfo.h" 18#include "llvm/CodeGen/MachineFunctionPass.h" 19#include "llvm/CodeGen/MachineInstrBuilder.h" 20#include "llvm/CodeGen/LiveVariables.h" 21#include "llvm/CodeGen/Passes.h" 22#include "llvm/Target/TargetInstrInfo.h" 23#include "llvm/Target/TargetMachine.h" 24#include "Support/Debug.h" 25#include "Support/Statistic.h" 26#include <algorithm> 27#include <iostream> 28using namespace llvm; 29 30namespace { 31 Statistic<> NumFXCH("x86-codegen", "Number of fxch instructions inserted"); 32 Statistic<> NumFP ("x86-codegen", "Number of floating point instructions"); 33 34 struct FPS : public MachineFunctionPass { 35 virtual bool runOnMachineFunction(MachineFunction &MF); 36 37 virtual const char *getPassName() const { return "X86 FP Stackifier"; } 38 39 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 40 AU.addRequired<LiveVariables>(); 41 MachineFunctionPass::getAnalysisUsage(AU); 42 } 43 private: 44 LiveVariables *LV; // Live variable info for current function... 45 MachineBasicBlock *MBB; // Current basic block 46 unsigned Stack[8]; // FP<n> Registers in each stack slot... 47 unsigned RegMap[8]; // Track which stack slot contains each register 48 unsigned StackTop; // The current top of the FP stack. 49 50 void dumpStack() const { 51 std::cerr << "Stack contents:"; 52 for (unsigned i = 0; i != StackTop; ++i) { 53 std::cerr << " FP" << Stack[i]; 54 assert(RegMap[Stack[i]] == i && "Stack[] doesn't match RegMap[]!"); 55 } 56 std::cerr << "\n"; 57 } 58 private: 59 // getSlot - Return the stack slot number a particular register number is 60 // in... 61 unsigned getSlot(unsigned RegNo) const { 62 assert(RegNo < 8 && "Regno out of range!"); 63 return RegMap[RegNo]; 64 } 65 66 // getStackEntry - Return the X86::FP<n> register in register ST(i) 67 unsigned getStackEntry(unsigned STi) const { 68 assert(STi < StackTop && "Access past stack top!"); 69 return Stack[StackTop-1-STi]; 70 } 71 72 // getSTReg - Return the X86::ST(i) register which contains the specified 73 // FP<RegNo> register 74 unsigned getSTReg(unsigned RegNo) const { 75 return StackTop - 1 - getSlot(RegNo) + llvm::X86::ST0; 76 } 77 78 // pushReg - Push the specifiex FP<n> register onto the stack 79 void pushReg(unsigned Reg) { 80 assert(Reg < 8 && "Register number out of range!"); 81 assert(StackTop < 8 && "Stack overflow!"); 82 Stack[StackTop] = Reg; 83 RegMap[Reg] = StackTop++; 84 } 85 86 bool isAtTop(unsigned RegNo) const { return getSlot(RegNo) == StackTop-1; } 87 void moveToTop(unsigned RegNo, MachineBasicBlock::iterator &I) { 88 if (!isAtTop(RegNo)) { 89 unsigned Slot = getSlot(RegNo); 90 unsigned STReg = getSTReg(RegNo); 91 unsigned RegOnTop = getStackEntry(0); 92 93 // Swap the slots the regs are in 94 std::swap(RegMap[RegNo], RegMap[RegOnTop]); 95 96 // Swap stack slot contents 97 assert(RegMap[RegOnTop] < StackTop); 98 std::swap(Stack[RegMap[RegOnTop]], Stack[StackTop-1]); 99 100 // Emit an fxch to update the runtime processors version of the state 101 MachineInstr *MI = BuildMI(X86::FXCH, 1).addReg(STReg); 102 I = 1+MBB->insert(I, MI); 103 NumFXCH++; 104 } 105 } 106 107 void duplicateToTop(unsigned RegNo, unsigned AsReg, 108 MachineBasicBlock::iterator &I) { 109 unsigned STReg = getSTReg(RegNo); 110 pushReg(AsReg); // New register on top of stack 111 112 MachineInstr *MI = BuildMI(X86::FLDrr, 1).addReg(STReg); 113 I = 1+MBB->insert(I, MI); 114 } 115 116 // popStackAfter - Pop the current value off of the top of the FP stack 117 // after the specified instruction. 118 void popStackAfter(MachineBasicBlock::iterator &I); 119 120 bool processBasicBlock(MachineFunction &MF, MachineBasicBlock &MBB); 121 122 void handleZeroArgFP(MachineBasicBlock::iterator &I); 123 void handleOneArgFP(MachineBasicBlock::iterator &I); 124 void handleTwoArgFP(MachineBasicBlock::iterator &I); 125 void handleSpecialFP(MachineBasicBlock::iterator &I); 126 }; 127} 128 129FunctionPass *llvm::createX86FloatingPointStackifierPass() { return new FPS(); } 130 131/// runOnMachineFunction - Loop over all of the basic blocks, transforming FP 132/// register references into FP stack references. 133/// 134bool FPS::runOnMachineFunction(MachineFunction &MF) { 135 LV = &getAnalysis<LiveVariables>(); 136 StackTop = 0; 137 138 bool Changed = false; 139 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) 140 Changed |= processBasicBlock(MF, *I); 141 return Changed; 142} 143 144/// processBasicBlock - Loop over all of the instructions in the basic block, 145/// transforming FP instructions into their stack form. 146/// 147bool FPS::processBasicBlock(MachineFunction &MF, MachineBasicBlock &BB) { 148 const TargetInstrInfo &TII = MF.getTarget().getInstrInfo(); 149 bool Changed = false; 150 MBB = &BB; 151 152 for (MachineBasicBlock::iterator I = BB.begin(); I != BB.end(); ++I) { 153 MachineInstr *MI = *I; 154 MachineInstr *PrevMI = I == BB.begin() ? 0 : *(I-1); 155 unsigned Flags = TII.get(MI->getOpcode()).TSFlags; 156 157 if ((Flags & X86II::FPTypeMask) == 0) continue; // Ignore non-fp insts! 158 159 ++NumFP; // Keep track of # of pseudo instrs 160 DEBUG(std::cerr << "\nFPInst:\t"; 161 MI->print(std::cerr, MF.getTarget())); 162 163 // Get dead variables list now because the MI pointer may be deleted as part 164 // of processing! 165 LiveVariables::killed_iterator IB = LV->dead_begin(MI); 166 LiveVariables::killed_iterator IE = LV->dead_end(MI); 167 168 DEBUG(const MRegisterInfo *MRI = MF.getTarget().getRegisterInfo(); 169 LiveVariables::killed_iterator I = LV->killed_begin(MI); 170 LiveVariables::killed_iterator E = LV->killed_end(MI); 171 if (I != E) { 172 std::cerr << "Killed Operands:"; 173 for (; I != E; ++I) 174 std::cerr << " %" << MRI->getName(I->second); 175 std::cerr << "\n"; 176 }); 177 178 switch (Flags & X86II::FPTypeMask) { 179 case X86II::ZeroArgFP: handleZeroArgFP(I); break; 180 case X86II::OneArgFP: handleOneArgFP(I); break; 181 182 case X86II::OneArgFPRW: // ST(0) = fsqrt(ST(0)) 183 assert(0 && "FP instr type not handled yet!"); 184 185 case X86II::TwoArgFP: handleTwoArgFP(I); break; 186 case X86II::SpecialFP: handleSpecialFP(I); break; 187 default: assert(0 && "Unknown FP Type!"); 188 } 189 190 // Check to see if any of the values defined by this instruction are dead 191 // after definition. If so, pop them. 192 for (; IB != IE; ++IB) { 193 unsigned Reg = IB->second; 194 if (Reg >= X86::FP0 && Reg <= X86::FP6) { 195 DEBUG(std::cerr << "Register FP#" << Reg-X86::FP0 << " is dead!\n"); 196 ++I; // Insert fxch AFTER the instruction 197 moveToTop(Reg-X86::FP0, I); // Insert fxch if necessary 198 --I; // Move to fxch or old instruction 199 popStackAfter(I); // Pop the top of the stack, killing value 200 } 201 } 202 203 // Print out all of the instructions expanded to if -debug 204 DEBUG(if (*I == PrevMI) { 205 std::cerr<< "Just deleted pseudo instruction\n"; 206 } else { 207 MachineBasicBlock::iterator Start = I; 208 // Rewind to first instruction newly inserted. 209 while (Start != BB.begin() && *(Start-1) != PrevMI) --Start; 210 std::cerr << "Inserted instructions:\n\t"; 211 (*Start)->print(std::cerr, MF.getTarget()); 212 while (++Start != I+1); 213 } 214 dumpStack(); 215 ); 216 217 Changed = true; 218 } 219 220 assert(StackTop == 0 && "Stack not empty at end of basic block?"); 221 return Changed; 222} 223 224//===----------------------------------------------------------------------===// 225// Efficient Lookup Table Support 226//===----------------------------------------------------------------------===// 227 228namespace { 229 struct TableEntry { 230 unsigned from; 231 unsigned to; 232 bool operator<(const TableEntry &TE) const { return from < TE.from; } 233 bool operator<(unsigned V) const { return from < V; } 234 }; 235} 236 237static bool TableIsSorted(const TableEntry *Table, unsigned NumEntries) { 238 for (unsigned i = 0; i != NumEntries-1; ++i) 239 if (!(Table[i] < Table[i+1])) return false; 240 return true; 241} 242 243static int Lookup(const TableEntry *Table, unsigned N, unsigned Opcode) { 244 const TableEntry *I = std::lower_bound(Table, Table+N, Opcode); 245 if (I != Table+N && I->from == Opcode) 246 return I->to; 247 return -1; 248} 249 250#define ARRAY_SIZE(TABLE) \ 251 (sizeof(TABLE)/sizeof(TABLE[0])) 252 253#ifdef NDEBUG 254#define ASSERT_SORTED(TABLE) 255#else 256#define ASSERT_SORTED(TABLE) \ 257 { static bool TABLE##Checked = false; \ 258 if (!TABLE##Checked) \ 259 assert(TableIsSorted(TABLE, ARRAY_SIZE(TABLE)) && \ 260 "All lookup tables must be sorted for efficient access!"); \ 261 } 262#endif 263 264 265//===----------------------------------------------------------------------===// 266// Helper Methods 267//===----------------------------------------------------------------------===// 268 269// PopTable - Sorted map of instructions to their popping version. The first 270// element is an instruction, the second is the version which pops. 271// 272static const TableEntry PopTable[] = { 273 { X86::FADDrST0 , X86::FADDPrST0 }, 274 275 { X86::FDIVRrST0, X86::FDIVRPrST0 }, 276 { X86::FDIVrST0 , X86::FDIVPrST0 }, 277 278 { X86::FISTr16 , X86::FISTPr16 }, 279 { X86::FISTr32 , X86::FISTPr32 }, 280 281 { X86::FMULrST0 , X86::FMULPrST0 }, 282 283 { X86::FSTr32 , X86::FSTPr32 }, 284 { X86::FSTr64 , X86::FSTPr64 }, 285 { X86::FSTrr , X86::FSTPrr }, 286 287 { X86::FSUBRrST0, X86::FSUBRPrST0 }, 288 { X86::FSUBrST0 , X86::FSUBPrST0 }, 289 290 { X86::FUCOMPr , X86::FUCOMPPr }, 291 { X86::FUCOMr , X86::FUCOMPr }, 292}; 293 294/// popStackAfter - Pop the current value off of the top of the FP stack after 295/// the specified instruction. This attempts to be sneaky and combine the pop 296/// into the instruction itself if possible. The iterator is left pointing to 297/// the last instruction, be it a new pop instruction inserted, or the old 298/// instruction if it was modified in place. 299/// 300void FPS::popStackAfter(MachineBasicBlock::iterator &I) { 301 ASSERT_SORTED(PopTable); 302 assert(StackTop > 0 && "Cannot pop empty stack!"); 303 RegMap[Stack[--StackTop]] = ~0; // Update state 304 305 // Check to see if there is a popping version of this instruction... 306 int Opcode = Lookup(PopTable, ARRAY_SIZE(PopTable), (*I)->getOpcode()); 307 if (Opcode != -1) { 308 (*I)->setOpcode(Opcode); 309 if (Opcode == X86::FUCOMPPr) 310 (*I)->RemoveOperand(0); 311 312 } else { // Insert an explicit pop 313 MachineInstr *MI = BuildMI(X86::FSTPrr, 1).addReg(X86::ST0); 314 I = MBB->insert(I+1, MI); 315 } 316} 317 318static unsigned getFPReg(const MachineOperand &MO) { 319 assert(MO.isPhysicalRegister() && "Expected an FP register!"); 320 unsigned Reg = MO.getReg(); 321 assert(Reg >= X86::FP0 && Reg <= X86::FP6 && "Expected FP register!"); 322 return Reg - X86::FP0; 323} 324 325 326//===----------------------------------------------------------------------===// 327// Instruction transformation implementation 328//===----------------------------------------------------------------------===// 329 330/// handleZeroArgFP - ST(0) = fld0 ST(0) = flds <mem> 331// 332void FPS::handleZeroArgFP(MachineBasicBlock::iterator &I) { 333 MachineInstr *MI = *I; 334 unsigned DestReg = getFPReg(MI->getOperand(0)); 335 MI->RemoveOperand(0); // Remove the explicit ST(0) operand 336 337 // Result gets pushed on the stack... 338 pushReg(DestReg); 339} 340 341/// handleOneArgFP - fst ST(0), <mem> 342// 343void FPS::handleOneArgFP(MachineBasicBlock::iterator &I) { 344 MachineInstr *MI = *I; 345 assert(MI->getNumOperands() == 5 && "Can only handle fst* instructions!"); 346 347 unsigned Reg = getFPReg(MI->getOperand(4)); 348 bool KillsSrc = false; 349 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI), 350 E = LV->killed_end(MI); KI != E; ++KI) 351 KillsSrc |= KI->second == X86::FP0+Reg; 352 353 // FSTPr80 and FISTPr64 are strange because there are no non-popping versions. 354 // If we have one _and_ we don't want to pop the operand, duplicate the value 355 // on the stack instead of moving it. This ensure that popping the value is 356 // always ok. 357 // 358 if ((MI->getOpcode() == X86::FSTPr80 || 359 MI->getOpcode() == X86::FISTPr64) && !KillsSrc) { 360 duplicateToTop(Reg, 7 /*temp register*/, I); 361 } else { 362 moveToTop(Reg, I); // Move to the top of the stack... 363 } 364 MI->RemoveOperand(4); // Remove explicit ST(0) operand 365 366 if (MI->getOpcode() == X86::FSTPr80 || MI->getOpcode() == X86::FISTPr64) { 367 assert(StackTop > 0 && "Stack empty??"); 368 --StackTop; 369 } else if (KillsSrc) { // Last use of operand? 370 popStackAfter(I); 371 } 372} 373 374//===----------------------------------------------------------------------===// 375// Define tables of various ways to map pseudo instructions 376// 377 378// ForwardST0Table - Map: A = B op C into: ST(0) = ST(0) op ST(i) 379static const TableEntry ForwardST0Table[] = { 380 { X86::FpADD, X86::FADDST0r }, 381 { X86::FpDIV, X86::FDIVST0r }, 382 { X86::FpMUL, X86::FMULST0r }, 383 { X86::FpSUB, X86::FSUBST0r }, 384 { X86::FpUCOM, X86::FUCOMr }, 385}; 386 387// ReverseST0Table - Map: A = B op C into: ST(0) = ST(i) op ST(0) 388static const TableEntry ReverseST0Table[] = { 389 { X86::FpADD, X86::FADDST0r }, // commutative 390 { X86::FpDIV, X86::FDIVRST0r }, 391 { X86::FpMUL, X86::FMULST0r }, // commutative 392 { X86::FpSUB, X86::FSUBRST0r }, 393 { X86::FpUCOM, ~0 }, 394}; 395 396// ForwardSTiTable - Map: A = B op C into: ST(i) = ST(0) op ST(i) 397static const TableEntry ForwardSTiTable[] = { 398 { X86::FpADD, X86::FADDrST0 }, // commutative 399 { X86::FpDIV, X86::FDIVRrST0 }, 400 { X86::FpMUL, X86::FMULrST0 }, // commutative 401 { X86::FpSUB, X86::FSUBRrST0 }, 402 { X86::FpUCOM, X86::FUCOMr }, 403}; 404 405// ReverseSTiTable - Map: A = B op C into: ST(i) = ST(i) op ST(0) 406static const TableEntry ReverseSTiTable[] = { 407 { X86::FpADD, X86::FADDrST0 }, 408 { X86::FpDIV, X86::FDIVrST0 }, 409 { X86::FpMUL, X86::FMULrST0 }, 410 { X86::FpSUB, X86::FSUBrST0 }, 411 { X86::FpUCOM, ~0 }, 412}; 413 414 415/// handleTwoArgFP - Handle instructions like FADD and friends which are virtual 416/// instructions which need to be simplified and possibly transformed. 417/// 418/// Result: ST(0) = fsub ST(0), ST(i) 419/// ST(i) = fsub ST(0), ST(i) 420/// ST(0) = fsubr ST(0), ST(i) 421/// ST(i) = fsubr ST(0), ST(i) 422/// 423/// In addition to three address instructions, this also handles the FpUCOM 424/// instruction which only has two operands, but no destination. This 425/// instruction is also annoying because there is no "reverse" form of it 426/// available. 427/// 428void FPS::handleTwoArgFP(MachineBasicBlock::iterator &I) { 429 ASSERT_SORTED(ForwardST0Table); ASSERT_SORTED(ReverseST0Table); 430 ASSERT_SORTED(ForwardSTiTable); ASSERT_SORTED(ReverseSTiTable); 431 MachineInstr *MI = *I; 432 433 unsigned NumOperands = MI->getNumOperands(); 434 assert(NumOperands == 3 || 435 (NumOperands == 2 && MI->getOpcode() == X86::FpUCOM) && 436 "Illegal TwoArgFP instruction!"); 437 unsigned Dest = getFPReg(MI->getOperand(0)); 438 unsigned Op0 = getFPReg(MI->getOperand(NumOperands-2)); 439 unsigned Op1 = getFPReg(MI->getOperand(NumOperands-1)); 440 bool KillsOp0 = false, KillsOp1 = false; 441 442 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI), 443 E = LV->killed_end(MI); KI != E; ++KI) { 444 KillsOp0 |= (KI->second == X86::FP0+Op0); 445 KillsOp1 |= (KI->second == X86::FP0+Op1); 446 } 447 448 // If this is an FpUCOM instruction, we must make sure the first operand is on 449 // the top of stack, the other one can be anywhere... 450 if (MI->getOpcode() == X86::FpUCOM) 451 moveToTop(Op0, I); 452 453 unsigned TOS = getStackEntry(0); 454 455 // One of our operands must be on the top of the stack. If neither is yet, we 456 // need to move one. 457 if (Op0 != TOS && Op1 != TOS) { // No operand at TOS? 458 // We can choose to move either operand to the top of the stack. If one of 459 // the operands is killed by this instruction, we want that one so that we 460 // can update right on top of the old version. 461 if (KillsOp0) { 462 moveToTop(Op0, I); // Move dead operand to TOS. 463 TOS = Op0; 464 } else if (KillsOp1) { 465 moveToTop(Op1, I); 466 TOS = Op1; 467 } else { 468 // All of the operands are live after this instruction executes, so we 469 // cannot update on top of any operand. Because of this, we must 470 // duplicate one of the stack elements to the top. It doesn't matter 471 // which one we pick. 472 // 473 duplicateToTop(Op0, Dest, I); 474 Op0 = TOS = Dest; 475 KillsOp0 = true; 476 } 477 } else if (!KillsOp0 && !KillsOp1 && MI->getOpcode() != X86::FpUCOM) { 478 // If we DO have one of our operands at the top of the stack, but we don't 479 // have a dead operand, we must duplicate one of the operands to a new slot 480 // on the stack. 481 duplicateToTop(Op0, Dest, I); 482 Op0 = TOS = Dest; 483 KillsOp0 = true; 484 } 485 486 // Now we know that one of our operands is on the top of the stack, and at 487 // least one of our operands is killed by this instruction. 488 assert((TOS == Op0 || TOS == Op1) && 489 (KillsOp0 || KillsOp1 || MI->getOpcode() == X86::FpUCOM) && 490 "Stack conditions not set up right!"); 491 492 // We decide which form to use based on what is on the top of the stack, and 493 // which operand is killed by this instruction. 494 const TableEntry *InstTable; 495 bool isForward = TOS == Op0; 496 bool updateST0 = (TOS == Op0 && !KillsOp1) || (TOS == Op1 && !KillsOp0); 497 if (updateST0) { 498 if (isForward) 499 InstTable = ForwardST0Table; 500 else 501 InstTable = ReverseST0Table; 502 } else { 503 if (isForward) 504 InstTable = ForwardSTiTable; 505 else 506 InstTable = ReverseSTiTable; 507 } 508 509 int Opcode = Lookup(InstTable, ARRAY_SIZE(ForwardST0Table), MI->getOpcode()); 510 assert(Opcode != -1 && "Unknown TwoArgFP pseudo instruction!"); 511 512 // NotTOS - The register which is not on the top of stack... 513 unsigned NotTOS = (TOS == Op0) ? Op1 : Op0; 514 515 // Replace the old instruction with a new instruction 516 *I = BuildMI(Opcode, 1).addReg(getSTReg(NotTOS)); 517 518 // If both operands are killed, pop one off of the stack in addition to 519 // overwriting the other one. 520 if (KillsOp0 && KillsOp1 && Op0 != Op1) { 521 assert(!updateST0 && "Should have updated other operand!"); 522 popStackAfter(I); // Pop the top of stack 523 } 524 525 // Insert an explicit pop of the "updated" operand for FUCOM 526 if (MI->getOpcode() == X86::FpUCOM) { 527 if (KillsOp0 && !KillsOp1) 528 popStackAfter(I); // If we kill the first operand, pop it! 529 else if (KillsOp1 && Op0 != Op1) { 530 if (getStackEntry(0) == Op1) { 531 popStackAfter(I); // If it's right at the top of stack, just pop it 532 } else { 533 // Otherwise, move the top of stack into the dead slot, killing the 534 // operand without having to add in an explicit xchg then pop. 535 // 536 unsigned STReg = getSTReg(Op1); 537 unsigned OldSlot = getSlot(Op1); 538 unsigned TopReg = Stack[StackTop-1]; 539 Stack[OldSlot] = TopReg; 540 RegMap[TopReg] = OldSlot; 541 RegMap[Op1] = ~0; 542 Stack[--StackTop] = ~0; 543 544 MachineInstr *MI = BuildMI(X86::FSTPrr, 1).addReg(STReg); 545 I = MBB->insert(I+1, MI); 546 } 547 } 548 } 549 550 // Update stack information so that we know the destination register is now on 551 // the stack. 552 if (MI->getOpcode() != X86::FpUCOM) { 553 unsigned UpdatedSlot = getSlot(updateST0 ? TOS : NotTOS); 554 assert(UpdatedSlot < StackTop && Dest < 7); 555 Stack[UpdatedSlot] = Dest; 556 RegMap[Dest] = UpdatedSlot; 557 } 558 delete MI; // Remove the old instruction 559} 560 561 562/// handleSpecialFP - Handle special instructions which behave unlike other 563/// floating point instructions. This is primarily intended for use by pseudo 564/// instructions. 565/// 566void FPS::handleSpecialFP(MachineBasicBlock::iterator &I) { 567 MachineInstr *MI = *I; 568 switch (MI->getOpcode()) { 569 default: assert(0 && "Unknown SpecialFP instruction!"); 570 case X86::FpGETRESULT: // Appears immediately after a call returning FP type! 571 assert(StackTop == 0 && "Stack should be empty after a call!"); 572 pushReg(getFPReg(MI->getOperand(0))); 573 break; 574 case X86::FpSETRESULT: 575 assert(StackTop == 1 && "Stack should have one element on it to return!"); 576 --StackTop; // "Forget" we have something on the top of stack! 577 break; 578 case X86::FpMOV: { 579 unsigned SrcReg = getFPReg(MI->getOperand(1)); 580 unsigned DestReg = getFPReg(MI->getOperand(0)); 581 bool KillsSrc = false; 582 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI), 583 E = LV->killed_end(MI); KI != E; ++KI) 584 KillsSrc |= KI->second == X86::FP0+SrcReg; 585 586 if (KillsSrc) { 587 // If the input operand is killed, we can just change the owner of the 588 // incoming stack slot into the result. 589 unsigned Slot = getSlot(SrcReg); 590 assert(Slot < 7 && DestReg < 7 && "FpMOV operands invalid!"); 591 Stack[Slot] = DestReg; 592 RegMap[DestReg] = Slot; 593 594 } else { 595 // For FMOV we just duplicate the specified value to a new stack slot. 596 // This could be made better, but would require substantial changes. 597 duplicateToTop(SrcReg, DestReg, I); 598 } 599 break; 600 } 601 } 602 603 I = MBB->erase(I)-1; // Remove the pseudo instruction 604} 605 606namespace { 607 struct FPK : public MachineFunctionPass { 608 virtual const char *getPassName() const { return "X86 FP Killer"; } 609 virtual bool runOnMachineFunction(MachineFunction &MF); 610 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 611 AU.addPreserved<LiveVariables>(); 612 AU.addRequired<LiveVariables>(); 613 AU.addPreservedID(PHIEliminationID); 614 AU.addRequiredID(PHIEliminationID); 615 MachineFunctionPass::getAnalysisUsage(AU); 616 } 617 }; 618} 619 620FunctionPass *llvm::createX86FloatingPointKillerPass() { return new FPK(); } 621 622bool FPK::runOnMachineFunction(MachineFunction &MF) { 623 const TargetInstrInfo& tii = MF.getTarget().getInstrInfo();; 624 LiveVariables &LV = getAnalysis<LiveVariables>(); 625 626 for (MachineFunction::iterator 627 mbbi = MF.begin(), mbbe = MF.end(); mbbi != mbbe; ++mbbi) { 628 MachineBasicBlock& mbb = *mbbi; 629 MachineBasicBlock::reverse_iterator mii = mbb.rbegin(); 630 // rewind to the last non terminating instruction 631 while (mii != mbb.rend() && tii.isTerminatorInstr((*mii)->getOpcode())) 632 ++mii; 633 634 // add implicit def for all virtual floating point registers so that 635 // they are spilled at the end of each basic block, since our 636 // register stackifier doesn't handle them otherwise. 637 MachineInstr* instr = BuildMI(X86::IMPLICIT_DEF, 7) 638 .addReg(X86::FP6, MOTy::Def) 639 .addReg(X86::FP5, MOTy::Def) 640 .addReg(X86::FP4, MOTy::Def) 641 .addReg(X86::FP3, MOTy::Def) 642 .addReg(X86::FP2, MOTy::Def) 643 .addReg(X86::FP1, MOTy::Def) 644 .addReg(X86::FP0, MOTy::Def); 645 646 mbb.insert(mii.base(), instr); 647 648 for (unsigned i = 0; i < instr->getNumOperands(); ++i) { 649 LV.HandlePhysRegDef(instr->getOperand(i).getAllocatedRegNum(), instr); 650 651 // force live variables to compute that these registers are dead 652 LV.HandlePhysRegDef(instr->getOperand(i).getAllocatedRegNum(), 0); 653 } 654 } 655 return true; 656} 657