X86FloatingPoint.cpp revision 0e0a7a45d3d0a8c865a078459d2e1c6d8967a100
1//===-- X86FloatingPoint.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. This pass uses live 12// variable information to indicate where the FPn registers are used and their 13// lifetimes. 14// 15// This pass is hampered by the lack of decent CFG manipulation routines for 16// machine code. In particular, this wants to be able to split critical edges 17// as necessary, traverse the machine basic block CFG in depth-first order, and 18// allow there to be multiple machine basic blocks for each LLVM basicblock 19// (needed for critical edge splitting). 20// 21// In particular, this pass currently barfs on critical edges. Because of this, 22// it requires the instruction selector to insert FP_REG_KILL instructions on 23// the exits of any basic block that has critical edges going from it, or which 24// branch to a critical basic block. 25// 26// FIXME: this is not implemented yet. The stackifier pass only works on local 27// basic blocks. 28// 29//===----------------------------------------------------------------------===// 30 31#define DEBUG_TYPE "fp" 32#include "X86.h" 33#include "X86InstrInfo.h" 34#include "llvm/CodeGen/MachineFunctionPass.h" 35#include "llvm/CodeGen/MachineInstrBuilder.h" 36#include "llvm/CodeGen/LiveVariables.h" 37#include "llvm/CodeGen/Passes.h" 38#include "llvm/Target/TargetInstrInfo.h" 39#include "llvm/Target/TargetMachine.h" 40#include "llvm/Support/Debug.h" 41#include "llvm/ADT/DepthFirstIterator.h" 42#include "llvm/ADT/Statistic.h" 43#include "llvm/ADT/STLExtras.h" 44#include <algorithm> 45#include <set> 46using namespace llvm; 47 48namespace { 49 Statistic<> NumFXCH("x86-codegen", "Number of fxch instructions inserted"); 50 Statistic<> NumFP ("x86-codegen", "Number of floating point instructions"); 51 52 struct FPS : public MachineFunctionPass { 53 virtual bool runOnMachineFunction(MachineFunction &MF); 54 55 virtual const char *getPassName() const { return "X86 FP Stackifier"; } 56 57 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 58 AU.addRequired<LiveVariables>(); 59 MachineFunctionPass::getAnalysisUsage(AU); 60 } 61 private: 62 LiveVariables *LV; // Live variable info for current function... 63 MachineBasicBlock *MBB; // Current basic block 64 unsigned Stack[8]; // FP<n> Registers in each stack slot... 65 unsigned RegMap[8]; // Track which stack slot contains each register 66 unsigned StackTop; // The current top of the FP stack. 67 68 void dumpStack() const { 69 std::cerr << "Stack contents:"; 70 for (unsigned i = 0; i != StackTop; ++i) { 71 std::cerr << " FP" << Stack[i]; 72 assert(RegMap[Stack[i]] == i && "Stack[] doesn't match RegMap[]!"); 73 } 74 std::cerr << "\n"; 75 } 76 private: 77 // getSlot - Return the stack slot number a particular register number is 78 // in... 79 unsigned getSlot(unsigned RegNo) const { 80 assert(RegNo < 8 && "Regno out of range!"); 81 return RegMap[RegNo]; 82 } 83 84 // getStackEntry - Return the X86::FP<n> register in register ST(i) 85 unsigned getStackEntry(unsigned STi) const { 86 assert(STi < StackTop && "Access past stack top!"); 87 return Stack[StackTop-1-STi]; 88 } 89 90 // getSTReg - Return the X86::ST(i) register which contains the specified 91 // FP<RegNo> register 92 unsigned getSTReg(unsigned RegNo) const { 93 return StackTop - 1 - getSlot(RegNo) + llvm::X86::ST0; 94 } 95 96 // pushReg - Push the specified FP<n> register onto the stack 97 void pushReg(unsigned Reg) { 98 assert(Reg < 8 && "Register number out of range!"); 99 assert(StackTop < 8 && "Stack overflow!"); 100 Stack[StackTop] = Reg; 101 RegMap[Reg] = StackTop++; 102 } 103 104 bool isAtTop(unsigned RegNo) const { return getSlot(RegNo) == StackTop-1; } 105 void moveToTop(unsigned RegNo, MachineBasicBlock::iterator &I) { 106 if (!isAtTop(RegNo)) { 107 unsigned Slot = getSlot(RegNo); 108 unsigned STReg = getSTReg(RegNo); 109 unsigned RegOnTop = getStackEntry(0); 110 111 // Swap the slots the regs are in 112 std::swap(RegMap[RegNo], RegMap[RegOnTop]); 113 114 // Swap stack slot contents 115 assert(RegMap[RegOnTop] < StackTop); 116 std::swap(Stack[RegMap[RegOnTop]], Stack[StackTop-1]); 117 118 // Emit an fxch to update the runtime processors version of the state 119 BuildMI(*MBB, I, X86::FXCH, 1).addReg(STReg); 120 NumFXCH++; 121 } 122 } 123 124 void duplicateToTop(unsigned RegNo, unsigned AsReg, MachineInstr *I) { 125 unsigned STReg = getSTReg(RegNo); 126 pushReg(AsReg); // New register on top of stack 127 128 BuildMI(*MBB, I, X86::FLDrr, 1).addReg(STReg); 129 } 130 131 // popStackAfter - Pop the current value off of the top of the FP stack 132 // after the specified instruction. 133 void popStackAfter(MachineBasicBlock::iterator &I); 134 135 // freeStackSlotAfter - Free the specified register from the register stack, 136 // so that it is no longer in a register. If the register is currently at 137 // the top of the stack, we just pop the current instruction, otherwise we 138 // store the current top-of-stack into the specified slot, then pop the top 139 // of stack. 140 void freeStackSlotAfter(MachineBasicBlock::iterator &I, unsigned Reg); 141 142 bool processBasicBlock(MachineFunction &MF, MachineBasicBlock &MBB); 143 144 void handleZeroArgFP(MachineBasicBlock::iterator &I); 145 void handleOneArgFP(MachineBasicBlock::iterator &I); 146 void handleOneArgFPRW(MachineBasicBlock::iterator &I); 147 void handleTwoArgFP(MachineBasicBlock::iterator &I); 148 void handleCompareFP(MachineBasicBlock::iterator &I); 149 void handleCondMovFP(MachineBasicBlock::iterator &I); 150 void handleSpecialFP(MachineBasicBlock::iterator &I); 151 }; 152} 153 154FunctionPass *llvm::createX86FloatingPointStackifierPass() { return new FPS(); } 155 156/// runOnMachineFunction - Loop over all of the basic blocks, transforming FP 157/// register references into FP stack references. 158/// 159bool FPS::runOnMachineFunction(MachineFunction &MF) { 160 // We only need to run this pass if there are any FP registers used in this 161 // function. If it is all integer, there is nothing for us to do! 162 const bool *PhysRegsUsed = MF.getUsedPhysregs(); 163 bool FPIsUsed = false; 164 165 assert(X86::FP6 == X86::FP0+6 && "Register enums aren't sorted right!"); 166 for (unsigned i = 0; i <= 6; ++i) 167 if (PhysRegsUsed[X86::FP0+i]) { 168 FPIsUsed = true; 169 break; 170 } 171 172 // Early exit. 173 if (!FPIsUsed) return false; 174 175 LV = &getAnalysis<LiveVariables>(); 176 StackTop = 0; 177 178 // Process the function in depth first order so that we process at least one 179 // of the predecessors for every reachable block in the function. 180 std::set<MachineBasicBlock*> Processed; 181 MachineBasicBlock *Entry = MF.begin(); 182 183 bool Changed = false; 184 for (df_ext_iterator<MachineBasicBlock*, std::set<MachineBasicBlock*> > 185 I = df_ext_begin(Entry, Processed), E = df_ext_end(Entry, Processed); 186 I != E; ++I) 187 Changed |= processBasicBlock(MF, **I); 188 189 return Changed; 190} 191 192/// processBasicBlock - Loop over all of the instructions in the basic block, 193/// transforming FP instructions into their stack form. 194/// 195bool FPS::processBasicBlock(MachineFunction &MF, MachineBasicBlock &BB) { 196 const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo(); 197 bool Changed = false; 198 MBB = &BB; 199 200 for (MachineBasicBlock::iterator I = BB.begin(); I != BB.end(); ++I) { 201 MachineInstr *MI = I; 202 unsigned Flags = TII.get(MI->getOpcode()).TSFlags; 203 if ((Flags & X86II::FPTypeMask) == X86II::NotFP) 204 continue; // Efficiently ignore non-fp insts! 205 206 MachineInstr *PrevMI = 0; 207 if (I != BB.begin()) 208 PrevMI = prior(I); 209 210 ++NumFP; // Keep track of # of pseudo instrs 211 DEBUG(std::cerr << "\nFPInst:\t"; MI->print(std::cerr, &(MF.getTarget()))); 212 213 // Get dead variables list now because the MI pointer may be deleted as part 214 // of processing! 215 LiveVariables::killed_iterator IB = LV->dead_begin(MI); 216 LiveVariables::killed_iterator IE = LV->dead_end(MI); 217 218 DEBUG( 219 const MRegisterInfo *MRI = MF.getTarget().getRegisterInfo(); 220 LiveVariables::killed_iterator I = LV->killed_begin(MI); 221 LiveVariables::killed_iterator E = LV->killed_end(MI); 222 if (I != E) { 223 std::cerr << "Killed Operands:"; 224 for (; I != E; ++I) 225 std::cerr << " %" << MRI->getName(I->second); 226 std::cerr << "\n"; 227 } 228 ); 229 230 switch (Flags & X86II::FPTypeMask) { 231 case X86II::ZeroArgFP: handleZeroArgFP(I); break; 232 case X86II::OneArgFP: handleOneArgFP(I); break; // fstp ST(0) 233 case X86II::OneArgFPRW: handleOneArgFPRW(I); break; // ST(0) = fsqrt(ST(0)) 234 case X86II::TwoArgFP: handleTwoArgFP(I); break; 235 case X86II::CompareFP: handleCompareFP(I); break; 236 case X86II::CondMovFP: handleCondMovFP(I); break; 237 case X86II::SpecialFP: handleSpecialFP(I); break; 238 default: assert(0 && "Unknown FP Type!"); 239 } 240 241 // Check to see if any of the values defined by this instruction are dead 242 // after definition. If so, pop them. 243 for (; IB != IE; ++IB) { 244 unsigned Reg = IB->second; 245 if (Reg >= X86::FP0 && Reg <= X86::FP6) { 246 DEBUG(std::cerr << "Register FP#" << Reg-X86::FP0 << " is dead!\n"); 247 freeStackSlotAfter(I, Reg-X86::FP0); 248 } 249 } 250 251 // Print out all of the instructions expanded to if -debug 252 DEBUG( 253 MachineBasicBlock::iterator PrevI(PrevMI); 254 if (I == PrevI) { 255 std::cerr << "Just deleted pseudo instruction\n"; 256 } else { 257 MachineBasicBlock::iterator Start = I; 258 // Rewind to first instruction newly inserted. 259 while (Start != BB.begin() && prior(Start) != PrevI) --Start; 260 std::cerr << "Inserted instructions:\n\t"; 261 Start->print(std::cerr, &MF.getTarget()); 262 while (++Start != next(I)); 263 } 264 dumpStack(); 265 ); 266 267 Changed = true; 268 } 269 270 assert(StackTop == 0 && "Stack not empty at end of basic block?"); 271 return Changed; 272} 273 274//===----------------------------------------------------------------------===// 275// Efficient Lookup Table Support 276//===----------------------------------------------------------------------===// 277 278namespace { 279 struct TableEntry { 280 unsigned from; 281 unsigned to; 282 bool operator<(const TableEntry &TE) const { return from < TE.from; } 283 bool operator<(unsigned V) const { return from < V; } 284 }; 285} 286 287static bool TableIsSorted(const TableEntry *Table, unsigned NumEntries) { 288 for (unsigned i = 0; i != NumEntries-1; ++i) 289 if (!(Table[i] < Table[i+1])) return false; 290 return true; 291} 292 293static int Lookup(const TableEntry *Table, unsigned N, unsigned Opcode) { 294 const TableEntry *I = std::lower_bound(Table, Table+N, Opcode); 295 if (I != Table+N && I->from == Opcode) 296 return I->to; 297 return -1; 298} 299 300#define ARRAY_SIZE(TABLE) \ 301 (sizeof(TABLE)/sizeof(TABLE[0])) 302 303#ifdef NDEBUG 304#define ASSERT_SORTED(TABLE) 305#else 306#define ASSERT_SORTED(TABLE) \ 307 { static bool TABLE##Checked = false; \ 308 if (!TABLE##Checked) \ 309 assert(TableIsSorted(TABLE, ARRAY_SIZE(TABLE)) && \ 310 "All lookup tables must be sorted for efficient access!"); \ 311 } 312#endif 313 314 315//===----------------------------------------------------------------------===// 316// Helper Methods 317//===----------------------------------------------------------------------===// 318 319// PopTable - Sorted map of instructions to their popping version. The first 320// element is an instruction, the second is the version which pops. 321// 322static const TableEntry PopTable[] = { 323 { X86::FADDrST0 , X86::FADDPrST0 }, 324 325 { X86::FDIVRrST0, X86::FDIVRPrST0 }, 326 { X86::FDIVrST0 , X86::FDIVPrST0 }, 327 328 { X86::FIST16m , X86::FISTP16m }, 329 { X86::FIST32m , X86::FISTP32m }, 330 331 { X86::FMULrST0 , X86::FMULPrST0 }, 332 333 { X86::FST32m , X86::FSTP32m }, 334 { X86::FST64m , X86::FSTP64m }, 335 { X86::FSTrr , X86::FSTPrr }, 336 337 { X86::FSUBRrST0, X86::FSUBRPrST0 }, 338 { X86::FSUBrST0 , X86::FSUBPrST0 }, 339 340 { X86::FUCOMIr , X86::FUCOMIPr }, 341 342 { X86::FUCOMPr , X86::FUCOMPPr }, 343 { X86::FUCOMr , X86::FUCOMPr }, 344}; 345 346/// popStackAfter - Pop the current value off of the top of the FP stack after 347/// the specified instruction. This attempts to be sneaky and combine the pop 348/// into the instruction itself if possible. The iterator is left pointing to 349/// the last instruction, be it a new pop instruction inserted, or the old 350/// instruction if it was modified in place. 351/// 352void FPS::popStackAfter(MachineBasicBlock::iterator &I) { 353 ASSERT_SORTED(PopTable); 354 assert(StackTop > 0 && "Cannot pop empty stack!"); 355 RegMap[Stack[--StackTop]] = ~0; // Update state 356 357 // Check to see if there is a popping version of this instruction... 358 int Opcode = Lookup(PopTable, ARRAY_SIZE(PopTable), I->getOpcode()); 359 if (Opcode != -1) { 360 I->setOpcode(Opcode); 361 if (Opcode == X86::FUCOMPPr) 362 I->RemoveOperand(0); 363 364 } else { // Insert an explicit pop 365 I = BuildMI(*MBB, ++I, X86::FSTPrr, 1).addReg(X86::ST0); 366 } 367} 368 369/// freeStackSlotAfter - Free the specified register from the register stack, so 370/// that it is no longer in a register. If the register is currently at the top 371/// of the stack, we just pop the current instruction, otherwise we store the 372/// current top-of-stack into the specified slot, then pop the top of stack. 373void FPS::freeStackSlotAfter(MachineBasicBlock::iterator &I, unsigned FPRegNo) { 374 if (getStackEntry(0) == FPRegNo) { // already at the top of stack? easy. 375 popStackAfter(I); 376 return; 377 } 378 379 // Otherwise, store the top of stack into the dead slot, killing the operand 380 // without having to add in an explicit xchg then pop. 381 // 382 unsigned STReg = getSTReg(FPRegNo); 383 unsigned OldSlot = getSlot(FPRegNo); 384 unsigned TopReg = Stack[StackTop-1]; 385 Stack[OldSlot] = TopReg; 386 RegMap[TopReg] = OldSlot; 387 RegMap[FPRegNo] = ~0; 388 Stack[--StackTop] = ~0; 389 I = BuildMI(*MBB, ++I, X86::FSTPrr, 1).addReg(STReg); 390} 391 392 393static unsigned getFPReg(const MachineOperand &MO) { 394 assert(MO.isRegister() && "Expected an FP register!"); 395 unsigned Reg = MO.getReg(); 396 assert(Reg >= X86::FP0 && Reg <= X86::FP6 && "Expected FP register!"); 397 return Reg - X86::FP0; 398} 399 400 401//===----------------------------------------------------------------------===// 402// Instruction transformation implementation 403//===----------------------------------------------------------------------===// 404 405/// handleZeroArgFP - ST(0) = fld0 ST(0) = flds <mem> 406/// 407void FPS::handleZeroArgFP(MachineBasicBlock::iterator &I) { 408 MachineInstr *MI = I; 409 unsigned DestReg = getFPReg(MI->getOperand(0)); 410 MI->RemoveOperand(0); // Remove the explicit ST(0) operand 411 412 // Result gets pushed on the stack... 413 pushReg(DestReg); 414} 415 416/// handleOneArgFP - fst <mem>, ST(0) 417/// 418void FPS::handleOneArgFP(MachineBasicBlock::iterator &I) { 419 MachineInstr *MI = I; 420 assert((MI->getNumOperands() == 5 || MI->getNumOperands() == 1) && 421 "Can only handle fst* & ftst instructions!"); 422 423 // Is this the last use of the source register? 424 unsigned Reg = getFPReg(MI->getOperand(MI->getNumOperands()-1)); 425 bool KillsSrc = false; 426 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI), 427 E = LV->killed_end(MI); KI != E; ++KI) 428 KillsSrc |= KI->second == X86::FP0+Reg; 429 430 // FSTP80r and FISTP64r are strange because there are no non-popping versions. 431 // If we have one _and_ we don't want to pop the operand, duplicate the value 432 // on the stack instead of moving it. This ensure that popping the value is 433 // always ok. 434 // 435 if ((MI->getOpcode() == X86::FSTP80m || 436 MI->getOpcode() == X86::FISTP64m) && !KillsSrc) { 437 duplicateToTop(Reg, 7 /*temp register*/, I); 438 } else { 439 moveToTop(Reg, I); // Move to the top of the stack... 440 } 441 MI->RemoveOperand(MI->getNumOperands()-1); // Remove explicit ST(0) operand 442 443 if (MI->getOpcode() == X86::FSTP80m || MI->getOpcode() == X86::FISTP64m) { 444 assert(StackTop > 0 && "Stack empty??"); 445 --StackTop; 446 } else if (KillsSrc) { // Last use of operand? 447 popStackAfter(I); 448 } 449} 450 451 452/// handleOneArgFPRW: Handle instructions that read from the top of stack and 453/// replace the value with a newly computed value. These instructions may have 454/// non-fp operands after their FP operands. 455/// 456/// Examples: 457/// R1 = fchs R2 458/// R1 = fadd R2, [mem] 459/// 460void FPS::handleOneArgFPRW(MachineBasicBlock::iterator &I) { 461 MachineInstr *MI = I; 462 assert(MI->getNumOperands() >= 2 && "FPRW instructions must have 2 ops!!"); 463 464 // Is this the last use of the source register? 465 unsigned Reg = getFPReg(MI->getOperand(1)); 466 bool KillsSrc = false; 467 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI), 468 E = LV->killed_end(MI); KI != E; ++KI) 469 KillsSrc |= KI->second == X86::FP0+Reg; 470 471 if (KillsSrc) { 472 // If this is the last use of the source register, just make sure it's on 473 // the top of the stack. 474 moveToTop(Reg, I); 475 assert(StackTop > 0 && "Stack cannot be empty!"); 476 --StackTop; 477 pushReg(getFPReg(MI->getOperand(0))); 478 } else { 479 // If this is not the last use of the source register, _copy_ it to the top 480 // of the stack. 481 duplicateToTop(Reg, getFPReg(MI->getOperand(0)), I); 482 } 483 484 MI->RemoveOperand(1); // Drop the source operand. 485 MI->RemoveOperand(0); // Drop the destination operand. 486} 487 488 489//===----------------------------------------------------------------------===// 490// Define tables of various ways to map pseudo instructions 491// 492 493// ForwardST0Table - Map: A = B op C into: ST(0) = ST(0) op ST(i) 494static const TableEntry ForwardST0Table[] = { 495 { X86::FpADD , X86::FADDST0r }, 496 { X86::FpDIV , X86::FDIVST0r }, 497 { X86::FpMUL , X86::FMULST0r }, 498 { X86::FpSUB , X86::FSUBST0r }, 499}; 500 501// ReverseST0Table - Map: A = B op C into: ST(0) = ST(i) op ST(0) 502static const TableEntry ReverseST0Table[] = { 503 { X86::FpADD , X86::FADDST0r }, // commutative 504 { X86::FpDIV , X86::FDIVRST0r }, 505 { X86::FpMUL , X86::FMULST0r }, // commutative 506 { X86::FpSUB , X86::FSUBRST0r }, 507}; 508 509// ForwardSTiTable - Map: A = B op C into: ST(i) = ST(0) op ST(i) 510static const TableEntry ForwardSTiTable[] = { 511 { X86::FpADD , X86::FADDrST0 }, // commutative 512 { X86::FpDIV , X86::FDIVRrST0 }, 513 { X86::FpMUL , X86::FMULrST0 }, // commutative 514 { X86::FpSUB , X86::FSUBRrST0 }, 515}; 516 517// ReverseSTiTable - Map: A = B op C into: ST(i) = ST(i) op ST(0) 518static const TableEntry ReverseSTiTable[] = { 519 { X86::FpADD , X86::FADDrST0 }, 520 { X86::FpDIV , X86::FDIVrST0 }, 521 { X86::FpMUL , X86::FMULrST0 }, 522 { X86::FpSUB , X86::FSUBrST0 }, 523}; 524 525 526/// handleTwoArgFP - Handle instructions like FADD and friends which are virtual 527/// instructions which need to be simplified and possibly transformed. 528/// 529/// Result: ST(0) = fsub ST(0), ST(i) 530/// ST(i) = fsub ST(0), ST(i) 531/// ST(0) = fsubr ST(0), ST(i) 532/// ST(i) = fsubr ST(0), ST(i) 533/// 534void FPS::handleTwoArgFP(MachineBasicBlock::iterator &I) { 535 ASSERT_SORTED(ForwardST0Table); ASSERT_SORTED(ReverseST0Table); 536 ASSERT_SORTED(ForwardSTiTable); ASSERT_SORTED(ReverseSTiTable); 537 MachineInstr *MI = I; 538 539 unsigned NumOperands = MI->getNumOperands(); 540 assert(NumOperands == 3 && "Illegal TwoArgFP instruction!"); 541 unsigned Dest = getFPReg(MI->getOperand(0)); 542 unsigned Op0 = getFPReg(MI->getOperand(NumOperands-2)); 543 unsigned Op1 = getFPReg(MI->getOperand(NumOperands-1)); 544 bool KillsOp0 = false, KillsOp1 = false; 545 546 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI), 547 E = LV->killed_end(MI); KI != E; ++KI) { 548 KillsOp0 |= (KI->second == X86::FP0+Op0); 549 KillsOp1 |= (KI->second == X86::FP0+Op1); 550 } 551 552 unsigned TOS = getStackEntry(0); 553 554 // One of our operands must be on the top of the stack. If neither is yet, we 555 // need to move one. 556 if (Op0 != TOS && Op1 != TOS) { // No operand at TOS? 557 // We can choose to move either operand to the top of the stack. If one of 558 // the operands is killed by this instruction, we want that one so that we 559 // can update right on top of the old version. 560 if (KillsOp0) { 561 moveToTop(Op0, I); // Move dead operand to TOS. 562 TOS = Op0; 563 } else if (KillsOp1) { 564 moveToTop(Op1, I); 565 TOS = Op1; 566 } else { 567 // All of the operands are live after this instruction executes, so we 568 // cannot update on top of any operand. Because of this, we must 569 // duplicate one of the stack elements to the top. It doesn't matter 570 // which one we pick. 571 // 572 duplicateToTop(Op0, Dest, I); 573 Op0 = TOS = Dest; 574 KillsOp0 = true; 575 } 576 } else if (!KillsOp0 && !KillsOp1) { 577 // If we DO have one of our operands at the top of the stack, but we don't 578 // have a dead operand, we must duplicate one of the operands to a new slot 579 // on the stack. 580 duplicateToTop(Op0, Dest, I); 581 Op0 = TOS = Dest; 582 KillsOp0 = true; 583 } 584 585 // Now we know that one of our operands is on the top of the stack, and at 586 // least one of our operands is killed by this instruction. 587 assert((TOS == Op0 || TOS == Op1) && (KillsOp0 || KillsOp1) && 588 "Stack conditions not set up right!"); 589 590 // We decide which form to use based on what is on the top of the stack, and 591 // which operand is killed by this instruction. 592 const TableEntry *InstTable; 593 bool isForward = TOS == Op0; 594 bool updateST0 = (TOS == Op0 && !KillsOp1) || (TOS == Op1 && !KillsOp0); 595 if (updateST0) { 596 if (isForward) 597 InstTable = ForwardST0Table; 598 else 599 InstTable = ReverseST0Table; 600 } else { 601 if (isForward) 602 InstTable = ForwardSTiTable; 603 else 604 InstTable = ReverseSTiTable; 605 } 606 607 int Opcode = Lookup(InstTable, ARRAY_SIZE(ForwardST0Table), MI->getOpcode()); 608 assert(Opcode != -1 && "Unknown TwoArgFP pseudo instruction!"); 609 610 // NotTOS - The register which is not on the top of stack... 611 unsigned NotTOS = (TOS == Op0) ? Op1 : Op0; 612 613 // Replace the old instruction with a new instruction 614 MBB->remove(I++); 615 I = BuildMI(*MBB, I, Opcode, 1).addReg(getSTReg(NotTOS)); 616 617 // If both operands are killed, pop one off of the stack in addition to 618 // overwriting the other one. 619 if (KillsOp0 && KillsOp1 && Op0 != Op1) { 620 assert(!updateST0 && "Should have updated other operand!"); 621 popStackAfter(I); // Pop the top of stack 622 } 623 624 // Update stack information so that we know the destination register is now on 625 // the stack. 626 unsigned UpdatedSlot = getSlot(updateST0 ? TOS : NotTOS); 627 assert(UpdatedSlot < StackTop && Dest < 7); 628 Stack[UpdatedSlot] = Dest; 629 RegMap[Dest] = UpdatedSlot; 630 delete MI; // Remove the old instruction 631} 632 633/// handleCompareFP - Handle FUCOM and FUCOMI instructions, which have two FP 634/// register arguments and no explicit destinations. 635/// 636void FPS::handleCompareFP(MachineBasicBlock::iterator &I) { 637 ASSERT_SORTED(ForwardST0Table); ASSERT_SORTED(ReverseST0Table); 638 ASSERT_SORTED(ForwardSTiTable); ASSERT_SORTED(ReverseSTiTable); 639 MachineInstr *MI = I; 640 641 unsigned NumOperands = MI->getNumOperands(); 642 assert(NumOperands == 2 && "Illegal FUCOM* instruction!"); 643 unsigned Op0 = getFPReg(MI->getOperand(NumOperands-2)); 644 unsigned Op1 = getFPReg(MI->getOperand(NumOperands-1)); 645 bool KillsOp0 = false, KillsOp1 = false; 646 647 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI), 648 E = LV->killed_end(MI); KI != E; ++KI) { 649 KillsOp0 |= (KI->second == X86::FP0+Op0); 650 KillsOp1 |= (KI->second == X86::FP0+Op1); 651 } 652 653 // Make sure the first operand is on the top of stack, the other one can be 654 // anywhere. 655 moveToTop(Op0, I); 656 657 MI->getOperand(0).setReg(getSTReg(Op1)); 658 MI->RemoveOperand(1); 659 660 // If any of the operands are killed by this instruction, free them. 661 if (KillsOp0) freeStackSlotAfter(I, Op0); 662 if (KillsOp1 && Op0 != Op1) freeStackSlotAfter(I, Op1); 663} 664 665/// handleCondMovFP - Handle two address conditional move instructions. These 666/// instructions move a st(i) register to st(0) iff a condition is true. These 667/// instructions require that the first operand is at the top of the stack, but 668/// otherwise don't modify the stack at all. 669void FPS::handleCondMovFP(MachineBasicBlock::iterator &I) { 670 MachineInstr *MI = I; 671 672 unsigned Op0 = getFPReg(MI->getOperand(0)); 673 unsigned Op1 = getFPReg(MI->getOperand(1)); 674 675 // The first operand *must* be on the top of the stack. 676 moveToTop(Op0, I); 677 678 // Change the second operand to the stack register that the operand is in. 679 MI->RemoveOperand(0); 680 MI->getOperand(0).setReg(getSTReg(Op1)); 681 682 // If we kill the second operand, make sure to pop it from the stack. 683 if (Op0 != Op1) 684 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI), 685 E = LV->killed_end(MI); KI != E; ++KI) 686 if (KI->second == X86::FP0+Op1) { 687 // Get this value off of the register stack. 688 freeStackSlotAfter(I, Op1); 689 break; 690 } 691} 692 693 694/// handleSpecialFP - Handle special instructions which behave unlike other 695/// floating point instructions. This is primarily intended for use by pseudo 696/// instructions. 697/// 698void FPS::handleSpecialFP(MachineBasicBlock::iterator &I) { 699 MachineInstr *MI = I; 700 switch (MI->getOpcode()) { 701 default: assert(0 && "Unknown SpecialFP instruction!"); 702 case X86::FpGETRESULT: // Appears immediately after a call returning FP type! 703 assert(StackTop == 0 && "Stack should be empty after a call!"); 704 pushReg(getFPReg(MI->getOperand(0))); 705 break; 706 case X86::FpSETRESULT: 707 assert(StackTop == 1 && "Stack should have one element on it to return!"); 708 --StackTop; // "Forget" we have something on the top of stack! 709 break; 710 case X86::FpMOV: { 711 unsigned SrcReg = getFPReg(MI->getOperand(1)); 712 unsigned DestReg = getFPReg(MI->getOperand(0)); 713 bool KillsSrc = false; 714 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI), 715 E = LV->killed_end(MI); KI != E; ++KI) 716 KillsSrc |= KI->second == X86::FP0+SrcReg; 717 718 if (KillsSrc) { 719 // If the input operand is killed, we can just change the owner of the 720 // incoming stack slot into the result. 721 unsigned Slot = getSlot(SrcReg); 722 assert(Slot < 7 && DestReg < 7 && "FpMOV operands invalid!"); 723 Stack[Slot] = DestReg; 724 RegMap[DestReg] = Slot; 725 726 } else { 727 // For FMOV we just duplicate the specified value to a new stack slot. 728 // This could be made better, but would require substantial changes. 729 duplicateToTop(SrcReg, DestReg, I); 730 } 731 break; 732 } 733 } 734 735 I = MBB->erase(I); // Remove the pseudo instruction 736 --I; 737} 738