Renamed files to have the `X86' prefix for uniqueness purposes.

All CVS history was renamed, the *,v were copied over.  No worries.

llvm-svn: 15238

1 files changed, 721 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86FloatingPoint.cpp b/llvm/lib/Target/X86/X86FloatingPoint.cpp
new file mode 100644
index 00000000000..fa2632f6fa8
--- /dev/null
+++ b/llvm/lib/Target/X86/X86FloatingPoint.cpp
@@ -0,0 +1,721 @@
+//===-- FloatingPoint.cpp - Floating point Reg -> Stack converter ---------===//
+// 
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+// 
+//===----------------------------------------------------------------------===//
+//
+// This file defines the pass which converts floating point instructions from
+// virtual registers into register stack instructions.  This pass uses live
+// variable information to indicate where the FPn registers are used and their
+// lifetimes.
+//
+// This pass is hampered by the lack of decent CFG manipulation routines for
+// machine code.  In particular, this wants to be able to split critical edges
+// as necessary, traverse the machine basic block CFG in depth-first order, and
+// allow there to be multiple machine basic blocks for each LLVM basicblock
+// (needed for critical edge splitting).
+//
+// In particular, this pass currently barfs on critical edges.  Because of this,
+// it requires the instruction selector to insert FP_REG_KILL instructions on
+// the exits of any basic block that has critical edges going from it, or which
+// branch to a critical basic block.
+//
+// FIXME: this is not implemented yet.  The stackifier pass only works on local
+// basic blocks.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "fp"
+#include "X86.h"
+#include "X86InstrInfo.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/LiveVariables.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "Support/Debug.h"
+#include "Support/DepthFirstIterator.h"
+#include "Support/Statistic.h"
+#include "Support/STLExtras.h"
+#include <algorithm>
+#include <set>
+using namespace llvm;
+
+namespace {
+  Statistic<> NumFXCH("x86-codegen", "Number of fxch instructions inserted");
+  Statistic<> NumFP  ("x86-codegen", "Number of floating point instructions");
+
+  struct FPS : public MachineFunctionPass {
+    virtual bool runOnMachineFunction(MachineFunction &MF);
+
+    virtual const char *getPassName() const { return "X86 FP Stackifier"; }
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addRequired<LiveVariables>();
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+  private:
+    LiveVariables     *LV;    // Live variable info for current function...
+    MachineBasicBlock *MBB;   // Current basic block
+    unsigned Stack[8];        // FP<n> Registers in each stack slot...
+    unsigned RegMap[8];       // Track which stack slot contains each register
+    unsigned StackTop;        // The current top of the FP stack.
+
+    void dumpStack() const {
+      std::cerr << "Stack contents:";
+      for (unsigned i = 0; i != StackTop; ++i) {
+	std::cerr << " FP" << Stack[i];
+	assert(RegMap[Stack[i]] == i && "Stack[] doesn't match RegMap[]!"); 
+      }
+      std::cerr << "\n";
+    }
+  private:
+    // getSlot - Return the stack slot number a particular register number is
+    // in...
+    unsigned getSlot(unsigned RegNo) const {
+      assert(RegNo < 8 && "Regno out of range!");
+      return RegMap[RegNo];
+    }
+
+    // getStackEntry - Return the X86::FP<n> register in register ST(i)
+    unsigned getStackEntry(unsigned STi) const {
+      assert(STi < StackTop && "Access past stack top!");
+      return Stack[StackTop-1-STi];
+    }
+
+    // getSTReg - Return the X86::ST(i) register which contains the specified
+    // FP<RegNo> register
+    unsigned getSTReg(unsigned RegNo) const {
+      return StackTop - 1 - getSlot(RegNo) + llvm::X86::ST0;
+    }
+
+    // pushReg - Push the specified FP<n> register onto the stack
+    void pushReg(unsigned Reg) {
+      assert(Reg < 8 && "Register number out of range!");
+      assert(StackTop < 8 && "Stack overflow!");
+      Stack[StackTop] = Reg;
+      RegMap[Reg] = StackTop++;
+    }
+
+    bool isAtTop(unsigned RegNo) const { return getSlot(RegNo) == StackTop-1; }
+    void moveToTop(unsigned RegNo, MachineBasicBlock::iterator &I) {
+      if (!isAtTop(RegNo)) {
+	unsigned Slot = getSlot(RegNo);
+	unsigned STReg = getSTReg(RegNo);
+	unsigned RegOnTop = getStackEntry(0);
+
+	// Swap the slots the regs are in
+	std::swap(RegMap[RegNo], RegMap[RegOnTop]);
+
+	// Swap stack slot contents
+	assert(RegMap[RegOnTop] < StackTop);
+	std::swap(Stack[RegMap[RegOnTop]], Stack[StackTop-1]);
+
+	// Emit an fxch to update the runtime processors version of the state
+	BuildMI(*MBB, I, X86::FXCH, 1).addReg(STReg);
+	NumFXCH++;
+      }
+    }
+
+    void duplicateToTop(unsigned RegNo, unsigned AsReg, MachineInstr *I) {
+      unsigned STReg = getSTReg(RegNo);
+      pushReg(AsReg);   // New register on top of stack
+
+      BuildMI(*MBB, I, X86::FLDrr, 1).addReg(STReg);
+    }
+
+    // popStackAfter - Pop the current value off of the top of the FP stack
+    // after the specified instruction.
+    void popStackAfter(MachineBasicBlock::iterator &I);
+
+    // freeStackSlotAfter - Free the specified register from the register stack,
+    // so that it is no longer in a register.  If the register is currently at
+    // the top of the stack, we just pop the current instruction, otherwise we
+    // store the current top-of-stack into the specified slot, then pop the top
+    // of stack.
+    void freeStackSlotAfter(MachineBasicBlock::iterator &I, unsigned Reg);
+
+    bool processBasicBlock(MachineFunction &MF, MachineBasicBlock &MBB);
+
+    void handleZeroArgFP(MachineBasicBlock::iterator &I);
+    void handleOneArgFP(MachineBasicBlock::iterator &I);
+    void handleOneArgFPRW(MachineBasicBlock::iterator &I);
+    void handleTwoArgFP(MachineBasicBlock::iterator &I);
+    void handleCompareFP(MachineBasicBlock::iterator &I);
+    void handleCondMovFP(MachineBasicBlock::iterator &I);
+    void handleSpecialFP(MachineBasicBlock::iterator &I);
+  };
+}
+
+FunctionPass *llvm::createX86FloatingPointStackifierPass() { return new FPS(); }
+
+/// runOnMachineFunction - Loop over all of the basic blocks, transforming FP
+/// register references into FP stack references.
+///
+bool FPS::runOnMachineFunction(MachineFunction &MF) {
+  LV = &getAnalysis<LiveVariables>();
+  StackTop = 0;
+
+  // Process the function in depth first order so that we process at least one
+  // of the predecessors for every reachable block in the function.
+  std::set<MachineBasicBlock*> Processed;
+  MachineBasicBlock *Entry = MF.begin();
+
+  bool Changed = false;
+  for (df_ext_iterator<MachineBasicBlock*, std::set<MachineBasicBlock*> >
+         I = df_ext_begin(Entry, Processed), E = df_ext_end(Entry, Processed);
+       I != E; ++I)
+    Changed |= processBasicBlock(MF, **I);
+
+  return Changed;
+}
+
+/// processBasicBlock - Loop over all of the instructions in the basic block,
+/// transforming FP instructions into their stack form.
+///
+bool FPS::processBasicBlock(MachineFunction &MF, MachineBasicBlock &BB) {
+  const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
+  bool Changed = false;
+  MBB = &BB;
+  
+  for (MachineBasicBlock::iterator I = BB.begin(); I != BB.end(); ++I) {
+    MachineInstr *MI = I;
+    unsigned Flags = TII.get(MI->getOpcode()).TSFlags;
+    if ((Flags & X86II::FPTypeMask) == X86II::NotFP)
+      continue;  // Efficiently ignore non-fp insts!
+
+    MachineInstr *PrevMI = 0;
+    if (I != BB.begin())
+        PrevMI = prior(I);
+
+    ++NumFP;  // Keep track of # of pseudo instrs
+    DEBUG(std::cerr << "\nFPInst:\t";
+	  MI->print(std::cerr, &(MF.getTarget())));
+
+    // Get dead variables list now because the MI pointer may be deleted as part
+    // of processing!
+    LiveVariables::killed_iterator IB = LV->dead_begin(MI);
+    LiveVariables::killed_iterator IE = LV->dead_end(MI);
+
+    DEBUG(const MRegisterInfo *MRI = MF.getTarget().getRegisterInfo();
+	  LiveVariables::killed_iterator I = LV->killed_begin(MI);
+	  LiveVariables::killed_iterator E = LV->killed_end(MI);
+	  if (I != E) {
+	    std::cerr << "Killed Operands:";
+	    for (; I != E; ++I)
+	      std::cerr << " %" << MRI->getName(I->second);
+	    std::cerr << "\n";
+	  });
+
+    switch (Flags & X86II::FPTypeMask) {
+    case X86II::ZeroArgFP:  handleZeroArgFP(I); break;
+    case X86II::OneArgFP:   handleOneArgFP(I);  break;  // fstp ST(0)
+    case X86II::OneArgFPRW: handleOneArgFPRW(I); break; // ST(0) = fsqrt(ST(0))
+    case X86II::TwoArgFP:   handleTwoArgFP(I); break;
+    case X86II::CompareFP:  handleCompareFP(I); break;
+    case X86II::CondMovFP:  handleCondMovFP(I); break;
+    case X86II::SpecialFP:  handleSpecialFP(I); break;
+    default: assert(0 && "Unknown FP Type!");
+    }
+
+    // Check to see if any of the values defined by this instruction are dead
+    // after definition.  If so, pop them.
+    for (; IB != IE; ++IB) {
+      unsigned Reg = IB->second;
+      if (Reg >= X86::FP0 && Reg <= X86::FP6) {
+	DEBUG(std::cerr << "Register FP#" << Reg-X86::FP0 << " is dead!\n");
+        freeStackSlotAfter(I, Reg-X86::FP0);
+      }
+    }
+    
+    // Print out all of the instructions expanded to if -debug
+    DEBUG(
+      MachineBasicBlock::iterator PrevI(PrevMI);
+      if (I == PrevI) {
+        std::cerr << "Just deleted pseudo instruction\n";
+      } else {
+        MachineBasicBlock::iterator Start = I;
+        // Rewind to first instruction newly inserted.
+        while (Start != BB.begin() && prior(Start) != PrevI) --Start;
+        std::cerr << "Inserted instructions:\n\t";
+        Start->print(std::cerr, &MF.getTarget());
+        while (++Start != next(I));
+      }
+      dumpStack();
+    );
+
+    Changed = true;
+  }
+
+  assert(StackTop == 0 && "Stack not empty at end of basic block?");
+  return Changed;
+}
+
+//===----------------------------------------------------------------------===//
+// Efficient Lookup Table Support
+//===----------------------------------------------------------------------===//
+
+namespace {
+  struct TableEntry {
+    unsigned from;
+    unsigned to;
+    bool operator<(const TableEntry &TE) const { return from < TE.from; }
+    bool operator<(unsigned V) const { return from < V; }
+  };
+}
+
+static bool TableIsSorted(const TableEntry *Table, unsigned NumEntries) {
+  for (unsigned i = 0; i != NumEntries-1; ++i)
+    if (!(Table[i] < Table[i+1])) return false;
+  return true;
+}
+
+static int Lookup(const TableEntry *Table, unsigned N, unsigned Opcode) {
+  const TableEntry *I = std::lower_bound(Table, Table+N, Opcode);
+  if (I != Table+N && I->from == Opcode)
+    return I->to;
+  return -1;
+}
+
+#define ARRAY_SIZE(TABLE)  \
+   (sizeof(TABLE)/sizeof(TABLE[0]))
+
+#ifdef NDEBUG
+#define ASSERT_SORTED(TABLE)
+#else
+#define ASSERT_SORTED(TABLE)                                              \
+  { static bool TABLE##Checked = false;                                   \
+    if (!TABLE##Checked)                                                  \
+       assert(TableIsSorted(TABLE, ARRAY_SIZE(TABLE)) &&                  \
+              "All lookup tables must be sorted for efficient access!");  \
+  }
+#endif
+
+
+//===----------------------------------------------------------------------===//
+// Helper Methods
+//===----------------------------------------------------------------------===//
+
+// PopTable - Sorted map of instructions to their popping version.  The first
+// element is an instruction, the second is the version which pops.
+//
+static const TableEntry PopTable[] = {
+  { X86::FADDrST0 , X86::FADDPrST0  },
+
+  { X86::FDIVRrST0, X86::FDIVRPrST0 },
+  { X86::FDIVrST0 , X86::FDIVPrST0  },
+
+  { X86::FIST16m  , X86::FISTP16m   },
+  { X86::FIST32m  , X86::FISTP32m   },
+
+  { X86::FMULrST0 , X86::FMULPrST0  },
+
+  { X86::FST32m   , X86::FSTP32m    },
+  { X86::FST64m   , X86::FSTP64m    },
+  { X86::FSTrr    , X86::FSTPrr     },
+
+  { X86::FSUBRrST0, X86::FSUBRPrST0 },
+  { X86::FSUBrST0 , X86::FSUBPrST0  },
+
+  { X86::FUCOMIr  , X86::FUCOMIPr   },
+
+  { X86::FUCOMPr  , X86::FUCOMPPr   },
+  { X86::FUCOMr   , X86::FUCOMPr    },
+};
+
+/// popStackAfter - Pop the current value off of the top of the FP stack after
+/// the specified instruction.  This attempts to be sneaky and combine the pop
+/// into the instruction itself if possible.  The iterator is left pointing to
+/// the last instruction, be it a new pop instruction inserted, or the old
+/// instruction if it was modified in place.
+///
+void FPS::popStackAfter(MachineBasicBlock::iterator &I) {
+  ASSERT_SORTED(PopTable);
+  assert(StackTop > 0 && "Cannot pop empty stack!");
+  RegMap[Stack[--StackTop]] = ~0;     // Update state
+
+  // Check to see if there is a popping version of this instruction...
+  int Opcode = Lookup(PopTable, ARRAY_SIZE(PopTable), I->getOpcode());
+  if (Opcode != -1) {
+    I->setOpcode(Opcode);
+    if (Opcode == X86::FUCOMPPr)
+      I->RemoveOperand(0);
+
+  } else {    // Insert an explicit pop
+    I = BuildMI(*MBB, ++I, X86::FSTPrr, 1).addReg(X86::ST0);
+  }
+}
+
+/// freeStackSlotAfter - Free the specified register from the register stack, so
+/// that it is no longer in a register.  If the register is currently at the top
+/// of the stack, we just pop the current instruction, otherwise we store the
+/// current top-of-stack into the specified slot, then pop the top of stack.
+void FPS::freeStackSlotAfter(MachineBasicBlock::iterator &I, unsigned FPRegNo) {
+  if (getStackEntry(0) == FPRegNo) {  // already at the top of stack? easy.
+    popStackAfter(I);
+    return;
+  }
+
+  // Otherwise, store the top of stack into the dead slot, killing the operand
+  // without having to add in an explicit xchg then pop.
+  //
+  unsigned STReg    = getSTReg(FPRegNo);
+  unsigned OldSlot  = getSlot(FPRegNo);
+  unsigned TopReg   = Stack[StackTop-1];
+  Stack[OldSlot]    = TopReg;
+  RegMap[TopReg]    = OldSlot;
+  RegMap[FPRegNo]   = ~0;
+  Stack[--StackTop] = ~0;
+  I = BuildMI(*MBB, ++I, X86::FSTPrr, 1).addReg(STReg);
+}
+
+
+static unsigned getFPReg(const MachineOperand &MO) {
+  assert(MO.isRegister() && "Expected an FP register!");
+  unsigned Reg = MO.getReg();
+  assert(Reg >= X86::FP0 && Reg <= X86::FP6 && "Expected FP register!");
+  return Reg - X86::FP0;
+}
+
+
+//===----------------------------------------------------------------------===//
+// Instruction transformation implementation
+//===----------------------------------------------------------------------===//
+
+/// handleZeroArgFP - ST(0) = fld0    ST(0) = flds <mem>
+///
+void FPS::handleZeroArgFP(MachineBasicBlock::iterator &I) {
+  MachineInstr *MI = I;
+  unsigned DestReg = getFPReg(MI->getOperand(0));
+  MI->RemoveOperand(0);   // Remove the explicit ST(0) operand
+
+  // Result gets pushed on the stack...
+  pushReg(DestReg);
+}
+
+/// handleOneArgFP - fst <mem>, ST(0)
+///
+void FPS::handleOneArgFP(MachineBasicBlock::iterator &I) {
+  MachineInstr *MI = I;
+  assert((MI->getNumOperands() == 5 || MI->getNumOperands() == 1) &&
+         "Can only handle fst* & ftst instructions!");
+
+  // Is this the last use of the source register?
+  unsigned Reg = getFPReg(MI->getOperand(MI->getNumOperands()-1));
+  bool KillsSrc = false;
+  for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
+	 E = LV->killed_end(MI); KI != E; ++KI)
+    KillsSrc |= KI->second == X86::FP0+Reg;
+
+  // FSTP80r and FISTP64r are strange because there are no non-popping versions.
+  // If we have one _and_ we don't want to pop the operand, duplicate the value
+  // on the stack instead of moving it.  This ensure that popping the value is
+  // always ok.
+  //
+  if ((MI->getOpcode() == X86::FSTP80m ||
+       MI->getOpcode() == X86::FISTP64m) && !KillsSrc) {
+    duplicateToTop(Reg, 7 /*temp register*/, I);
+  } else {
+    moveToTop(Reg, I);            // Move to the top of the stack...
+  }
+  MI->RemoveOperand(MI->getNumOperands()-1);    // Remove explicit ST(0) operand
+  
+  if (MI->getOpcode() == X86::FSTP80m || MI->getOpcode() == X86::FISTP64m) {
+    assert(StackTop > 0 && "Stack empty??");
+    --StackTop;
+  } else if (KillsSrc) { // Last use of operand?
+    popStackAfter(I);
+  }
+}
+
+
+/// handleOneArgFPRW: Handle instructions that read from the top of stack and
+/// replace the value with a newly computed value.  These instructions may have
+/// non-fp operands after their FP operands.
+///
+///  Examples:
+///     R1 = fchs R2
+///     R1 = fadd R2, [mem]
+///
+void FPS::handleOneArgFPRW(MachineBasicBlock::iterator &I) {
+  MachineInstr *MI = I;
+  assert(MI->getNumOperands() >= 2 && "FPRW instructions must have 2 ops!!");
+
+  // Is this the last use of the source register?
+  unsigned Reg = getFPReg(MI->getOperand(1));
+  bool KillsSrc = false;
+  for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
+	 E = LV->killed_end(MI); KI != E; ++KI)
+    KillsSrc |= KI->second == X86::FP0+Reg;
+
+  if (KillsSrc) {
+    // If this is the last use of the source register, just make sure it's on
+    // the top of the stack.
+    moveToTop(Reg, I);
+    assert(StackTop > 0 && "Stack cannot be empty!");
+    --StackTop;
+    pushReg(getFPReg(MI->getOperand(0)));
+  } else {
+    // If this is not the last use of the source register, _copy_ it to the top
+    // of the stack.
+    duplicateToTop(Reg, getFPReg(MI->getOperand(0)), I);
+  }
+
+  MI->RemoveOperand(1);   // Drop the source operand.
+  MI->RemoveOperand(0);   // Drop the destination operand.
+}
+
+
+//===----------------------------------------------------------------------===//
+// Define tables of various ways to map pseudo instructions
+//
+
+// ForwardST0Table - Map: A = B op C  into: ST(0) = ST(0) op ST(i)
+static const TableEntry ForwardST0Table[] = {
+  { X86::FpADD  , X86::FADDST0r },
+  { X86::FpDIV  , X86::FDIVST0r },
+  { X86::FpMUL  , X86::FMULST0r },
+  { X86::FpSUB  , X86::FSUBST0r },
+};
+
+// ReverseST0Table - Map: A = B op C  into: ST(0) = ST(i) op ST(0)
+static const TableEntry ReverseST0Table[] = {
+  { X86::FpADD  , X86::FADDST0r  },   // commutative
+  { X86::FpDIV  , X86::FDIVRST0r },
+  { X86::FpMUL  , X86::FMULST0r  },   // commutative
+  { X86::FpSUB  , X86::FSUBRST0r },
+};
+
+// ForwardSTiTable - Map: A = B op C  into: ST(i) = ST(0) op ST(i)
+static const TableEntry ForwardSTiTable[] = {
+  { X86::FpADD  , X86::FADDrST0  },   // commutative
+  { X86::FpDIV  , X86::FDIVRrST0 },
+  { X86::FpMUL  , X86::FMULrST0  },   // commutative
+  { X86::FpSUB  , X86::FSUBRrST0 },
+};
+
+// ReverseSTiTable - Map: A = B op C  into: ST(i) = ST(i) op ST(0)
+static const TableEntry ReverseSTiTable[] = {
+  { X86::FpADD  , X86::FADDrST0 },
+  { X86::FpDIV  , X86::FDIVrST0 },
+  { X86::FpMUL  , X86::FMULrST0 },
+  { X86::FpSUB  , X86::FSUBrST0 },
+};
+
+
+/// handleTwoArgFP - Handle instructions like FADD and friends which are virtual
+/// instructions which need to be simplified and possibly transformed.
+///
+/// Result: ST(0) = fsub  ST(0), ST(i)
+///         ST(i) = fsub  ST(0), ST(i)
+///         ST(0) = fsubr ST(0), ST(i)
+///         ST(i) = fsubr ST(0), ST(i)
+/// 
+void FPS::handleTwoArgFP(MachineBasicBlock::iterator &I) {
+  ASSERT_SORTED(ForwardST0Table); ASSERT_SORTED(ReverseST0Table);
+  ASSERT_SORTED(ForwardSTiTable); ASSERT_SORTED(ReverseSTiTable);
+  MachineInstr *MI = I;
+
+  unsigned NumOperands = MI->getNumOperands();
+  assert(NumOperands == 3 && "Illegal TwoArgFP instruction!");
+  unsigned Dest = getFPReg(MI->getOperand(0));
+  unsigned Op0 = getFPReg(MI->getOperand(NumOperands-2));
+  unsigned Op1 = getFPReg(MI->getOperand(NumOperands-1));
+  bool KillsOp0 = false, KillsOp1 = false;
+
+  for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
+	 E = LV->killed_end(MI); KI != E; ++KI) {
+    KillsOp0 |= (KI->second == X86::FP0+Op0);
+    KillsOp1 |= (KI->second == X86::FP0+Op1);
+  }
+
+  unsigned TOS = getStackEntry(0);
+
+  // One of our operands must be on the top of the stack.  If neither is yet, we
+  // need to move one.
+  if (Op0 != TOS && Op1 != TOS) {   // No operand at TOS?
+    // We can choose to move either operand to the top of the stack.  If one of
+    // the operands is killed by this instruction, we want that one so that we
+    // can update right on top of the old version.
+    if (KillsOp0) {
+      moveToTop(Op0, I);         // Move dead operand to TOS.
+      TOS = Op0;
+    } else if (KillsOp1) {
+      moveToTop(Op1, I);
+      TOS = Op1;
+    } else {
+      // All of the operands are live after this instruction executes, so we
+      // cannot update on top of any operand.  Because of this, we must
+      // duplicate one of the stack elements to the top.  It doesn't matter
+      // which one we pick.
+      //
+      duplicateToTop(Op0, Dest, I);
+      Op0 = TOS = Dest;
+      KillsOp0 = true;
+    }
+  } else if (!KillsOp0 && !KillsOp1) {
+    // If we DO have one of our operands at the top of the stack, but we don't
+    // have a dead operand, we must duplicate one of the operands to a new slot
+    // on the stack.
+    duplicateToTop(Op0, Dest, I);
+    Op0 = TOS = Dest;
+    KillsOp0 = true;
+  }
+
+  // Now we know that one of our operands is on the top of the stack, and at
+  // least one of our operands is killed by this instruction.
+  assert((TOS == Op0 || TOS == Op1) && (KillsOp0 || KillsOp1) && 
+	 "Stack conditions not set up right!");
+
+  // We decide which form to use based on what is on the top of the stack, and
+  // which operand is killed by this instruction.
+  const TableEntry *InstTable;
+  bool isForward = TOS == Op0;
+  bool updateST0 = (TOS == Op0 && !KillsOp1) || (TOS == Op1 && !KillsOp0);
+  if (updateST0) {
+    if (isForward)
+      InstTable = ForwardST0Table;
+    else
+      InstTable = ReverseST0Table;
+  } else {
+    if (isForward)
+      InstTable = ForwardSTiTable;
+    else
+      InstTable = ReverseSTiTable;
+  }
+  
+  int Opcode = Lookup(InstTable, ARRAY_SIZE(ForwardST0Table), MI->getOpcode());
+  assert(Opcode != -1 && "Unknown TwoArgFP pseudo instruction!");
+
+  // NotTOS - The register which is not on the top of stack...
+  unsigned NotTOS = (TOS == Op0) ? Op1 : Op0;
+
+  // Replace the old instruction with a new instruction
+  MBB->remove(I++);
+  I = BuildMI(*MBB, I, Opcode, 1).addReg(getSTReg(NotTOS));
+
+  // If both operands are killed, pop one off of the stack in addition to
+  // overwriting the other one.
+  if (KillsOp0 && KillsOp1 && Op0 != Op1) {
+    assert(!updateST0 && "Should have updated other operand!");
+    popStackAfter(I);   // Pop the top of stack
+  }
+
+  // Update stack information so that we know the destination register is now on
+  // the stack.
+  unsigned UpdatedSlot = getSlot(updateST0 ? TOS : NotTOS);
+  assert(UpdatedSlot < StackTop && Dest < 7);
+  Stack[UpdatedSlot]   = Dest;
+  RegMap[Dest]         = UpdatedSlot;
+  delete MI;   // Remove the old instruction
+}
+
+/// handleCompareFP - Handle FUCOM and FUCOMI instructions, which have two FP
+/// register arguments and no explicit destinations.
+/// 
+void FPS::handleCompareFP(MachineBasicBlock::iterator &I) {
+  ASSERT_SORTED(ForwardST0Table); ASSERT_SORTED(ReverseST0Table);
+  ASSERT_SORTED(ForwardSTiTable); ASSERT_SORTED(ReverseSTiTable);
+  MachineInstr *MI = I;
+
+  unsigned NumOperands = MI->getNumOperands();
+  assert(NumOperands == 2 && "Illegal FUCOM* instruction!");
+  unsigned Op0 = getFPReg(MI->getOperand(NumOperands-2));
+  unsigned Op1 = getFPReg(MI->getOperand(NumOperands-1));
+  bool KillsOp0 = false, KillsOp1 = false;
+
+  for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
+	 E = LV->killed_end(MI); KI != E; ++KI) {
+    KillsOp0 |= (KI->second == X86::FP0+Op0);
+    KillsOp1 |= (KI->second == X86::FP0+Op1);
+  }
+
+  // Make sure the first operand is on the top of stack, the other one can be
+  // anywhere.
+  moveToTop(Op0, I);
+
+  MI->getOperand(0).setReg(getSTReg(Op1));
+  MI->RemoveOperand(1);
+
+  // If any of the operands are killed by this instruction, free them.
+  if (KillsOp0) freeStackSlotAfter(I, Op0);
+  if (KillsOp1 && Op0 != Op1) freeStackSlotAfter(I, Op1);
+}
+
+/// handleCondMovFP - Handle two address conditional move instructions.  These
+/// instructions move a st(i) register to st(0) iff a condition is true.  These
+/// instructions require that the first operand is at the top of the stack, but
+/// otherwise don't modify the stack at all.
+void FPS::handleCondMovFP(MachineBasicBlock::iterator &I) {
+  MachineInstr *MI = I;
+
+  unsigned Op0 = getFPReg(MI->getOperand(0));
+  unsigned Op1 = getFPReg(MI->getOperand(1));
+
+  // The first operand *must* be on the top of the stack.
+  moveToTop(Op0, I);
+
+  // Change the second operand to the stack register that the operand is in.
+  MI->RemoveOperand(0);
+  MI->getOperand(0).setReg(getSTReg(Op1));
+
+  // If we kill the second operand, make sure to pop it from the stack.
+  if (Op0 != Op1) 
+    for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
+           E = LV->killed_end(MI); KI != E; ++KI)
+      if (KI->second == X86::FP0+Op1) {
+        // Get this value off of the register stack.
+        freeStackSlotAfter(I, Op1);
+        break;
+      }
+}
+
+
+/// handleSpecialFP - Handle special instructions which behave unlike other
+/// floating point instructions.  This is primarily intended for use by pseudo
+/// instructions.
+///
+void FPS::handleSpecialFP(MachineBasicBlock::iterator &I) {
+  MachineInstr *MI = I;
+  switch (MI->getOpcode()) {
+  default: assert(0 && "Unknown SpecialFP instruction!");
+  case X86::FpGETRESULT:  // Appears immediately after a call returning FP type!
+    assert(StackTop == 0 && "Stack should be empty after a call!");
+    pushReg(getFPReg(MI->getOperand(0)));
+    break;
+  case X86::FpSETRESULT:
+    assert(StackTop == 1 && "Stack should have one element on it to return!");
+    --StackTop;   // "Forget" we have something on the top of stack!
+    break;
+  case X86::FpMOV: {
+    unsigned SrcReg = getFPReg(MI->getOperand(1));
+    unsigned DestReg = getFPReg(MI->getOperand(0));
+    bool KillsSrc = false;
+    for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
+	   E = LV->killed_end(MI); KI != E; ++KI)
+      KillsSrc |= KI->second == X86::FP0+SrcReg;
+
+    if (KillsSrc) {
+      // If the input operand is killed, we can just change the owner of the
+      // incoming stack slot into the result.
+      unsigned Slot = getSlot(SrcReg);
+      assert(Slot < 7 && DestReg < 7 && "FpMOV operands invalid!");
+      Stack[Slot] = DestReg;
+      RegMap[DestReg] = Slot;
+
+    } else {
+      // For FMOV we just duplicate the specified value to a new stack slot.
+      // This could be made better, but would require substantial changes.
+      duplicateToTop(SrcReg, DestReg, I);
+    }
+    break;
+  }
+  }
+
+  I = MBB->erase(I);  // Remove the pseudo instruction
+  --I;
+}