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42e25b387f
llvm-6502/lib/Target/X86/X86FloatingPoint.cpp
Chris Lattner 42e25b387f Allow the FP stackifier to completely ignore functions that do not use FP at 
all.  This should speed up the X86 backend fairly significantly on integer
codes.  Now if only we didn't have to compute livevar still... ;-)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@19796 91177308-0d34-0410-b5e6-96231b3b80d8
2005-01-23 23:13:59 +00:00

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//===-- X86FloatingPoint.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 "llvm/Support/Debug.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/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) {
// We only need to run this pass if there are any FP registers used in this
// function. If it is all integer, there is nothing for us to do!
const bool *PhysRegsUsed = MF.getUsedPhysregs();
bool FPIsUsed = false;
assert(X86::FP6 == X86::FP0+6 && "Register enums aren't sorted right!");
for (unsigned i = 0; i <= 6; ++i)
if (PhysRegsUsed[X86::FP0+i]) {
FPIsUsed = true;
break;
}
// Early exit.
if (!FPIsUsed) return false;
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;
}
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