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llvm-project/llvm/lib/Target/X86/X86FloatingPoint.cpp

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//===-- X86FloatingPoint.cpp - Floating point Reg -> Stack converter ------===//
//
// The LLVM Compiler Infrastructure
//
// This file 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
// pseudo registers into register stack instructions. This pass uses live
// variable information to indicate where the FPn registers are used and their
// lifetimes.
//
// The x87 hardware tracks liveness of the stack registers, so it is necessary
// to implement exact liveness tracking between basic blocks. The CFG edges are
// partitioned into bundles where the same FP registers must be live in
// identical stack positions. Instructions are inserted at the end of each basic
// block to rearrange the live registers to match the outgoing bundle.
//
// This approach avoids splitting critical edges at the potential cost of more
// live register shuffling instructions when critical edges are present.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "x86-codegen"
#include "X86.h"
#include "X86InstrInfo.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/EdgeBundles.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include <algorithm>
using namespace llvm;
STATISTIC(NumFXCH, "Number of fxch instructions inserted");
STATISTIC(NumFP , "Number of floating point instructions");
namespace {
struct FPS : public MachineFunctionPass {
static char ID;
FPS() : MachineFunctionPass(ID) {
initializeEdgeBundlesPass(*PassRegistry::getPassRegistry());
// This is really only to keep valgrind quiet.
// The logic in isLive() is too much for it.
memset(Stack, 0, sizeof(Stack));
memset(RegMap, 0, sizeof(RegMap));
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
AU.addRequired<EdgeBundles>();
AU.addPreservedID(MachineLoopInfoID);
AU.addPreservedID(MachineDominatorsID);
MachineFunctionPass::getAnalysisUsage(AU);
}
virtual bool runOnMachineFunction(MachineFunction &MF);
virtual const char *getPassName() const { return "X86 FP Stackifier"; }
private:
const TargetInstrInfo *TII; // Machine instruction info.
// Two CFG edges are related if they leave the same block, or enter the same
// block. The transitive closure of an edge under this relation is a
// LiveBundle. It represents a set of CFG edges where the live FP stack
// registers must be allocated identically in the x87 stack.
//
// A LiveBundle is usually all the edges leaving a block, or all the edges
// entering a block, but it can contain more edges if critical edges are
// present.
//
// The set of live FP registers in a LiveBundle is calculated by bundleCFG,
// but the exact mapping of FP registers to stack slots is fixed later.
struct LiveBundle {
// Bit mask of live FP registers. Bit 0 = FP0, bit 1 = FP1, &c.
unsigned Mask;
// Number of pre-assigned live registers in FixStack. This is 0 when the
// stack order has not yet been fixed.
unsigned FixCount;
// Assigned stack order for live-in registers.
// FixStack[i] == getStackEntry(i) for all i < FixCount.
unsigned char FixStack[8];
LiveBundle() : Mask(0), FixCount(0) {}
// Have the live registers been assigned a stack order yet?
bool isFixed() const { return !Mask || FixCount; }
};
// Numbered LiveBundle structs. LiveBundles[0] is used for all CFG edges
// with no live FP registers.
SmallVector<LiveBundle, 8> LiveBundles;
// The edge bundle analysis provides indices into the LiveBundles vector.
EdgeBundles *Bundles;
// Return a bitmask of FP registers in block's live-in list.
static unsigned calcLiveInMask(MachineBasicBlock *MBB) {
unsigned Mask = 0;
for (MachineBasicBlock::livein_iterator I = MBB->livein_begin(),
E = MBB->livein_end(); I != E; ++I) {
unsigned Reg = *I - X86::FP0;
if (Reg < 8)
Mask |= 1 << Reg;
}
return Mask;
}
// Partition all the CFG edges into LiveBundles.
void bundleCFG(MachineFunction &MF);
MachineBasicBlock *MBB; // Current basic block
// The hardware keeps track of how many FP registers are live, so we have
// to model that exactly. Usually, each live register corresponds to an
// FP<n> register, but when dealing with calls, returns, and inline
// assembly, it is sometimes necessary to have live scratch registers.
unsigned Stack[8]; // FP<n> Registers in each stack slot...
unsigned StackTop; // The current top of the FP stack.
enum {
NumFPRegs = 16 // Including scratch pseudo-registers.
};
// For each live FP<n> register, point to its Stack[] entry.
// The first entries correspond to FP0-FP6, the rest are scratch registers
// used when we need slightly different live registers than what the
// register allocator thinks.
unsigned RegMap[NumFPRegs];
// Pending fixed registers - Inline assembly needs FP registers to appear
// in fixed stack slot positions. This is handled by copying FP registers
// to ST registers before the instruction, and copying back after the
// instruction.
//
// This is modeled with pending ST registers. NumPendingSTs is the number
// of ST registers (ST0-STn) we are tracking. PendingST[n] points to an FP
// register that holds the ST value. The ST registers are not moved into
// place until immediately before the instruction that needs them.
//
// It can happen that we need an ST register to be live when no FP register
// holds the value:
//
// %ST0 = COPY %FP4<kill>
//
// When that happens, we allocate a scratch FP register to hold the ST
// value. That means every register in PendingST must be live.
unsigned NumPendingSTs;
unsigned char PendingST[8];
// Set up our stack model to match the incoming registers to MBB.
void setupBlockStack();
// Shuffle live registers to match the expectations of successor blocks.
void finishBlockStack();
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void dumpStack() const {
dbgs() << "Stack contents:";
for (unsigned i = 0; i != StackTop; ++i) {
dbgs() << " FP" << Stack[i];
assert(RegMap[Stack[i]] == i && "Stack[] doesn't match RegMap[]!");
}
for (unsigned i = 0; i != NumPendingSTs; ++i)
dbgs() << ", ST" << i << " in FP" << unsigned(PendingST[i]);
dbgs() << "\n";
}
#endif
/// getSlot - Return the stack slot number a particular register number is
/// in.
unsigned getSlot(unsigned RegNo) const {
assert(RegNo < NumFPRegs && "Regno out of range!");
return RegMap[RegNo];
}
/// isLive - Is RegNo currently live in the stack?
bool isLive(unsigned RegNo) const {
unsigned Slot = getSlot(RegNo);
return Slot < StackTop && Stack[Slot] == RegNo;
}
/// getScratchReg - Return an FP register that is not currently in use.
unsigned getScratchReg() const {
for (int i = NumFPRegs - 1; i >= 8; --i)
if (!isLive(i))
return i;
llvm_unreachable("Ran out of scratch FP registers");
}
/// isScratchReg - Returns trus if RegNo is a scratch FP register.
static bool isScratchReg(unsigned RegNo) {
return RegNo > 8 && RegNo < NumFPRegs;
}
/// getStackEntry - Return the X86::FP<n> register in register ST(i).
unsigned getStackEntry(unsigned STi) const {
if (STi >= StackTop)
report_fatal_error("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) + X86::ST0;
}
// pushReg - Push the specified FP<n> register onto the stack.
void pushReg(unsigned Reg) {
assert(Reg < NumFPRegs && "Register number out of range!");
if (StackTop >= 8)
report_fatal_error("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) {
DebugLoc dl = I == MBB->end() ? DebugLoc() : I->getDebugLoc();
if (isAtTop(RegNo)) return;
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.
if (RegMap[RegOnTop] >= StackTop)
report_fatal_error("Access past stack top!");
std::swap(Stack[RegMap[RegOnTop]], Stack[StackTop-1]);
// Emit an fxch to update the runtime processors version of the state.
BuildMI(*MBB, I, dl, TII->get(X86::XCH_F)).addReg(STReg);
++NumFXCH;
}
void duplicateToTop(unsigned RegNo, unsigned AsReg, MachineInstr *I) {
DebugLoc dl = I == MBB->end() ? DebugLoc() : I->getDebugLoc();
unsigned STReg = getSTReg(RegNo);
pushReg(AsReg); // New register on top of stack
BuildMI(*MBB, I, dl, TII->get(X86::LD_Frr)).addReg(STReg);
}
/// duplicatePendingSTBeforeKill - The instruction at I is about to kill
/// RegNo. If any PendingST registers still need the RegNo value, duplicate
/// them to new scratch registers.
void duplicatePendingSTBeforeKill(unsigned RegNo, MachineInstr *I) {
for (unsigned i = 0; i != NumPendingSTs; ++i) {
if (PendingST[i] != RegNo)
continue;
unsigned SR = getScratchReg();
DEBUG(dbgs() << "Duplicating pending ST" << i
<< " in FP" << RegNo << " to FP" << SR << '\n');
duplicateToTop(RegNo, SR, I);
PendingST[i] = SR;
}
}
/// 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);
/// freeStackSlotBefore - Just the pop, no folding. Return the inserted
/// instruction.
MachineBasicBlock::iterator
freeStackSlotBefore(MachineBasicBlock::iterator I, unsigned FPRegNo);
/// Adjust the live registers to be the set in Mask.
void adjustLiveRegs(unsigned Mask, MachineBasicBlock::iterator I);
/// Shuffle the top FixCount stack entries such that FP reg FixStack[0] is
/// st(0), FP reg FixStack[1] is st(1) etc.
void shuffleStackTop(const unsigned char *FixStack, unsigned FixCount,
MachineBasicBlock::iterator I);
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);
// Check if a COPY instruction is using FP registers.
static bool isFPCopy(MachineInstr *MI) {
unsigned DstReg = MI->getOperand(0).getReg();
unsigned SrcReg = MI->getOperand(1).getReg();
return X86::RFP80RegClass.contains(DstReg) ||
X86::RFP80RegClass.contains(SrcReg);
}
};
char FPS::ID = 0;
}
FunctionPass *llvm::createX86FloatingPointStackifierPass() { return new FPS(); }
/// getFPReg - Return the X86::FPx register number for the specified operand.
/// For example, this returns 3 for X86::FP3.
static unsigned getFPReg(const MachineOperand &MO) {
assert(MO.isReg() && "Expected an FP register!");
unsigned Reg = MO.getReg();
assert(Reg >= X86::FP0 && Reg <= X86::FP6 && "Expected FP register!");
return Reg - X86::FP0;
}
/// 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!
bool FPIsUsed = false;
assert(X86::FP6 == X86::FP0+6 && "Register enums aren't sorted right!");
for (unsigned i = 0; i <= 6; ++i)
if (MF.getRegInfo().isPhysRegUsed(X86::FP0+i)) {
FPIsUsed = true;
break;
}
// Early exit.
if (!FPIsUsed) return false;
Bundles = &getAnalysis<EdgeBundles>();
TII = MF.getTarget().getInstrInfo();
// Prepare cross-MBB liveness.
bundleCFG(MF);
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.
SmallPtrSet<MachineBasicBlock*, 8> Processed;
MachineBasicBlock *Entry = MF.begin();
bool Changed = false;
for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*, 8> >
I = df_ext_begin(Entry, Processed), E = df_ext_end(Entry, Processed);
I != E; ++I)
Changed |= processBasicBlock(MF, **I);
// Process any unreachable blocks in arbitrary order now.
if (MF.size() != Processed.size())
for (MachineFunction::iterator BB = MF.begin(), E = MF.end(); BB != E; ++BB)
if (Processed.insert(BB))
Changed |= processBasicBlock(MF, *BB);
LiveBundles.clear();
return Changed;
}
/// bundleCFG - Scan all the basic blocks to determine consistent live-in and
/// live-out sets for the FP registers. Consistent means that the set of
/// registers live-out from a block is identical to the live-in set of all
/// successors. This is not enforced by the normal live-in lists since
/// registers may be implicitly defined, or not used by all successors.
void FPS::bundleCFG(MachineFunction &MF) {
assert(LiveBundles.empty() && "Stale data in LiveBundles");
LiveBundles.resize(Bundles->getNumBundles());
// Gather the actual live-in masks for all MBBs.
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
MachineBasicBlock *MBB = I;
const unsigned Mask = calcLiveInMask(MBB);
if (!Mask)
continue;
// Update MBB ingoing bundle mask.
LiveBundles[Bundles->getBundle(MBB->getNumber(), false)].Mask |= Mask;
}
}
/// 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) {
bool Changed = false;
MBB = &BB;
NumPendingSTs = 0;
setupBlockStack();
for (MachineBasicBlock::iterator I = BB.begin(); I != BB.end(); ++I) {
MachineInstr *MI = I;
uint64_t Flags = MI->getDesc().TSFlags;
unsigned FPInstClass = Flags & X86II::FPTypeMask;
if (MI->isInlineAsm())
FPInstClass = X86II::SpecialFP;
if (MI->isCopy() && isFPCopy(MI))
FPInstClass = X86II::SpecialFP;
if (MI->isImplicitDef() &&
X86::RFP80RegClass.contains(MI->getOperand(0).getReg()))
FPInstClass = X86II::SpecialFP;
if (FPInstClass == 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(dbgs() << "\nFPInst:\t" << *MI);
// Get dead variables list now because the MI pointer may be deleted as part
// of processing!
SmallVector<unsigned, 8> DeadRegs;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (MO.isReg() && MO.isDead())
DeadRegs.push_back(MO.getReg());
}
switch (FPInstClass) {
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: llvm_unreachable("Unknown FP Type!");
}
// Check to see if any of the values defined by this instruction are dead
// after definition. If so, pop them.
for (unsigned i = 0, e = DeadRegs.size(); i != e; ++i) {
unsigned Reg = DeadRegs[i];
if (Reg >= X86::FP0 && Reg <= X86::FP6) {
DEBUG(dbgs() << "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) {
dbgs() << "Just deleted pseudo instruction\n";
} else {
MachineBasicBlock::iterator Start = I;
// Rewind to first instruction newly inserted.
while (Start != BB.begin() && prior(Start) != PrevI) --Start;
dbgs() << "Inserted instructions:\n\t";
Start->print(dbgs(), &MF.getTarget());
while (++Start != llvm::next(I)) {}
}
dumpStack();
);
(void)PrevMI;
Changed = true;
}
finishBlockStack();
return Changed;
}
/// setupBlockStack - Use the live bundles to set up our model of the stack
/// to match predecessors' live out stack.
void FPS::setupBlockStack() {
DEBUG(dbgs() << "\nSetting up live-ins for BB#" << MBB->getNumber()
<< " derived from " << MBB->getName() << ".\n");
StackTop = 0;
// Get the live-in bundle for MBB.
const LiveBundle &Bundle =
LiveBundles[Bundles->getBundle(MBB->getNumber(), false)];
if (!Bundle.Mask) {
DEBUG(dbgs() << "Block has no FP live-ins.\n");
return;
}
// Depth-first iteration should ensure that we always have an assigned stack.
assert(Bundle.isFixed() && "Reached block before any predecessors");
// Push the fixed live-in registers.
for (unsigned i = Bundle.FixCount; i > 0; --i) {
MBB->addLiveIn(X86::ST0+i-1);
DEBUG(dbgs() << "Live-in st(" << (i-1) << "): %FP"
<< unsigned(Bundle.FixStack[i-1]) << '\n');
pushReg(Bundle.FixStack[i-1]);
}
// Kill off unwanted live-ins. This can happen with a critical edge.
// FIXME: We could keep these live registers around as zombies. They may need
// to be revived at the end of a short block. It might save a few instrs.
adjustLiveRegs(calcLiveInMask(MBB), MBB->begin());
DEBUG(MBB->dump());
}
/// finishBlockStack - Revive live-outs that are implicitly defined out of
/// MBB. Shuffle live registers to match the expected fixed stack of any
/// predecessors, and ensure that all predecessors are expecting the same
/// stack.
void FPS::finishBlockStack() {
// The RET handling below takes care of return blocks for us.
if (MBB->succ_empty())
return;
DEBUG(dbgs() << "Setting up live-outs for BB#" << MBB->getNumber()
<< " derived from " << MBB->getName() << ".\n");
// Get MBB's live-out bundle.
unsigned BundleIdx = Bundles->getBundle(MBB->getNumber(), true);
LiveBundle &Bundle = LiveBundles[BundleIdx];
// We may need to kill and define some registers to match successors.
// FIXME: This can probably be combined with the shuffle below.
MachineBasicBlock::iterator Term = MBB->getFirstTerminator();
adjustLiveRegs(Bundle.Mask, Term);
if (!Bundle.Mask) {
DEBUG(dbgs() << "No live-outs.\n");
return;
}
// Has the stack order been fixed yet?
DEBUG(dbgs() << "LB#" << BundleIdx << ": ");
if (Bundle.isFixed()) {
DEBUG(dbgs() << "Shuffling stack to match.\n");
shuffleStackTop(Bundle.FixStack, Bundle.FixCount, Term);
} else {
// Not fixed yet, we get to choose.
DEBUG(dbgs() << "Fixing stack order now.\n");
Bundle.FixCount = StackTop;
for (unsigned i = 0; i < StackTop; ++i)
Bundle.FixStack[i] = getStackEntry(i);
}
}
//===----------------------------------------------------------------------===//
// Efficient Lookup Table Support
//===----------------------------------------------------------------------===//
namespace {
struct TableEntry {
uint16_t from;
uint16_t to;
bool operator<(const TableEntry &TE) const { return from < TE.from; }
friend bool operator<(const TableEntry &TE, unsigned V) {
return TE.from < V;
}
friend bool LLVM_ATTRIBUTE_UNUSED operator<(unsigned V,
const TableEntry &TE) {
return V < TE.from;
}
};
}
#ifndef NDEBUG
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;
}
#endif
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;
}
#ifdef NDEBUG
#define ASSERT_SORTED(TABLE)
#else
#define ASSERT_SORTED(TABLE) \
{ static bool TABLE##Checked = false; \
if (!TABLE##Checked) { \
assert(TableIsSorted(TABLE, array_lengthof(TABLE)) && \
"All lookup tables must be sorted for efficient access!"); \
TABLE##Checked = true; \
} \
}
#endif
//===----------------------------------------------------------------------===//
// Register File -> Register Stack Mapping Methods
//===----------------------------------------------------------------------===//
// OpcodeTable - Sorted map of register instructions to their stack version.
// The first element is an register file pseudo instruction, the second is the
// concrete X86 instruction which uses the register stack.
//
static const TableEntry OpcodeTable[] = {
{ X86::ABS_Fp32 , X86::ABS_F },
{ X86::ABS_Fp64 , X86::ABS_F },
{ X86::ABS_Fp80 , X86::ABS_F },
{ X86::ADD_Fp32m , X86::ADD_F32m },
{ X86::ADD_Fp64m , X86::ADD_F64m },
{ X86::ADD_Fp64m32 , X86::ADD_F32m },
{ X86::ADD_Fp80m32 , X86::ADD_F32m },
{ X86::ADD_Fp80m64 , X86::ADD_F64m },
{ X86::ADD_FpI16m32 , X86::ADD_FI16m },
{ X86::ADD_FpI16m64 , X86::ADD_FI16m },
{ X86::ADD_FpI16m80 , X86::ADD_FI16m },
{ X86::ADD_FpI32m32 , X86::ADD_FI32m },
{ X86::ADD_FpI32m64 , X86::ADD_FI32m },
{ X86::ADD_FpI32m80 , X86::ADD_FI32m },
{ X86::CHS_Fp32 , X86::CHS_F },
{ X86::CHS_Fp64 , X86::CHS_F },
{ X86::CHS_Fp80 , X86::CHS_F },
{ X86::CMOVBE_Fp32 , X86::CMOVBE_F },
{ X86::CMOVBE_Fp64 , X86::CMOVBE_F },
{ X86::CMOVBE_Fp80 , X86::CMOVBE_F },
{ X86::CMOVB_Fp32 , X86::CMOVB_F },
{ X86::CMOVB_Fp64 , X86::CMOVB_F },
{ X86::CMOVB_Fp80 , X86::CMOVB_F },
{ X86::CMOVE_Fp32 , X86::CMOVE_F },
{ X86::CMOVE_Fp64 , X86::CMOVE_F },
{ X86::CMOVE_Fp80 , X86::CMOVE_F },
{ X86::CMOVNBE_Fp32 , X86::CMOVNBE_F },
{ X86::CMOVNBE_Fp64 , X86::CMOVNBE_F },
{ X86::CMOVNBE_Fp80 , X86::CMOVNBE_F },
{ X86::CMOVNB_Fp32 , X86::CMOVNB_F },
{ X86::CMOVNB_Fp64 , X86::CMOVNB_F },
{ X86::CMOVNB_Fp80 , X86::CMOVNB_F },
{ X86::CMOVNE_Fp32 , X86::CMOVNE_F },
{ X86::CMOVNE_Fp64 , X86::CMOVNE_F },
{ X86::CMOVNE_Fp80 , X86::CMOVNE_F },
{ X86::CMOVNP_Fp32 , X86::CMOVNP_F },
{ X86::CMOVNP_Fp64 , X86::CMOVNP_F },
{ X86::CMOVNP_Fp80 , X86::CMOVNP_F },
{ X86::CMOVP_Fp32 , X86::CMOVP_F },
{ X86::CMOVP_Fp64 , X86::CMOVP_F },
{ X86::CMOVP_Fp80 , X86::CMOVP_F },
{ X86::COS_Fp32 , X86::COS_F },
{ X86::COS_Fp64 , X86::COS_F },
{ X86::COS_Fp80 , X86::COS_F },
{ X86::DIVR_Fp32m , X86::DIVR_F32m },
{ X86::DIVR_Fp64m , X86::DIVR_F64m },
{ X86::DIVR_Fp64m32 , X86::DIVR_F32m },
{ X86::DIVR_Fp80m32 , X86::DIVR_F32m },
{ X86::DIVR_Fp80m64 , X86::DIVR_F64m },
{ X86::DIVR_FpI16m32, X86::DIVR_FI16m},
{ X86::DIVR_FpI16m64, X86::DIVR_FI16m},
{ X86::DIVR_FpI16m80, X86::DIVR_FI16m},
{ X86::DIVR_FpI32m32, X86::DIVR_FI32m},
{ X86::DIVR_FpI32m64, X86::DIVR_FI32m},
{ X86::DIVR_FpI32m80, X86::DIVR_FI32m},
{ X86::DIV_Fp32m , X86::DIV_F32m },
{ X86::DIV_Fp64m , X86::DIV_F64m },
{ X86::DIV_Fp64m32 , X86::DIV_F32m },
{ X86::DIV_Fp80m32 , X86::DIV_F32m },
{ X86::DIV_Fp80m64 , X86::DIV_F64m },
{ X86::DIV_FpI16m32 , X86::DIV_FI16m },
{ X86::DIV_FpI16m64 , X86::DIV_FI16m },
{ X86::DIV_FpI16m80 , X86::DIV_FI16m },
{ X86::DIV_FpI32m32 , X86::DIV_FI32m },
{ X86::DIV_FpI32m64 , X86::DIV_FI32m },
{ X86::DIV_FpI32m80 , X86::DIV_FI32m },
{ X86::ILD_Fp16m32 , X86::ILD_F16m },
{ X86::ILD_Fp16m64 , X86::ILD_F16m },
{ X86::ILD_Fp16m80 , X86::ILD_F16m },
{ X86::ILD_Fp32m32 , X86::ILD_F32m },
{ X86::ILD_Fp32m64 , X86::ILD_F32m },
{ X86::ILD_Fp32m80 , X86::ILD_F32m },
{ X86::ILD_Fp64m32 , X86::ILD_F64m },
{ X86::ILD_Fp64m64 , X86::ILD_F64m },
{ X86::ILD_Fp64m80 , X86::ILD_F64m },
{ X86::ISTT_Fp16m32 , X86::ISTT_FP16m},
{ X86::ISTT_Fp16m64 , X86::ISTT_FP16m},
{ X86::ISTT_Fp16m80 , X86::ISTT_FP16m},
{ X86::ISTT_Fp32m32 , X86::ISTT_FP32m},
{ X86::ISTT_Fp32m64 , X86::ISTT_FP32m},
{ X86::ISTT_Fp32m80 , X86::ISTT_FP32m},
{ X86::ISTT_Fp64m32 , X86::ISTT_FP64m},
{ X86::ISTT_Fp64m64 , X86::ISTT_FP64m},
{ X86::ISTT_Fp64m80 , X86::ISTT_FP64m},
{ X86::IST_Fp16m32 , X86::IST_F16m },
{ X86::IST_Fp16m64 , X86::IST_F16m },
{ X86::IST_Fp16m80 , X86::IST_F16m },
{ X86::IST_Fp32m32 , X86::IST_F32m },
{ X86::IST_Fp32m64 , X86::IST_F32m },
{ X86::IST_Fp32m80 , X86::IST_F32m },
{ X86::IST_Fp64m32 , X86::IST_FP64m },
{ X86::IST_Fp64m64 , X86::IST_FP64m },
{ X86::IST_Fp64m80 , X86::IST_FP64m },
{ X86::LD_Fp032 , X86::LD_F0 },
{ X86::LD_Fp064 , X86::LD_F0 },
{ X86::LD_Fp080 , X86::LD_F0 },
{ X86::LD_Fp132 , X86::LD_F1 },
{ X86::LD_Fp164 , X86::LD_F1 },
{ X86::LD_Fp180 , X86::LD_F1 },
{ X86::LD_Fp32m , X86::LD_F32m },
{ X86::LD_Fp32m64 , X86::LD_F32m },
{ X86::LD_Fp32m80 , X86::LD_F32m },
{ X86::LD_Fp64m , X86::LD_F64m },
{ X86::LD_Fp64m80 , X86::LD_F64m },
{ X86::LD_Fp80m , X86::LD_F80m },
{ X86::MUL_Fp32m , X86::MUL_F32m },
{ X86::MUL_Fp64m , X86::MUL_F64m },
{ X86::MUL_Fp64m32 , X86::MUL_F32m },
{ X86::MUL_Fp80m32 , X86::MUL_F32m },
{ X86::MUL_Fp80m64 , X86::MUL_F64m },
{ X86::MUL_FpI16m32 , X86::MUL_FI16m },
{ X86::MUL_FpI16m64 , X86::MUL_FI16m },
{ X86::MUL_FpI16m80 , X86::MUL_FI16m },
{ X86::MUL_FpI32m32 , X86::MUL_FI32m },
{ X86::MUL_FpI32m64 , X86::MUL_FI32m },
{ X86::MUL_FpI32m80 , X86::MUL_FI32m },
{ X86::SIN_Fp32 , X86::SIN_F },
{ X86::SIN_Fp64 , X86::SIN_F },
{ X86::SIN_Fp80 , X86::SIN_F },
{ X86::SQRT_Fp32 , X86::SQRT_F },
{ X86::SQRT_Fp64 , X86::SQRT_F },
{ X86::SQRT_Fp80 , X86::SQRT_F },
{ X86::ST_Fp32m , X86::ST_F32m },
{ X86::ST_Fp64m , X86::ST_F64m },
{ X86::ST_Fp64m32 , X86::ST_F32m },
{ X86::ST_Fp80m32 , X86::ST_F32m },
{ X86::ST_Fp80m64 , X86::ST_F64m },
{ X86::ST_FpP80m , X86::ST_FP80m },
{ X86::SUBR_Fp32m , X86::SUBR_F32m },
{ X86::SUBR_Fp64m , X86::SUBR_F64m },
{ X86::SUBR_Fp64m32 , X86::SUBR_F32m },
{ X86::SUBR_Fp80m32 , X86::SUBR_F32m },
{ X86::SUBR_Fp80m64 , X86::SUBR_F64m },
{ X86::SUBR_FpI16m32, X86::SUBR_FI16m},
{ X86::SUBR_FpI16m64, X86::SUBR_FI16m},
{ X86::SUBR_FpI16m80, X86::SUBR_FI16m},
{ X86::SUBR_FpI32m32, X86::SUBR_FI32m},
{ X86::SUBR_FpI32m64, X86::SUBR_FI32m},
{ X86::SUBR_FpI32m80, X86::SUBR_FI32m},
{ X86::SUB_Fp32m , X86::SUB_F32m },
{ X86::SUB_Fp64m , X86::SUB_F64m },
{ X86::SUB_Fp64m32 , X86::SUB_F32m },
{ X86::SUB_Fp80m32 , X86::SUB_F32m },
{ X86::SUB_Fp80m64 , X86::SUB_F64m },
{ X86::SUB_FpI16m32 , X86::SUB_FI16m },
{ X86::SUB_FpI16m64 , X86::SUB_FI16m },
{ X86::SUB_FpI16m80 , X86::SUB_FI16m },
{ X86::SUB_FpI32m32 , X86::SUB_FI32m },
{ X86::SUB_FpI32m64 , X86::SUB_FI32m },
{ X86::SUB_FpI32m80 , X86::SUB_FI32m },
{ X86::TST_Fp32 , X86::TST_F },
{ X86::TST_Fp64 , X86::TST_F },
{ X86::TST_Fp80 , X86::TST_F },
{ X86::UCOM_FpIr32 , X86::UCOM_FIr },
{ X86::UCOM_FpIr64 , X86::UCOM_FIr },
{ X86::UCOM_FpIr80 , X86::UCOM_FIr },
{ X86::UCOM_Fpr32 , X86::UCOM_Fr },
{ X86::UCOM_Fpr64 , X86::UCOM_Fr },
{ X86::UCOM_Fpr80 , X86::UCOM_Fr },
};
static unsigned getConcreteOpcode(unsigned Opcode) {
ASSERT_SORTED(OpcodeTable);
int Opc = Lookup(OpcodeTable, array_lengthof(OpcodeTable), Opcode);
assert(Opc != -1 && "FP Stack instruction not in OpcodeTable!");
return Opc;
}
//===----------------------------------------------------------------------===//
// 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::ADD_FrST0 , X86::ADD_FPrST0 },
{ X86::DIVR_FrST0, X86::DIVR_FPrST0 },
{ X86::DIV_FrST0 , X86::DIV_FPrST0 },
{ X86::IST_F16m , X86::IST_FP16m },
{ X86::IST_F32m , X86::IST_FP32m },
{ X86::MUL_FrST0 , X86::MUL_FPrST0 },
{ X86::ST_F32m , X86::ST_FP32m },
{ X86::ST_F64m , X86::ST_FP64m },
{ X86::ST_Frr , X86::ST_FPrr },
{ X86::SUBR_FrST0, X86::SUBR_FPrST0 },
{ X86::SUB_FrST0 , X86::SUB_FPrST0 },
{ X86::UCOM_FIr , X86::UCOM_FIPr },
{ X86::UCOM_FPr , X86::UCOM_FPPr },
{ X86::UCOM_Fr , X86::UCOM_FPr },
};
/// 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) {
MachineInstr* MI = I;
DebugLoc dl = MI->getDebugLoc();
ASSERT_SORTED(PopTable);
if (StackTop == 0)
report_fatal_error("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_lengthof(PopTable), I->getOpcode());
if (Opcode != -1) {
I->setDesc(TII->get(Opcode));
if (Opcode == X86::UCOM_FPPr)
I->RemoveOperand(0);
} else { // Insert an explicit pop
I = BuildMI(*MBB, ++I, dl, TII->get(X86::ST_FPrr)).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.
//
I = freeStackSlotBefore(++I, FPRegNo);
}
/// freeStackSlotBefore - Free the specified register without trying any
/// folding.
MachineBasicBlock::iterator
FPS::freeStackSlotBefore(MachineBasicBlock::iterator I, unsigned FPRegNo) {
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;
return BuildMI(*MBB, I, DebugLoc(), TII->get(X86::ST_FPrr)).addReg(STReg);
}
/// adjustLiveRegs - Kill and revive registers such that exactly the FP
/// registers with a bit in Mask are live.
void FPS::adjustLiveRegs(unsigned Mask, MachineBasicBlock::iterator I) {
unsigned Defs = Mask;
unsigned Kills = 0;
for (unsigned i = 0; i < StackTop; ++i) {
unsigned RegNo = Stack[i];
if (!(Defs & (1 << RegNo)))
// This register is live, but we don't want it.
Kills |= (1 << RegNo);
else
// We don't need to imp-def this live register.
Defs &= ~(1 << RegNo);
}
assert((Kills & Defs) == 0 && "Register needs killing and def'ing?");
// Produce implicit-defs for free by using killed registers.
while (Kills && Defs) {
unsigned KReg = CountTrailingZeros_32(Kills);
unsigned DReg = CountTrailingZeros_32(Defs);
DEBUG(dbgs() << "Renaming %FP" << KReg << " as imp %FP" << DReg << "\n");
std::swap(Stack[getSlot(KReg)], Stack[getSlot(DReg)]);
std::swap(RegMap[KReg], RegMap[DReg]);
Kills &= ~(1 << KReg);
Defs &= ~(1 << DReg);
}
// Kill registers by popping.
if (Kills && I != MBB->begin()) {
MachineBasicBlock::iterator I2 = llvm::prior(I);
while (StackTop) {
unsigned KReg = getStackEntry(0);
if (!(Kills & (1 << KReg)))
break;
DEBUG(dbgs() << "Popping %FP" << KReg << "\n");
popStackAfter(I2);
Kills &= ~(1 << KReg);
}
}
// Manually kill the rest.
while (Kills) {
unsigned KReg = CountTrailingZeros_32(Kills);
DEBUG(dbgs() << "Killing %FP" << KReg << "\n");
freeStackSlotBefore(I, KReg);
Kills &= ~(1 << KReg);
}
// Load zeros for all the imp-defs.
while(Defs) {
unsigned DReg = CountTrailingZeros_32(Defs);
DEBUG(dbgs() << "Defining %FP" << DReg << " as 0\n");
BuildMI(*MBB, I, DebugLoc(), TII->get(X86::LD_F0));
pushReg(DReg);
Defs &= ~(1 << DReg);
}
// Now we should have the correct registers live.
DEBUG(dumpStack());
assert(StackTop == CountPopulation_32(Mask) && "Live count mismatch");
}
/// shuffleStackTop - emit fxch instructions before I to shuffle the top
/// FixCount entries into the order given by FixStack.
/// FIXME: Is there a better algorithm than insertion sort?
void FPS::shuffleStackTop(const unsigned char *FixStack,
unsigned FixCount,
MachineBasicBlock::iterator I) {
// Move items into place, starting from the desired stack bottom.
while (FixCount--) {
// Old register at position FixCount.
unsigned OldReg = getStackEntry(FixCount);
// Desired register at position FixCount.
unsigned Reg = FixStack[FixCount];
if (Reg == OldReg)
continue;
// (Reg st0) (OldReg st0) = (Reg OldReg st0)
moveToTop(Reg, I);
if (FixCount > 0)
moveToTop(OldReg, I);
}
DEBUG(dumpStack());
}
//===----------------------------------------------------------------------===//
// 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));
// Change from the pseudo instruction to the concrete instruction.
MI->RemoveOperand(0); // Remove the explicit ST(0) operand
MI->setDesc(TII->get(getConcreteOpcode(MI->getOpcode())));
// Result gets pushed on the stack.
pushReg(DestReg);
}
/// handleOneArgFP - fst <mem>, ST(0)
///
void FPS::handleOneArgFP(MachineBasicBlock::iterator &I) {
MachineInstr *MI = I;
unsigned NumOps = MI->getDesc().getNumOperands();
assert((NumOps == X86::AddrNumOperands + 1 || NumOps == 1) &&
"Can only handle fst* & ftst instructions!");
// Is this the last use of the source register?
unsigned Reg = getFPReg(MI->getOperand(NumOps-1));
bool KillsSrc = MI->killsRegister(X86::FP0+Reg);
if (KillsSrc)
duplicatePendingSTBeforeKill(Reg, I);
// FISTP64m is strange because there isn't a 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.
// Ditto FISTTP16m, FISTTP32m, FISTTP64m, ST_FpP80m.
//
if (!KillsSrc &&
(MI->getOpcode() == X86::IST_Fp64m32 ||
MI->getOpcode() == X86::ISTT_Fp16m32 ||
MI->getOpcode() == X86::ISTT_Fp32m32 ||
MI->getOpcode() == X86::ISTT_Fp64m32 ||
MI->getOpcode() == X86::IST_Fp64m64 ||
MI->getOpcode() == X86::ISTT_Fp16m64 ||
MI->getOpcode() == X86::ISTT_Fp32m64 ||
MI->getOpcode() == X86::ISTT_Fp64m64 ||
MI->getOpcode() == X86::IST_Fp64m80 ||
MI->getOpcode() == X86::ISTT_Fp16m80 ||
MI->getOpcode() == X86::ISTT_Fp32m80 ||
MI->getOpcode() == X86::ISTT_Fp64m80 ||
MI->getOpcode() == X86::ST_FpP80m)) {
duplicateToTop(Reg, getScratchReg(), I);
} else {
moveToTop(Reg, I); // Move to the top of the stack...
}
// Convert from the pseudo instruction to the concrete instruction.
MI->RemoveOperand(NumOps-1); // Remove explicit ST(0) operand
MI->setDesc(TII->get(getConcreteOpcode(MI->getOpcode())));
if (MI->getOpcode() == X86::IST_FP64m ||
MI->getOpcode() == X86::ISTT_FP16m ||
MI->getOpcode() == X86::ISTT_FP32m ||
MI->getOpcode() == X86::ISTT_FP64m ||
MI->getOpcode() == X86::ST_FP80m) {
if (StackTop == 0)
report_fatal_error("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;
#ifndef NDEBUG
unsigned NumOps = MI->getDesc().getNumOperands();
assert(NumOps >= 2 && "FPRW instructions must have 2 ops!!");
#endif
// Is this the last use of the source register?
unsigned Reg = getFPReg(MI->getOperand(1));
bool KillsSrc = MI->killsRegister(X86::FP0+Reg);
if (KillsSrc) {
duplicatePendingSTBeforeKill(Reg, I);
// If this is the last use of the source register, just make sure it's on
// the top of the stack.
moveToTop(Reg, I);
if (StackTop == 0)
report_fatal_error("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);
}
// Change from the pseudo instruction to the concrete instruction.
MI->RemoveOperand(1); // Drop the source operand.
MI->RemoveOperand(0); // Drop the destination operand.
MI->setDesc(TII->get(getConcreteOpcode(MI->getOpcode())));
}
//===----------------------------------------------------------------------===//
// 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::ADD_Fp32 , X86::ADD_FST0r },
{ X86::ADD_Fp64 , X86::ADD_FST0r },
{ X86::ADD_Fp80 , X86::ADD_FST0r },
{ X86::DIV_Fp32 , X86::DIV_FST0r },
{ X86::DIV_Fp64 , X86::DIV_FST0r },
{ X86::DIV_Fp80 , X86::DIV_FST0r },
{ X86::MUL_Fp32 , X86::MUL_FST0r },
{ X86::MUL_Fp64 , X86::MUL_FST0r },
{ X86::MUL_Fp80 , X86::MUL_FST0r },
{ X86::SUB_Fp32 , X86::SUB_FST0r },
{ X86::SUB_Fp64 , X86::SUB_FST0r },
{ X86::SUB_Fp80 , X86::SUB_FST0r },
};
// ReverseST0Table - Map: A = B op C into: ST(0) = ST(i) op ST(0)
static const TableEntry ReverseST0Table[] = {
{ X86::ADD_Fp32 , X86::ADD_FST0r }, // commutative
{ X86::ADD_Fp64 , X86::ADD_FST0r }, // commutative
{ X86::ADD_Fp80 , X86::ADD_FST0r }, // commutative
{ X86::DIV_Fp32 , X86::DIVR_FST0r },
{ X86::DIV_Fp64 , X86::DIVR_FST0r },
{ X86::DIV_Fp80 , X86::DIVR_FST0r },
{ X86::MUL_Fp32 , X86::MUL_FST0r }, // commutative
{ X86::MUL_Fp64 , X86::MUL_FST0r }, // commutative
{ X86::MUL_Fp80 , X86::MUL_FST0r }, // commutative
{ X86::SUB_Fp32 , X86::SUBR_FST0r },
{ X86::SUB_Fp64 , X86::SUBR_FST0r },
{ X86::SUB_Fp80 , X86::SUBR_FST0r },
};
// ForwardSTiTable - Map: A = B op C into: ST(i) = ST(0) op ST(i)
static const TableEntry ForwardSTiTable[] = {
{ X86::ADD_Fp32 , X86::ADD_FrST0 }, // commutative
{ X86::ADD_Fp64 , X86::ADD_FrST0 }, // commutative
{ X86::ADD_Fp80 , X86::ADD_FrST0 }, // commutative
{ X86::DIV_Fp32 , X86::DIVR_FrST0 },
{ X86::DIV_Fp64 , X86::DIVR_FrST0 },
{ X86::DIV_Fp80 , X86::DIVR_FrST0 },
{ X86::MUL_Fp32 , X86::MUL_FrST0 }, // commutative
{ X86::MUL_Fp64 , X86::MUL_FrST0 }, // commutative
{ X86::MUL_Fp80 , X86::MUL_FrST0 }, // commutative
{ X86::SUB_Fp32 , X86::SUBR_FrST0 },
{ X86::SUB_Fp64 , X86::SUBR_FrST0 },
{ X86::SUB_Fp80 , X86::SUBR_FrST0 },
};
// ReverseSTiTable - Map: A = B op C into: ST(i) = ST(i) op ST(0)
static const TableEntry ReverseSTiTable[] = {
{ X86::ADD_Fp32 , X86::ADD_FrST0 },
{ X86::ADD_Fp64 , X86::ADD_FrST0 },
{ X86::ADD_Fp80 , X86::ADD_FrST0 },
{ X86::DIV_Fp32 , X86::DIV_FrST0 },
{ X86::DIV_Fp64 , X86::DIV_FrST0 },
{ X86::DIV_Fp80 , X86::DIV_FrST0 },
{ X86::MUL_Fp32 , X86::MUL_FrST0 },
{ X86::MUL_Fp64 , X86::MUL_FrST0 },
{ X86::MUL_Fp80 , X86::MUL_FrST0 },
{ X86::SUB_Fp32 , X86::SUB_FrST0 },
{ X86::SUB_Fp64 , X86::SUB_FrST0 },
{ X86::SUB_Fp80 , X86::SUB_FrST0 },
};
/// 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->getDesc().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 = MI->killsRegister(X86::FP0+Op0);
bool KillsOp1 = MI->killsRegister(X86::FP0+Op1);
DebugLoc dl = MI->getDebugLoc();
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_lengthof(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, dl, TII->get(Opcode)).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;
MBB->getParent()->DeleteMachineInstr(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->getDesc().getNumOperands();
assert(NumOperands == 2 && "Illegal FUCOM* instruction!");
unsigned Op0 = getFPReg(MI->getOperand(NumOperands-2));
unsigned Op1 = getFPReg(MI->getOperand(NumOperands-1));
bool KillsOp0 = MI->killsRegister(X86::FP0+Op0);
bool KillsOp1 = MI->killsRegister(X86::FP0+Op1);
// Make sure the first operand is on the top of stack, the other one can be
// anywhere.
moveToTop(Op0, I);
// Change from the pseudo instruction to the concrete instruction.
MI->getOperand(0).setReg(getSTReg(Op1));
MI->RemoveOperand(1);
MI->setDesc(TII->get(getConcreteOpcode(MI->getOpcode())));
// 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(2));
bool KillsOp1 = MI->killsRegister(X86::FP0+Op1);
// 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.
// Change from the pseudo instruction to the concrete instruction.
MI->RemoveOperand(0);
MI->RemoveOperand(1);
MI->getOperand(0).setReg(getSTReg(Op1));
MI->setDesc(TII->get(getConcreteOpcode(MI->getOpcode())));
// If we kill the second operand, make sure to pop it from the stack.
if (Op0 != Op1 && KillsOp1) {
// Get this value off of the register stack.
freeStackSlotAfter(I, Op1);
}
}
/// 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: llvm_unreachable("Unknown SpecialFP instruction!");
case TargetOpcode::COPY: {
// We handle three kinds of copies: FP <- FP, FP <- ST, and ST <- FP.
const MachineOperand &MO1 = MI->getOperand(1);
const MachineOperand &MO0 = MI->getOperand(0);
unsigned DstST = MO0.getReg() - X86::ST0;
unsigned SrcST = MO1.getReg() - X86::ST0;
bool KillsSrc = MI->killsRegister(MO1.getReg());
// ST = COPY FP. Set up a pending ST register.
if (DstST < 8) {
unsigned SrcFP = getFPReg(MO1);
assert(isLive(SrcFP) && "Cannot copy dead register");
assert(!MO0.isDead() && "Cannot copy to dead ST register");
// Unallocated STs are marked as the nonexistent FP255.
while (NumPendingSTs <= DstST)
PendingST[NumPendingSTs++] = NumFPRegs;
// STi could still be live from a previous inline asm.
if (isScratchReg(PendingST[DstST])) {
DEBUG(dbgs() << "Clobbering old ST in FP" << unsigned(PendingST[DstST])
<< '\n');
freeStackSlotBefore(MI, PendingST[DstST]);
}
// When the source is killed, allocate a scratch FP register.
if (KillsSrc) {
duplicatePendingSTBeforeKill(SrcFP, I);
unsigned Slot = getSlot(SrcFP);
unsigned SR = getScratchReg();
PendingST[DstST] = SR;
Stack[Slot] = SR;
RegMap[SR] = Slot;
} else
PendingST[DstST] = SrcFP;
break;
}
// FP = COPY ST. Extract fixed stack value.
// Any instruction defining ST registers must have assigned them to a
// scratch register.
if (SrcST < 8) {
unsigned DstFP = getFPReg(MO0);
assert(!isLive(DstFP) && "Cannot copy ST to live FP register");
assert(NumPendingSTs > SrcST && "Cannot copy from dead ST register");
unsigned SrcFP = PendingST[SrcST];
assert(isScratchReg(SrcFP) && "Expected ST in a scratch register");
assert(isLive(SrcFP) && "Scratch holding ST is dead");
// DstFP steals the stack slot from SrcFP.
unsigned Slot = getSlot(SrcFP);
Stack[Slot] = DstFP;
RegMap[DstFP] = Slot;
// Always treat the ST as killed.
PendingST[SrcST] = NumFPRegs;
while (NumPendingSTs && PendingST[NumPendingSTs - 1] == NumFPRegs)
--NumPendingSTs;
break;
}
// FP <- FP copy.
unsigned DstFP = getFPReg(MO0);
unsigned SrcFP = getFPReg(MO1);
assert(isLive(SrcFP) && "Cannot copy dead register");
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(SrcFP);
Stack[Slot] = DstFP;
RegMap[DstFP] = Slot;
} else {
// For COPY we just duplicate the specified value to a new stack slot.
// This could be made better, but would require substantial changes.
duplicateToTop(SrcFP, DstFP, I);
}
break;
}
case TargetOpcode::IMPLICIT_DEF: {
// All FP registers must be explicitly defined, so load a 0 instead.
unsigned Reg = MI->getOperand(0).getReg() - X86::FP0;
DEBUG(dbgs() << "Emitting LD_F0 for implicit FP" << Reg << '\n');
BuildMI(*MBB, I, MI->getDebugLoc(), TII->get(X86::LD_F0));
pushReg(Reg);
break;
}
case X86::FpPOP_RETVAL: {
// The FpPOP_RETVAL instruction is used after calls that return a value on
// the floating point stack. We cannot model this with ST defs since CALL
// instructions have fixed clobber lists. This instruction is interpreted
// to mean that there is one more live register on the stack than we
// thought.
//
// This means that StackTop does not match the hardware stack between a
// call and the FpPOP_RETVAL instructions. We do tolerate FP instructions
// between CALL and FpPOP_RETVAL as long as they don't overflow the
// hardware stack.
unsigned DstFP = getFPReg(MI->getOperand(0));
// Move existing stack elements up to reflect reality.
assert(StackTop < 8 && "Stack overflowed before FpPOP_RETVAL");
if (StackTop) {
std::copy_backward(Stack, Stack + StackTop, Stack + StackTop + 1);
for (unsigned i = 0; i != NumFPRegs; ++i)
++RegMap[i];
}
++StackTop;
// DstFP is the new bottom of the stack.
Stack[0] = DstFP;
RegMap[DstFP] = 0;
// DstFP will be killed by processBasicBlock if this was a dead def.
break;
}
case TargetOpcode::INLINEASM: {
// The inline asm MachineInstr currently only *uses* FP registers for the
// 'f' constraint. These should be turned into the current ST(x) register
// in the machine instr.
//
// There are special rules for x87 inline assembly. The compiler must know
// exactly how many registers are popped and pushed implicitly by the asm.
// Otherwise it is not possible to restore the stack state after the inline
// asm.
//
// There are 3 kinds of input operands:
//
// 1. Popped inputs. These must appear at the stack top in ST0-STn. A
// popped input operand must be in a fixed stack slot, and it is either
// tied to an output operand, or in the clobber list. The MI has ST use
// and def operands for these inputs.
//
// 2. Fixed inputs. These inputs appear in fixed stack slots, but are
// preserved by the inline asm. The fixed stack slots must be STn-STm
// following the popped inputs. A fixed input operand cannot be tied to
// an output or appear in the clobber list. The MI has ST use operands
// and no defs for these inputs.
//
// 3. Preserved inputs. These inputs use the "f" constraint which is
// represented as an FP register. The inline asm won't change these
// stack slots.
//
// Outputs must be in ST registers, FP outputs are not allowed. Clobbered
// registers do not count as output operands. The inline asm changes the
// stack as if it popped all the popped inputs and then pushed all the
// output operands.
// Scan the assembly for ST registers used, defined and clobbered. We can
// only tell clobbers from defs by looking at the asm descriptor.
unsigned STUses = 0, STDefs = 0, STClobbers = 0, STDeadDefs = 0;
unsigned NumOps = 0;
for (unsigned i = InlineAsm::MIOp_FirstOperand, e = MI->getNumOperands();
i != e && MI->getOperand(i).isImm(); i += 1 + NumOps) {
unsigned Flags = MI->getOperand(i).getImm();
NumOps = InlineAsm::getNumOperandRegisters(Flags);
if (NumOps != 1)
continue;
const MachineOperand &MO = MI->getOperand(i + 1);
if (!MO.isReg())
continue;
unsigned STReg = MO.getReg() - X86::ST0;
if (STReg >= 8)
continue;
switch (InlineAsm::getKind(Flags)) {
case InlineAsm::Kind_RegUse:
STUses |= (1u << STReg);
break;
case InlineAsm::Kind_RegDef:
case InlineAsm::Kind_RegDefEarlyClobber:
STDefs |= (1u << STReg);
if (MO.isDead())
STDeadDefs |= (1u << STReg);
break;
case InlineAsm::Kind_Clobber:
STClobbers |= (1u << STReg);
break;
default:
break;
}
}
if (STUses && !isMask_32(STUses))
MI->emitError("fixed input regs must be last on the x87 stack");
unsigned NumSTUses = CountTrailingOnes_32(STUses);
// Defs must be contiguous from the stack top. ST0-STn.
if (STDefs && !isMask_32(STDefs)) {
MI->emitError("output regs must be last on the x87 stack");
STDefs = NextPowerOf2(STDefs) - 1;
}
unsigned NumSTDefs = CountTrailingOnes_32(STDefs);
// So must the clobbered stack slots. ST0-STm, m >= n.
if (STClobbers && !isMask_32(STDefs | STClobbers))
MI->emitError("clobbers must be last on the x87 stack");
// Popped inputs are the ones that are also clobbered or defined.
unsigned STPopped = STUses & (STDefs | STClobbers);
if (STPopped && !isMask_32(STPopped))
MI->emitError("implicitly popped regs must be last on the x87 stack");
unsigned NumSTPopped = CountTrailingOnes_32(STPopped);
DEBUG(dbgs() << "Asm uses " << NumSTUses << " fixed regs, pops "
<< NumSTPopped << ", and defines " << NumSTDefs << " regs.\n");
// Scan the instruction for FP uses corresponding to "f" constraints.
// Collect FP registers to kill afer the instruction.
// Always kill all the scratch regs.
unsigned FPKills = ((1u << NumFPRegs) - 1) & ~0xff;
unsigned FPUsed = 0;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &Op = MI->getOperand(i);
if (!Op.isReg() || Op.getReg() < X86::FP0 || Op.getReg() > X86::FP6)
continue;
if (!Op.isUse())
MI->emitError("illegal \"f\" output constraint");
unsigned FPReg = getFPReg(Op);
FPUsed |= 1U << FPReg;
// If we kill this operand, make sure to pop it from the stack after the
// asm. We just remember it for now, and pop them all off at the end in
// a batch.
if (Op.isKill())
FPKills |= 1U << FPReg;
}
// The popped inputs will be killed by the instruction, so duplicate them
// if the FP register needs to be live after the instruction, or if it is
// used in the instruction itself. We effectively treat the popped inputs
// as early clobbers.
for (unsigned i = 0; i < NumSTPopped; ++i) {
if ((FPKills & ~FPUsed) & (1u << PendingST[i]))
continue;
unsigned SR = getScratchReg();
duplicateToTop(PendingST[i], SR, I);
DEBUG(dbgs() << "Duplicating ST" << i << " in FP"
<< unsigned(PendingST[i]) << " to avoid clobbering it.\n");
PendingST[i] = SR;
}
// Make sure we have a unique live register for every fixed use. Some of
// them could be undef uses, and we need to emit LD_F0 instructions.
for (unsigned i = 0; i < NumSTUses; ++i) {
if (i < NumPendingSTs && PendingST[i] < NumFPRegs) {
// Check for shared assignments.
for (unsigned j = 0; j < i; ++j) {
if (PendingST[j] != PendingST[i])
continue;
// STi and STj are inn the same register, create a copy.
unsigned SR = getScratchReg();
duplicateToTop(PendingST[i], SR, I);
DEBUG(dbgs() << "Duplicating ST" << i << " in FP"
<< unsigned(PendingST[i])
<< " to avoid collision with ST" << j << '\n');
PendingST[i] = SR;
}
continue;
}
unsigned SR = getScratchReg();
DEBUG(dbgs() << "Emitting LD_F0 for ST" << i << " in FP" << SR << '\n');
BuildMI(*MBB, I, MI->getDebugLoc(), TII->get(X86::LD_F0));
pushReg(SR);
PendingST[i] = SR;
if (NumPendingSTs == i)
++NumPendingSTs;
}
assert(NumPendingSTs >= NumSTUses && "Fixed registers should be assigned");
// Now we can rearrange the live registers to match what was requested.
shuffleStackTop(PendingST, NumPendingSTs, I);
DEBUG({dbgs() << "Before asm: "; dumpStack();});
// With the stack layout fixed, rewrite the FP registers.
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &Op = MI->getOperand(i);
if (!Op.isReg() || Op.getReg() < X86::FP0 || Op.getReg() > X86::FP6)
continue;
unsigned FPReg = getFPReg(Op);
Op.setReg(getSTReg(FPReg));
}
// Simulate the inline asm popping its inputs and pushing its outputs.
StackTop -= NumSTPopped;
// Hold the fixed output registers in scratch FP registers. They will be
// transferred to real FP registers by copies.
NumPendingSTs = 0;
for (unsigned i = 0; i < NumSTDefs; ++i) {
unsigned SR = getScratchReg();
pushReg(SR);
FPKills &= ~(1u << SR);
}
for (unsigned i = 0; i < NumSTDefs; ++i)
PendingST[NumPendingSTs++] = getStackEntry(i);
DEBUG({dbgs() << "After asm: "; dumpStack();});
// If any of the ST defs were dead, pop them immediately. Our caller only
// handles dead FP defs.
MachineBasicBlock::iterator InsertPt = MI;
for (unsigned i = 0; STDefs & (1u << i); ++i) {
if (!(STDeadDefs & (1u << i)))
continue;
freeStackSlotAfter(InsertPt, PendingST[i]);
PendingST[i] = NumFPRegs;
}
while (NumPendingSTs && PendingST[NumPendingSTs - 1] == NumFPRegs)
--NumPendingSTs;
// If this asm kills any FP registers (is the last use of them) we must
// explicitly emit pop instructions for them. Do this now after the asm has
// executed so that the ST(x) numbers are not off (which would happen if we
// did this inline with operand rewriting).
//
// Note: this might be a non-optimal pop sequence. We might be able to do
// better by trying to pop in stack order or something.
while (FPKills) {
unsigned FPReg = CountTrailingZeros_32(FPKills);
if (isLive(FPReg))
freeStackSlotAfter(InsertPt, FPReg);
FPKills &= ~(1U << FPReg);
}
// Don't delete the inline asm!
return;
}
case X86::WIN_FTOL_32:
case X86::WIN_FTOL_64: {
// Push the operand into ST0.
MachineOperand &Op = MI->getOperand(0);
assert(Op.isUse() && Op.isReg() &&
Op.getReg() >= X86::FP0 && Op.getReg() <= X86::FP6);
unsigned FPReg = getFPReg(Op);
if (Op.isKill())
moveToTop(FPReg, I);
else
duplicateToTop(FPReg, FPReg, I);
// Emit the call. This will pop the operand.
BuildMI(*MBB, I, MI->getDebugLoc(), TII->get(X86::CALLpcrel32))
.addExternalSymbol("_ftol2")
.addReg(X86::ST0, RegState::ImplicitKill)
.addReg(X86::EAX, RegState::Define | RegState::Implicit)
.addReg(X86::EDX, RegState::Define | RegState::Implicit)
.addReg(X86::EFLAGS, RegState::Define | RegState::Implicit);
--StackTop;
break;
}
case X86::RET:
case X86::RETI:
// If RET has an FP register use operand, pass the first one in ST(0) and
// the second one in ST(1).
// Find the register operands.
unsigned FirstFPRegOp = ~0U, SecondFPRegOp = ~0U;
unsigned LiveMask = 0;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &Op = MI->getOperand(i);
if (!Op.isReg() || Op.getReg() < X86::FP0 || Op.getReg() > X86::FP6)
continue;
// FP Register uses must be kills unless there are two uses of the same
// register, in which case only one will be a kill.
assert(Op.isUse() &&
(Op.isKill() || // Marked kill.
getFPReg(Op) == FirstFPRegOp || // Second instance.
MI->killsRegister(Op.getReg())) && // Later use is marked kill.
"Ret only defs operands, and values aren't live beyond it");
if (FirstFPRegOp == ~0U)
FirstFPRegOp = getFPReg(Op);
else {
assert(SecondFPRegOp == ~0U && "More than two fp operands!");
SecondFPRegOp = getFPReg(Op);
}
LiveMask |= (1 << getFPReg(Op));
// Remove the operand so that later passes don't see it.
MI->RemoveOperand(i);
--i, --e;
}
// We may have been carrying spurious live-ins, so make sure only the returned
// registers are left live.
adjustLiveRegs(LiveMask, MI);
if (!LiveMask) return; // Quick check to see if any are possible.
// There are only four possibilities here:
// 1) we are returning a single FP value. In this case, it has to be in
// ST(0) already, so just declare success by removing the value from the
// FP Stack.
if (SecondFPRegOp == ~0U) {
// Assert that the top of stack contains the right FP register.
assert(StackTop == 1 && FirstFPRegOp == getStackEntry(0) &&
"Top of stack not the right register for RET!");
// Ok, everything is good, mark the value as not being on the stack
// anymore so that our assertion about the stack being empty at end of
// block doesn't fire.
StackTop = 0;
return;
}
// Otherwise, we are returning two values:
// 2) If returning the same value for both, we only have one thing in the FP
// stack. Consider: RET FP1, FP1
if (StackTop == 1) {
assert(FirstFPRegOp == SecondFPRegOp && FirstFPRegOp == getStackEntry(0)&&
"Stack misconfiguration for RET!");
// Duplicate the TOS so that we return it twice. Just pick some other FPx
// register to hold it.
unsigned NewReg = getScratchReg();
duplicateToTop(FirstFPRegOp, NewReg, MI);
FirstFPRegOp = NewReg;
}
/// Okay we know we have two different FPx operands now:
assert(StackTop == 2 && "Must have two values live!");
/// 3) If SecondFPRegOp is currently in ST(0) and FirstFPRegOp is currently
/// in ST(1). In this case, emit an fxch.
if (getStackEntry(0) == SecondFPRegOp) {
assert(getStackEntry(1) == FirstFPRegOp && "Unknown regs live");
moveToTop(FirstFPRegOp, MI);
}
/// 4) Finally, FirstFPRegOp must be in ST(0) and SecondFPRegOp must be in
/// ST(1). Just remove both from our understanding of the stack and return.
assert(getStackEntry(0) == FirstFPRegOp && "Unknown regs live");
assert(getStackEntry(1) == SecondFPRegOp && "Unknown regs live");
StackTop = 0;
return;
}
I = MBB->erase(I); // Remove the pseudo instruction
// We want to leave I pointing to the previous instruction, but what if we
// just erased the first instruction?
if (I == MBB->begin()) {
DEBUG(dbgs() << "Inserting dummy KILL\n");
I = BuildMI(*MBB, I, DebugLoc(), TII->get(TargetOpcode::KILL));
} else
--I;
}
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