//===----------------------------------------------------------------------===//
//
// This file defines the pass which converts floating point instructions from
-// virtual registers into register stack instructions. This pass uses live
+// pseudo 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).
+// 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.
//
-// 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.
+// This approach avoids splitting critical edges at the potential cost of more
+// live register shuffling instructions when critical edges are present.
//
//===----------------------------------------------------------------------===//
#include "X86.h"
#include "X86InstrInfo.h"
#include "llvm/ADT/DepthFirstIterator.h"
+#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
-#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
STATISTIC(NumFP , "Number of floating point instructions");
namespace {
- struct VISIBILITY_HIDDEN FPS : public MachineFunctionPass {
+ struct FPS : public MachineFunctionPass {
static char ID;
- FPS() : MachineFunctionPass(&ID) {}
+ FPS() : MachineFunctionPass(ID) {
+ // 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();
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(unsigned m = 0) : Mask(m), 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;
+
+ // Map each MBB in the current function to an (ingoing, outgoing) index into
+ // LiveBundles. Blocks with no FP registers live in or out map to (0, 0)
+ // and are not actually stored in the map.
+ DenseMap<MachineBasicBlock*, std::pair<unsigned, unsigned> > BlockBundle;
+
+ // Return a bitmask of FP registers in block's live-in list.
+ 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
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.
+ // 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();
+
void dumpStack() const {
- errs() << "Stack contents:";
+ dbgs() << "Stack contents:";
for (unsigned i = 0; i != StackTop; ++i) {
- errs() << " FP" << Stack[i];
+ dbgs() << " FP" << Stack[i];
assert(RegMap[Stack[i]] == i && "Stack[] doesn't match RegMap[]!");
}
- errs() << "\n";
+ dbgs() << "\n";
}
- private:
- /// isStackEmpty - Return true if the FP stack is empty.
- bool isStackEmpty() const {
- return StackTop == 0;
- }
-
- // getSlot - Return the stack slot number a particular register number is
- // in.
+
+ /// 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).
+ /// 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() {
+ for (int i = 7; i >= 0; --i)
+ if (!isLive(i))
+ return i;
+ llvm_unreachable("Ran out of scratch FP registers");
+ }
+
+ /// getStackEntry - Return the X86::FP<n> register in register ST(i).
unsigned getStackEntry(unsigned STi) const {
- assert(STi < StackTop && "Access past stack top!");
+ 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.
+ /// 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!");
+ 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) {
- MachineInstr *MI = I;
- DebugLoc dl = MI->getDebugLoc();
+ DebugLoc dl = I == MBB->end() ? DebugLoc() : I->getDebugLoc();
if (isAtTop(RegNo)) return;
-
+
unsigned STReg = getSTReg(RegNo);
unsigned RegOnTop = getStackEntry(0);
std::swap(RegMap[RegNo], RegMap[RegOnTop]);
// Swap stack slot contents.
- assert(RegMap[RegOnTop] < StackTop);
+ 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++;
+ ++NumFXCH;
}
void duplicateToTop(unsigned RegNo, unsigned AsReg, MachineInstr *I) {
- DebugLoc dl = I->getDebugLoc();
+ 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);
}
- // popStackAfter - Pop the current value off of the top of the FP stack
- // after the specified instruction.
+ /// 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.
+ /// 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 susch 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 handleCompareFP(MachineBasicBlock::iterator &I);
void handleCondMovFP(MachineBasicBlock::iterator &I);
void handleSpecialFP(MachineBasicBlock::iterator &I);
+
+ bool translateCopy(MachineInstr*);
};
char FPS::ID = 0;
}
return Reg - X86::FP0;
}
-
/// runOnMachineFunction - Loop over all of the basic blocks, transforming FP
/// register references into FP stack references.
///
if (!FPIsUsed) return false;
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
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);
+
+ BlockBundle.clear();
+ 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");
+ assert(BlockBundle.empty() && "Stale data in BlockBundle");
+ SmallPtrSet<MachineBasicBlock*, 8> PropDown, PropUp;
+
+ // LiveBundle[0] is the empty live-in set.
+ LiveBundles.resize(1);
+
+ // First 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;
+ // Ingoing bundle index.
+ unsigned &Idx = BlockBundle[MBB].first;
+ // Already assigned an ingoing bundle?
+ if (Idx)
+ continue;
+ // Allocate a new LiveBundle struct for this block's live-ins.
+ const unsigned BundleIdx = Idx = LiveBundles.size();
+ DEBUG(dbgs() << "Creating LB#" << BundleIdx << ": in:BB#"
+ << MBB->getNumber());
+ LiveBundles.push_back(Mask);
+ LiveBundle &Bundle = LiveBundles.back();
+
+ // Make sure all predecessors have the same live-out set.
+ PropUp.insert(MBB);
+
+ // Keep pushing liveness up and down the CFG until convergence.
+ // Only critical edges cause iteration here, but when they do, multiple
+ // blocks can be assigned to the same LiveBundle index.
+ do {
+ // Assign BundleIdx as liveout from predecessors in PropUp.
+ for (SmallPtrSet<MachineBasicBlock*, 16>::iterator I = PropUp.begin(),
+ E = PropUp.end(); I != E; ++I) {
+ MachineBasicBlock *MBB = *I;
+ for (MachineBasicBlock::const_pred_iterator LinkI = MBB->pred_begin(),
+ LinkE = MBB->pred_end(); LinkI != LinkE; ++LinkI) {
+ MachineBasicBlock *PredMBB = *LinkI;
+ // PredMBB's liveout bundle should be set to LIIdx.
+ unsigned &Idx = BlockBundle[PredMBB].second;
+ if (Idx) {
+ assert(Idx == BundleIdx && "Inconsistent CFG");
+ continue;
+ }
+ Idx = BundleIdx;
+ DEBUG(dbgs() << " out:BB#" << PredMBB->getNumber());
+ // Propagate to siblings.
+ if (PredMBB->succ_size() > 1)
+ PropDown.insert(PredMBB);
+ }
+ }
+ PropUp.clear();
+
+ // Assign BundleIdx as livein to successors in PropDown.
+ for (SmallPtrSet<MachineBasicBlock*, 16>::iterator I = PropDown.begin(),
+ E = PropDown.end(); I != E; ++I) {
+ MachineBasicBlock *MBB = *I;
+ for (MachineBasicBlock::const_succ_iterator LinkI = MBB->succ_begin(),
+ LinkE = MBB->succ_end(); LinkI != LinkE; ++LinkI) {
+ MachineBasicBlock *SuccMBB = *LinkI;
+ // LinkMBB's livein bundle should be set to BundleIdx.
+ unsigned &Idx = BlockBundle[SuccMBB].first;
+ if (Idx) {
+ assert(Idx == BundleIdx && "Inconsistent CFG");
+ continue;
+ }
+ Idx = BundleIdx;
+ DEBUG(dbgs() << " in:BB#" << SuccMBB->getNumber());
+ // Propagate to siblings.
+ if (SuccMBB->pred_size() > 1)
+ PropUp.insert(SuccMBB);
+ // Also accumulate the bundle liveness mask from the liveins here.
+ Bundle.Mask |= calcLiveInMask(SuccMBB);
+ }
+ }
+ PropDown.clear();
+ } while (!PropUp.empty());
+ DEBUG({
+ dbgs() << " live:";
+ for (unsigned i = 0; i < 8; ++i)
+ if (Bundle.Mask & (1<<i))
+ dbgs() << " %FP" << i;
+ dbgs() << '\n';
+ });
+ }
+}
+
/// processBasicBlock - Loop over all of the instructions in the basic block,
/// transforming FP instructions into their stack form.
///
bool Changed = false;
MBB = &BB;
+ setupBlockStack();
+
for (MachineBasicBlock::iterator I = BB.begin(); I != BB.end(); ++I) {
MachineInstr *MI = I;
- unsigned Flags = MI->getDesc().TSFlags;
-
+ uint64_t Flags = MI->getDesc().TSFlags;
+
unsigned FPInstClass = Flags & X86II::FPTypeMask;
- if (MI->getOpcode() == TargetInstrInfo::INLINEASM)
+ if (MI->isInlineAsm())
FPInstClass = X86II::SpecialFP;
-
+
+ if (MI->isCopy() && translateCopy(MI))
+ FPInstClass = X86II::SpecialFP;
+
if (FPInstClass == X86II::NotFP)
continue; // Efficiently ignore non-fp insts!
PrevMI = prior(I);
++NumFP; // Keep track of # of pseudo instrs
- DEBUG(errs() << "\nFPInst:\t" << *MI);
+ DEBUG(dbgs() << "\nFPInst:\t" << *MI);
// Get dead variables list now because the MI pointer may be deleted as part
// of processing!
for (unsigned i = 0, e = DeadRegs.size(); i != e; ++i) {
unsigned Reg = DeadRegs[i];
if (Reg >= X86::FP0 && Reg <= X86::FP6) {
- DEBUG(errs() << "Register FP#" << Reg-X86::FP0 << " is dead!\n");
+ DEBUG(dbgs() << "Register FP#" << Reg-X86::FP0 << " is dead!\n");
freeStackSlotAfter(I, Reg-X86::FP0);
}
}
DEBUG(
MachineBasicBlock::iterator PrevI(PrevMI);
if (I == PrevI) {
- errs() << "Just deleted pseudo instruction\n";
+ 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;
- errs() << "Inserted instructions:\n\t";
- Start->print(errs(), &MF.getTarget());
- while (++Start != next(I)) {}
+ dbgs() << "Inserted instructions:\n\t";
+ Start->print(dbgs(), &MF.getTarget());
+ while (++Start != llvm::next(I)) {}
}
dumpStack();
);
Changed = true;
}
- assert(isStackEmpty() && "Stack not empty at end of basic block?");
+ finishBlockStack();
+
return Changed;
}
+/// setupBlockStack - Use the BlockBundle map 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;
+ const LiveBundle &Bundle = LiveBundles[BlockBundle.lookup(MBB).first];
+
+ 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");
+
+ unsigned BundleIdx = BlockBundle.lookup(MBB).second;
+ 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
//===----------------------------------------------------------------------===//
friend bool operator<(const TableEntry &TE, unsigned V) {
return TE.from < V;
}
- friend bool operator<(unsigned V, const TableEntry &TE) {
+ friend bool LLVM_ATTRIBUTE_USED operator<(unsigned V,
+ const TableEntry &TE) {
return V < TE.from;
}
};
MachineInstr* MI = I;
DebugLoc dl = MI->getDebugLoc();
ASSERT_SORTED(PopTable);
- assert(StackTop > 0 && "Cannot pop empty stack!");
+ 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...
// 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];
RegMap[TopReg] = OldSlot;
RegMap[FPRegNo] = ~0;
Stack[--StackTop] = ~0;
- MachineInstr *MI = I;
- DebugLoc dl = MI->getDebugLoc();
- I = BuildMI(*MBB, ++I, dl, TII->get(X86::ST_FPrr)).addReg(STReg);
+ 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);
+ for (;;) {
+ 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);
+ moveToTop(OldReg, I);
+ }
+ DEBUG(dumpStack());
}
void FPS::handleOneArgFP(MachineBasicBlock::iterator &I) {
MachineInstr *MI = I;
unsigned NumOps = MI->getDesc().getNumOperands();
- assert((NumOps == X86AddrNumOperands + 1 || NumOps == 1) &&
+ assert((NumOps == X86::AddrNumOperands + 1 || NumOps == 1) &&
"Can only handle fst* & ftst instructions!");
// Is this the last use of the source register?
MI->getOpcode() == X86::ISTT_Fp32m80 ||
MI->getOpcode() == X86::ISTT_Fp64m80 ||
MI->getOpcode() == X86::ST_FpP80m)) {
- duplicateToTop(Reg, 7 /*temp register*/, I);
+ duplicateToTop(Reg, getScratchReg(), I);
} else {
moveToTop(Reg, I); // Move to the top of the stack...
}
MI->getOpcode() == X86::ISTT_FP32m ||
MI->getOpcode() == X86::ISTT_FP64m ||
MI->getOpcode() == X86::ST_FP80m) {
- assert(StackTop > 0 && "Stack empty??");
+ if (StackTop == 0)
+ report_fatal_error("Stack empty??");
--StackTop;
} else if (KillsSrc) { // Last use of operand?
popStackAfter(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);
- assert(StackTop > 0 && "Stack cannot be empty!");
+ if (StackTop == 0)
+ report_fatal_error("Stack cannot be empty!");
--StackTop;
pushReg(getFPReg(MI->getOperand(0)));
} else {
///
void FPS::handleSpecialFP(MachineBasicBlock::iterator &I) {
MachineInstr *MI = I;
- DebugLoc dl = MI->getDebugLoc();
switch (MI->getOpcode()) {
default: llvm_unreachable("Unknown SpecialFP instruction!");
case X86::FpGET_ST0_32:// Appears immediately after a call returning FP type!
std::swap(RegMap[RegNo], RegMap[RegOnTop]);
// Swap stack slot contents.
- assert(RegMap[RegOnTop] < StackTop);
+ if (RegMap[RegOnTop] >= StackTop)
+ report_fatal_error("Access past stack top!");
std::swap(Stack[RegMap[RegOnTop]], Stack[StackTop-1]);
break;
}
case X86::FpSET_ST0_32:
case X86::FpSET_ST0_64:
case X86::FpSET_ST0_80: {
+ // FpSET_ST0_80 is generated by copyRegToReg for setting up inline asm
+ // arguments that use an st constraint. We expect a sequence of
+ // instructions: Fp_SET_ST0 Fp_SET_ST1? INLINEASM
unsigned Op0 = getFPReg(MI->getOperand(0));
- // FpSET_ST0_80 is generated by copyRegToReg for both function return
- // and inline assembly with the "st" constrain. In the latter case,
- // it is possible for ST(0) to be alive after this instruction.
if (!MI->killsRegister(X86::FP0 + Op0)) {
- // Duplicate Op0
- duplicateToTop(0, 7 /*temp register*/, I);
+ // Duplicate Op0 into a temporary on the stack top.
+ duplicateToTop(Op0, getScratchReg(), I);
} else {
+ // Op0 is killed, so just swap it into position.
moveToTop(Op0, I);
}
--StackTop; // "Forget" we have something on the top of stack!
}
case X86::FpSET_ST1_32:
case X86::FpSET_ST1_64:
- case X86::FpSET_ST1_80:
- // StackTop can be 1 if a FpSET_ST0_* was before this. Exchange them.
- if (StackTop == 1) {
- BuildMI(*MBB, I, dl, TII->get(X86::XCH_F)).addReg(X86::ST1);
- NumFXCH++;
- StackTop = 0;
- break;
+ case X86::FpSET_ST1_80: {
+ // Set up st(1) for inline asm. We are assuming that st(0) has already been
+ // set up by FpSET_ST0, and our StackTop is off by one because of it.
+ unsigned Op0 = getFPReg(MI->getOperand(0));
+ // Restore the actual StackTop from before Fp_SET_ST0.
+ // Note we can't handle Fp_SET_ST1 without a preceeding Fp_SET_ST0, and we
+ // are not enforcing the constraint.
+ ++StackTop;
+ unsigned RegOnTop = getStackEntry(0); // This reg must remain in st(0).
+ if (!MI->killsRegister(X86::FP0 + Op0)) {
+ duplicateToTop(Op0, getScratchReg(), I);
+ moveToTop(RegOnTop, I);
+ } else if (getSTReg(Op0) != X86::ST1) {
+ // We have the wrong value at st(1). Shuffle! Untested!
+ moveToTop(getStackEntry(1), I);
+ moveToTop(Op0, I);
+ moveToTop(RegOnTop, I);
}
- assert(StackTop == 2 && "Stack should have two element on it to return!");
- --StackTop; // "Forget" we have something on the top of stack!
+ assert(StackTop >= 2 && "Too few live registers");
+ StackTop -= 2; // "Forget" both st(0) and st(1).
break;
+ }
case X86::MOV_Fp3232:
case X86::MOV_Fp3264:
case X86::MOV_Fp6432:
unsigned SrcReg = getFPReg(MO1);
const MachineOperand &MO0 = MI->getOperand(0);
- // These can be created due to inline asm. Two address pass can introduce
- // copies from RFP registers to virtual registers.
- if (MO0.getReg() == X86::ST0 && SrcReg == 0) {
- assert(MO1.isKill());
- // Treat %ST0<def> = MOV_Fp8080 %FP0<kill>
- // like FpSET_ST0_80 %FP0<kill>, %ST0<imp-def>
- assert((StackTop == 1 || StackTop == 2)
- && "Stack should have one or two element on it to return!");
- --StackTop; // "Forget" we have something on the top of stack!
- break;
- } else if (MO0.getReg() == X86::ST1 && SrcReg == 1) {
- assert(MO1.isKill());
- // Treat %ST1<def> = MOV_Fp8080 %FP1<kill>
- // like FpSET_ST1_80 %FP0<kill>, %ST1<imp-def>
- // StackTop can be 1 if a FpSET_ST0_* was before this. Exchange them.
- if (StackTop == 1) {
- BuildMI(*MBB, I, dl, TII->get(X86::XCH_F)).addReg(X86::ST1);
- NumFXCH++;
- StackTop = 0;
- break;
- }
- assert(StackTop == 2 && "Stack should have two element on it to return!");
- --StackTop; // "Forget" we have something on the top of stack!
- break;
- }
-
unsigned DestReg = getFPReg(MO0);
if (MI->killsRegister(X86::FP0+SrcReg)) {
// If the input operand is killed, we can just change the owner of the
}
}
break;
- case TargetInstrInfo::INLINEASM: {
+ 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. Also, any kills should be explicitly popped after
// the inline asm.
- unsigned Kills[7];
- unsigned NumKills = 0;
+ unsigned Kills = 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)
// asm. We just remember it for now, and pop them all off at the end in
// a batch.
if (Op.isKill())
- Kills[NumKills++] = FPReg;
+ Kills |= 1U << FPReg;
}
// If this asm kills any FP registers (is the last use of them) we must
// 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.
MachineBasicBlock::iterator InsertPt = MI;
- while (NumKills)
- freeStackSlotAfter(InsertPt, Kills[--NumKills]);
-
+ while (Kills) {
+ unsigned FPReg = CountTrailingZeros_32(Kills);
+ freeStackSlotAfter(InsertPt, FPReg);
+ Kills &= ~(1U << FPReg);
+ }
// Don't delete the inline asm!
return;
}
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).
- if (isStackEmpty()) return; // Quick check to see if any are possible.
-
+
// 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)
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
// Duplicate the TOS so that we return it twice. Just pick some other FPx
// register to hold it.
- unsigned NewReg = (FirstFPRegOp+1)%7;
+ unsigned NewReg = getScratchReg();
duplicateToTop(FirstFPRegOp, NewReg, MI);
FirstFPRegOp = NewReg;
}
}
I = MBB->erase(I); // Remove the pseudo instruction
- --I;
+
+ // 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;
+}
+
+// Translate a COPY instruction to a pseudo-op that handleSpecialFP understands.
+bool FPS::translateCopy(MachineInstr *MI) {
+ unsigned DstReg = MI->getOperand(0).getReg();
+ unsigned SrcReg = MI->getOperand(1).getReg();
+
+ if (DstReg == X86::ST0) {
+ MI->setDesc(TII->get(X86::FpSET_ST0_80));
+ MI->RemoveOperand(0);
+ return true;
+ }
+ if (DstReg == X86::ST1) {
+ MI->setDesc(TII->get(X86::FpSET_ST1_80));
+ MI->RemoveOperand(0);
+ return true;
+ }
+ if (SrcReg == X86::ST0) {
+ MI->setDesc(TII->get(X86::FpGET_ST0_80));
+ return true;
+ }
+ if (SrcReg == X86::ST1) {
+ MI->setDesc(TII->get(X86::FpGET_ST1_80));
+ return true;
+ }
+ if (X86::RFP80RegClass.contains(DstReg, SrcReg)) {
+ MI->setDesc(TII->get(X86::MOV_Fp8080));
+ return true;
+ }
+ return false;
}
projects / oota-llvm.git / blobdiff