static RegisterPass<PEI>
X("prologepilog", "Prologue/Epilogue Insertion");
-// FIXME: For now, the frame index scavenging is off by default and only
-// used by the Thumb1 target. When it's the default and replaces the current
-// on-the-fly PEI scavenging for all targets, requiresRegisterScavenging()
-// will replace this.
-cl::opt<bool>
-FrameIndexVirtualScavenging("enable-frame-index-scavenging",
- cl::Hidden,
- cl::desc("Enable frame index elimination with"
- "virtual register scavenging"));
-
/// createPrologEpilogCodeInserter - This function returns a pass that inserts
/// prolog and epilog code, and eliminates abstract frame references.
///
const Function* F = Fn.getFunction();
const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
+ FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn);
// Get MachineModuleInfo so that we can track the construction of the
// frame.
/// pseudo instructions.
void PEI::calculateCallsInformation(MachineFunction &Fn) {
const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
+ MachineFrameInfo *FFI = Fn.getFrameInfo();
unsigned MaxCallFrameSize = 0;
- bool HasCalls = false;
+ bool HasCalls = FFI->hasCalls();
// Get the function call frame set-up and tear-down instruction opcode
int FrameSetupOpcode = RegInfo->getCallFrameSetupOpcode();
HasCalls = true;
}
- MachineFrameInfo *FFI = Fn.getFrameInfo();
FFI->setHasCalls(HasCalls);
FFI->setMaxCallFrameSize(MaxCallFrameSize);
// the TargetRegisterClass if the stack alignment is smaller. Use the
// min.
Align = std::min(Align, StackAlign);
- FrameIdx = FFI->CreateStackObject(RC->getSize(), Align);
+ FrameIdx = FFI->CreateStackObject(RC->getSize(), Align, true);
if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
} else {
// Spill it to the stack where we must.
- FrameIdx = FFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset);
+ FrameIdx = FFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset,
+ true, false);
}
I->setFrameIdx(FrameIdx);
// Make sure the special register scavenging spill slot is closest to the
// frame pointer if a frame pointer is required.
const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
- if (RS && RegInfo->hasFP(Fn)) {
+ if (RS && RegInfo->hasFP(Fn) && !RegInfo->needsStackRealignment(Fn)) {
int SFI = RS->getScavengingFrameIndex();
if (SFI >= 0)
AdjustStackOffset(FFI, SFI, StackGrowsDown, Offset, MaxAlign);
// Make sure the special register scavenging spill slot is closest to the
// stack pointer.
- if (RS && !RegInfo->hasFP(Fn)) {
+ if (RS && (!RegInfo->hasFP(Fn) || RegInfo->needsStackRealignment(Fn))) {
int SFI = RS->getScavengingFrameIndex();
if (SFI >= 0)
AdjustStackOffset(FFI, SFI, StackGrowsDown, Offset, MaxAlign);
if (PrevI == BB->end())
I = BB->begin(); // The replaced instr was the first in the block.
else
- I = next(PrevI);
+ I = llvm::next(PrevI);
continue;
}
// If this instruction has a FrameIndex operand, we need to
// use that target machine register info object to eliminate
// it.
-
- TRI.eliminateFrameIndex(MI, SPAdj, FrameIndexVirtualScavenging ?
- NULL : RS);
+ int Value;
+ unsigned VReg =
+ TRI.eliminateFrameIndex(MI, SPAdj, &Value,
+ FrameIndexVirtualScavenging ? NULL : RS);
+ if (VReg) {
+ assert (FrameIndexVirtualScavenging &&
+ "Not scavenging, but virtual returned from "
+ "eliminateFrameIndex()!");
+ FrameConstantRegMap[VReg] = FrameConstantEntry(Value, SPAdj);
+ }
// Reset the iterator if we were at the beginning of the BB.
if (AtBeginning) {
}
}
+/// findLastUseReg - find the killing use of the specified register within
+/// the instruciton range. Return the operand number of the kill in Operand.
+static MachineBasicBlock::iterator
+findLastUseReg(MachineBasicBlock::iterator I, MachineBasicBlock::iterator ME,
+ unsigned Reg) {
+ // Scan forward to find the last use of this virtual register
+ for (++I; I != ME; ++I) {
+ MachineInstr *MI = I;
+ bool isDefInsn = false;
+ bool isKillInsn = false;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
+ if (MI->getOperand(i).isReg()) {
+ unsigned OpReg = MI->getOperand(i).getReg();
+ if (OpReg == 0 || !TargetRegisterInfo::isVirtualRegister(OpReg))
+ continue;
+ assert (OpReg == Reg
+ && "overlapping use of scavenged index register!");
+ // If this is the killing use, we have a candidate.
+ if (MI->getOperand(i).isKill())
+ isKillInsn = true;
+ else if (MI->getOperand(i).isDef())
+ isDefInsn = true;
+ }
+ if (isKillInsn && !isDefInsn)
+ return I;
+ }
+ // If we hit the end of the basic block, there was no kill of
+ // the virtual register, which is wrong.
+ assert (0 && "scavenged index register never killed!");
+ return ME;
+}
+
/// scavengeFrameVirtualRegs - Replace all frame index virtual registers
/// with physical registers. Use the register scavenger to find an
/// appropriate register to use.
E = Fn.end(); BB != E; ++BB) {
RS->enterBasicBlock(BB);
+ // FIXME: The logic flow in this function is still too convoluted.
+ // It needs a cleanup refactoring. Do that in preparation for tracking
+ // more than one scratch register value and using ranges to find
+ // available scratch registers.
unsigned CurrentVirtReg = 0;
unsigned CurrentScratchReg = 0;
-
- for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
+ bool havePrevValue = false;
+ int PrevValue = 0;
+ MachineInstr *PrevLastUseMI = NULL;
+ unsigned PrevLastUseOp = 0;
+ bool trackingCurrentValue = false;
+ int SPAdj = 0;
+ int Value = 0;
+
+ // The instruction stream may change in the loop, so check BB->end()
+ // directly.
+ for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
MachineInstr *MI = I;
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
+ bool isDefInsn = false;
+ bool isKillInsn = false;
+ bool clobbersScratchReg = false;
+ bool DoIncr = true;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
if (MI->getOperand(i).isReg()) {
- unsigned Reg = MI->getOperand(i).getReg();
+ MachineOperand &MO = MI->getOperand(i);
+ unsigned Reg = MO.getReg();
if (Reg == 0)
continue;
if (!TargetRegisterInfo::isVirtualRegister(Reg)) {
- // If we have an active scavenged register, we shouldn't be
- // seeing any references to it.
- assert (Reg != CurrentScratchReg
- && "overlapping use of scavenged frame index register!");
+ // If we have a previous scratch reg, check and see if anything
+ // here kills whatever value is in there.
+ if (Reg == CurrentScratchReg) {
+ if (MO.isUse()) {
+ // Two-address operands implicitly kill
+ if (MO.isKill() || MI->isRegTiedToDefOperand(i))
+ clobbersScratchReg = true;
+ } else {
+ assert (MO.isDef());
+ clobbersScratchReg = true;
+ }
+ }
continue;
}
-
- // If we already have a scratch for this virtual register, use it
+ // If this is a def, remember that this insn defines the value.
+ // This lets us properly consider insns which re-use the scratch
+ // register, such as r2 = sub r2, #imm, in the middle of the
+ // scratch range.
+ if (MO.isDef())
+ isDefInsn = true;
+
+ // Have we already allocated a scratch register for this virtual?
if (Reg != CurrentVirtReg) {
// When we first encounter a new virtual register, it
// must be a definition.
// there's only a guarantee of one scavenged register at a time.
assert (CurrentVirtReg == 0 &&
"overlapping frame index virtual registers!");
+
+ // If the target gave us information about what's in the register,
+ // we can use that to re-use scratch regs.
+ DenseMap<unsigned, FrameConstantEntry>::iterator Entry =
+ FrameConstantRegMap.find(Reg);
+ trackingCurrentValue = Entry != FrameConstantRegMap.end();
+ if (trackingCurrentValue) {
+ SPAdj = (*Entry).second.second;
+ Value = (*Entry).second.first;
+ } else
+ SPAdj = Value = 0;
+
+ // If the scratch register from the last allocation is still
+ // available, see if the value matches. If it does, just re-use it.
+ if (trackingCurrentValue && havePrevValue && PrevValue == Value) {
+ // FIXME: This assumes that the instructions in the live range
+ // for the virtual register are exclusively for the purpose
+ // of populating the value in the register. That's reasonable
+ // for these frame index registers, but it's still a very, very
+ // strong assumption. rdar://7322732. Better would be to
+ // explicitly check each instruction in the range for references
+ // to the virtual register. Only delete those insns that
+ // touch the virtual register.
+
+ // Find the last use of the new virtual register. Remove all
+ // instruction between here and there, and update the current
+ // instruction to reference the last use insn instead.
+ MachineBasicBlock::iterator LastUseMI =
+ findLastUseReg(I, BB->end(), Reg);
+
+ // Remove all instructions up 'til the last use, since they're
+ // just calculating the value we already have.
+ BB->erase(I, LastUseMI);
+ MI = I = LastUseMI;
+
+ // Extend the live range of the scratch register
+ PrevLastUseMI->getOperand(PrevLastUseOp).setIsKill(false);
+ RS->setUsed(CurrentScratchReg);
+ CurrentVirtReg = Reg;
+
+ // We deleted the instruction we were scanning the operands of.
+ // Jump back to the instruction iterator loop. Don't increment
+ // past this instruction since we updated the iterator already.
+ DoIncr = false;
+ break;
+ }
+
+ // Scavenge a new scratch register
CurrentVirtReg = Reg;
const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
CurrentScratchReg = RS->FindUnusedReg(RC);
if (CurrentScratchReg == 0)
// No register is "free". Scavenge a register.
- // FIXME: Track SPAdj. Zero won't always be right
- CurrentScratchReg = RS->scavengeRegister(RC, I, 0);
+ CurrentScratchReg = RS->scavengeRegister(RC, I, SPAdj);
+
+ PrevValue = Value;
}
+ // replace this reference to the virtual register with the
+ // scratch register.
assert (CurrentScratchReg && "Missing scratch register!");
MI->getOperand(i).setReg(CurrentScratchReg);
- // If this is the last use of the register, stop tracking it.
- if (MI->getOperand(i).isKill())
- CurrentScratchReg = CurrentVirtReg = 0;
+ if (MI->getOperand(i).isKill()) {
+ isKillInsn = true;
+ PrevLastUseOp = i;
+ PrevLastUseMI = MI;
+ }
}
- RS->forward(MI);
+ }
+ // If this is the last use of the scratch, stop tracking it. The
+ // last use will be a kill operand in an instruction that does
+ // not also define the scratch register.
+ if (isKillInsn && !isDefInsn) {
+ CurrentVirtReg = 0;
+ havePrevValue = trackingCurrentValue;
+ }
+ // Similarly, notice if instruction clobbered the value in the
+ // register we're tracking for possible later reuse. This is noted
+ // above, but enforced here since the value is still live while we
+ // process the rest of the operands of the instruction.
+ if (clobbersScratchReg) {
+ havePrevValue = false;
+ CurrentScratchReg = 0;
+ }
+ if (DoIncr) {
+ RS->forward(I);
+ ++I;
+ }
}
}
}
projects / oota-llvm.git / blobdiff