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[AVR] Don't reserve the frame pointer when spilling registers #226

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Sep 29, 2016
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[AVR] Don't reserve the frame pointer when spilling registers #226

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52 changes: 1 addition & 51 deletions lib/CodeGen/RegAllocGreedy.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -135,9 +135,6 @@ class RAGreedy : public MachineFunctionPass,
std::unique_ptr<Spiller> SpillerInstance;
PQueue Queue;
unsigned NextCascade;

// AVR specific: have we already unallocated REG_Y after a spill was done?
bool IsYReserved;

// Live ranges pass through a number of stages as we try to allocate them.
// Some of the stages may also create new live ranges:
Expand Down Expand Up @@ -425,7 +422,6 @@ class RAGreedy : public MachineFunctionPass,
void collectHintInfo(unsigned, HintsInfo &);

bool isUnusedCalleeSavedReg(unsigned PhysReg) const;
void UndoRegYAllocation();
};
} // end anonymous namespace

Expand All @@ -452,7 +448,7 @@ FunctionPass* llvm::createGreedyRegisterAllocator() {
return new RAGreedy();
}

RAGreedy::RAGreedy(): MachineFunctionPass(ID), IsYReserved(false) {
RAGreedy::RAGreedy(): MachineFunctionPass(ID) {
initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
Expand Down Expand Up @@ -1642,34 +1638,6 @@ RAGreedy::tryInstructionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
return 0;
}

// AVR specific code used to handle the reservation of REG_Y if any other
// register has been spilled.
// :NOTE: KEEP THIS CONSTANT UPDATED with the backend!
// This has to be a define because of linkage problems between libraries.
#define REG_Y (51U)
namespace llvm {
bool RA_ReserveREG_Y = false;
bool RA_InSpillerCode = false;
} // end of namespace llvm

void RAGreedy::UndoRegYAllocation() {
// search through all virtual registers where REG_Y has been assigned and
// send them back to the work list for reallocation
for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
unsigned VirtReg = TargetRegisterInfo::index2VirtReg(i);
if (MRI->reg_nodbg_empty(VirtReg))
continue;

for (MCRegAliasIterator AI(REG_Y, TRI, true); AI.isValid(); ++AI)
if (VRM->getPhys(VirtReg) == *AI) {
LiveInterval &LI = LIS->getInterval(VirtReg);
Matrix->unassign(LI);
enqueue(&LI);
}
}
}
#undef REG_Y


//===----------------------------------------------------------------------===//
// Local Splitting
Expand Down Expand Up @@ -2610,25 +2578,10 @@ unsigned RAGreedy::selectOrSplitImpl(LiveInterval &VirtReg,
DEBUG(dbgs() << "Do as if this register is in memory\n");
NewVRegs.push_back(VirtReg.reg);
} else {
RA_InSpillerCode = true;
NamedRegionTimer T("Spiller", TimerGroupName, TimePassesIsEnabled);
LiveRangeEdit LRE(&VirtReg, NewVRegs, *MF, *LIS, VRM, this, &DeadRemats);
spiller().spill(LRE);
setStage(NewVRegs.begin(), NewVRegs.end(), RS_Done);
RA_InSpillerCode = false;

// AVR specific: If we have reached this point and the backend has notified
// it has inserted a spill via ReserveREG_Y, then search for any allocations
// of REG_Y in the live intervals and undo them.
if (!IsYReserved && RA_ReserveREG_Y) {
// do all this work only once
IsYReserved = true;
// update the reserved register list
MRI->freezeReservedRegs(VRM->getMachineFunction());
RegClassInfo.runOnMachineFunction(VRM->getMachineFunction());
// finally perform the real work
UndoRegYAllocation();
}

if (VerifyEnabled)
MF->verify(this, "After spilling");
Expand Down Expand Up @@ -2688,8 +2641,5 @@ bool RAGreedy::runOnMachineFunction(MachineFunction &mf) {
postOptimization();

releaseMemory();

IsYReserved = false;
RA_ReserveREG_Y = false;
return true;
}
12 changes: 1 addition & 11 deletions lib/Target/AVR/AVRInstrInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -36,13 +36,6 @@

namespace llvm {

// External variable defined inside the register allocator to indicate if
// we should reserve REG_Y if it is going to be used as the frame pointer.
extern bool RA_ReserveREG_Y;
// External variable defined inside the register allocator to indicate if
// the register allocator is executing code inside the spiller.
extern bool RA_InSpillerCode;

AVRInstrInfo::AVRInstrInfo()
: AVRGenInstrInfo(AVR::ADJCALLSTACKDOWN, AVR::ADJCALLSTACKUP), RI() {}

Expand Down Expand Up @@ -134,10 +127,7 @@ void AVRInstrInfo::storeRegToStackSlot(MachineBasicBlock &MBB,
MachineFunction &MF = *MBB.getParent();
AVRMachineFunctionInfo *AFI = MF.getInfo<AVRMachineFunctionInfo>();

if (RA_InSpillerCode && !AFI->getHasSpills()) {
AFI->setHasSpills(true);
RA_ReserveREG_Y = true;
}
AFI->setHasSpills(true);

DebugLoc DL;
if (MI != MBB.end()) {
Expand Down