void StackColoring::remapInstructions(DenseMap<int, int> &SlotRemap) {
unsigned FixedInstr = 0;
unsigned FixedMemOp = 0;
unsigned FixedDbg = 0;
MachineModuleInfo *MMI = &MF->getMMI();
// Remap debug information that refers to stack slots.
for (auto &VI : MMI->getVariableDbgInfo()) {
if (!VI.Var)
continue;
if (SlotRemap.count(VI.Slot)) {
DEBUG(dbgs() << "Remapping debug info for ["
<< cast<DILocalVariable>(VI.Var)->getName() << "].\n");
VI.Slot = SlotRemap[VI.Slot];
FixedDbg++;
}
}
// Keep a list of *allocas* which need to be remapped.
DenseMap<const AllocaInst*, const AllocaInst*> Allocas;
for (const std::pair<int, int> &SI : SlotRemap) {
const AllocaInst *From = MFI->getObjectAllocation(SI.first);
const AllocaInst *To = MFI->getObjectAllocation(SI.second);
assert(To && From && "Invalid allocation object");
Allocas[From] = To;
// AA might be used later for instruction scheduling, and we need it to be
// able to deduce the correct aliasing releationships between pointers
// derived from the alloca being remapped and the target of that remapping.
// The only safe way, without directly informing AA about the remapping
// somehow, is to directly update the IR to reflect the change being made
// here.
Instruction *Inst = const_cast<AllocaInst *>(To);
if (From->getType() != To->getType()) {
BitCastInst *Cast = new BitCastInst(Inst, From->getType());
Cast->insertAfter(Inst);
Inst = Cast;
}
// Allow the stack protector to adjust its value map to account for the
// upcoming replacement.
SP->adjustForColoring(From, To);
// The new alloca might not be valid in a llvm.dbg.declare for this
// variable, so undef out the use to make the verifier happy.
AllocaInst *FromAI = const_cast<AllocaInst *>(From);
if (FromAI->isUsedByMetadata())
ValueAsMetadata::handleRAUW(FromAI, UndefValue::get(FromAI->getType()));
for (auto &Use : FromAI->uses()) {
if (BitCastInst *BCI = dyn_cast<BitCastInst>(Use.get()))
if (BCI->isUsedByMetadata())
ValueAsMetadata::handleRAUW(BCI, UndefValue::get(BCI->getType()));
}
// Note that this will not replace uses in MMOs (which we'll update below),
// or anywhere else (which is why we won't delete the original
// instruction).
FromAI->replaceAllUsesWith(Inst);
}
// Remap all instructions to the new stack slots.
for (MachineBasicBlock &BB : *MF)
for (MachineInstr &I : BB) {
// Skip lifetime markers. We'll remove them soon.
if (I.getOpcode() == TargetOpcode::LIFETIME_START ||
I.getOpcode() == TargetOpcode::LIFETIME_END)
continue;
// Update the MachineMemOperand to use the new alloca.
for (MachineMemOperand *MMO : I.memoperands()) {
// FIXME: In order to enable the use of TBAA when using AA in CodeGen,
// we'll also need to update the TBAA nodes in MMOs with values
// derived from the merged allocas. When doing this, we'll need to use
// the same variant of GetUnderlyingObjects that is used by the
// instruction scheduler (that can look through ptrtoint/inttoptr
// pairs).
// We've replaced IR-level uses of the remapped allocas, so we only
// need to replace direct uses here.
const AllocaInst *AI = dyn_cast_or_null<AllocaInst>(MMO->getValue());
if (!AI)
continue;
if (!Allocas.count(AI))
continue;
MMO->setValue(Allocas[AI]);
FixedMemOp++;
}
// Update all of the machine instruction operands.
for (MachineOperand &MO : I.operands()) {
if (!MO.isFI())
continue;
int FromSlot = MO.getIndex();
// Don't touch arguments.
if (FromSlot<0)
continue;
// Only look at mapped slots.
if (!SlotRemap.count(FromSlot))
continue;
// In a debug build, check that the instruction that we are modifying is
// inside the expected live range. If the instruction is not inside
// the calculated range then it means that the alloca usage moved
// outside of the lifetime markers, or that the user has a bug.
// NOTE: Alloca address calculations which happen outside the lifetime
// zone are are okay, despite the fact that we don't have a good way
// for validating all of the usages of the calculation.
#ifndef NDEBUG
bool TouchesMemory = I.mayLoad() || I.mayStore();
// If we *don't* protect the user from escaped allocas, don't bother
// validating the instructions.
if (!I.isDebugValue() && TouchesMemory && ProtectFromEscapedAllocas) {
SlotIndex Index = Indexes->getInstructionIndex(I);
const LiveInterval *Interval = &*Intervals[FromSlot];
assert(Interval->find(Index) != Interval->end() &&
"Found instruction usage outside of live range.");
}
#endif
// Fix the machine instructions.
int ToSlot = SlotRemap[FromSlot];
MO.setIndex(ToSlot);
FixedInstr++;
}
}
// Update the location of C++ catch objects for the MSVC personality routine.
if (WinEHFuncInfo *EHInfo = MF->getWinEHFuncInfo())
for (WinEHTryBlockMapEntry &TBME : EHInfo->TryBlockMap)
for (WinEHHandlerType &H : TBME.HandlerArray)
if (H.CatchObj.FrameIndex != INT_MAX &&
SlotRemap.count(H.CatchObj.FrameIndex))
H.CatchObj.FrameIndex = SlotRemap[H.CatchObj.FrameIndex];
DEBUG(dbgs()<<"Fixed "<<FixedMemOp<<" machine memory operands.\n");
DEBUG(dbgs()<<"Fixed "<<FixedDbg<<" debug locations.\n");
DEBUG(dbgs()<<"Fixed "<<FixedInstr<<" machine instructions.\n");
}
