static cl::opt<bool>
DisableColoring("no-stack-coloring",
- cl::init(true), cl::Hidden,
- cl::desc("Suppress stack coloring"));
+ cl::init(false), cl::Hidden,
+ cl::desc("Disable stack coloring"));
-STATISTIC(NumMarkerSeen, "Number of life markers found.");
+/// The user may write code that uses allocas outside of the declared lifetime
+/// zone. This can happen when the user returns a reference to a local
+/// data-structure. We can detect these cases and decide not to optimize the
+/// code. If this flag is enabled, we try to save the user.
+static cl::opt<bool>
+ProtectFromEscapedAllocas("protect-from-escaped-allocas",
+ cl::init(false), cl::Hidden,
+ cl::desc("Do not optimize lifetime zones that are broken"));
+
+STATISTIC(NumMarkerSeen, "Number of lifetime markers found.");
STATISTIC(StackSpaceSaved, "Number of bytes saved due to merging slots.");
STATISTIC(StackSlotMerged, "Number of stack slot merged.");
+STATISTIC(EscapedAllocas,
+ "Number of allocas that escaped the lifetime region");
//===----------------------------------------------------------------------===//
// StackColoring Pass
/// VNInfo is used for the construction of LiveIntervals.
VNInfo::Allocator VNInfoAllocator;
/// SlotIndex analysis object.
- SlotIndexes* Indexes;
+ SlotIndexes *Indexes;
/// The list of lifetime markers found. These markers are to be removed
/// once the coloring is done.
/// slots to use the joint slots.
void remapInstructions(DenseMap<int, int> &SlotRemap);
+ /// The input program may contain intructions which are not inside lifetime
+ /// markers. This can happen due to a bug in the compiler or due to a bug in
+ /// user code (for example, returning a reference to a local variable).
+ /// This procedure checks all of the instructions in the function and
+ /// invalidates lifetime ranges which do not contain all of the instructions
+ /// which access that frame slot.
+ void removeInvalidSlotRanges();
+
/// Map entries which point to other entries to their destination.
/// A->B->C becomes A->C.
void expungeSlotMap(DenseMap<int, int> &SlotRemap, unsigned NumSlots);
const Value *Allocation = MFI->getObjectAllocation(Slot);
if (Allocation) {
- DEBUG(dbgs()<<"Found lifetime marker for allocation: "<<
- Allocation->getName()<<"\n");
+ DEBUG(dbgs()<<"Found a lifetime marker for slot #"<<Slot<<
+ " with allocation: "<< Allocation->getName()<<"\n");
}
if (IsStart) {
// 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.
+ // 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
- if (!I->isDebugValue()) {
+ 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);
- LiveInterval* Interval = Intervals[FromSlot];
+ LiveInterval *Interval = Intervals[FromSlot];
assert(Interval->find(Index) != Interval->end() &&
"Found instruction usage outside of live range.");
}
DEBUG(dbgs()<<"Fixed "<<FixedInstr<<" machine instructions.\n");
}
+void StackColoring::removeInvalidSlotRanges() {
+ MachineFunction::iterator BB, BBE;
+ MachineBasicBlock::iterator I, IE;
+ for (BB = MF->begin(), BBE = MF->end(); BB != BBE; ++BB)
+ for (I = BB->begin(), IE = BB->end(); I != IE; ++I) {
+
+ if (I->getOpcode() == TargetOpcode::LIFETIME_START ||
+ I->getOpcode() == TargetOpcode::LIFETIME_END || I->isDebugValue())
+ continue;
+
+ // Some intervals are suspicious! In some cases we find address
+ // calculations outside of the lifetime zone, but not actual memory
+ // read or write. Memory accesses outside of the lifetime zone are a clear
+ // violation, but address calculations are okay. This can happen when
+ // GEPs are hoisted outside of the lifetime zone.
+ // So, in here we only check instructions which can read or write memory.
+ if (!I->mayLoad() && !I->mayStore())
+ continue;
+
+ // Check all of the machine operands.
+ for (unsigned i = 0 ; i < I->getNumOperands(); ++i) {
+ MachineOperand &MO = I->getOperand(i);
+
+ if (!MO.isFI())
+ continue;
+
+ int Slot = MO.getIndex();
+
+ if (Slot<0)
+ continue;
+
+ if (Intervals[Slot]->empty())
+ continue;
+
+ // Check that the used slot is inside the calculated lifetime range.
+ // If it is not, warn about it and invalidate the range.
+ LiveInterval *Interval = Intervals[Slot];
+ SlotIndex Index = Indexes->getInstructionIndex(I);
+ if (Interval->find(Index) == Interval->end()) {
+ Intervals[Slot]->clear();
+ DEBUG(dbgs()<<"Invalidating range #"<<Slot<<"\n");
+ EscapedAllocas++;
+ }
+ }
+ }
+}
+
void StackColoring::expungeSlotMap(DenseMap<int, int> &SlotRemap,
unsigned NumSlots) {
// Expunge slot remap map.
DEBUG(dbgs()<<"Total Stack size: "<<TotalSize<<" bytes\n\n");
// Don't continue because there are not enough lifetime markers, or the
- // stack or too small, or we are told not to optimize the slots.
+ // stack is too small, or we are told not to optimize the slots.
if (NumMarkers < 2 || TotalSize < 16 || DisableColoring) {
DEBUG(dbgs()<<"Will not try to merge slots.\n");
return removeAllMarkers();
// Propagate the liveness information.
calculateLiveIntervals(NumSlots);
+ // Search for allocas which are used outside of the declared lifetime
+ // markers.
+ if (ProtectFromEscapedAllocas)
+ removeInvalidSlotRanges();
+
// Maps old slots to new slots.
DenseMap<int, int> SlotRemap;
unsigned RemovedSlots = 0;
projects / oota-llvm.git / blobdiff