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[arc] A value loaded from an @in_guaranteed parameter is @guaranteed. #1662

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Merged
merged 1 commit into from
Mar 13, 2016
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[arc] A value loaded from an @in_guaranteed parameter is @guaranteed. #1662

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56 changes: 39 additions & 17 deletions lib/SILOptimizer/ARC/RCStateTransitionVisitors.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,43 @@ visitAutoreleasePoolCall(ValueBase *V) {
return DataflowResult(RCStateTransitionDataflowResultKind::NoEffects);
}

// private helper method since C++ does not have extensions... *sigh*.
//
// TODO: This needs a better name.
template <class ARCState>
static bool isKnownSafe(BottomUpDataflowRCStateVisitor<ARCState> *State,
SILInstruction *I, SILValue Op) {
// If we are running with 'frozen' owned arg releases, check if we have a
// frozen use in the side table. If so, this release must be known safe.
if (State->FreezeOwnedArgEpilogueReleases)
if (auto *OwnedRelease =
State->EpilogueReleaseMatcher.getSingleReleaseForArgument(Op))
if (I != OwnedRelease)
return true;

// A guaranteed function argument is guaranteed to outlive the function we are
// processing. So bottom up for such a parameter, we are always known safe.
if (auto *Arg = dyn_cast<SILArgument>(Op)) {
if (Arg->isFunctionArg() &&
Arg->hasConvention(SILArgumentConvention::Direct_Guaranteed)) {
return true;
}
}

// If Op is a load from an in_guaranteed parameter, it is guaranteed as well.
if (auto *LI = dyn_cast<LoadInst>(Op)) {
SILValue RCIdentity = State->RCFI->getRCIdentityRoot(LI->getOperand());
if (auto *Arg = dyn_cast<SILArgument>(RCIdentity)) {
if (Arg->isFunctionArg() &&
Arg->hasConvention(SILArgumentConvention::Indirect_In_Guaranteed)) {
return true;
}
}
}

return false;
}

template <class ARCState>
typename BottomUpDataflowRCStateVisitor<ARCState>::DataflowResult
BottomUpDataflowRCStateVisitor<ARCState>::visitStrongDecrement(ValueBase *V) {
Expand All @@ -70,23 +107,8 @@ BottomUpDataflowRCStateVisitor<ARCState>::visitStrongDecrement(ValueBase *V) {
BottomUpRefCountState &State = DataflowState.getBottomUpRefCountState(Op);
bool NestingDetected = State.initWithMutatorInst(SetFactory.get(I), RCFI);

// If we are running with 'frozen' owned arg releases, check if we have a
// frozen use in the side table. If so, this release must be known safe.
if (FreezeOwnedArgEpilogueReleases) {
if (auto *OwnedRelease = EpilogueReleaseMatcher.getSingleReleaseForArgument(Op)) {
if (I != OwnedRelease) {
State.updateKnownSafe(true);
}
}
}

// A guaranteed function argument is guaranteed to outlive the function we are
// processing. So bottom up for such a parameter, we are always known safe.
if (auto *Arg = dyn_cast<SILArgument>(Op)) {
if (Arg->isFunctionArg() &&
Arg->hasConvention(SILArgumentConvention::Direct_Guaranteed)) {
State.updateKnownSafe(true);
}
if (isKnownSafe(this, I, Op)) {
State.updateKnownSafe(true);
}

DEBUG(llvm::dbgs() << " REF COUNT DECREMENT! Known Safe: "
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16 changes: 16 additions & 0 deletions test/SILOptimizer/arcsequenceopts.sil
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Expand Up @@ -2130,4 +2130,20 @@ bb0(%0 : $Builtin.NativeObject):
apply %1(%0) : $@convention(thin) (Builtin.NativeObject) -> ()
strong_release %0 : $Builtin.NativeObject
return undef : $()
}

// CHECK-LABEL: sil @in_guaranteed_always_known_safe_bu : $@convention(thin) (@in_guaranteed Builtin.NativeObject) -> () {
// CHECK: strong_retain
// CHECK-NOT: strong_retain
// CHECK-NOT: strong_release
sil @in_guaranteed_always_known_safe_bu : $@convention(thin) (@in_guaranteed Builtin.NativeObject) -> () {
bb0(%0 : $*Builtin.NativeObject):
%1 = load %0 : $*Builtin.NativeObject
strong_retain %1 : $Builtin.NativeObject
strong_retain %1 : $Builtin.NativeObject
%2 = function_ref @use : $@convention(thin) (Builtin.NativeObject) -> ()
apply %2(%1) : $@convention(thin) (Builtin.NativeObject) -> ()
apply %2(%1) : $@convention(thin) (Builtin.NativeObject) -> ()
strong_release %1 : $Builtin.NativeObject
return undef : $()
}