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[copy-propagation] Since this runs on OSSA and we have formalized consuming there, use that instead of our own handrolled consuming use impl.

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This is in preparation for adding a run of this around ownership lowering in
order to eliminate extra copies that passes may introduce as they transform IR.

The tests for the pass all still pass in the exact same way so no updates were
needed.
This commit is contained in:
Michael Gottesman
2020-10-23 15:44:59 -07:00
parent 303d88ce84
commit bdd7b42633
1 changed files with 36 additions and 222 deletions
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258
lib/SILOptimizer/Transforms/CopyPropagation.cpp
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@@ -145,200 +145,12 @@ STATISTIC(NumCopiesGenerated, "number of copy_value instructions created");
STATISTIC(NumDestroysGenerated, "number of destroy_value instructions created");
STATISTIC(NumUnknownUsers, "number of functions with unknown users");
//===----------------------------------------------------------------------===//
// Ownership Abstraction.
//
// FIXME: These helpers are only defined in this pass for prototyping. After
// bootstrapping, they should be moved to a central ownership API (shared by
// SILOwnershipVerifier, etc.).
//
// Categories of owned value users. (U1-U2 apply to any value, O3-O5 only apply
// to owned values).
//
// U1. Use the value instantaneously (copy_value, @guaranteed).
//
// U2. Escape the nontrivial contents of the value (ref_to_unowned,
// unchecked_trivial_bitcast).
//
// O3. Propagate the value without consuming it (mark_dependence, begin_borrow).
//
// O4. Consume the value immediately (store, destroy, @owned, destructure).
//
// O5. Consume the value indirectly via a move (tuple, struct).
// ===---------------------------------------------------------------------===//
// TODO: Figure out how to handle these cases if possible.
static bool isUnknownUse(Operand *use) {
switch (use->getUser()->getKind()) {
default:
return false;
// FIXME: (Category O3) mark_dependence requires recursion to find all
// uses. It should be replaced by begin/end dependence.
case SILInstructionKind::MarkDependenceInst: // Dependent
// FIXME: (Category O3) ref_tail_addr should require a borrow because it
// doesn't rely on fix_lifetime like other escaping instructions.
case SILInstructionKind::RefTailAddrInst:
// FIXME: (Category O3) dynamic_method_br seems to capture self, presumably
// propagating lifetime. This should probably borrow self, then be treated
// like mark_dependence.
case SILInstructionKind::DynamicMethodBranchInst:
// FIXME: (Category O3) The ownership verifier says project_box can accept an
// owned value as a normal use, but it projects the address. That's either an
// ownership bug or a special case.
case SILInstructionKind::ProjectBoxInst:
case SILInstructionKind::ProjectExistentialBoxInst:
// FIXME: (Category O3) The ownership verifier says open_existential_box can
// accept an owned value as a normal use, but it projects an address.
case SILInstructionKind::OpenExistentialBoxInst:
// Unmanaged operations hopefully don't apply to the same value as CopyValue?
case SILInstructionKind::UnmanagedRetainValueInst:
case SILInstructionKind::UnmanagedReleaseValueInst:
case SILInstructionKind::UnmanagedAutoreleaseValueInst:
return true;
}
}
/// Return true if the given owned operand is consumed by the given call.
static bool isAppliedArgConsumed(ApplySite apply, Operand *oper) {
ParameterConvention paramConv;
if (oper->get() == apply.getCallee()) {
assert(oper->getOperandNumber() == 0
&& "function can't be passed to itself");
paramConv = apply.getSubstCalleeType()->getCalleeConvention();
} else {
unsigned argIndex = apply.getCalleeArgIndex(*oper);
paramConv = apply.getSubstCalleeConv()
.getParamInfoForSILArg(argIndex)
.getConvention();
}
return isConsumedParameter(paramConv);
}
/// Return true if the given builtin consumes its operand.
static bool isBuiltinArgConsumed(BuiltinInst *BI) {
const BuiltinInfo &Builtin = BI->getBuiltinInfo();
switch (Builtin.ID) {
default:
llvm_unreachable("Unexpected Builtin with owned value operand.");
// Extend lifetime without consuming.
case BuiltinValueKind::ErrorInMain:
case BuiltinValueKind::UnexpectedError:
case BuiltinValueKind::WillThrow:
return false;
// UnsafeGuaranteed moves the value, which will later be destroyed.
case BuiltinValueKind::UnsafeGuaranteed:
return true;
}
}
/// Return true if the given operand is consumed by its user.
///
/// TODO: Review the semantics of operations that extend the lifetime *without*
/// propagating the value. Ideally, that never happens without borrowing first.
static bool isConsuming(Operand *use) {
auto *user = use->getUser();
if (isa<ApplySite>(user))
return isAppliedArgConsumed(ApplySite(user), use);
if (auto *BI = dyn_cast<BuiltinInst>(user))
return isBuiltinArgConsumed(BI);
switch (user->getKind()) {
default:
llvm::dbgs() << *user;
llvm_unreachable("Unexpected use of a loadable owned value.");
// Consume the value.
case SILInstructionKind::AutoreleaseValueInst:
case SILInstructionKind::DeallocBoxInst:
case SILInstructionKind::DeallocExistentialBoxInst:
case SILInstructionKind::DeallocRefInst:
case SILInstructionKind::DeinitExistentialValueInst:
case SILInstructionKind::DestroyValueInst:
case SILInstructionKind::EndLifetimeInst:
case SILInstructionKind::InitExistentialRefInst:
case SILInstructionKind::InitExistentialValueInst:
case SILInstructionKind::KeyPathInst:
case SILInstructionKind::ReleaseValueInst:
case SILInstructionKind::ReleaseValueAddrInst:
case SILInstructionKind::StoreInst:
case SILInstructionKind::StrongReleaseInst:
case SILInstructionKind::UnownedReleaseInst:
case SILInstructionKind::UnconditionalCheckedCastValueInst:
return true;
// Terminators must consume their owned values.
case SILInstructionKind::BranchInst:
case SILInstructionKind::CheckedCastBranchInst:
case SILInstructionKind::CheckedCastValueBranchInst:
case SILInstructionKind::CondBranchInst:
case SILInstructionKind::ReturnInst:
case SILInstructionKind::ThrowInst:
return true;
case SILInstructionKind::DeallocPartialRefInst:
return cast<DeallocPartialRefInst>(user)->getInstance() == use->get();
// Move the value.
case SILInstructionKind::TupleInst:
case SILInstructionKind::StructInst:
case SILInstructionKind::ObjectInst:
case SILInstructionKind::EnumInst:
case SILInstructionKind::OpenExistentialRefInst:
case SILInstructionKind::UpcastInst:
case SILInstructionKind::UncheckedRefCastInst:
case SILInstructionKind::ConvertFunctionInst:
case SILInstructionKind::RefToBridgeObjectInst:
case SILInstructionKind::BridgeObjectToRefInst:
case SILInstructionKind::UnconditionalCheckedCastInst:
case SILInstructionKind::MarkUninitializedInst:
case SILInstructionKind::UncheckedEnumDataInst:
case SILInstructionKind::DestructureStructInst:
case SILInstructionKind::DestructureTupleInst:
return true;
// BeginBorrow should already be skipped.
// EndBorrow extends the lifetime like a normal use.
case SILInstructionKind::EndBorrowInst:
return false;
// Extend the lifetime without borrowing, propagating, or destroying it.
case SILInstructionKind::BridgeObjectToWordInst:
case SILInstructionKind::ClassMethodInst:
case SILInstructionKind::CopyBlockInst:
case SILInstructionKind::CopyValueInst:
case SILInstructionKind::DebugValueInst:
case SILInstructionKind::ExistentialMetatypeInst:
case SILInstructionKind::FixLifetimeInst:
case SILInstructionKind::SelectEnumInst:
case SILInstructionKind::SetDeallocatingInst:
case SILInstructionKind::StoreWeakInst:
case SILInstructionKind::ValueMetatypeInst:
return false;
// Escape the value. The lifetime must already be enforced via something like
// fix_lifetime.
case SILInstructionKind::RefToRawPointerInst:
case SILInstructionKind::RefToUnmanagedInst:
case SILInstructionKind::RefToUnownedInst:
case SILInstructionKind::UncheckedBitwiseCastInst:
case SILInstructionKind::UncheckedTrivialBitCastInst:
return false;
// Dynamic dispatch without capturing self.
case SILInstructionKind::ObjCMethodInst:
case SILInstructionKind::ObjCSuperMethodInst:
case SILInstructionKind::SuperMethodInst:
case SILInstructionKind::WitnessMethodInst:
return false;
}
}
//===----------------------------------------------------------------------===//
// CopyPropagationState: shared state for the pass's analysis and transforms.
//===----------------------------------------------------------------------===//
namespace {
/// LiveWithin blocks have at least one use and/or def within the block, but are
/// not LiveOut.
///
@@ -357,9 +169,10 @@ class LivenessInfo {
// used value is consumed. (Non-consuming uses within a block that is already
// known to be live are uninteresting.)
DenseMap<SILInstruction *, bool> users;
// Original points in the CFG where the current value was consumed or
// destroyed.
typedef SmallSetVector<SILBasicBlock *, 8> BlockSetVec;
using BlockSetVec = SmallSetVector<SILBasicBlock *, 8>;
BlockSetVec originalDestroyBlocks;
public:
@@ -409,7 +222,7 @@ public:
//
// This call cannot be allowed to destroy %val.
void recordUser(Operand *use) {
bool consume = isConsuming(use);
bool consume = use->isConsumingUse();
auto iterAndSuccess = users.try_emplace(use->getUser(), consume);
if (!iterAndSuccess.second)
iterAndSuccess.first->second &= consume;
@@ -468,7 +281,7 @@ public:
/// This pass' shared state.
struct CopyPropagationState {
SILFunction *F;
SILFunction *func;
// Per-function invalidation state.
unsigned invalidation;
@@ -483,7 +296,7 @@ struct CopyPropagationState {
DestroyInfo destroys;
CopyPropagationState(SILFunction *F)
: F(F), invalidation(SILAnalysis::InvalidationKind::Nothing) {}
: func(F), invalidation(SILAnalysis::InvalidationKind::Nothing) {}
bool isValueOwned() const {
return currDef.getOwnershipKind() == ValueOwnershipKind::Owned;
@@ -600,27 +413,23 @@ static bool computeLiveness(CopyPropagationState &pass) {
for (Operand *use : value->getUses()) {
auto *user = use->getUser();
// Bailout if we cannot yet determine the ownership of a use.
if (isUnknownUse(use)) {
LLVM_DEBUG(llvm::dbgs() << "Unknown owned value user: "; user->dump());
++NumUnknownUsers;
return false;
}
// Recurse through copies.
if (auto *copy = dyn_cast<CopyValueInst>(user)) {
defUseWorkList.insert(copy);
continue;
}
// An entire borrow scope is considered a single use that occurs at the
// point of the end_borrow.
if (auto *BBI = dyn_cast<BeginBorrowInst>(user)) {
for (Operand *use : BBI->getUses()) {
if (auto *bbi = dyn_cast<BeginBorrowInst>(user)) {
for (Operand *use : bbi->getUses()) {
if (isa<EndBorrowInst>(use->getUser()))
computeUseLiveness(use, pass);
}
continue;
}
if (isConsuming(use)) {
if (use->isConsumingUse()) {
pass.liveness.recordOriginalDestroy(use);
// Destroying a values does not force liveness.
if (isa<DestroyValueInst>(user))
@@ -649,13 +458,14 @@ static void insertDestroyOnCFGEdge(SILBasicBlock *predBB, SILBasicBlock *succBB,
if (destroyBB != succBB)
pass.markInvalid(SILAnalysis::InvalidationKind::Branches);
SILBuilderWithScope B(destroyBB->begin());
auto *DI = B.createDestroyValue(succBB->begin()->getLoc(), pass.currDef);
SILBuilderWithScope builder(destroyBB->begin());
auto *di =
builder.createDestroyValue(succBB->begin()->getLoc(), pass.currDef);
pass.destroys.recordFinalDestroy(DI);
pass.destroys.recordFinalDestroy(di);
++NumDestroysGenerated;
LLVM_DEBUG(llvm::dbgs() << " Destroy on edge "; DI->dump());
LLVM_DEBUG(llvm::dbgs() << " Destroy on edge "; di->dump());
pass.markInvalid(SILAnalysis::InvalidationKind::Instructions);
}
@@ -665,11 +475,11 @@ static void insertDestroyOnCFGEdge(SILBasicBlock *predBB, SILBasicBlock *succBB,
/// Create a final destroy, immediately after `pos`.
static void insertDestroyAtInst(SILBasicBlock::iterator pos,
CopyPropagationState &pass) {
SILBuilderWithScope B(pos);
auto *DI = B.createDestroyValue((*pos).getLoc(), pass.currDef);
pass.destroys.recordFinalDestroy(DI);
SILBuilderWithScope builder(pos);
auto *di = builder.createDestroyValue((*pos).getLoc(), pass.currDef);
pass.destroys.recordFinalDestroy(di);
++NumDestroysGenerated;
LLVM_DEBUG(llvm::dbgs() << " Destroy at last use "; DI->dump());
LLVM_DEBUG(llvm::dbgs() << " Destroy at last use "; di->dump());
pass.markInvalid(SILAnalysis::InvalidationKind::Instructions);
}
@@ -679,9 +489,9 @@ static void insertDestroyAtInst(SILBasicBlock::iterator pos,
static void findOrInsertDestroyInBlock(SILBasicBlock *bb,
CopyPropagationState &pass) {
auto *defInst = pass.currDef->getDefiningInstruction();
auto I = bb->getTerminator()->getIterator();
auto instIter = bb->getTerminator()->getIterator();
while (true) {
auto *inst = &*I;
auto *inst = &*instIter;
Optional<bool> isConsumingResult = pass.liveness.isConsumingUser(inst);
if (isConsumingResult.hasValue()) {
if (isConsumingResult.getValue()) {
@@ -691,20 +501,20 @@ static void findOrInsertDestroyInBlock(SILBasicBlock *bb,
}
// Insert a destroy after this non-consuming use.
assert(inst != bb->getTerminator() && "Terminator must consume operand.");
insertDestroyAtInst(std::next(I), pass);
insertDestroyAtInst(std::next(instIter), pass);
break;
}
// This is not a potential last user. Keep scanning.
// If the original destroy is reached, this is a dead live range. Insert a
// destroy immediately after the def.
if (I == bb->begin()) {
if (instIter == bb->begin()) {
assert(cast<SILArgument>(pass.currDef)->getParent() == bb);
insertDestroyAtInst(I, pass);
insertDestroyAtInst(instIter, pass);
break;
}
--I;
if (&*I == defInst) {
insertDestroyAtInst(std::next(I), pass);
--instIter;
if (&*instIter == defInst) {
insertDestroyAtInst(std::next(instIter), pass);
break;
}
}
@@ -799,6 +609,7 @@ static void rewriteCopies(CopyPropagationState &pass) {
defUseWorklist.insert(copy);
return;
}
if (auto *destroy = dyn_cast<DestroyValueInst>(user)) {
// If this destroy was marked as a final destroy, ignore it; otherwise,
// delete it.
@@ -809,8 +620,9 @@ static void rewriteCopies(CopyPropagationState &pass) {
}
return;
}
// Nonconsuming uses do not need copies and cannot be marked as destroys.
if (!isConsuming(use))
if (!use->isConsumingUse())
return;
// If this use was marked as a final destroy *and* this is the first
@@ -862,6 +674,7 @@ static SILValue stripCopies(SILValue v) {
v = srcCopy->getOperand();
continue;
}
return v;
}
}
@@ -885,12 +698,13 @@ void CopyPropagation::run() {
// Step 1. Find all copied defs.
CopyPropagationState pass(getFunction());
SmallSetVector<SILValue, 16> copiedDefs;
for (auto &BB : *pass.F) {
for (auto &I : BB) {
if (auto *copy = dyn_cast<CopyValueInst>(&I))
for (auto &bb : *pass.func) {
for (auto &i : bb) {
if (auto *copy = dyn_cast<CopyValueInst>(&i))
copiedDefs.insert(stripCopies(copy));
}
}
for (auto &def : copiedDefs) {
pass.resetDef(def);
// Step 2: computeLiveness