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[SILCombine] Skip load-only unchecked_take_enum_data_addr with noncopyable base. #83404

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Merged
merged 1 commit into from
Jul 31, 2025
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[SILCombine] Skip load-only unchecked_take_enum_data_addr with noncopyable base. #83404

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10 changes: 10 additions & 0 deletions lib/SILOptimizer/SILCombiner/SILCombinerMiscVisitors.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1118,12 +1118,17 @@ SILInstruction *SILCombiner::visitUncheckedTakeEnumDataAddrInst(
return nullptr;

bool onlyLoads = true;
bool anyLoadCopies = false;
bool onlyDestroys = true;
for (auto U : getNonDebugUses(tedai)) {
// Check if it is load. If it is not a load, bail...
if (!isa<LoadInst>(U->getUser()) && !isa<LoadBorrowInst>(U->getUser()))
onlyLoads = false;

if (auto *li = dyn_cast<LoadInst>(U->getUser()))
if (li->getOwnershipQualifier() == LoadOwnershipQualifier::Copy)
anyLoadCopies = true;

// If we have a load_borrow, perform an additional check that we do not have
// any reborrow uses. We do not handle reborrows in this optimization.
if (auto *lbi = dyn_cast<LoadBorrowInst>(U->getUser())) {
Expand Down Expand Up @@ -1166,6 +1171,11 @@ SILInstruction *SILCombiner::visitUncheckedTakeEnumDataAddrInst(
if (tedai->getOperand()->getType().isAddressOnly(*tedai->getFunction()))
return nullptr;

// If the enum is noncopyable and any loads cause copies, the transformation
// would be illegal because it would introduce a copy of the noncopyable enum.
if (tedai->getOperand()->getType().isMoveOnly() && anyLoadCopies)
return nullptr;

// Grab the EnumAddr.
SILLocation loc = tedai->getLoc();
Builder.setCurrentDebugScope(tedai->getDebugScope());
Expand Down
49 changes: 49 additions & 0 deletions test/SILOptimizer/sil_combine_ossa.sil
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Original file line number Diff line number Diff line change
Expand Up @@ -102,6 +102,14 @@ struct MoveOnlyStruct: ~Copyable {
var value: MyInt
}

enum NoncopyableEnum : ~Copyable {
case i(CopyableStruct)
}

struct CopyableStruct {
var guts: AnyObject
}

//////////////////////
// Simple DCE Tests //
//////////////////////
Expand Down Expand Up @@ -5530,3 +5538,44 @@ bb0:
return %6
}

// unchecked_take_enum_data_addr of a noncopyable base must not be combined if
// there are any load [copy] users.
// CHECK-LABEL: sil [ossa] @no_combine_uteda_load_copy_noncopyable {{.*}} {
// CHECK: unchecked_take_enum_data_addr
// CHECK-LABEL: } // end sil function 'no_combine_uteda_load_copy_noncopyable'
sil [ossa] @no_combine_uteda_load_copy_noncopyable : $@convention(thin) (@in NoncopyableEnum) -> () {
entry(%e_addr : $*NoncopyableEnum):
%i_addr = unchecked_take_enum_data_addr %e_addr : $*NoncopyableEnum, #NoncopyableEnum.i!enumelt
%i_copy = load [copy] %i_addr : $*CopyableStruct
apply undef(%i_copy) : $@convention(thin) (@owned CopyableStruct) -> ()
%i = load [take] %i_addr : $*CopyableStruct
apply undef(%i) : $@convention(thin) (@owned CopyableStruct) -> ()
return undef : $()
}

// unchecked_take_enum_data_addr of a noncopyable base should be combined if
// there are only load [take] users.
// CHECK-LABEL: sil [ossa] @combine_uteda_load_take_noncopyable {{.*}} {
// CHECK-NOT: unchecked_take_enum_data_addr
// CHECK-LABEL: } // end sil function 'combine_uteda_load_take_noncopyable'
sil [ossa] @combine_uteda_load_take_noncopyable : $@convention(thin) (@in NoncopyableEnum) -> () {
entry(%e_addr : $*NoncopyableEnum):
%i_addr = unchecked_take_enum_data_addr %e_addr : $*NoncopyableEnum, #NoncopyableEnum.i!enumelt
%i = load [take] %i_addr : $*CopyableStruct
apply undef(%i) : $@convention(thin) (@owned CopyableStruct) -> ()
return undef : $()
}

// unchecked_take_enum_data_addr of a noncopyable base should be combined if
// there are only load_borrow users.
// CHECK-LABEL: sil [ossa] @combine_uteda_load_borrow_noncopyable {{.*}} {
// CHECK-NOT: unchecked_take_enum_data_addr
// CHECK-LABEL: } // end sil function 'combine_uteda_load_borrow_noncopyable'
sil [ossa] @combine_uteda_load_borrow_noncopyable : $@convention(thin) (@in_guaranteed NoncopyableEnum) -> () {
entry(%e_addr : $*NoncopyableEnum):
%i_addr = unchecked_take_enum_data_addr %e_addr : $*NoncopyableEnum, #NoncopyableEnum.i!enumelt
%i = load_borrow %i_addr : $*CopyableStruct
apply undef(%i) : $@convention(thin) (@guaranteed CopyableStruct) -> ()
end_borrow %i : $CopyableStruct
return undef : $()
}