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DeadObjectElimination: handle OSSA instructions when analyzing class destructors #78361

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Merged
merged 1 commit into from
Jan 2, 2025
Merged

DeadObjectElimination: handle OSSA instructions when analyzing class destructors #78361

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1 change: 1 addition & 0 deletions lib/SIL/Utils/InstructionUtils.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -172,6 +172,7 @@ SILValue swift::stripCasts(SILValue v) {
if (auto *svi = dyn_cast<SingleValueInstruction>(v)) {
if (isIdentityPreservingRefCast(svi) ||
isa<UncheckedTrivialBitCastInst>(v) || isa<MarkDependenceInst>(v) ||
isa<UncheckedOwnershipConversionInst>(v) ||
isa<BeginAccessInst>(v)) {
v = cast<SingleValueInstruction>(v)->getOperand(0);
continue;
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4 changes: 4 additions & 0 deletions lib/SILOptimizer/Transforms/DeadObjectElimination.cpp
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Expand Up @@ -204,6 +204,10 @@ static DestructorEffects doesDestructorHaveSideEffects(AllocRefInstBase *ARI) {
continue;
}

if (isa<BeginBorrowInst>(I) || isa<EndBorrowInst>(I) || isa<EndLifetimeInst>(I)) {
continue;
}

// dealloc_ref on self can be ignored, but dealloc_ref on anything else
// cannot be eliminated.
if (auto *DeallocRef = dyn_cast<DeallocRefInst>(&I)) {
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38 changes: 38 additions & 0 deletions test/SILOptimizer/dead_alloc_elim_ossa.sil
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Expand Up @@ -28,6 +28,11 @@ class ArrayStorage {
init()
}

class Kl2 {
@_hasStorage var i: Int
}


protocol P { }
struct X : P { }

Expand Down Expand Up @@ -65,6 +70,19 @@ bb0(%0 : @owned $NontrivialDestructor):
return %7 : $()
}

sil [ossa] @$s4main3Kl2CfD : $@convention(method) (@owned Kl2) -> () {
bb0(%0 : @owned $Kl2):
%1 = begin_borrow %0
%2 = unchecked_ref_cast %1 to $Builtin.NativeObject
%3 = unchecked_ownership_conversion %2, @guaranteed to @owned
end_borrow %1
end_lifetime %0
%6 = unchecked_ref_cast %3 to $Kl2
dealloc_ref %6
%8 = tuple ()
return %8
}

sil @ptr_user : $@convention(thin) (Builtin.NativeObject) -> ()
sil @int_user : $@convention(thin) (Builtin.Int32) -> ()

Expand Down Expand Up @@ -541,3 +559,23 @@ bb0(%0 : @owned $_ContiguousArrayStorage<Element>):
return %15 : $()
}

// CHECK-LABEL: sil [ossa] @dead_alloc_with_complex_ossa_destructor
// CHECK-NOT: alloc_ref
// CHECK: } // end sil function 'dead_alloc_with_complex_ossa_destructor'
sil [ossa] @dead_alloc_with_complex_ossa_destructor : $@convention(thin) () -> Int {
bb0:
%0 = alloc_ref $Kl2
%1 = move_value [lexical] %0
%2 = end_init_let_ref %1
%3 = begin_borrow %2
%4 = integer_literal $Builtin.Int64, 27
%5 = struct $Int (%4)
%6 = ref_element_addr %3, #Kl2.i
store %5 to [trivial] %6
end_borrow %3
%9 = move_value [lexical] [var_decl] %2
debug_value %9, let, name "k"
destroy_value %9
return %5
}