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[Mem2Reg] Instantiate arbitrary empty types. #64356

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Merged
nate-chandler merged 1 commit into from
Mar 16, 2023
Merged

[Mem2Reg] Instantiate arbitrary empty types. #64356

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54 changes: 39 additions & 15 deletions lib/SILOptimizer/Transforms/SILMem2Reg.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -327,19 +327,43 @@ replaceLoad(SILInstruction *inst, SILValue newValue, AllocStackInst *asi,
}
}

/// Create a tuple value for an empty tuple or a tuple of empty tuples.
static SILValue createValueForEmptyTuple(SILType ty,
SILInstruction *insertionPoint,
SILBuilderContext &ctx) {
auto tupleTy = ty.castTo<TupleType>();
SmallVector<SILValue, 4> elements;
for (unsigned idx : range(tupleTy->getNumElements())) {
SILType elementTy = ty.getTupleElementType(idx);
elements.push_back(
createValueForEmptyTuple(elementTy, insertionPoint, ctx));
/// Instantiate the specified empty type by recursively tupling and structing
/// the empty types aggregated together at each level.
static SILValue createValueForEmptyType(SILType ty,
SILInstruction *insertionPoint,
SILBuilderContext &ctx) {
auto *function = insertionPoint->getFunction();
assert(ty.isEmpty(*function));
if (auto tupleTy = ty.getAs<TupleType>()) {
SmallVector<SILValue, 4> elements;
for (unsigned idx : range(tupleTy->getNumElements())) {
SILType elementTy = ty.getTupleElementType(idx);
auto element = createValueForEmptyType(elementTy, insertionPoint, ctx);
elements.push_back(element);
}
SILBuilderWithScope builder(insertionPoint, ctx);
return builder.createTuple(insertionPoint->getLoc(), ty, elements);
} else if (auto *decl = ty.getStructOrBoundGenericStruct()) {
TypeExpansionContext tec = *function;
auto &module = function->getModule();
if (decl->isResilient(tec.getContext()->getParentModule(),
tec.getResilienceExpansion())) {
llvm::errs() << "Attempting to create value for illegal empty type:\n";
ty.print(llvm::errs());
llvm::report_fatal_error("illegal empty type: resilient struct");
}
SmallVector<SILValue, 4> elements;
for (auto *field : decl->getStoredProperties()) {
auto elementTy = ty.getFieldType(field, module, tec);
auto element = createValueForEmptyType(elementTy, insertionPoint, ctx);
elements.push_back(element);
}
SILBuilderWithScope builder(insertionPoint, ctx);
return builder.createStruct(insertionPoint->getLoc(), ty, elements);
}
SILBuilderWithScope builder(insertionPoint, ctx);
return builder.createTuple(insertionPoint->getLoc(), ty, elements);
llvm::errs() << "Attempting to create value for illegal empty type:\n";
ty.print(llvm::errs());
llvm::report_fatal_error("illegal empty type: neither tuple nor struct.");
}

/// Whether lexical lifetimes should be added for the values stored into the
Expand Down Expand Up @@ -1607,11 +1631,11 @@ void MemoryToRegisters::removeSingleBlockAllocation(AllocStackInst *asi) {
// with our running value.
if (isLoadFromStack(inst, asi)) {
if (!runningVals) {
// Loading without a previous store is only acceptable if the type is
// Void (= empty tuple) or a tuple of Voids.
// Loading from uninitialized memory is only acceptable if the type is
// empty--an aggregate of types without storage.
runningVals = {
LiveValues::toReplace(asi,
/*replacement=*/createValueForEmptyTuple(
/*replacement=*/createValueForEmptyType(
asi->getElementType(), inst, ctx)),
/*isStorageValid=*/true};
}
Expand Down
26 changes: 26 additions & 0 deletions test/SILOptimizer/mem2reg.sil
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,12 @@ struct LargeCodesizeStruct {
var s5: SmallCodesizeStruct
}

struct EmptyStruct {}
struct Pair<T, U> {
var t: T
var u: U
}

///////////
// Tests //
///////////
Expand Down Expand Up @@ -492,3 +498,23 @@ bb3:
%11 = tuple ()
return %11 : $()
}

// CHECK-LABEL: sil @load_from_uninitialized_empty : {{.*}} {
// CHECK: [[V_3_0:%[^,]+]] = struct $EmptyStruct
// CHECK: [[V_3_1:%[^,]+]] = struct $EmptyStruct
// CHECK: [[V_2_0:%[^,]+]] = struct $Pair{{.*}} ([[V_3_0]]{{.*}}, [[V_3_1]]
// CHECK: [[V_2_1:%[^,]+]] = struct $EmptyStruct ()
// CHECK: [[V_1_0:%[^,]+]] = struct $Pair{{.*}} ([[V_2_0]]{{.*}}, [[V_2_1]]
// CHECK: [[V_2_2:%[^,]+]] = struct $EmptyStruct
// CHECK: [[V_2_3:%[^,]+]] = struct $EmptyStruct
// CHECK: [[V_1_1:%[^,]+]] = tuple ([[V_2_2]]{{.*}}, [[V_2_3]]
// CHECK: [[V_1_2:%[^,]+]] = struct $EmptyStruct
// CHECK: [[V_0:%[^,]+]] = tuple ([[V_1_0]]{{.*}}, [[V_1_1]]{{.*}}, [[V_1_2]]{{.*}})
// CHECK: return [[V_0]]
// CHECK-LABEL: } // end sil function 'load_from_uninitialized_empty'
sil @load_from_uninitialized_empty : $@convention(thin) () -> (Pair<Pair<EmptyStruct, EmptyStruct>, EmptyStruct>, (EmptyStruct, EmptyStruct), EmptyStruct) {
%addr = alloc_stack $(Pair<Pair<EmptyStruct, EmptyStruct>, EmptyStruct>, (EmptyStruct, EmptyStruct), EmptyStruct)
%value = load %addr : $*(Pair<Pair<EmptyStruct, EmptyStruct>, EmptyStruct>, (EmptyStruct, EmptyStruct), EmptyStruct)
dealloc_stack %addr : $*(Pair<Pair<EmptyStruct, EmptyStruct>, EmptyStruct>, (EmptyStruct, EmptyStruct), EmptyStruct)
return %value : $(Pair<Pair<EmptyStruct, EmptyStruct>, EmptyStruct>, (EmptyStruct, EmptyStruct), EmptyStruct)
}