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[llvm][NFC] Simplify alignment calculations in TrailingObjects #161134

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Merged
merged 1 commit into from
Sep 29, 2025
+8 −25
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[llvm][NFC] Simplify alignment calculations in TrailingObjects #161134

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33 changes: 8 additions & 25 deletions llvm/include/llvm/Support/TrailingObjects.h
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Original file line number Diff line number Diff line change
Expand Up @@ -57,25 +57,9 @@
namespace llvm {

namespace trailing_objects_internal {
/// Helper template to calculate the max alignment requirement for a set of
/// objects.
template <typename First, typename... Rest> class AlignmentCalcHelper {
private:
enum {
FirstAlignment = alignof(First),
RestAlignment = AlignmentCalcHelper<Rest...>::Alignment,
};

public:
enum {
Alignment = FirstAlignment > RestAlignment ? FirstAlignment : RestAlignment
};
};

template <typename First> class AlignmentCalcHelper<First> {
public:
enum { Alignment = alignof(First) };
};
template <typename... T>
inline constexpr size_t MaxAlignment = std::max({alignof(T)...});

/// The base class for TrailingObjects* classes.
class TrailingObjectsBase {
Expand Down Expand Up @@ -209,20 +193,19 @@ class alignas(Align) TrailingObjectsImpl<Align, BaseTy, TopTrailingObj, PrevTy>
/// See the file comment for details on the usage of the
/// TrailingObjects type.
template <typename BaseTy, typename... TrailingTys>
class TrailingObjects : private trailing_objects_internal::TrailingObjectsImpl<
trailing_objects_internal::AlignmentCalcHelper<
TrailingTys...>::Alignment,
BaseTy, TrailingObjects<BaseTy, TrailingTys...>,
BaseTy, TrailingTys...> {
class TrailingObjects
: private trailing_objects_internal::TrailingObjectsImpl<
trailing_objects_internal::MaxAlignment<TrailingTys...>, BaseTy,
TrailingObjects<BaseTy, TrailingTys...>, BaseTy, TrailingTys...> {

template <int A, typename B, typename T, typename P, typename... M>
friend class trailing_objects_internal::TrailingObjectsImpl;

template <typename... Tys> class Foo {};

typedef trailing_objects_internal::TrailingObjectsImpl<
trailing_objects_internal::AlignmentCalcHelper<TrailingTys...>::Alignment,
BaseTy, TrailingObjects<BaseTy, TrailingTys...>, BaseTy, TrailingTys...>
trailing_objects_internal::MaxAlignment<TrailingTys...>, BaseTy,
TrailingObjects<BaseTy, TrailingTys...>, BaseTy, TrailingTys...>
ParentType;
using TrailingObjectsBase = trailing_objects_internal::TrailingObjectsBase;

Expand Down