[llvm] f1025e6 - [Support] Replace deprecated std::aligned_union, NFCI. (#127417)

[via llvm-commits]

Author: Jonas Hahnfeld
Date: 2025-02-25T21:00:14+01:00
New Revision: f1025e671ef1c1d6a65944cdb3989608cfbc7f0c

URL: https://github.com/llvm/llvm-project/commit/f1025e671ef1c1d6a65944cdb3989608cfbc7f0c
DIFF: https://github.com/llvm/llvm-project/commit/f1025e671ef1c1d6a65944cdb3989608cfbc7f0c.diff

LOG: [Support] Replace deprecated std::aligned_union, NFCI. (#127417)

All std::aligned_* are deprecated in C++23. Implement the replacement
suggested in P1413R3 using alignas and std::max.

Added: 
    

Modified: 
    llvm/include/llvm/Support/AlignOf.h

Removed: 
    


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diff  --git a/llvm/include/llvm/Support/AlignOf.h b/llvm/include/llvm/Support/AlignOf.h
index f586d7f182aab..635bb8b101ef9 100644
--- a/llvm/include/llvm/Support/AlignOf.h
+++ b/llvm/include/llvm/Support/AlignOf.h
@@ -13,20 +13,14 @@
 #ifndef LLVM_SUPPORT_ALIGNOF_H
 #define LLVM_SUPPORT_ALIGNOF_H
 
-#include <type_traits>
+#include <algorithm>
 
 namespace llvm {
 
 /// A suitably aligned and sized character array member which can hold elements
 /// of any type.
-///
-/// This template is equivalent to std::aligned_union_t<1, ...>, but we cannot
-/// use it due to a bug in the MSVC x86 compiler:
-/// https://github.com/microsoft/STL/issues/1533
-/// Using `alignas` here works around the bug.
 template <typename T, typename... Ts> struct AlignedCharArrayUnion {
-  using AlignedUnion = std::aligned_union_t<1, T, Ts...>;
-  alignas(alignof(AlignedUnion)) char buffer[sizeof(AlignedUnion)];
+  alignas(T) alignas(Ts...) char buffer[std::max({sizeof(T), sizeof(Ts)...})];
 };
 
 } // end namespace llvm