[PATCH] D64417: [Support] Remove MSVC specific AlignedCharArray implementation

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: rnk, aaron.ballman, chapuni, mehdi_amini.
Herald added a subscriber: kristina.
Herald added a project: LLVM.

Now that D64326 <https://reviews.llvm.org/D64326> has landed we can remove the old MSVC AlignedCharArray implementations as VS2017+ can correctly handles alignas with by-value arguments.

This patch raises the question of whether we want to use llvm::AlignedCharArray directly in the codebase or whether some/all cases should be replaced with a type that uses alignas() directly?


Repository:
  rL LLVM

https://reviews.llvm.org/D64417

Files:
  include/llvm/Support/AlignOf.h


Index: include/llvm/Support/AlignOf.h
===================================================================
--- include/llvm/Support/AlignOf.h
+++ include/llvm/Support/AlignOf.h
@@ -22,85 +22,13 @@
 /// Helper for building an aligned character array type.
 ///
 /// This template is used to explicitly build up a collection of aligned
-/// character array types. We have to build these up using a macro and explicit
-/// specialization to cope with MSVC (at least till 2015) where only an
-/// integer literal can be used to specify an alignment constraint. Once built
-/// up here, we can then begin to indirect between these using normal C++
-/// template parameters.
+/// character array types. Once built up here, we can then begin to indirect
+/// between these using normal C++ template parameters.
 
-// MSVC requires special handling here.
-#ifndef _MSC_VER
-
-template<std::size_t Alignment, std::size_t Size>
-struct AlignedCharArray {
+template <std::size_t Alignment, std::size_t Size> struct AlignedCharArray {
   alignas(Alignment) char buffer[Size];
 };
 
-#else // _MSC_VER
-
-/// Create a type with an aligned char buffer.
-template<std::size_t Alignment, std::size_t Size>
-struct AlignedCharArray;
-
-// We provide special variations of this template for the most common
-// alignments because __declspec(align(...)) doesn't actually work when it is
-// a member of a by-value function argument in MSVC, even if the alignment
-// request is something reasonably like 8-byte or 16-byte. Note that we can't
-// even include the declspec with the union that forces the alignment because
-// MSVC warns on the existence of the declspec despite the union member forcing
-// proper alignment.
-
-template<std::size_t Size>
-struct AlignedCharArray<1, Size> {
-  union {
-    char aligned;
-    char buffer[Size];
-  };
-};
-
-template<std::size_t Size>
-struct AlignedCharArray<2, Size> {
-  union {
-    short aligned;
-    char buffer[Size];
-  };
-};
-
-template<std::size_t Size>
-struct AlignedCharArray<4, Size> {
-  union {
-    int aligned;
-    char buffer[Size];
-  };
-};
-
-template<std::size_t Size>
-struct AlignedCharArray<8, Size> {
-  union {
-    double aligned;
-    char buffer[Size];
-  };
-};
-
-
-// The rest of these are provided with a __declspec(align(...)) and we simply
-// can't pass them by-value as function arguments on MSVC.
-
-#define LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(x) \
-  template<std::size_t Size> \
-  struct AlignedCharArray<x, Size> { \
-    __declspec(align(x)) char buffer[Size]; \
-  };
-
-LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(16)
-LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(32)
-LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(64)
-LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT(128)
-
-#undef LLVM_ALIGNEDCHARARRAY_TEMPLATE_ALIGNMENT
-
-#endif // _MSC_VER
-
 namespace detail {
 template <typename T1,
           typename T2 = char, typename T3 = char, typename T4 = char,


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