[libc] More resilient arch dependent include selection

[gchatelet]

Summary

I intend to use this approach for arch dependant include selection, it is more resilient to refactoring.

[gchatelet]

• Fix reordered include

[gchatelet]

This has been adopted through various patches.

libc/src/string/memory_utils/elements.h

 using _16 = Repeated<_8, 2>;
 using _32 = Repeated<_8, 4>;
 using _64 = Repeated<_8, 8>;
 using _128 = Repeated<_8, 16>;
 
 } // namespace scalar
 } // namespace __llvm_libc
 
+#if defined(LLVM_LIBC_ARCH_AARCH64)
 #include <src/string/memory_utils/elements_aarch64.h>
+#elif defined(LLVM_LIBC_ARCH_X86)
 #include <src/string/memory_utils/elements_x86.h>
+#endif
 
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_ELEMENTS_H

libc/src/string/memory_utils/elements_aarch64.h

 //===-- Elementary operations for aarch64 --------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_LIBC_SRC_STRING_MEMORY_UTILS_ELEMENTS_AARCH64_H
 #define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_ELEMENTS_AARCH64_H
 
 #include "src/__support/architectures.h"
 
-#if defined(LLVM_LIBC_ARCH_AARCH64)
+#if !defined(LLVM_LIBC_ARCH_AARCH64)
+#error "Invalid include"
+#endif
 
 #include <src/string/memory_utils/elements.h>
 #include <stddef.h> // size_t
 #include <stdint.h> // uint8_t, uint16_t, uint32_t, uint64_t
 
 #ifdef __ARM_NEON
 #include <arm_neon.h>
 #endif

 #else
 using _32 = __llvm_libc::scalar::_32;
 using _64 = __llvm_libc::scalar::_64;
 #endif // __ARM_NEON
 
 } // namespace aarch64
 } // namespace __llvm_libc
 
-#endif // defined(LLVM_LIBC_ARCH_AARCH64)
-
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_ELEMENTS_AARCH64_H

libc/src/string/memory_utils/elements_x86.h

 //===-- Elementary operations for x86 -------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_LIBC_SRC_STRING_MEMORY_UTILS_ELEMENTS_X86_H
 #define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_ELEMENTS_X86_H
 
 #include "src/__support/architectures.h"
 
-#if defined(LLVM_LIBC_ARCH_X86)
+#if !defined(LLVM_LIBC_ARCH_X86)
+#error "Invalid include"
+#endif
 
 #include <stddef.h> // size_t
 #include <stdint.h> // uint8_t, uint16_t, uint32_t, uint64_t
 
 #ifdef __SSE2__
 #include <immintrin.h>
 #endif //  __SSE2__
 
struct Accelerator {
   static void Copy(char *dst, const char *src, size_t count) {
     asm volatile("rep movsb" : "+D"(dst), "+S"(src), "+c"(count) : : "memory");
   }
 };
 
 } // namespace x86
 } // namespace __llvm_libc
 
-#endif // defined(LLVM_LIBC_ARCH_X86)
-
 #endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_ELEMENTS_X86_H