[libc][NFC] Fix some issues with LIBC_INLINE

[abrachet]

Summary

We define LIBC_INLINE to include [[clang::internal_linkage]], and these
must appear before other specifiers. Additionally, there was also a
missing cast that was causing warnings.

[gchatelet]

Thx!

libc/src/string/memory_utils/op_generic.h

 // This is useful when implementing lexicograhic comparisons as big endian
 // scalar comparison directly maps to lexicographic byte comparisons.
 template <typename T> LIBC_INLINE static T load_be(CPtr ptr, size_t offset) {
   return Endian::to_big_endian(load<T>(ptr, offset));
 }
 
 // Equality: returns true iff values at locations (p1 + offset) and (p2 +
 // offset) compare equal.
-template <typename T> static bool eq(CPtr p1, CPtr p2, size_t offset);
+template <typename T> LIBC_INLINE static bool eq(CPtr p1, CPtr p2, size_t offset);
 
 // Not equals: returns non-zero iff values at locations (p1 + offset) and (p2 +
 // offset) differ.
-template <typename T> static uint32_t neq(CPtr p1, CPtr p2, size_t offset);
+template <typename T> LIBC_INLINE static uint32_t neq(CPtr p1, CPtr p2, size_t offset);
 
 // Lexicographic comparison:
 // - returns 0 iff values at locations (p1 + offset) and (p2 + offset) compare
 //   equal.
 // - returns a negative value if value at location (p1 + offset) is
 //   lexicographically less than value at (p2 + offset).
 // - returns a positive value if value at location (p1 + offset) is
 //   lexicographically greater than value at (p2 + offset).
 template <typename T>
-static MemcmpReturnType cmp(CPtr p1, CPtr p2, size_t offset);
+LIBC_INLINE static MemcmpReturnType cmp(CPtr p1, CPtr p2, size_t offset);
 
 // Lexicographic comparison of non-equal values:
 // - returns a negative value if value at location (p1 + offset) is
 //   lexicographically less than value at (p2 + offset).
 // - returns a positive value if value at location (p1 + offset) is
 //   lexicographically greater than value at (p2 + offset).
 template <typename T>
-static MemcmpReturnType cmp_neq(CPtr p1, CPtr p2, size_t offset);
+LIBC_INLINE static MemcmpReturnType cmp_neq(CPtr p1, CPtr p2, size_t offset);
 
 ///////////////////////////////////////////////////////////////////////////////
 // Memcmp implementation
 //
 // When building memcmp, not all types are considered equals.
 //
 // For instance, the lexicographic comparison of two uint8_t can be implemented
 // as a simple subtraction, but for wider operations the logic can be much more

libc/src/string/memory_utils/op_x86.h

 #endif
 #if !defined(__SSE2__) && (defined(_MSC_VER) || defined(__SCE__))
 #define _mm_movemask_epi8(A) 0
 #endif
 
 namespace __llvm_libc::x86 {
 
 // A set of constants to check compile time features.
-static LIBC_INLINE constexpr bool kSse2 = LLVM_LIBC_IS_DEFINED(__SSE2__);
-static LIBC_INLINE constexpr bool kSse41 = LLVM_LIBC_IS_DEFINED(__SSE4_1__);
-static LIBC_INLINE constexpr bool kAvx = LLVM_LIBC_IS_DEFINED(__AVX__);
-static LIBC_INLINE constexpr bool kAvx2 = LLVM_LIBC_IS_DEFINED(__AVX2__);
-static LIBC_INLINE constexpr bool kAvx512F = LLVM_LIBC_IS_DEFINED(__AVX512F__);
-static LIBC_INLINE constexpr bool kAvx512BW =
+LIBC_INLINE static constexpr bool kSse2 = LLVM_LIBC_IS_DEFINED(__SSE2__);
+LIBC_INLINE static constexpr bool kSse41 = LLVM_LIBC_IS_DEFINED(__SSE4_1__);
+LIBC_INLINE static constexpr bool kAvx = LLVM_LIBC_IS_DEFINED(__AVX__);
+LIBC_INLINE static constexpr bool kAvx2 = LLVM_LIBC_IS_DEFINED(__AVX2__);
+LIBC_INLINE static constexpr bool kAvx512F = LLVM_LIBC_IS_DEFINED(__AVX512F__);
+LIBC_INLINE static constexpr bool kAvx512BW =
     LLVM_LIBC_IS_DEFINED(__AVX512BW__);
 
 ///////////////////////////////////////////////////////////////////////////////
 // Memcpy repmovsb implementation
 struct Memcpy {
   static void repmovsb(void *dst, const void *src, size_t count) {
     asm volatile("rep movsb" : "+D"(dst), "+S"(src), "+c"(count) : : "memory");
   }

 LIBC_INLINE __m128i bytewise_max(__m128i a, __m128i b) {
   return _mm_max_epu8(a, b);
 }
 LIBC_INLINE __m128i bytewise_reverse(__m128i value) {
   return _mm_shuffle_epi8(value, _mm_set_epi8(0, 1, 2, 3, 4, 5, 6, 7, //
                                               8, 9, 10, 11, 12, 13, 14, 15));
 }
 LIBC_INLINE uint16_t big_endian_cmp_mask(__m128i max, __m128i value) {
-  return _mm_movemask_epi8(bytewise_reverse(_mm_cmpeq_epi8(max, value)));
+  return static_cast<uint16_t>(_mm_movemask_epi8(bytewise_reverse(_mm_cmpeq_epi8(max, value))));
 }
 template <> LIBC_INLINE bool eq<__m128i>(CPtr p1, CPtr p2, size_t offset) {
   const auto a = load<__m128i>(p1, offset);
   const auto b = load<__m128i>(p2, offset);
   const auto xored = _mm_xor_si128(a, b);
   return _mm_testz_si128(xored, xored) == 1; // 1 iff xored == 0
 }
 template <> LIBC_INLINE uint32_t neq<__m128i>(CPtr p1, CPtr p2, size_t offset) {