[libc] [llvm] Add vector-based strlen implementation for x86_64 and aarch64 (PR #152389)

[via llvm-commits]

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@@ -0,0 +1,113 @@
+//===-- Strlen implementation for x86_64 ----------------------------------===//
+//
+// 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_X86_64_INLINE_STRLEN_H
+#define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_X86_64_INLINE_STRLEN_H
+
+#include "src/string/memory_utils/op_x86.h" // K_AVX
+
+#include <stddef.h> // size_t
+#include <x86intrin.h>
+namespace LIBC_NAMESPACE_DECL {
+
+#if defined(__SSE2__)
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overmighty wrote:

All x86-64 CPUs have SSE2. There is no `#if defined(__SSE2__)` guard around the call to `string_length_sse2` from `string_length_x86_64` anyway.

https://github.com/llvm/llvm-project/pull/152389