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//===-- Strlen implementation 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_AARCH64_INLINE_STRLEN_H
#define LLVM_LIBC_SRC_STRING_MEMORY_UTILS_AARCH64_INLINE_STRLEN_H
#if defined(__ARM_NEON)
#include "src/__support/CPP/bit.h" // countr_zero
#include <arm_neon.h>
#include <stddef.h> // size_t
namespace LIBC_NAMESPACE_DECL {
namespace neon {
[[maybe_unused]] LIBC_NO_SANITIZE_OOB_ACCESS LIBC_INLINE static size_t
string_length(const char *src) {
using Vector __attribute__((may_alias)) = uint8x8_t;
uintptr_t misalign_bytes = reinterpret_cast<uintptr_t>(src) % sizeof(Vector);
const Vector *block_ptr =
reinterpret_cast<const Vector *>(src - misalign_bytes);
Vector v = *block_ptr;
Vector vcmp = vceqz_u8(v);
uint64x1_t cmp_mask = vreinterpret_u64_u8(vcmp);
uint64_t cmp = vget_lane_u64(cmp_mask, 0);
cmp = cmp >> (misalign_bytes << 3);
if (cmp)
return cpp::countr_zero(cmp) >> 3;
while (true) {
++block_ptr;
v = *block_ptr;
vcmp = vceqz_u8(v);
cmp_mask = vreinterpret_u64_u8(vcmp);
cmp = vget_lane_u64(cmp_mask, 0);
if (cmp)
return static_cast<size_t>(reinterpret_cast<uintptr_t>(block_ptr) -
reinterpret_cast<uintptr_t>(src) +
(cpp::countr_zero(cmp) >> 3));
}
}
} // namespace neon
namespace string_length_impl = neon;
} // namespace LIBC_NAMESPACE_DECL
#endif // __ARM_NEON
#endif // LLVM_LIBC_SRC_STRING_MEMORY_UTILS_AARCH64_INLINE_STRLEN_H
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