8751f26a1b
This PR creates an SVE-based implementation for strlen by translating from the AOR code in tree. Microbenchmark shows improvements against NEON when N>=64. Although both implementations fall behind glibc by a large margin, this may be a good start point to explore SVE implementations. Together with the PR: 1. Added two more tests of strlen with special nul symbols. 2. Added strlen's fuzzer and fix a typo in previous heap fuzzer. ``` === strlen(16 bytes) === libc: 1.56115 ns/call, 9.54499 GiB/s neon: 1.59393 ns/call, 9.34867 GiB/s sve: 1.66097 ns/call, 8.97134 GiB/s === strlen(64 bytes) === libc: 2.06967 ns/call, 28.7991 GiB/s neon: 2.59914 ns/call, 22.9325 GiB/s sve: 2.58628 ns/call, 23.0465 GiB/s === strlen(256 bytes) === libc: 3.74165 ns/call, 63.7202 GiB/s neon: 8.98243 ns/call, 26.5428 GiB/s sve: 7.36426 ns/call, 32.3751 GiB/s === strlen(1024 bytes) === libc: 10.5327 ns/call, 90.5438 GiB/s neon: 34.363 ns/call, 27.7529 GiB/s sve: 26.9329 ns/call, 35.4092 GiB/s === strlen(4096 bytes) === libc: 37.7304 ns/call, 101.104 GiB/s neon: 145.911 ns/call, 26.144 GiB/s sve: 103.208 ns/call, 36.9612 GiB/s === strlen(1048576 bytes) === libc: 9623.4 ns/call, 101.478 GiB/s neon: 36138.2 ns/call, 27.023 GiB/s sve: 26605.6 ns/call, 36.7051 GiB/s ```
33 lines
1.2 KiB
C++
33 lines
1.2 KiB
C++
//===-- strlen_fuzz.cpp ---------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// Fuzzing test for llvm-libc strlen implementation.
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///
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//===----------------------------------------------------------------------===//
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#include "src/string/strlen.h"
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#include <cstdint>
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#include <cstring>
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// always null terminate the data
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extern "C" size_t LLVMFuzzerMutate(uint8_t *data, size_t size, size_t max_size);
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extern "C" size_t LLVMFuzzerCustomMutator(uint8_t *data, size_t size,
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size_t max_size, unsigned int seed) {
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size = LLVMFuzzerMutate(data, size, max_size);
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data[size - 1] = '\0';
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return size;
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}
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extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
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size_t ref = ::strlen(reinterpret_cast<const char *>(data));
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size_t impl = LIBC_NAMESPACE::strlen(reinterpret_cast<const char *>(data));
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if (ref != impl)
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__builtin_trap();
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return 0;
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}
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