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borysp
3014a0dd1c
Mostly adds missing "memory" clobber which caused some nasty bugs - gcc optimized those inline asms and assumed values returned by them never change.
46 lines
1.4 KiB
C
46 lines
1.4 KiB
C
/* SPDX-License-Identifier: LGPL-3.0-or-later */
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#include <stdint.h>
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#include "api.h"
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void* memcpy(void* restrict dest, const void* restrict src, size_t count) {
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char* d = dest;
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#if defined(__x86_64__)
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/* "Beginning with processors based on Intel microarchitecture code name Ivy Bridge, REP string
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* operation using MOVSB and STOSB can provide both flexible and high-performance REP string
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* operations for software in common situations like memory copy and set operations" (c)
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* Intel 64 and IA-32 Architectures Optimization Reference Manual.
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*
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* memcpy() is heavily used in Linux-SGX PAL to copy data in/out of SGX enclave. Experiments
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* with Redis 5.0 show perf improvement of using "rep movsb" at 3-5% for 4KB payloads over
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* previous implementation taken from Glibc 2.23. */
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__asm__ volatile("rep movsb" : "+D"(d), "+c"(count), "+S"(src) :: "cc", "memory");
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#else
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const char* s = src;
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while (count--)
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*d++ = *s++;
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#endif
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return dest;
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}
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void* memmove(void* dest, const void* src, size_t count) {
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char* d = dest;
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const char* s = src;
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if (d == s)
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return d;
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if (s + count <= d || d + count <= s)
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return memcpy(d, s, count);
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if (d < s) {
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while (count--)
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*d++ = *s++;
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} else {
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while (count--)
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d[count] = s[count];
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}
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return dest;
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}
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