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[libc] Change memcpy back to rep movsb

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Influenced by other libc implementations, I had tried to make memcpy
smarter for differently-sized ranges, but my benchmarks showed no real
change. So change memcpy back to the simple rep movsb implementation.
This commit is contained in:
Justin C. Miller
2022-02-28 18:56:38 -08:00
parent 467c2408c4
commit 19105542e5
1 changed files with 1 additions and 26 deletions
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27
src/libraries/libc/string/memcpy.cpp
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@@ -10,33 +10,8 @@
#include <string.h>
#include <stddef.h>
#include <__j6libc/copy.h>
using namespace __j6libc;
inline void memcpy_dispatch(char *s1, const char *s2, size_t n) {
if (n == 0) return;
if (n == 1) return do_copy<1>(s1, s2);
if (n == 2) return do_copy<2>(s1, s2);
if (n == 3) return do_copy<3>(s1, s2);
if (n == 4) return do_copy<4>(s1, s2);
if (n < 8) return do_double_copy<4>(s1, s2, n);
if (n == 8) return do_copy<8>(s1, s2);
if (n < 16) return do_double_copy<8>(s1, s2, n);
if (n < 32) return do_double_copy<16>(s1, s2, n);
if (n < 64) return do_double_copy<32>(s1, s2, n);
if (n < 128)
return do_double_copy<64>(s1, s2, n);
else
return do_large_copy(s1, s2, n);
}
void *memcpy(void * restrict s1, const void * restrict s2, size_t n) {
memcpy_dispatch(
reinterpret_cast<char*>(s1),
reinterpret_cast<const char*>(s2),
n);
asm volatile ("rep movsb" : "+D"(s1), "+S"(s2), "+c"(n) :: "memory");
return s1;
}