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| author | David 'Digit' Turner <digit@google.com> | 2010-09-26 22:40:02 +0200 |
|---|---|---|
| committer | David 'Digit' Turner <digit@google.com> | 2010-09-27 17:34:41 +0200 |
| commit | 80fba9a2fe4eacaabee99cf0bbead872c2792231 (patch) | |
| tree | 35cf24d62149365bdad0994d837654e3d05399d9 | |
| parent | b9e49ad56e5776ace7c6eab2e997d5b7acb16792 (diff) | |
| download | bionic-80fba9a2fe4eacaabee99cf0bbead872c2792231.zip bionic-80fba9a2fe4eacaabee99cf0bbead872c2792231.tar.gz bionic-80fba9a2fe4eacaabee99cf0bbead872c2792231.tar.bz2 | |
libc: memmove(): non-overlapping block optim.
Change-Id: I5652f4f97ca59d95176443fc27c737ef76258183
| -rw-r--r-- | libc/string/memmove.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/libc/string/memmove.c b/libc/string/memmove.c index fcaf4ee..948a766 100644 --- a/libc/string/memmove.c +++ b/libc/string/memmove.c @@ -31,7 +31,11 @@ void *memmove(void *dst, const void *src, size_t n) { const char *p = src; char *q = dst; - if (__builtin_expect(q < p, 1)) { + + /* we can use highgly-optimized memcpy() if the destination + * is before the source, or if the two blocks are non-overlapping + */ + if (__builtin_expect((q < p || (q-p) <= (ptrdiff_t)n), 1)) { return memcpy(dst, src, n); } else { #define PRELOAD_DISTANCE 64 |