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| author | Rob Pike <r@golang.org> | 2009-12-07 11:28:02 -0800 |
|---|---|---|
| committer | Rob Pike <r@golang.org> | 2009-12-07 11:28:02 -0800 |
| commit | 20c1ec263a8910ae1b794cb017f59e73997a9296 (patch) | |
| tree | e037e0913cdf47f06644edf063afd7ad90af1c23 | |
| parent | 80e17d67976b29c4de6173d858efbe0955648404 (diff) | |
| download | go-20c1ec263a8910ae1b794cb017f59e73997a9296.tar.gz go-20c1ec263a8910ae1b794cb017f59e73997a9296.zip | |
pick off special one-byte case in copy. worth 2x in benchmarks (38ns->16ns).
the one-item case could be generalized easily with no cost. worth considering.
R=rsc
CC=golang-dev, cw
https://golang.org/cl/167044
| -rw-r--r-- | src/pkg/runtime/slice.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/src/pkg/runtime/slice.c b/src/pkg/runtime/slice.c index ba4be331b5..1d7a56e7ba 100644 --- a/src/pkg/runtime/slice.c +++ b/src/pkg/runtime/slice.c @@ -208,7 +208,11 @@ runtime·slicecopy(Slice to, Slice fm, uintptr width, int32 ret) if(to.len < ret) ret = to.len; - memmove(to.array, fm.array, ret*width); + if(ret == 1 && width == 1) { // common case worth about 2x to do here + *to.array = *fm.array; // known to be a byte pointer + } else { + memmove(to.array, fm.array, ret*width); + } out: FLUSH(&ret); |