From fc42cf8b8ccf6753c01e063ac090b2a60e70f077 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Daniel=20Mart=C3=AD?= Date: Sun, 25 Nov 2018 14:53:24 +0000 Subject: [PATCH] encoding/base64: lift nil check out of encode loop MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Most of the encoding time is spent in the first Encode loop, since the rest of the function only deals with the few remaining bytes. Any unnecessary work done in that loop body matters tremendously. One such unnecessary bottleneck was the use of the enc.encode table. Since enc is a pointer receiver, and the field is first used within the loop, the encoder must perform a nil check at every iteration. Add a dummy use of the field before the start of the loop, to move the nil check there. After that line, the compiler now knows that enc can't be nil, and thus the hot loop is free of nil checks. name old time/op new time/op delta EncodeToString-4 14.7µs ± 0% 13.7µs ± 1% -6.53% (p=0.000 n=10+10) name old speed new speed delta EncodeToString-4 559MB/s ± 0% 598MB/s ± 1% +6.99% (p=0.000 n=10+10) Updates #20206. Change-Id: Icbb523a7bd9e470a8be0a448d1d78ade97ed4ff6 Reviewed-on: https://go-review.googlesource.com/c/151158 Run-TryBot: Daniel Martí TryBot-Result: Gobot Gobot Reviewed-by: Brad Fitzpatrick --- src/encoding/base64/base64.go | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/src/encoding/base64/base64.go b/src/encoding/base64/base64.go index 0bb37b311a099..a90e4dfa1270a 100644 --- a/src/encoding/base64/base64.go +++ b/src/encoding/base64/base64.go @@ -123,6 +123,10 @@ func (enc *Encoding) Encode(dst, src []byte) { if len(src) == 0 { return } + // enc is a pointer receiver, so the use of enc.encode within the hot + // loop below means a nil check at every operation. Lift that nil check + // outside of the loop to speed up the encoder. + _ = enc.encode di, si := 0, 0 n := (len(src) / 3) * 3