• Daniel Martí's avatar
    encoding/json: various minor decoder speed-ups · 6d4787af
    Daniel Martí authored
    Reuse v.Type() and cachedTypeFields(t) when decoding maps and structs.
    
    Always use the same data slices when in hot loops, to ensure that the
    compiler generates good code. "for i < len(data) { use(d.data[i]) }"
    makes it harder for the compiler.
    
    Finally, do other minor clean-ups, such as deduplicating switch cases,
    and using a switch instead of three chained ifs.
    
    The decoder sees a noticeable speed-up, in particular when decoding
    structs.
    
    name           old time/op    new time/op    delta
    CodeDecoder-4    29.8ms ± 1%    27.5ms ± 0%  -7.83%  (p=0.002 n=6+6)
    
    name           old speed      new speed      delta
    CodeDecoder-4  65.0MB/s ± 1%  70.6MB/s ± 0%  +8.49%  (p=0.002 n=6+6)
    
    Updates #5683.
    
    Change-Id: I9d751e22502221962da696e48996ffdeb777277d
    Reviewed-on: https://go-review.googlesource.com/122468
    Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarBrad Fitzpatrick <bradfitz@golang.org>
    6d4787af
stream.go 12.4 KB