encoding/json: prevent duplicate slicebytetostring
When storing literal to JSON number v, if s is valid number, the slicebytetostring operation will be performed twice. In fact, the operation is unavoidable on any code path, so just perform it at the very beginning.
This is not a big optimization, but better than nothing:
$ ../bin/go test ./encoding/json/ -bench UnmarshalNumber -run NOTEST -benchtime 10000000x -count 16 > old.txt
$ ../bin/go test ./encoding/json/ -bench UnmarshalNumber -run NOTEST -benchtime 10000000x -count 16 > new.txt
$ benchstat old.txt new.txt
│ old.txt │ new.txt │
│ sec/op │ sec/op vs base │
UnmarshalNumber-8 234.5n ± 3% 228.2n ± 4% -2.67% (p=0.033 n=16)
│ old.txt │ new.txt │
│ B/op │ B/op vs base │
UnmarshalNumber-8 168.0 ± 0% 168.0 ± 0% ~ (p=1.000 n=16) ¹
¹ all samples are equal
│ old.txt │ new.txt │
│ allocs/op │ allocs/op vs base │
UnmarshalNumber-8 2.000 ± 0% 2.000 ± 0% ~ (p=1.000 n=16) ¹
¹ all samples are equal
Change-Id: I1dfdb1ed0883e385f753b2046b7f047c792aa4e3
GitHub-Last-Rev:
d236dd7265f110dbb6e0b9b0a824aab9ba7c36be
GitHub-Pull-Request: golang/go#61242
Reviewed-on: https://go-review.googlesource.com/c/go/+/508556
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Joseph Tsai <joetsai@digital-static.net>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: qiulaidongfeng <2645477756@qq.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>