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internal/impl: inline small tag decoding

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Inline varint decoding of small (1- and 2-byte) field tags in the
fast-path unmarshaler.

name                             old time/op  new time/op  delta
EmptyMessage/Wire/Unmarshal      40.6ns ± 1%  40.2ns ± 1%   -1.02%  (p=0.000 n=37+35)
EmptyMessage/Wire/Unmarshal-12   6.77ns ± 2%  7.13ns ± 5%   +5.32%  (p=0.000 n=37+37)
RepeatedInt32/Wire/Unmarshal     9.46µs ± 1%  6.57µs ± 1%  -30.56%  (p=0.000 n=38+39)
RepeatedInt32/Wire/Unmarshal-12  1.50µs ± 2%  1.05µs ± 2%  -30.00%  (p=0.000 n=39+37)
Required/Wire/Unmarshal           371ns ± 1%   258ns ± 1%  -30.44%  (p=0.000 n=38+32)
Required/Wire/Unmarshal-12       60.3ns ± 1%  44.3ns ± 2%  -26.45%  (p=0.000 n=38+36)

Change-Id: Ie80415dea8cb6b840eafa52f0572046a1910a9b1
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/216419
Reviewed-by: Joe Tsai <joetsai@google.com>
This commit is contained in:
Damien Neil 2020-01-24 16:00:20 -08:00
parent 8729675da7
commit ce8f7f6353
2 changed files with 19 additions and 8 deletions
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2
internal/encoding/wire/wire.go
View File

@ -176,7 +176,6 @@ func SizeTag(num Number) int {
// AppendVarint appends v to b as a varint-encoded uint64.
func AppendVarint(b []byte, v uint64) []byte {
// TODO: Specialize for sizes 1 and 2 with mid-stack inlining.
switch {
case v < 1<<7:
b = append(b, byte(v))
@ -259,7 +258,6 @@ func AppendVarint(b []byte, v uint64) []byte {
// ConsumeVarint parses b as a varint-encoded uint64, reporting its length.
// This returns a negative length upon an error (see ParseError).
func ConsumeVarint(b []byte) (v uint64, n int) {
// TODO: Specialize for sizes 1 and 2 with mid-stack inlining.
var y uint64
if len(b) <= 0 {
return 0, errCodeTruncated

25
internal/impl/decode.go
View File

@ -97,15 +97,27 @@ func (mi *MessageInfo) unmarshalPointer(b []byte, p pointer, groupTag wire.Numbe
start := len(b)
for len(b) > 0 {
// Parse the tag (field number and wire type).
// TODO: inline 1 and 2 byte variants?
num, wtyp, n := wire.ConsumeTag(b)
if n < 0 {
return out, wire.ParseError(n)
var tag uint64
if b[0] < 0x80 {
tag = uint64(b[0])
b = b[1:]
} else if len(b) >= 2 && b[1] < 128 {
tag = uint64(b[0]&0x7f) + uint64(b[1])<<7
b = b[2:]
} else {
var n int
tag, n = wire.ConsumeVarint(b)
if n < 0 {
return out, wire.ParseError(n)
}
b = b[n:]
}
if num > wire.MaxValidNumber {
num := wire.Number(tag >> 3)
wtyp := wire.Type(tag & 7)
if num < wire.MinValidNumber || num > wire.MaxValidNumber {
return out, errors.New("invalid field number")
}
b = b[n:]
if wtyp == wire.EndGroupType {
if num != groupTag {
@ -121,6 +133,7 @@ func (mi *MessageInfo) unmarshalPointer(b []byte, p pointer, groupTag wire.Numbe
} else {
f = mi.coderFields[num]
}
var n int
err := errUnknown
switch {
case f != nil: