commit cedb595154455cd6d77ac2307fec360092456951
author Damien Neil <dneil@google.com> Fri Jun 21 12:04:07 2019 -0700
committer Damien Neil <dneil@google.com> Mon Jun 24 17:41:45 2019 +0000
tree 0b43f28e2f9e0b106c4214803d3d0c9288fe37d7
parent 8c86fc5e7dbb1fbd3fc70bf8e190a541b75bc756

proto, internal/impl: avoid string->[]byte conversions

We trust the compiler to optimize away the string->[]byte conversion in
code like:

	b = wire.AppendBytes(b, []byte(s))

In testing (go 1.12.5 linux/amd64), this optimization is not happening.
Perhaps newer versions of the compiler will optimize this, but we
shouldn't rely on it; avoid unnecessary conversions.

Benchmark differences vs https://golang.org/cl/171462:

  name                                   old time/op    new time/op    delta
  Wire/Marshal/google_message1_proto2-6     310ns ± 2%     189ns ± 3%  -39.20%  (p=0.000 n=8+8)
  Wire/Marshal/google_message1_proto3-6     389ns ± 8%     261ns ± 2%  -33.03%  (p=0.000 n=8+8)
  Wire/Marshal/google_message2-6            103µs ±11%      59µs ± 4%  -42.17%  (p=0.000 n=8+8)

  name                                   old alloc/op   new alloc/op   delta
  Wire/Marshal/google_message1_proto2-6      592B ± 0%      240B ± 0%  -59.46%  (p=0.000 n=8+8)
  Wire/Marshal/google_message1_proto3-6      576B ± 0%      224B ± 0%  -61.11%  (p=0.000 n=8+8)
  Wire/Marshal/google_message2-6            196kB ± 0%      90kB ± 0%  -54.05%  (p=0.000 n=8+8)

  name                                   old allocs/op  new allocs/op  delta
  Wire/Marshal/google_message1_proto2-6      5.00 ± 0%      1.00 ± 0%  -80.00%  (p=0.000 n=8+8)
  Wire/Marshal/google_message1_proto3-6      5.00 ± 0%      1.00 ± 0%  -80.00%  (p=0.000 n=8+8)
  Wire/Marshal/google_message2-6            1.66k ± 0%     0.00k ± 0%  -99.94%  (p=0.000 n=8+8)

Change-Id: Idab7634b8c86604dffa46895ba2e61be38c9bd9c
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/183380
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>