runtime: improve interface equality check performance

[ugorji]

Interface equality check is expensive compared to integer comparison check.

In the benchmark, I compare two integers. I then wrap them in interface{} and compare
them.

As interface{}, the comparison check takes over 20X the time taken by just plain
comparison check.

See http://play.golang.org/p/1evwkTYYlB

Results:
BenchmarkIntfEqual  100000000            14.5 ns/op
BenchmarkReflectTypeEqual   100000000    14.4 ns/op
BenchmarkPtrEqual   2000000000           1.06 ns/op
BenchmarkIntEqual   2000000000           0.70 ns/op
BenchmarkIntMapAccess   500000000            5.22 ns/op
BenchmarkReflectTypeMapAccess   50000000     57.6 ns/op
BenchmarkIntMapAccessMiss   100000000           16.4 ns/op
BenchmarkReflectTypeMapAccessMiss   50000000    58.3 ns/op

Which compiler are you using (5g, 6g, 8g, gccgo)?
6g

Which operating system are you using?
Linux 3.8.0-27-generic #40-Ubuntu SMP Tue Jul 9 00:17:05 UTC 2013 x86_64 x86_64 x86_64
GNU/Linux

Which version are you using?  (run 'go version')
go version devel +21ae2c5817da Fri Aug 09 23:23:34 2013 +1000 linux/amd64


Please provide any additional information below.

[ugorji]

Comment 1:

Groups discussion leading to this is at:
https://groups.google.com/d/msg/golang-dev/Oik3353DJ2w/aNxNhwC9J_kJ

[cznic]

Comment 2:

Seems like a duplicate of #6106 to me. Merge?

[robpike]

Comment 3:

Status changed to Duplicate.

Merged into issue #6106.