go: cmd/compile: slow compile/build compared to Go 1.4

It’s been a while, we still use 1.4 because of this issue, it affect to much to our build-test-debug cycle.

$ uname -a
Linux f9988 4.1.14-1-lts #1 SMP Thu Dec 10 21:34:50 CET 2015 x86_64 GNU/Linux

# go 1.1 and go 1.2 failed to compile github.com/yosuke-furukawa/json5/encoding/json5

$ rm -rf $GOPATH/pkg/* 2>1 > /dev/null; go version ; time go build
go version go1.3.3 linux/amd64

CPU: 5.35s      Real: 3.34s     RAM: 287316KB
CPU: 5.63s      Real: 3.40s     RAM: 287316KB
CPU: 5.87s      Real: 3.41s     RAM: 287272KB

$ rm -rf $GOPATH/pkg/* 2>1 > /dev/null; go version ; time go build
go version go1.4.2 linux/amd64

CPU: 5.83s      Real: 3.34s     RAM: 290024KB
CPU: 5.71s      Real: 3.45s     RAM: 290024KB
CPU: 5.96s      Real: 3.46s     RAM: 289948KB

$ rm -rf $GOPATH/pkg/* 2>1 > /dev/null; go version ; time go build
go version go1.5.2 linux/amd64

CPU: 21.93s     Real: 7.92s     RAM: 310148KB
CPU: 21.07s     Real: 7.46s     RAM: 318660KB
CPU: 21.45s     Real: 7.58s     RAM: 310160KB

packages from: http://seblu.net/a/archive/packages/g/go/

for comparison, it’s now as slow as gcc-go:

# for comparison:
$ rm -rf $GOPATH/pkg/* 2>1 > /dev/null; go version ; time go build
go version go1.4.2 gccgo (GCC) 5.3.0 linux/amd64

CPU: 20.76s     Real: 9.65s     RAM: 203212KB
CPU: 21.33s     Real: 9.83s     RAM: 203340KB
CPU: 21.09s     Real: 9.85s     RAM: 203336KB