cmd/compile: combine phielim and copyelim into a single pass?

[surechen]

What version of Go are you using (go version)?

$ go version
go version go1.14.3 windows/amd64

Does this issue reproduce with the latest release?

yes

What did you do?

I find a todo tag in line 419 of the file cmd/compile/internal/ssa/compile.go. It seems that the previous developer was considering combing phielim and copyelim. Whether there's still interest in this? In fact I am reading the compiler source code recently and interested in this. Can I try to do this work. Could you give me some advices about what I should pay attention to?

[randall77]

There's interest if it actually helps, which might be the case or it might not. "Helps" here means it makes the compiler faster.

You can check compiler phase timings by giving flags like -d="ssa/early copyelim/time" to the compiler (more examples described in compile.go:PhaseOption).

[surechen]

-d="ssa/early copyelim/time"

Ok, thank you very much. I'll give it a try.

[josharian]

You might also find github.com/josharian/compilecmp handy for testing compiler performance.