cmd/compile: inline function calls that return a closure

[potocnyj]

https://go-review.googlesource.com/#/c/8200/ added a benchmark to the strings package that shows strings.Trim and its variants allocate memory. The allocation is caused by the call to makeCutsetFunc here. Inlining this call removes the allocation and provides a nice performance boost to Trim. You can see the effect on the benchmark using Go Tip (commit 6262192) below:

benchmark         old ns/op     new ns/op     delta
BenchmarkTrim     3204          2323          -27.50%

benchmark         old allocs     new allocs     delta
BenchmarkTrim     11             0              -100.00%

benchmark         old bytes     new bytes     delta
BenchmarkTrim     352           0             -100.00%

makeCutsetFunc is a pretty simple function (all it does is return a closure), and it was pointed out in review that it might be nice to inline functions like it in the compiler rather than changing strings.Trim explicitly.

[bradfitz]

/cc @dr2chase @dvyukov

[bradfitz]

In case the link above breaks, the code in question is:

func makeCutsetFunc(cutset string) func(rune) bool {
    return func(r rune) bool { return IndexRune(cutset, r) >= 0 }
}

// Trim returns a slice of the string s with all leading and
// trailing Unicode code points contained in cutset removed.
func Trim(s string, cutset string) string {
    if s == "" || cutset == "" {
        return s
    }
    return TrimFunc(s, makeCutsetFunc(cutset))
}

[huguesb]

I have a WIP for this, which seems to work fine when building a single-package executable but fails as soon as multiple packages are involved since the exporter/importer do not handle OCLOSURE.

@griesemer I'm trying to add support for the OCLOSURE node in the export format but I'm not able to test my changes because I keep getting the following error when I try compile code with: cannot import "runtime/internal/sys" due to version skew - reinstall package (unknown export format version 6 ("version 6"))

How does one test changes to the export format? Is the workflow affected by the recent caching work by @rsc ?

edit: nevermind, I stupidly forgot to update the version check in bimport.go...

[davecheney]

Hughes, how are you testing/recompiling the Compiler after you change? Perhaps I can suggest a solution.

…

On 9 Nov 2017, at 09:38, Hugues ***@***.***> wrote: I have a WIP for this, which seems to work fine when building a single-package executable but fails as soon as multiple packages are involved since the exporter/importer do not handle OCLOSURE. @griesemer I'm trying to add support for the OCLOSURE node in the export format but I'm not able to test my changes because I keep getting the following error when I try compile code with: cannot import "runtime/internal/sys" due to version skew - reinstall package (unknown export format version 6 ("version 6")) How does one test changes to the export format? Is the workflow affected by the recent caching work by @rsc ? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.

[huguesb]

@davecheney I figured out what was going wrong. Thanks for the offer to help though :)

At this point, my WIP can inline functions with closures that do not capture variables and works fine across packages. I'll upload a CL as soon as I figure out how to properly handle captures (or when I get stuck and need to ask for help).

Interestingly, Trim is no longer a good benchmark for this since the introduction of an ASCII fast path brought a loop into makeCutsetFunc which prevents inlining (this is #14768).