cmd/compile: method calls for indirect imports not inlined

[ArsenySamoylov]

Go version

go version devel go1.24-6d39245514 Thu Oct 31 01:28:37 2024 +0000 linux/arm64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='arm64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/home/asamoylov/.cache/go-build'
GOENV='/home/asamoylov/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/asamoylov/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/asamoylov/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/asamoylov/repos/go-gh/'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/asamoylov/repos/go-gh/pkg/tool/linux_arm64'
GOVCS=''
GOVERSION='devel go1.24-6d39245514 Thu Oct 31 01:28:37 2024 +0000'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/asamoylov/.config/go/telemetry'
GCCGO='gccgo'
GOARM64='v8.0'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2613944426=/tmp/go-build -gno-record-gcc-switches'

What did you do?

Hello! I found error in inlining. Basically, if module A imports module B. Module B imports module C. Module A can call functions from module C but can't inline them! However, if you directly import module C into A, then inlining succeeds.

Here is a example:

project/
--- go.mod
--- transform.go
--- Descriptor/
  --- go.mod
  --- descriptor.go
--- DescriptorWrapper/
  --- go.mod
  --- wrapper.go

descriptor.go

package Descriptor

type Descriptor struct {
	numberKind int64
}

func (d Descriptor) NumberKind() int64 {
	return d.numberKind
}

wrapper.go

package DescriptorWrapper

import "Descriptor"

type Wrapper struct {
	Desc Descriptor.Descriptor
}

transform.go

package transform

import (
   "DescriptorWrapper"
)

func GaugeArray(wr DescriptorWrapper.Wrapper) {
   desc := wr.Desc
   _ = desc.NumberKind()
}

Here we can see that call to NumberKind() wasn't inlined:

go build -a -gcflags="-m" transform.go 
# command-line-arguments
./transform.go:8:6: can inline GaugeArray

However, if we add direct import of "Descriptor":
transform.go

package transform

import (
	_ "Descriptor"
	"DescriptorWrapper"
)

func GaugeArray(wr DescriptorWrapper.Wrapper) {
	desc := wr.Desc
	_ = desc.NumberKind()
}

Here call to NumberKind() is inlined!

go build -a -gcflags="-m" transform.go 
# command-line-arguments
./transform.go:8:6: can inline GaugeArray
./transform.go:10:21: inlining call to Descriptor.Descriptor.NumberKind

In this example, in first case (when inlining do not happen) 'bodyReaderFor' from 'unifiedHaveInlineBody' return false and inlining fails (in second case it returns true):

cmd/compile/internal/noder/reader.go

// unifiedHaveInlineBody reports whether we have the function body for
// fn, so we can inline it.
func unifiedHaveInlineBody(fn *ir.Func) bool {
	if fn.Inl == nil {
		return false
	}

	_, ok := bodyReaderFor(fn)
	return ok
}

What did you see happen?

Function that can be inlined wasn't inlined.

What did you expect to see?

Inlining of function that can be inlined