cmd/compile: some case can be inlined before unified ir(go1.19-), but can't be inilned after unified ir(go1.20+)

[peter-xiao]

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

$ go version
devel go1.22-126db88cc8 Fri Oct 20 16:12:52 2023 +0800

Does this issue reproduce with the latest release?

// a.go
package a

type A struct {
}

func (*A) Print() {
}

// b.go
package b

import "./a"

var B *a.A
}

// main.go
package main

import "./b"

func main() {
	b.B.Print()
}

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE='on'

GOARCH='amd64'

GOBIN=''

GOCACHE='/Users/bytedance/Library/Caches/go-build'

GOENV='/Users/bytedance/Library/Application Support/go/env'

GOEXE=''

GOEXPERIMENT=''

GOFLAGS=''

GOHOSTARCH='amd64'

GOHOSTOS='darwin'

GOINSECURE=''

GOMODCACHE='/Users/bytedance/gopackage/pkg/mod'

GONOPROXY='.byted.org,.everphoto.cn,git.smartisan.com'

GONOSUMDB='.byted.org,.everphoto.cn,git.smartisan.com'

GOOS='darwin'

GOPATH='/Users/bytedance/gopackage'

GOPRIVATE='.byted.org,.everphoto.cn,git.smartisan.com'

GOPROXY='https://goproxy.byted.org|https://goproxy.cn|direct'

GOROOT='/Users/bytedance/go_google'

GOSUMDB=''

GOTMPDIR=''

GOTOOLCHAIN=''

GOTOOLDIR='/Users/bytedance/go_google/pkg/tool/darwin_amd64'

GOVCS=''

GOVERSION='devel go1.22-126db88cc8 Fri Oct 20 16:12:52 2023 +0800'

GCCGO='gccgo'

GOAMD64='v1'

AR='ar'

CC='clang'

CXX='clang++'

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 -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/b1/0fd1b6hs7lz0fm_mh346lybm0000gn/T/go-build831658170=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

go build -gcflags="-m"

What did you expect to see?

./main.go:5:6: can inline main
./main.go:6:11: inlining call to a.(*A).Print

What did you see instead?

./main.go:5:6: can inline main

[gopherbot]

Change https://go.dev/cl/537035 mentions this issue: cmd/compile: import methods which is exported in another package but not used and make more functions inlined

[dr2chase]

@mdempsky can you give this a look? I'd swear I had heard about this bug before in some other context, and that perhaps there was something subtle involved in the fix. OTOH, maybe I remember wrong.

[peter-xiao]

Could you please help review the patch?