cmd/compile: internal compiler error on : "tried to free an already free register" with generic function and type >= 192 bytes

[Janso123]

Go version

go version go1.26.0 linux/amd64

Output of go env in your module/workspace:

AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='gccgo'
GO111MODULE=''
GOAMD64='v1'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN='/home/user/.local/share/mise/installs/go/1.25.3/bin'
GOCACHE='/home/user/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/home/user/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build1675535395=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/home/user/Documents/projects/test/go.mod'
GOMODCACHE='/home/user/go/pkg/mod'
GONOPROXY='gitlab.prive.sh'
GONOSUMDB='gitlab.prive.sh'
GOOS='linux'
GOPATH='/home/user/go'
GOPRIVATE='gitlab.prive.sh'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/user/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.26.0.linux-amd64'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/user/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/user/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.26.0.linux-amd64/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.26.0'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

ompiling a program that uses github.com/go-fuego/fuego v0.19.0 with a route handler returning a type >= 192 bytes produces an internal compiler error tested on linux/amd64 and darwin/arm64.

Minimal reproducer:

package main

import "github.com/go-fuego/fuego"

func handler(c fuego.ContextNoBody) ([192]byte, error) {
	return [192]byte{}, nil
}

func main() {
	s := fuego.NewServer()
	fuego.Get(s, "/test", handler)
}

To reproduce:

mkdir /tmp/go-ice-repro && cd /tmp/go-ice-repro
go mod init repro
go mod edit -go=1.26.0          # must use Go 1.26.0 toolchain
go get github.com/go-fuego/fuego@v0.19.0
# save the above code as main.go
go build .

What did you see happen?

# repro
/home/user/go/pkg/mod/github.com/go-fuego/fuego@v0.19.0/serialization.go:40:19: internal compiler error: 'transformOut[go.shape.[192]uint8]': tried to free an already free register 1


Please file a bug report including a short program that triggers the error.
https://go.dev/issue/new

What did you expect to see?

Successful compilation.

[gabyhelp]

Related Issues

• cmd/compile: ICE when using unsafe.Sizeof on generic type #77382 (closed)
• cmd/compile: generic type cause "internal compiler error: 'main': Value live at entry. It shouldn't be." #56652 (closed)
• cmd/compile: internal compiler error: 'Float64D3': no register available..." (1.20 regression?) #57846 (closed)
• cmd/compile: ICE instantiating a generic type `B` in `type A[T] struct{}; type B[T] A[[]T]` with `error` #56626 (closed)
• cmd/compile: internal compiler error using `archsimd.Int8x16` as type parameter #77444 (closed)
• cmd/compile: compiler failing for generic code #50841 (closed)
• cmd/compile: internal compiler error: assertion failed #53762 (closed)
• cmd/compile: internal compiler error too many arguments to function call #74260 (closed)
• cmd/compile: internal compiler error: panic: runtime error: invalid memory address or nil pointer dereference #54746 (closed)
• cmd/compile: internal compiler error: Value live at entry #58349 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[JunyangShao]

@golang/compiler

[randall77]

Sorry about that. This looks like regalloc gets confused by no-op copy instructions. The copy instruction's source and destination are the same location, so it takes only one register to pass both arguments. But then it tries to deallocate that argument register twice :(.

Should be a simple fix.

[randall77]

@gopherbot please open a backport issue to go 1.26. This is a rare but triggerable ICE.

[gopherbot]

Backport issue(s) opened: #77623 (for 1.26).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases.

[gopherbot]

Change https://go.dev/cl/745621 mentions this issue: cmd/compile: don't drop same register twice