go: cmd/compile: cmd/compile/internal/gc.buildssa panic

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

$ go version
go version go1.14.2 linux/amd64

Does this issue reproduce with the latest release?

Yes, this was done on 1.14.2

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

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN="/gobin"
GOCACHE="/gocache"
GOENV="/home/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build048816231=/tmp/go-build -gno-record-gcc-switches"

This was built inside a docker image: gcr.io/istio-testing/build-tools:master-2020-04-10T20-55-56.

What did you do?

Tried to build our application.

What did you expect to see?

Build succeeds

What did you see instead?

STATIC=0 GOOS=windows LDFLAGS='-extldflags -static -s -w' common/scripts/gobuild.sh /tmp/tmp.W9NXZv7L5L/build/work/src/istio.io/istio/out/linux_amd64/release/istioctl-win.exe ./istioctl/cmd/istioctl
go: downloading github.com/inconshreveable/mousetrap v1.0.0
# k8s.io/apimachinery/pkg/util/runtime
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x74 pc=0xce6f4f]
goroutine 8 [running]:
cmd/compile/internal/gc.buildssa(0x0, 0x3, 0x0)
	/usr/local/go/src/cmd/compile/internal/gc/ssa.go:297 +0xdf
cmd/compile/internal/gc.compileSSA(0x0, 0x3)
	/usr/local/go/src/cmd/compile/internal/gc/pgen.go:298 +0x5d
cmd/compile/internal/gc.compileFunctions.func2(0xc0000ef4a0, 0xc000018e10, 0x3)
	/usr/local/go/src/cmd/compile/internal/gc/pgen.go:363 +0x49
created by cmd/compile/internal/gc.compileFunctions
	/usr/local/go/src/cmd/compile/internal/gc/pgen.go:361 +0x128

Full CI log: https://prow.istio.io/view/gcs/istio-prow/pr-logs/pull/istio_istio/22958/release-test_istio/11141 Rerunning the job with the same code the build succeeds: https://prow.istio.io/view/gcs/istio-prow/pr-logs/pull/istio_istio/22958/release-test_istio/11153

The referenced gobuild.sh script is https://github.com/istio/istio/blob/master/common/scripts/gobuild.sh.

I think the fact its in the compile code path means its a golang bug and not an issue with our code, but maybe not. Let me know if more info is needed.