Repository: go
Issue: runtime: GODEBUG=efence=1 causes panic during build on M1
Labels: NeedsInvestigation,arch-arm64,compiler/runtime

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### What version of Go are you using (`go version`)?

<pre>
$ go version
go version go1.16.2 darwin/arm64
</pre>


### Does this issue reproduce with the latest release?

Yes.

### What operating system and processor architecture are you using (`go env`)?

macOS Big Sur 11.2.2

<details><summary><code>go env</code> Output</summary><br><pre>
$ go env
GO111MODULE=""
GOARCH="arm64"
GOBIN=""
GOCACHE="/Users/bart/Library/Caches/go-build"
GOENV="/Users/bart/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="arm64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/bart/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/bart/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_arm64"
GOVCS=""
GOVERSION="go1.16.2"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
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 -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/qc/mhy1mvh13w993fhyg5xmb_880000gn/T/go-build915245815=/tmp/go-build -gno-record-gcc-switches -fno-common"
</pre></details>

### What did you do?

```
$ cat << EOF > test.go
package main

import "fmt"

func main() {
    fmt.Println("Hello, World")
}
EOF
$ export GODEBUG=efence=1
$ go build test.go
# command-line-arguments
unexpected fault address 0x14000d235c8
fatal error: fault
[signal SIGBUS: bus error code=0x1 addr=0x14000d235c8 pc=0x100e49b94]

goroutine 1 [running]:
runtime.throw(0x100f64a2a, 0x5)
	/usr/local/go/src/runtime/panic.go:1117 +0x54 fp=0x1014f2640 sp=0x1014f2610 pc=0x100d7e824
runtime.sigpanic()
	/usr/local/go/src/runtime/signal_unix.go:731 +0x284 fp=0x1014f2680 sp=0x1014f2640 pc=0x100d96044
cmd/link/internal/loader.(*Loader).SymName(0x1400060a000, 0xf125, 0xf484, 0x38)
	/usr/local/go/src/cmd/link/internal/loader/loader.go:756 +0x144 fp=0x1014f26f0 sp=0x1014f2690 pc=0x100e49b94
cmd/link/internal/ld.(*dwctxt).nameFromDIESym(...)
	/usr/local/go/src/cmd/link/internal/ld/dwarf.go:737
cmd/link/internal/ld.(*dwctxt).synthesizemaptypes(0x1014f2b10, 0x140000f2000, 0x1400104f980)
	/usr/local/go/src/cmd/link/internal/ld/dwarf.go:912 +0x3a8 fp=0x1014f28e0 sp=0x1014f26f0 pc=0x100ebc088
cmd/link/internal/ld.dwarfGenerateDebugInfo(0x140000f2000)
	/usr/local/go/src/cmd/link/internal/ld/dwarf.go:1950 +0x127c fp=0x1014f2cb0 sp=0x1014f28e0 pc=0x100ec390c
cmd/link/internal/ld.Main(0x10117b500, 0x10, 0x20, 0x1, 0x1f, 0x1e, 0x100f6c384, 0x14, 0x100f6f9a9, 0x1a, ...)
	/usr/local/go/src/cmd/link/internal/ld/main.go:260 +0xd48 fp=0x1014f2f10 sp=0x1014f2cb0 pc=0x100ef3438
main.main()
	/usr/local/go/src/cmd/link/main.go:68 +0x1bc fp=0x1014f3f70 sp=0x1014f2f10 pc=0x100f6324c
runtime.main()
	/usr/local/go/src/runtime/proc.go:225 +0x26c fp=0x1014f3fd0 sp=0x1014f3f70 pc=0x100d80ccc
runtime.goexit()
	/usr/local/go/src/runtime/asm_arm64.s:1130 +0x4 fp=0x1014f3fd0 sp=0x1014f3fd0 pc=0x100db1c14
```

### What did you expect to see?

Silent, successful build.

### What did you see instead?

Compiler stack trace as shown above.