cmd/compile: "missing stack map index" for unreasonable type

[josharian]

package p

type S struct {
	i interface {
		f() [1 << 27]S
	}
}

Compiling this results in a panic:

$ go tool compile x.go
<autogenerated>:1:0: internal compiler error: missing stack map index for v16 = CALLinter <mem> [2147483656] v12 v15

goroutine 1 [running]:
runtime/debug.Stack(0x0, 0x0, 0x0)
	/Users/josh/go/tip/src/runtime/debug/stack.go:24 +0xa7
cmd/compile/internal/gc.Fatalf(0x176870a, 0x1e, 0xc420332760, 0x1, 0x1)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/subr.go:181 +0x230
cmd/compile/internal/gc.(*SSAGenState).Call(0xc42031f140, 0xc420334700, 0xc4200ca7e8)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/ssa.go:4776 +0x364
cmd/compile/internal/amd64.ssaGenValue(0xc42031f140, 0xc420334700)
	/Users/josh/go/tip/src/cmd/compile/internal/amd64/ssa.go:757 +0x38db
cmd/compile/internal/gc.genssa(0xc420320140, 0xc420086690)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/ssa.go:4444 +0xbdb
cmd/compile/internal/gc.compileSSA(0xc420388000, 0x0)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/pgen.go:242 +0x7e
cmd/compile/internal/gc.compile(0xc420388000)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/pgen.go:219 +0x218
cmd/compile/internal/gc.funccompile(0xc420388000)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/dcl.go:1049 +0xb7
cmd/compile/internal/gc.genwrapper(0xc4203158c0, 0xc4202f3240, 0xc42031e7e0, 0x0)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/subr.go:1786 +0x73e
cmd/compile/internal/gc.imethods(0xc4203158c0, 0xc420322a10, 0x10102dc, 0xc42031a3c8)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/reflect.go:424 +0x318
cmd/compile/internal/gc.dtypesym(0xc4203158c0, 0xc4202ebae0)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/reflect.go:1189 +0x13d5
cmd/compile/internal/gc.dtypesym(0xc420315800, 0xc4202ebc80)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/reflect.go:1277 +0xe14
cmd/compile/internal/gc.dumpsignats()
	/Users/josh/go/tip/src/cmd/compile/internal/gc/reflect.go:1441 +0x3e7
cmd/compile/internal/gc.dumpobj1(0xc42001239c, 0x3, 0x3)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/obj.go:141 +0x2af
cmd/compile/internal/gc.dumpobj()
	/Users/josh/go/tip/src/cmd/compile/internal/gc/obj.go:51 +0x61
cmd/compile/internal/gc.Main(0x17756e8)
	/Users/josh/go/tip/src/cmd/compile/internal/gc/main.go:631 +0x24f7
main.main()
	/Users/josh/go/tip/src/cmd/compile/main.go:49 +0x89

1.8 panics too, albeit differently:

$ go tool compile x.go
<autogenerated>:1: stack frame too large (>2GB)
<unknown line number>: internal compiler error: NewFunc called without previous Free

goroutine 1 [running]:
runtime/debug.Stack(0x0, 0x0, 0x0)
	/Users/josh/go/1.8/src/runtime/debug/stack.go:24 +0x79
cmd/compile/internal/gc.Fatalf(0x16c89ef, 0x24, 0x0, 0x0, 0x0)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/subr.go:167 +0x226
cmd/compile/internal/gc.(*ssaExport).Fatalf(0x19cdb95, 0xc400000000, 0x16c89ef, 0x24, 0x0, 0x0, 0x0)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/ssa.go:4984 +0x5d
cmd/compile/internal/ssa.(*Config).Fatalf(0xc42034a000, 0xc400000000, 0x16c89ef, 0x24, 0x0, 0x0, 0x0)
	/Users/josh/go/1.8/src/cmd/compile/internal/ssa/config.go:343 +0x6e
cmd/compile/internal/ssa.(*Config).NewFunc(0xc42034a000, 0x16d2570)
	/Users/josh/go/1.8/src/cmd/compile/internal/ssa/config.go:334 +0x16e
cmd/compile/internal/gc.buildssa(0xc420348e10, 0x0)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/ssa.go:65 +0x1ae
cmd/compile/internal/gc.compile(0xc420348e10)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/pgen.go:385 +0x204
cmd/compile/internal/gc.funccompile(0xc420348e10)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/dcl.go:1292 +0xdc
cmd/compile/internal/gc.genhash(0xc42039e3f0, 0xc42031f4a0)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/alg.go:319 +0x78e
cmd/compile/internal/gc.dalgsym(0xc42031f4a0, 0xffffffffffffffff)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/reflect.go:1546 +0x10da
cmd/compile/internal/gc.dcommontype(0xc42039e150, 0x0, 0xc42031f4a0, 0x0)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/reflect.go:834 +0xac
cmd/compile/internal/gc.dtypesym(0xc42031f4a0, 0xc420322860)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/reflect.go:1168 +0xb34
cmd/compile/internal/gc.dtypesym(0xc42031f5c0, 0xc42000c5f0)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/reflect.go:1199 +0x306
cmd/compile/internal/gc.dtypesym(0xc42031f2c0, 0xc420322600)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/reflect.go:1232 +0x114d
cmd/compile/internal/gc.dtypesym(0xc42031f200, 0x0)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/reflect.go:1318 +0xc79
cmd/compile/internal/gc.dumptypestructs()
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/reflect.go:1394 +0xd5
cmd/compile/internal/gc.dumpobj1(0xc420011455, 0x3, 0x3)
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/obj.go:134 +0x28b
cmd/compile/internal/gc.dumpobj()
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/obj.go:45 +0x52
cmd/compile/internal/gc.Main()
	/Users/josh/go/1.8/src/cmd/compile/internal/gc/main.go:492 +0x21c4
main.main()
	/Users/josh/go/1.8/src/cmd/compile/main.go:50 +0xfe

If the array bound is 1<<26, it takes forever to compile. If the array bound is plausible (like 1<<10), it compiles fine.

Marking as unplanned, pending actual code encountering this problem, which seems very unlikely.

Found with go-fuzz.

[josharian]

This appears fixed on tip:

$ go tool compile x.go
<autogenerated>:1: stack frame too large (>1GB): 0 MB locals + 2048 MB args