cmd/compile: nil pointer dereference

[dvyukov]

on dev.ssa branch
go version devel +be2a3e2 Thu Jul 2 08:29:33 2015 +0000 linux/amd64

compile crashes on the following program:

package a
func f_ssa() {return;return}

panic: runtime error: invalid memory address or nil pointer dereference [recovered]
    panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x8 pc=0x5d516f]

goroutine 1 [running]:
cmd/compile/internal/gc.buildssa.func1(0xc8201633f0)
    src/cmd/compile/internal/gc/ssa.go:46 +0x4d
cmd/compile/internal/gc.(*state).stmt(0xc8200f1778, 0xc8201cf320)
    src/cmd/compile/internal/gc/ssa.go:377 +0x213f
cmd/compile/internal/gc.(*state).stmtList(0xc8200f1778, 0xc8201a3560)
    src/cmd/compile/internal/gc/ssa.go:280 +0x3a
cmd/compile/internal/gc.buildssa(0xc8201ce510, 0x0, 0xc8201cf600)
    src/cmd/compile/internal/gc/ssa.go:95 +0x944
cmd/compile/internal/gc.compile(0xc8201ce510)
    src/cmd/compile/internal/gc/pgen.go:412 +0x608
cmd/compile/internal/gc.funccompile(0xc8201ce510)
    src/cmd/compile/internal/gc/dcl.go:1480 +0x1c9
cmd/compile/internal/gc.Main()
    src/cmd/compile/internal/gc/lex.go:473 +0x1f08
cmd/compile/internal/amd64.Main()
    src/cmd/compile/internal/amd64/galign.go:127 +0x58d
main.main()
    src/cmd/compile/main.go:26 +0x189

[dvyukov]

@josharian @DanielMorsing

[josharian]

Fixed by CL 12445.