panic when compiling SHA

[Kazu Yamamoto (=?iso-2022-jp?B?GyRCOzNLXE9CSScbKEI=?=)]

Ben,

> Note that removing the flag isn't a "solution" to the underlying
> problem of the intermediate code being awful. Switching to the
> linear allocator just permits compilation of core code that was
> worse than before. Now it needs to spill more registers when
> compiling the same source code.

So, would you reopen #5361 by yourself?

	https://ghc.haskell.org/trac/ghc/ticket/5361

--Kazu