SCC call-stack from `error` missing call-sites

For some reason the -prof stack that error attaches only includes the top-level CAF. This is with the default build settings (which I believe are the release settings?)

$ cat Foo.hs
main = print (foo [1])
foo xs = tail (tail xs)

$ ./inplace/bin/ghc-stage2 --make -prof -fprof-auto-calls Foo.hs
[1 of 1] Compiling Main             ( Foo.hs, Foo.o ) [flags changed]
Linking Foo ...

$ ./Foo
Foo: Prelude.tail: empty list
CallStack (from -prof):
  GHC.List.CAF (<entire-module>)

I would expect to at least see the call-site of foo (if not also tail) in the stack.

Trac metadata

Trac field	Value
Version	8.0.1-rc1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Profiling
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	simonmar
Operating system
Architecture