Even though there is only one "return" from a SILFunction, there may be multiple
non-failure exits via no return functions. findAllNonFailureExitBBs
The verifier currently enforces that all no-return function applications must be
immediately followed by an unreachable. Thus to identify all such functions, we
must just visit all unreachables and visit the previous instruction of the
unreachable. If we don't have an apply in such case, then we must be in a
failure code path.
This code attempts to identify all ways of exiting a function in a non-failure
code path. Thus it places into the result vector the return from the BB and all
no-return function applications that it can not identify as a "failure"
function. The function ignores any paths that it identifies as failure paths.
Failure functions will be identified in the future via an @semantic tag but for
now we just check for functions with the appropriate "fatal error" suffix as we
do in the ARC optimizer.
I am going to use this in the closure specializer to insert releases for
"copied" closures that were originally passed in @guaranteed. Since the closure
was passed in originally @guaranteed there will be no matching -1 unless we
insert it ourselves.
Swift SVN r25051
