The following constraints hold for swifterror values:
A swifterror value (either the parameter or the alloca) can only
be loaded and stored from, or used as a swifterror argument.
This patch updates instcombine to not try to convert a bitcast of a
function into a bitcast of a swifterror argument.
Reviewed By: rjmccall
Differential Revision: https://reviews.llvm.org/D90258
Florian Hahn