With llvm-12 thera are more stringent requirement on the propagation of
DebugLoc on CallInst and InvokeInst.
Various CallInst and InvokeInst created during lifting did not fulfill
these requirements, causing the Module to not verify() with llvm-12.
This commit fixes the problem, properly propagating the debug locations.
This commit ensures that FunctionIsolation and EnforceABI do only
thing. This means that they no longer modify `root`.
Instead, we have a new pass, `invoke-isolated-functions` that needs to
be run after them and replaces the entry point of the functions with
invokes to the isolated functions, possibly with the appropriate
arguments.
Pietro Fezzardi