The order of global variables is generated in the order of recursively materializing variables if the global variable has the attribute of hasLocalLinkage or hasLinkOnceLinkage during the module merging. In practice, it is often the exact reverse of source order. This new order may cause performance regression.
The change is to preserve the original lexical order for global variables.
Reviewed By: jdoerfert, dexonsmith
Differential Revision: https://reviews.llvm.org/D94202
When linking llvm.global_ctors with the optional third element we have to handle
it specially and only copy the elements whose keys were also copied.
llvm-svn: 217281