Extern global merging is good for code-size. There's definitely potential for
performance too, but there's one regression in a benchmark that needs
investigating, so that's why we enable it only when we optimise for size for
now.
Patch by Ramakota Reddy and Sjoerd Meijer.
Differential Revision: https://reviews.llvm.org/D61947
llvm-svn: 363130
Sjoerd Meijer