This patch teaches ias for mips to handle expressions such as
(8*4)+(8*31)($sp). Such expression typically occur from the expansion
of multiple macro definitions.
This partially resolves PR/30383.
Thanks to Sean Bruno for reporting the issue!
Reviewers: zoran.jovanovic, vkalintiris
Differential Revision: https://reviews.llvm.org/D24667
llvm-svn: 284485