[mips] Add code to do tail call optimization.

Currently, it is enabled only if option "enable-mips-tail-calls" is given and
all of the callee's arguments are passed in registers.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@166342 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed