[mips] Fix expansion of memory operation if destination register is not a GPR.
Summary:
The assembler tries to reuse the destination register for memory operations whenever
it can but it's not possible to do so if the destination register is not a GPR.
Example:
ldc1 $f0, sym
should expand to:
lui $at, %hi(sym)
ldc1 $f0, %lo(sym)($at)
It's entirely wrong to expand to:
lui $f0, %hi(sym)
ldc1 $f0, %lo(sym)($f0)
Reviewers: dsanders
Reviewed By: dsanders
Differential Revision: http://reviews.llvm.org/D4173
llvm-svn: 211169