Don't expand SDIV with an immediate that is a power of 2 if we optimise for
minimum code size. For example:
sdiv %1, i32 4
gets expanded to a sequence of 3 instructions, but this is suboptimal for
minimum code size so instead we just generate a MOV and a SDIV if integer
division is supported.
Differential Revision: https://reviews.llvm.org/D54546
llvm-svn: 347965