[PATCH] Add sign/zero extend to mips fast-isel

[reed kotler]

There is no reason to be concerned with mips32/r1 which is an old processor version as far as I know. We don't even have any build bots at Mips that test if we can pass test-suite with mips32/r1 as the processor as far as I know . If need a special sequence for mips32/r1, then I think it should be on an if statement of some kind rather that use a more obscure sequence that happens to to work on both mips32/r2 and mips32/r1. I used the most clear sequence for mips32/r2 which is our first target for mips fast-isel.

http://reviews.llvm.org/D4827