Codegen x < 0 | y < 0 as (x|y) < 0. This allows us to compile this to:

_foo:
        or r2, r4, r3
        srwi r3, r2, 31
        blr

instead of:

_foo:
        srwi r2, r4, 31
        srwi r3, r3, 31
        or r3, r2, r3
        blr

llvm-svn: 21544