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

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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@21544 91177308-0d34-0410-b5e6-96231b3b80d8