LFS/STFS load and store FP values, not integer ones. This change allows us

to codegen this: float foo() { return 1.245; }

into this:

_foo:
        lis r2, ha16(.CPI_foo_0)
        lfs f1, lo16(.CPI_foo_0)(r2)
        blr

instead of this:

_foo:
        lis r2, ha16(.CPI_foo_0)
        lfs r2, lo16(.CPI_foo_0)(r2)   <-- ouch
        or f1, r2, r2                  <-- ouch
        blr

with the dag isel.

llvm-svn: 23033