Combine simplify_set WORD_REGISTER_OPERATIONS

[Jeff Law]

On 01/31/2016 03:16 PM, Alan Modra wrote:
> The comment says this test is supposed to prevent "a narrower
> operation than requested", but it actually only allows a larger
> subreg, not one the same size.  Fix that.
>
> Bootstrapped and regression tested powerpc64-linux.  OK for stage1?
>
> Note that this bug was found when investigating why gcc-6 does not
> suffer from pr69548, ie. this bug was masking a powerpc backend bug.
>
> 	* combine.c (simplify_set): Correct WORD_REGISTER_OPERATIONS test.
This is fine.  Please install.

THanks,
Jeff