target-ppc: Altivec 2.07: Change Bit Masks to Support 64-bit Rotates and Shifts

target-ppc: Altivec 2.07: Change Bit Masks to Support 64-bit Rotates and Shifts

Existing code in the VROTATE, VSL and VSR macros for the Altivec rotate and shift
helpers uses a formula to compute a bit mask used to extract the rotate/shift
amount from the VRB register.  What is desired is:

    mask = (1 << (3 + log2(sizeof(element)))) - 1

but what is implemented is:

    mask = (1 << (3 + (sizeof(element)/2))) - 1

This produces correct answers when "element" is uint8_t, uint16_t or uint_32t.  But
it breaks down when element is uint64_t.

This patch corrects the situation.  Since the mask is known at compile time, the
macros are changed to simply accept the mask as an argument.

Subsequent patches in this series will add double-word variants of rotates and
shifts and thus take advantage of this fix.

Signed-off-by: Tom Musta <tommusta@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>