re PR middle-end/22156 (bit-field copying regressed)

re PR middle-end/22156 (bit-field copying regressed)

PR middle-end/22156
* tree-sra.c (instantiate_element): Use BYTES_BIG_ENDIAN for
bit-field layout.
(sra_build_assignment): Likewise.  Set up mask depending on
precision, not type.
(sra_build_bf_assignment): Use BYTES_BIG_ENDIAN.  Don't overflow
computing bit masks.
(sra_build_elt_assignment): Don't view-convert from signed to
unsigned.
(sra_explode_bitfield_assignment): Use bit-field type if
possible.  Use BYTES_BIG_ENDIAN.

From-SVN: r129150