PR middle-end/22156

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.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@129150 138bc75d-0d04-0410-961f-82ee72b054a4