PR middle-end/22156
* tree-sra.c (struct sra_elt): Add in_bitfld_block.
(sra_hash_tree): Handle BIT_FIELD_REFs.
(sra_elt_hash): Don't hash bitfld blocks.
(sra_elt_eq): Skip them in parent compares as well.  Handle
BIT_FIELD_REFs.
(build_element_name_1): Handle BIT_FIELD_REFs.
(instantiate_element): Propagate nowarn from parents.  Create
BIT_FIELD_REF for variables that are widened by scalarization.
Gimple-zero-initialize all bit-field variables that are not
part of parameters that are going to be scalarized on entry.
(instantiate_missing_elements_1): Return the sra_elt.
(canon_type_for_field): New.
(try_instantiate_multiple_fields): New.  Infer widest possible
access mode from decl or member type, but clip it at word
size, and only widen it if a field crosses an alignment
boundary.
(instantiate_missing_elements): Use them.
(generate_one_element_ref): Handle BIT_FIELD_REFs.
(scalar_bitfield_p): New.
(sra_build_assignment): Optimize assignments from scalarizable
BIT_FIELD_REFs.  Use BITS_BIG_ENDIAN to determine shift
counts.
(REPLDUP): New.
(sra_build_bf_assignment): New.  Optimize assignments to
scalarizable BIT_FIELD_REFs.
(sra_build_elt_assignment): New.  Optimize BIT_FIELD_REF
assignments to full variables.
(generate_copy_inout): Use the new macros and functions.
(generate_element_copy): Likewise.  Handle bitfld differences.
(generate_element_zero): Don't recurse for blocks.  Use
sra_build_elt_assignment.
(generate_one_element_init): Take elt instead of var.  Use
sra_build_elt_assignment.
(generate_element_init_1): Adjust.
(bitfield_overlap_info): New struct.
(bitfield_overlaps_p): New.
(sra_explode_bitfield_assignment): New.  Adjust widened
variables to account for endianness.
(sra_sync_for_bitfield_assignment): New.
(scalarize_use): Re-expand assignment to/from scalarized
BIT_FIELD_REFs.  Explode or sync needed members for
BIT_FIELD_REFs accesses or assignments.  Use REPLDUP.
(scalarize_copy): Use REPLDUP.
(scalarize_ldst): Move assert before dereference.  Adjust EH
handling.
(dump_sra_elt_name): Handle BIT_FIELD_REFs.

From-SVN: r128908