tree-optimization/111779 - Handle some BIT_FIELD_REFs in SRA

The following handles byte-aligned, power-of-two and byte-multiple
sized BIT_FIELD_REF reads in SRA.  In particular this should cover
BIT_FIELD_REFs created by optimize_bit_field_compare.

For gcc.dg/tree-ssa/ssa-dse-26.c we now SRA the BIT_FIELD_REF
appearing there leading to more DSE, fully eliding the aggregates.

This results in the same false positive -Wuninitialized as the
older attempt to remove the folding from optimize_bit_field_compare,
fixed by initializing part of the aggregate unconditionally.

	PR tree-optimization/111779
gcc/
	* tree-sra.cc (sra_handled_bf_read_p): New function.
	(build_access_from_expr_1): Handle some BIT_FIELD_REFs.
	(sra_modify_expr): Likewise.
	(make_fancy_name_1): Skip over BIT_FIELD_REF.

gcc/fortran/
	* trans-expr.cc (gfc_trans_assignment_1): Initialize
	lhs_caf_attr and rhs_caf_attr codimension flag to avoid
	false positive -Wuninitialized.

gcc/testsuite/
	* gcc.dg/tree-ssa/ssa-dse-26.c: Adjust for more DSE.
	* gcc.dg/vect/vect-pr111779.c: New testcase.

1 files changed, 4 insertions, 1 deletions

diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index 7beefa2..1b8be08 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -12015,7 +12015,10 @@ gfc_trans_assignment_1 (gfc_expr * expr1, gfc_expr * expr2, bool init_flag,
 		 && !is_runtime_conformable (expr1, expr2);
 
   /* Only analyze the expressions for coarray properties, when in coarray-lib
-     mode.  */
+     mode.  Avoid false-positive uninitialized diagnostics with initializing
+     the codimension flag unconditionally.  */
+  lhs_caf_attr.codimension = false;
+  rhs_caf_attr.codimension = false;
   if (flag_coarray == GFC_FCOARRAY_LIB)
     {
       lhs_caf_attr = gfc_caf_attr (expr1, false, &lhs_refs_comp);