https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94482
--- Comment #18 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #17)
> This:
>
> if (write)
> {
> gassign *stmt;
>
> if (access->grp_partial_lhs)
> ref = force_gimple_operand_gsi (gsi, ref, true, NULL_TREE,
> false, GSI_NEW_STMT);
> stmt = gimple_build_assign (repl, ref);
> gimple_set_location (stmt, loc);
> gsi_insert_after (gsi, stmt, GSI_NEW_STMT);
>
> is definitely wrong.
That is, it would need to be a read-modify-write operation.
> And in the else case grp_partial_lhs is never true.
OK, I see now how grp_partial_lhs is used.
> The whole bfr path looks fisy, too. The following fixes the testcase:
It'll likely break in some cases of course.
I understand the motivation is to analyze accesses ignoring outermost
bitfield refs and imag/realpart so we generate replacements for the
"base" accesses. All OK I guess, so it's the replacement process that
needs fixing up.
Similar issues exist in generate_subtree_copies.
> diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
> index b2056b58750..e16b641c9bb 100644
> --- a/gcc/tree-sra.c
> +++ b/gcc/tree-sra.c
> @@ -3737,36 +3737,8 @@ sra_modify_expr (tree *expr, gimple_stmt_iterator
> *gsi, bool write)
> type conversion (see PR42196) and when scalarized unions are
> involved
> in assembler statements (see PR42398). */
> if (!useless_type_conversion_p (type, access->type))
> - {
> - tree ref;
> -
> - ref = build_ref_for_model (loc, orig_expr, 0, access, gsi, false);
> -
> - if (write)
> - {
> - gassign *stmt;
> -
> - if (access->grp_partial_lhs)
> - ref = force_gimple_operand_gsi (gsi, ref, true, NULL_TREE,
> - false, GSI_NEW_STMT);
> - stmt = gimple_build_assign (repl, ref);
> - gimple_set_location (stmt, loc);
> - gsi_insert_after (gsi, stmt, GSI_NEW_STMT);
> - }
> - else
> - {
> - gassign *stmt;
> -
> - if (access->grp_partial_lhs)
> - repl = force_gimple_operand_gsi (gsi, repl, true, NULL_TREE,
> - true, GSI_SAME_STMT);
> - stmt = gimple_build_assign (ref, repl);
> - gimple_set_location (stmt, loc);
> - gsi_insert_before (gsi, stmt, GSI_SAME_STMT);
> - }
> - }
> - else
> - *expr = repl;
> + repl = build1 (VIEW_CONVERT_EXPR, type, repl);
> + *expr = repl;
> sra_stats.exprs++;
> }
> else if (write && access->grp_to_be_debug_replaced)
