https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103271
--- Comment #12 from Richard Biener <rguenth at gcc dot gnu.org> --- diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c index 6ac3460d538..08f94b7a17a 100644 --- a/gcc/internal-fn.c +++ b/gcc/internal-fn.c @@ -3050,6 +3050,23 @@ expand_DEFERRED_INIT (internal_fn, gcall *stmt) lhs_base = TREE_OPERAND (lhs_base, 0); reg_lhs = (mem_ref_refers_to_non_mem_p (lhs_base) || non_mem_decl_p (lhs_base)); + /* If this expands to a register and the underlying decl is wrapped in + a MEM_REF that just serves as an access type change expose the decl + if it is of correct size. This avoids a situation as in PR103271 + if the target does not support a direct move to the registers mode. */ + if (reg_lhs + && TREE_CODE (lhs_base) == MEM_REF + && TREE_CODE (TREE_OPERAND (lhs_base, 0)) == ADDR_EXPR + && DECL_P (TREE_OPERAND (TREE_OPERAND (lhs_base, 0), 0)) + && integer_zerop (TREE_OPERAND (lhs_base, 1)) + && tree_fits_uhwi_p (var_size) + && tree_int_cst_equal + (var_size, + DECL_SIZE_UNIT (TREE_OPERAND (TREE_OPERAND (lhs_base, 0), 0)))) + { + lhs = TREE_OPERAND (TREE_OPERAND (lhs_base, 0), 0); + var_type = TREE_TYPE (lhs); + } } if (!reg_lhs) solves the issue. There might be a situation where that's not enough though, I'm giving the above some testing.