> The type has BLKmode and size 32. DECL_SIZE of the FIELD_DECL is however 24
> (see it printed as Ada size).
Yes, no wonder since it's a bitfield, i.e. DECL_BIT_FIELD is set.
> The DECL_MODE of the FIELD_DECL is VOIDmode (not printed), while the
> TYPE_MODE of type contained is BLKmode.
No, the DECL_MODE of a FIELD_DECL cannot be VOIDmode, it's SImode (printed).
> Because
> get_inner_reference compute mode based on DECL_MODE:
> if (TREE_CODE (exp) == COMPONENT_REF)
> {
> tree field = TREE_OPERAND (exp, 1);
> size_tree = DECL_SIZE (field);
> if (flag_strict_volatile_bitfields > 0
> && TREE_THIS_VOLATILE (exp)
> && DECL_BIT_FIELD_TYPE (field)
> && DECL_MODE (field) != BLKmode)
> /* Volatile bitfields should be accessed in the mode of the
> field's type, not the mode computed based on the bit
> size. */
> mode = TYPE_MODE (DECL_BIT_FIELD_TYPE (field));
> else if (!DECL_BIT_FIELD (field))
> mode = DECL_MODE (field);
> else if (DECL_MODE (field) == BLKmode)
> blkmode_bitfield = true;
>
> *punsignedp = DECL_UNSIGNED (field);
> }
> We miss the check
> else if (mode == BLKmode)
> and fail to convert the register and die in horrible death.
>
> What is the reason behind this construct? Is that Ada bug?
No, it's a BLKmode bitfield and we have had it for a couple of decades.
> Anyway, the following patch fixes the issue by caring about mode of the
> temporary (which is controled by the type) instead of the mode of the field.
> I am testing it on x86_64-linux now.
>
> Honza
>
> Index: expr.c
> ===================================================================
> --- expr.c (revision 228604)
> +++ expr.c (working copy)
> @@ -6703,7 +6704,7 @@ store_field (rtx target, HOST_WIDE_INT b
> emit_group_store (temp_target, temp, TREE_TYPE (exp), size);
> temp = temp_target;
> }
> - else if (mode == BLKmode)
> + else if (GET_MODE (temp) == BLKmode)
> {
> /* Handle calls that return BLKmode values in registers. */
> if (REG_P (temp) && TREE_CODE (exp) == CALL_EXPR)
This cannot be right, you're short-circuiting the REG_P (temp) test below.
--
Eric Botcazou
