> I see that gimple_canonical_types_compatible_p winds up using > operand_equal_p on expressions which represent the array size and that is > why you need walk_simple_constant_arithmetic and operand_equal_p change.
Not just array size, but also offsets via gimple_compare_field_offset. > I wonder how much code quality we would lose by simply treating only > constantly sized arrays and considering all VLAs of the same type to be > compatible? There are interesting issues WRT C standard and the canonical > types of arrays have just secondary role (i.e. they are hardly used by > themselves and only are used to compute canonical types of structures) and > there may be lower hanging fruits in TBAA improvement than trying to handle > sturctures containng VLAs right. Yes, array types themselves can probably be kludged around, but the main issue in Ada are record types with dynamic offsets, which are first-class citizens. -- Eric Botcazou
