> 1. is easy, see patch below. 2. is much harder - we need to > compute the bit-offset relative to the bitfield group start, > thus in get_bit_range we do > > /* Compute the adjustment to bitpos from the offset of the field > relative to the representative. */ > offset = size_diffop (DECL_FIELD_OFFSET (field), > DECL_FIELD_OFFSET (repr)); > bitoffset = (tree_low_cst (offset, 1) * BITS_PER_UNIT > + tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1) > - tree_low_cst (DECL_FIELD_BIT_OFFSET (repr), 1)); > > and we cannot generally assume offset is zero (well, maybe we could > arrange that though, at least we could assert that for all fields > in a bitfield group DECL_FIELD_OFFSET is the same?).
I'm skeptical. > Any suggestion? Apart from trying to make sure that offset will > be zero by construction? Or by simply not handling bitfields > properly that start at a variable offset? Computing the offset in stor-layout.c and storing it in DECL_INITIAL? > The finish_bitfield_representative hunk implements the fix for 1., > the rest the proposed zero-by-construction solution for 2. Thanks! -- Eric Botcazou
