On Wed, Jul 26, 2017 at 04:13:30PM +0200, Richard Biener wrote: > > > You don't seem to use 'size' anywhere. > > > > size I thought about but then decided not to do anything with it. > > There are two cases, one is where there is no ADDR_EXPR and it actually > > a memory reference. > > In that case in theory the size could be used, but it would need > > to be used only for the positive offsets, so like: > > if (off > 0) { > > if (ptr + off + size < ptr) > > runtime_fail; > > } else if (ptr + off > ptr) > > runtime_fail; > > but when it is actually a memory reference, I suppose it will fail > > at runtime anyway when performing such an access, so I think it is > > unnecessary. And for the ADDR_EXPR case, the size is irrelevant, we > > are just taking address of the start of the object. > > > > > You fail to allow other handled components -- for no good reason? > > > > I was trying to have a quick bail out. What other handled components might > > be relevant? I guess IMAGPART_EXPR. For say BIT_FIELD_REF I don't think > > I can > > tree ptr = build1 (ADDR_EXPR, build_pointer_type (TREE_TYPE (t)), t); > > REALPART/IMAGPART_EXPR, yes. You can't address BIT_FIELD_REF > apart those on byte boundary (&vector[4] is eventually folded to > a BIT_FIELD_REF). Similar for VIEW_CONVERT_EXPR, but you are > only building the address on the base? > > > > You fail to handle > > > &MEM[ptr + CST] a canonical gimple invariant way of ptr +p CST, > > > the early out bitpos == 0 will cause non-instrumentation here. > > > > Guess I could use: > > if ((offset == NULL_TREE > > && bitpos == 0 > > && (TREE_CODE (inner) != MEM_REF > > || integer_zerop (TREE_OPERAND (inner, 1)))) > > The rest of the code will handle it. > > Yeah. > > > > > > (I'd just round down in the case of bitpos % BITS_PER_UNIT != 0) > > > > But then the > > tree ptr = build1 (ADDR_EXPR, build_pointer_type (TREE_TYPE (t)), t); > > won't work again. > > Hmm. So instead of building the address on the original tree you > could build the difference based on what get_inner_reference returns > in bitpos/offset?
I'm building both addresses and subtracting them to get the offset. I guess the other option is to compute just the address of the base (i.e. base_addr), and add offset (if non-NULL) plus bitpos / BITS_PER_UNIT plus offset from the MEM_REF (if any). In that case it would probably handle any handled_component_p and bitfields too. Jakub