On Mon, 31 Jul 2017, Jakub Jelinek wrote:
> Hi!
>
> ipa_polymorphic_call_context offset field is in bits (for whatever reason),
> and the following computations can overflow and invoke UB.
> This patch computes it in offset_int instead and punts if there is overflow.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Ok. As said in the PR the machinery should probably use byte offsets
throughout (do we support any target where HWI < size of ptr_mode? That
is, 128bit pointers?)
Richard.
> 2017-07-31 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/81603
> * ipa-polymorphic-call.c
> (ipa_polymorphic_call_context::ipa_polymorphic_call_context): Perform
> offset arithmetic in offset_int, bail out if the resulting bit offset
> doesn't fit into shwi.
>
> --- gcc/ipa-polymorphic-call.c.jj 2017-06-12 12:41:55.000000000 +0200
> +++ gcc/ipa-polymorphic-call.c 2017-07-28 15:02:43.747354910 +0200
> @@ -921,9 +921,13 @@ ipa_polymorphic_call_context::ipa_polymo
> and MEM_REF is meaningless, but we can look futher. */
> if (TREE_CODE (base) == MEM_REF)
> {
> + offset_int o = mem_ref_offset (base) * BITS_PER_UNIT;
> + o += offset;
> + o += offset2;
> + if (!wi::fits_shwi_p (o))
> + break;
> base_pointer = TREE_OPERAND (base, 0);
> - offset
> - += offset2 + mem_ref_offset (base).to_short_addr () *
> BITS_PER_UNIT;
> + offset = o.to_shwi ();
> outer_type = NULL;
> }
> /* We found base object. In this case the outer_type
> @@ -961,10 +965,15 @@ ipa_polymorphic_call_context::ipa_polymo
> break;
> }
> else if (TREE_CODE (base_pointer) == POINTER_PLUS_EXPR
> - && tree_fits_uhwi_p (TREE_OPERAND (base_pointer, 1)))
> + && TREE_CODE (TREE_OPERAND (base_pointer, 1)) == INTEGER_CST)
> {
> - offset += tree_to_shwi (TREE_OPERAND (base_pointer, 1))
> - * BITS_PER_UNIT;
> + offset_int o = offset_int::from (TREE_OPERAND (base_pointer, 1),
> + SIGNED);
> + o *= BITS_PER_UNIT;
> + o += offset;
> + if (!wi::fits_shwi_p (o))
> + break;
> + offset = o.to_shwi ();
> base_pointer = TREE_OPERAND (base_pointer, 0);
> }
> else
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
