On Tue, 8 Jan 2019, Jakub Jelinek wrote:
> Hi!
>
> As mentioned in the PR, if a VECTOR_CST is not VECTOR_CST_STEPPED_P,
> it is sufficient to recurse just on all the encoded elt, because if
> the vector has more elts than encoded, all the remaining ones are equal to
> the last one.
> But, if it is stepped, there is the possibility that while the penultimate
> and last encoded elt could be zero or one, the first non-encoded one could
> be two or minus one.
>
> The patch as committed is doing:
> unsigned HOST_WIDE_INT nelts = vector_cst_encoded_nelts (expr);
> if (VECTOR_CST_STEPPED_P (expr)
> && !TYPE_VECTOR_SUBPARTS (TREE_TYPE (expr)).is_constant (&nelts))
> return false;
> so if it is stepped, it updates nelts to the subparts count and thus
> attempts to verify all elts rather than just the encoded ones. But that
> fails because VECTOR_CST_ENCODED_ELT can't really access the non-encoded
> ones. The following patch fixes it by using vector_cst_elt there instead,
> for the encoded elt it just returns VECTOR_CST_ENCODED_ELT immediately and
> for the next value it will likely fail the predicate.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2019-01-08 Jelinek <ja...@redhat.com>
>
> PR middle-end/88758
> * tree.c (initializer_each_zero_or_onep) <case VECTOR_CST>: Use
> vector_cst_elt instead of VECTOR_CST_ENCODED_ELT.
>
> --- gcc/tree.c.jj 2019-01-07 17:59:22.883951743 +0100
> +++ gcc/tree.c 2019-01-08 18:15:01.956087119 +0100
> @@ -11255,7 +11255,7 @@ initializer_each_zero_or_onep (const_tre
>
> for (unsigned int i = 0; i < nelts; ++i)
> {
> - tree elt = VECTOR_CST_ENCODED_ELT (expr, i);
> + tree elt = vector_cst_elt (expr, i);
> if (!initializer_each_zero_or_onep (elt))
> return false;
> }
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
