Hi Tom,
Beware of doing something just because the default target hook does it that way.
See https://gcc.gnu.org/pipermail/gcc-patches/2020-June/549128.html
which fixes PR middle-end/90597 by correcting default_vector_alignment to do
it the same way as proposed by this nvptx backend patch.
Many thanks for pointing out that the nvptx problem is PR target/90932.
Roger
--
-----Original Message-----
From: Tom de Vries <tdevr...@suse.de>
Sent: 02 July 2020 13:09
To: Roger Sayle <ro...@nextmovesoftware.com>; gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] nvptx: Fix ICE in nvptx_vector_alignment on
gcc.dg/attr-vector_size.c
On 6/29/20 7:19 PM, Roger Sayle wrote:
> This patch addresses the ICE in gcc.dg/attr-vector_size.c during make
> -k check on nvptx-none. The actual ICE looks like:
>
> testsuite/gcc.dg/attr-vector_size.c:29:1: internal compiler error: in
> tree_to_shwi, at tree.c:7321
> 0xf53bf2 tree_to_shwi(tree_node const*)
> ../../gcc/gcc/tree.c:7321
> 0xff1969 nvptx_vector_alignment
> ../../gcc/gcc/config/nvptx/nvptx.c:5105^M
>
> The problem is that the caller has ensured that TYPE_SIZE(type) is
> representable as an unsigned HOST_WIDE_INT, but nvptx_vector_alignment
> is accessing it as a signed HOST_WIDE_INT which overflows in
> pathological conditions. Amongst those pathological conditions is
> that a TYPE_SIZE of zero can sometimes reach this function, prior to
> an error being emitted. Making sure the result is not less than the
> mode's alignment and not greater than BIGGEST_ALIGNMENT fixes the ICEs, and
> generates the expected compile-time error messages.
>
> Tested on --target=nvptx-none, with a "make" and "make check" which
> results in four fewer unexpected failures and three more expected passes.
> Ok for mainline?
>
>
> 2020-06-29 Roger Sayle <ro...@nextmovesoftware.com>
>
> gcc/ChangeLog:
> * config/nvptx/nvptx.c (nvptx_vector_alignment): Use tree_to_uhwi
> to access TYPE_SIZE (type). Return at least the mode's alignment.
>
> Thanks,
> Roger
> --
> Roger Sayle
> NextMove Software
> Cambridge, UK
>
> diff --git a/gcc/config/nvptx/nvptx.c b/gcc/config/nvptx/nvptx.c index
> e3e84df..bfad91b 100644
> --- a/gcc/config/nvptx/nvptx.c
> +++ b/gcc/config/nvptx/nvptx.c
> @@ -5102,9 +5102,10 @@ static const struct attribute_spec
> nvptx_attribute_table[] = static HOST_WIDE_INT
> nvptx_vector_alignment (const_tree type) {
> - HOST_WIDE_INT align = tree_to_shwi (TYPE_SIZE (type));
> -
> - return MIN (align, BIGGEST_ALIGNMENT);
> + unsigned HOST_WIDE_INT align = tree_to_uhwi (TYPE_SIZE (type));
In the default target hook, we test tree_fits_uhwi_p, so I prefer we do the
same.
> + if (align > BIGGEST_ALIGNMENT)
> + return BIGGEST_ALIGNMENT;
I prefer using MIN to make code easier to read.
> + return MAX (align, GET_MODE_ALIGNMENT (TYPE_MODE (type)));
> }
>
> /* Indicate that INSN cannot be duplicated. */
Also, this is related to a PR, number included in commit log.
As of yet untested updated patch attached.
Thanks,
- Tom
