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Re: [PATCH] Fix simd attribute handling on aarch64
- From: Richard Sandiford <richard dot sandiford at arm dot com>
- To: Steve Ellcey <sellcey at marvell dot com>
- Cc: "gcc-patches\@gcc.gnu.org" <gcc-patches at gcc dot gnu dot org>, "Richard.Earnshaw\@arm.com" <Richard dot Earnshaw at arm dot com>, "Szabolcs.Nagy\@arm.com" <Szabolcs dot Nagy at arm dot com>
- Date: Thu, 18 Jul 2019 08:37:21 +0100
- Subject: Re: [PATCH] Fix simd attribute handling on aarch64
- References: <firstname.lastname@example.org>
Steve Ellcey <email@example.com> writes:
> This patch fixes a bug with SIMD functions on Aarch64. I found it
> while trying to run SPEC with ToT GCC and a glibc that defines vector
> math functions for aarch64. When a function is declared with the simd
> attribute GCC creates vector clones of that function with the return
> and argument types changed to vector types. On Aarch64 the vector
> clones are also marked with the aarch64_vector_pcs attribute to signify
> that they use an alternate calling convention. Due to a bug in GCC the
> non-vector version of the function being cloned was also being marked
> with this attribute.
> Because simd_clone_adjust and expand_simd_clones are calling
> targetm.simd_clone.adjust (which attached the aarch64_vector_pcs
> attribute to the function type) before calling
> simd_clone_adjust_return_type (which created a new distinct type tree
> for the cloned function) the attribute got attached to both the
> 'normal' scalar version of the SIMD function and any vector versions of
> the function. The attribute should only be on the vector versions.
> My fix is to call simd_clone_adjust_return_type and create the new type
> before calling targetm.simd_clone.adjust which adds the attribute. The
> only other platform that this patch could affect is x86 because that is
> the only other platform to use targetm.simd_clone.adjust. I did a
> bootstrap and gcc test run on x86 (as well as Aarch64) and got no
> OK to checkin?
> Steve Ellcey
> 2019-07-17 Steve Ellcey <firstname.lastname@example.org>
> * omp-simd-clone.c (simd_clone_adjust): Call targetm.simd_clone.adjust
> after calling simd_clone_adjust_return_type.
> (expand_simd_clones): Ditto.
It should be pretty easy to add a test for this, now that we use
.variant_pcs to mark symbols with the attribute.
> diff --git a/gcc/omp-simd-clone.c b/gcc/omp-simd-clone.c
> index caa8da3cba5..6a6b439d146 100644
> --- a/gcc/omp-simd-clone.c
> +++ b/gcc/omp-simd-clone.c
> @@ -1164,9 +1164,8 @@ simd_clone_adjust (struct cgraph_node *node)
> push_cfun (DECL_STRUCT_FUNCTION (node->decl));
> - targetm.simd_clone.adjust (node);
> tree retval = simd_clone_adjust_return_type (node);
> + targetm.simd_clone.adjust (node);
> ipa_parm_adjustment_vec adjustments
> = simd_clone_adjust_argument_types (node);
> @@ -1737,8 +1736,8 @@ expand_simd_clones (struct cgraph_node *node)
> simd_clone_adjust (n);
> - targetm.simd_clone.adjust (n);
> simd_clone_adjust_return_type (n);
> + targetm.simd_clone.adjust (n);
> simd_clone_adjust_argument_types (n);
I don't think this is enough, since simd_clone_adjust_return_type
does nothing for functions that return void (e.g. sincos).
I think instead aarch64_simd_clone_adjust should do something like:
TREE_TYPE (node->decl) = build_distinct_type_copy (TREE_TYPE (node->decl));
But maybe that has consequences that I've not thought about...