On Tue, 26 Jan 2016, Martin Jambor wrote:
> Hi,
>
> PR 69355 has revealed that when SRA attempts total scalarization of an
> aggregate but this fails because the user type-casts a scalar field
> and stores into a it a smaller aggregate (and the scalar field is not
> written to, whether directly or as a part of an aggregate store), the
> pass can loose track of unscalarized data there.
>
> I think that this can happen only when violating strict aliasing rules
> but with -fno-strict-aliasing it should work.
>
> Fixed thusly with the patch below (the condition is there to avoid
> detecting padding after aggregate-fields in totally-scalarized
> aggregates as unscalarized data). Bootstrapped and tested on
> x86_64-linux. OK for trunk? And the gcc-5 branch?
Ok.
Thanks,
Richard.
> Thanks,
>
> Martin
>
>
> 2016-01-26 Martin Jambor <mjam...@suse.cz>
>
> PR tree-optimization/69355
> * tree-sra.c (analyze_access_subtree): Correct hole detection when
> total_scalarization fails.
>
> testsuite/
> * gcc.dg/tree-ssa/pr69355.c: New test.
>
> ---
> gcc/testsuite/gcc.dg/tree-ssa/pr69355.c | 44
> +++++++++++++++++++++++++++++++++
> gcc/tree-sra.c | 2 +-
> 2 files changed, 45 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr69355.c
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr69355.c
> b/gcc/testsuite/gcc.dg/tree-ssa/pr69355.c
> new file mode 100644
> index 0000000..f515c21
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr69355.c
> @@ -0,0 +1,44 @@
> +/* { dg-do run } */
> +/* { dg-options "-O -fno-strict-aliasing" } */
> +
> +struct S
> +{
> + void *a;
> + long double b;
> +};
> +
> +struct Z
> +{
> + long long l;
> + short s;
> +} __attribute__((packed));
> +
> +struct S __attribute__((noclone, noinline))
> +foo (void *v, struct Z *z)
> +{
> + struct S t;
> + t.a = v;
> + *(struct Z *) &t.b = *z;
> + return t;
> +}
> +
> +struct Z gz;
> +
> +int
> +main (int argc, char **argv)
> +{
> + struct S s;
> +
> + if (sizeof (long double) < sizeof (struct Z))
> + return 0;
> +
> + gz.l = 0xbeef;
> + gz.s = 0xab;
> +
> + s = foo ((void *) 0, &gz);
> +
> + if ((((struct Z *) &s.b)->l != gz.l)
> + || (((struct Z *) &s.b)->s != gz.s))
> + __builtin_abort ();
> + return 0;
> +}
> diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
> index 740542f..b0e737a 100644
> --- a/gcc/tree-sra.c
> +++ b/gcc/tree-sra.c
> @@ -2421,7 +2421,7 @@ analyze_access_subtree (struct access *root, struct
> access *parent,
>
> if (covered_to < limit)
> hole = true;
> - if (scalar)
> + if (scalar || !allow_replacements)
> root->grp_total_scalarization = 0;
> }
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
