Re: [PATCH] Fix PR70013

[Richard Biener <richard dot guenther at gmail dot com>]

On Fri, Mar 11, 2016 at 11:14 AM, Alan Lawrence <alan.lawrence@arm.com> wrote:
> In this PR, a packed structure containing bitfields, loses part of its constant-pool initialization in SRA.
>
> A fuller explanation is on the PR:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70013#c11. In short we need to
> treat constant-pool entries, like function parameters, as both come
> 'pre-initialized' before the function starts.
>
> Bootstrapped + regtest (gcc, g++) on AArch64; same with addition of Ada, on ARM
> and x86.
>
> OK for trunk?

Ok.

Richard.

> gcc/ChangeLog:
>
>         PR tree-optimization/70013
>         * tree-sra.c (analyze_access_subtree): Also set grp_unscalarized_data
>         for constant-pool entries.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.dg/tree-ssa/sra-20.c: New.
> ---
>  gcc/testsuite/gcc.dg/tree-ssa/sra-20.c | 20 ++++++++++++++++++++
>  gcc/tree-sra.c                         |  3 ++-
>  2 files changed, 22 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/sra-20.c
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/sra-20.c b/gcc/testsuite/gcc.dg/tree-ssa/sra-20.c
> new file mode 100644
> index 0000000..5002c24
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/sra-20.c
> @@ -0,0 +1,20 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -Wall" } */
> +/* PR/70013, SRA of constant-pool loads removes initialization of part of d.  */
> +#pragma pack (1)
> +struct S0 {
> +  unsigned f0 : 17;
> +};
> +
> +int c;
> +
> +int
> +main (int argc, char **argv)
> +{
> +  struct S0 d[] = { { 1 }, { 2 } };
> +  struct S0 e = d[1];
> +
> +  c = d[0].f0;
> +  __builtin_printf ("%x\n", e.f0);
> +  return 0;
> +}
> diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
> index 72157ed..24eac6a 100644
> --- a/gcc/tree-sra.c
> +++ b/gcc/tree-sra.c
> @@ -2427,7 +2427,8 @@ analyze_access_subtree (struct access *root, struct access *parent,
>
>    if (!hole || root->grp_total_scalarization)
>      root->grp_covered = 1;
> -  else if (root->grp_write || TREE_CODE (root->base) == PARM_DECL)
> +  else if (root->grp_write || TREE_CODE (root->base) == PARM_DECL
> +          || constant_decl_p (root->base))
>      root->grp_unscalarized_data = 1; /* not covered and written to */
>    return sth_created;
>  }
> --
> 1.9.1
>