Re: [PATCH] rs6000: Fix wrong align passed to build_aligned_type [PR88309]

[Richard Biener <richard.guenther@gmail.com>]

On Mon, Apr 8, 2024 at 11:22 AM Kewen.Lin <linkw@linux.ibm.com> wrote:
>
> Hi,
>
> As the comments in PR88309 show, there are two oversights
> in rs6000_gimple_fold_builtin that pass align in bytes to
> build_aligned_type but which actually requires align in
> bits, it causes unexpected ICE or hanging in function
> is_miss_rate_acceptable due to zero align_unit value.
>
> This patch is to fix them by converting bytes to bits, add
> an assertion on positive align_unit value and notes function
> build_aligned_type requires align measured in bits in its
> function comment.
>
> Bootstrapped and regtested on x86_64-redhat-linux,
> powerpc64-linux-gnu P8/P9 and powerpc64le-linux-gnu P9 and P10.
>
> Is it (the generic part code change) ok for trunk?

OK

> BR,
> Kewen
> -----
>         PR target/88309
>
> Co-authored-by: Andrew Pinski <quic_apinski@quicinc.com>
>
> gcc/ChangeLog:
>
>         * config/rs6000/rs6000-builtin.cc (rs6000_gimple_fold_builtin): Fix
>         wrong align passed to function build_aligned_type.
>         * tree-ssa-loop-prefetch.cc (is_miss_rate_acceptable): Add an
>         assertion to ensure align_unit should be positive.
>         * tree.cc (build_qualified_type): Update function comments.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.target/powerpc/pr88309.c: New test.
> ---
>  gcc/config/rs6000/rs6000-builtin.cc        |  4 ++--
>  gcc/testsuite/gcc.target/powerpc/pr88309.c | 27 ++++++++++++++++++++++
>  gcc/tree-ssa-loop-prefetch.cc              |  2 ++
>  gcc/tree.cc                                |  3 ++-
>  4 files changed, 33 insertions(+), 3 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/powerpc/pr88309.c
>
> diff --git a/gcc/config/rs6000/rs6000-builtin.cc b/gcc/config/rs6000/rs6000-builtin.cc
> index 6698274031b..e7d6204074c 100644
> --- a/gcc/config/rs6000/rs6000-builtin.cc
> +++ b/gcc/config/rs6000/rs6000-builtin.cc
> @@ -1900,7 +1900,7 @@ rs6000_gimple_fold_builtin (gimple_stmt_iterator *gsi)
>         tree lhs_type = TREE_TYPE (lhs);
>         /* In GIMPLE the type of the MEM_REF specifies the alignment.  The
>           required alignment (power) is 4 bytes regardless of data type.  */
> -       tree align_ltype = build_aligned_type (lhs_type, 4);
> +       tree align_ltype = build_aligned_type (lhs_type, 32);
>         /* POINTER_PLUS_EXPR wants the offset to be of type 'sizetype'.  Create
>            the tree using the value from arg0.  The resulting type will match
>            the type of arg1.  */
> @@ -1944,7 +1944,7 @@ rs6000_gimple_fold_builtin (gimple_stmt_iterator *gsi)
>         tree arg2_type = ptr_type_node;
>         /* In GIMPLE the type of the MEM_REF specifies the alignment.  The
>            required alignment (power) is 4 bytes regardless of data type.  */
> -       tree align_stype = build_aligned_type (arg0_type, 4);
> +       tree align_stype = build_aligned_type (arg0_type, 32);
>         /* POINTER_PLUS_EXPR wants the offset to be of type 'sizetype'.  Create
>            the tree using the value from arg1.  */
>         gimple_seq stmts = NULL;
> diff --git a/gcc/testsuite/gcc.target/powerpc/pr88309.c b/gcc/testsuite/gcc.target/powerpc/pr88309.c
> new file mode 100644
> index 00000000000..c0078cf2b8c
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/pr88309.c
> @@ -0,0 +1,27 @@
> +/* { dg-require-effective-target powerpc_vsx_ok } */
> +/* { dg-options "-mvsx -O2 -fprefetch-loop-arrays" } */
> +
> +/* Verify there is no ICE or hanging.  */
> +
> +#include <altivec.h>
> +
> +void b(float *c, vector float a, vector float, vector float)
> +{
> +  vector float d;
> +  vector char ahbc;
> +  vec_xst(vec_perm(a, d, ahbc), 0, c);
> +}
> +
> +vector float e(vector unsigned);
> +
> +void f() {
> +  float *dst;
> +  int g = 0;
> +  for (;; g += 16) {
> +    vector unsigned m, i;
> +    vector unsigned n, j;
> +    vector unsigned k, l;
> +    b(dst + g * 3, e(m), e(n), e(k));
> +    b(dst + (g + 4) * 3, e(i), e(j), e(l));
> +  }
> +}
> diff --git a/gcc/tree-ssa-loop-prefetch.cc b/gcc/tree-ssa-loop-prefetch.cc
> index bbd98e03254..70073cc4fe4 100644
> --- a/gcc/tree-ssa-loop-prefetch.cc
> +++ b/gcc/tree-ssa-loop-prefetch.cc
> @@ -739,6 +739,8 @@ is_miss_rate_acceptable (unsigned HOST_WIDE_INT cache_line_size,
>    if (delta >= (HOST_WIDE_INT) cache_line_size)
>      return false;
>
> +  gcc_assert (align_unit > 0);
> +
>    miss_positions = 0;
>    total_positions = (cache_line_size / align_unit) * distinct_iters;
>    max_allowed_miss_positions = (ACCEPTABLE_MISS_RATE * total_positions) / 1000;
> diff --git a/gcc/tree.cc b/gcc/tree.cc
> index f801712c9dd..6f8400e6640 100644
> --- a/gcc/tree.cc
> +++ b/gcc/tree.cc
> @@ -5689,7 +5689,8 @@ build_qualified_type (tree type, int type_quals MEM_STAT_DECL)
>    return t;
>  }
>
> -/* Create a variant of type T with alignment ALIGN.  */
> +/* Create a variant of type T with alignment ALIGN which
> +   is measured in bits.  */
>
>  tree
>  build_aligned_type (tree type, unsigned int align)
> --
> 2.43.0