[PATCH] optabs: Don't use scalar conversions for vectors [PR93843]

[Richard Biener]

On Wed, Feb 26, 2020 at 12:43 PM Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> In this PR we had a conversion between two integer vectors that
> both had scalar integer modes.  We then tried to implement the
> conversion using the scalar optab for those modes, instead of
> doing the conversion elementwise.
>
> I wondered about letting through scalar modes for single-element
> vectors, but I don't have any evidence that that's useful/necessary,
> so it seemed better to keep things simple.
>
> Tested on aarch64-linux-gnu, armeb-eabi and x86_64-linux-gnu.
> OK to install?

OK.

Thanks,
Richard.

> Richard
>
>
> 2020-02-26  Richard Sandiford  <richard.sandiford@arm.com>
>
> gcc/
>         PR middle-end/93843
>         * optabs-tree.c (supportable_convert_operation): Reject types with
>         scalar modes.
>
> gcc/testsuite/
>         PR middle-end/93843
>         * gcc.dg/vect/pr93843-1.c: New test.
>         * gcc.dg/vect/pr93843-2.c: Likewise.
> ---
>  gcc/optabs-tree.c                     |  5 +++++
>  gcc/testsuite/gcc.dg/vect/pr93843-1.c | 21 +++++++++++++++++++++
>  gcc/testsuite/gcc.dg/vect/pr93843-2.c | 11 +++++++++++
>  3 files changed, 37 insertions(+)
>  create mode 100644 gcc/testsuite/gcc.dg/vect/pr93843-1.c
>  create mode 100644 gcc/testsuite/gcc.dg/vect/pr93843-2.c
>
> diff --git a/gcc/optabs-tree.c b/gcc/optabs-tree.c
> index 3d829c27826..badd30bfda8 100644
> --- a/gcc/optabs-tree.c
> +++ b/gcc/optabs-tree.c
> @@ -284,9 +284,14 @@ supportable_convert_operation (enum tree_code code,
>    machine_mode m1,m2;
>    bool truncp;
>
> +  gcc_assert (VECTOR_TYPE_P (vectype_out) && VECTOR_TYPE_P (vectype_in));
> +
>    m1 = TYPE_MODE (vectype_out);
>    m2 = TYPE_MODE (vectype_in);
>
> +  if (!VECTOR_MODE_P (m1) || !VECTOR_MODE_P (m2))
> +    return false;
> +
>    /* First check if we can done conversion directly.  */
>    if ((code == FIX_TRUNC_EXPR
>         && can_fix_p (m1,m2,TYPE_UNSIGNED (vectype_out), &truncp)
> diff --git a/gcc/testsuite/gcc.dg/vect/pr93843-1.c b/gcc/testsuite/gcc.dg/vect/pr93843-1.c
> new file mode 100644
> index 00000000000..23a79ca4c96
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/pr93843-1.c
> @@ -0,0 +1,21 @@
> +char a;
> +struct S { short b, c; } d;
> +
> +__attribute__((noipa)) void
> +foo (int x)
> +{
> +  if (x != 4)
> +    __builtin_abort ();
> +}
> +
> +int
> +main ()
> +{
> +  short *g = &d.c, *h = &d.b;
> +  char e = 4 - a;
> +  int f;
> +  *h = *g = e;
> +  for (f = 0; f < 2; f++)
> +    foo (d.c);
> +  return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/vect/pr93843-2.c b/gcc/testsuite/gcc.dg/vect/pr93843-2.c
> new file mode 100644
> index 00000000000..5fae3e5be17
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/pr93843-2.c
> @@ -0,0 +1,11 @@
> +char in[2] = {2, 2};
> +short out[2] = {};
> +
> +int
> +main()
> +{
> +  for (int i = 0; i < 2; ++i)
> +    out[i] = in[i];
> +  asm("":::"memory");
> +  if (out[0] != 2) __builtin_abort();
> +}