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Re: [PATCH, rs6000] Gimple folding of splat_uX


On Wed, Dec 6, 2017 at 5:36 PM, Will Schmidt <will_schmidt@vnet.ibm.com> wrote:
> Hi,
> Add support for gimple folding of splat_u{8,16,32}.
> Testcase coverage is primarily handled by existing tests
> testsuite/gcc.target/powerpc/fold-vec-splat_*.c
>
> One new test added to verify we continue to receive
> an 'invalid argument, must be a 5-bit immediate' error
> when we try to splat a non-constant value.
>
> Regtests currently running across assorted power systems.
> OK for trunk with successful results?
>
> Thanks
> -Will
>
> [gcc]
>
> 2017-12-05  Will Schmidt  <will_schmidt@vnet.ibm.com>
>
>         * config/rs6000/rs6000.c (rs6000_gimple_fold_builtin): Add support for
>         early folding of splat_u{8,16,32}.
>
> [testsuite]
>
> 2017-12-05  Will Schmidt  <will_schmidt@vnet.ibm.com>
>
>         * gcc.target/powerpc/fold-vec-splat-misc-invalid.c: New.
>
> diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
> index 045a014..1470557 100644
> --- a/gcc/config/rs6000/rs6000.c
> +++ b/gcc/config/rs6000/rs6000.c
> @@ -16614,10 +16614,33 @@ rs6000_gimple_fold_builtin (gimple_stmt_iterator *gsi)
>      case VSX_BUILTIN_CMPLE_2DI:
>      case VSX_BUILTIN_CMPLE_U2DI:
>        fold_compare_helper (gsi, LE_EXPR, stmt);
>        return true;
>
> +    /* flavors of vec_splat_[us]{8,16,32}.  */
> +    case ALTIVEC_BUILTIN_VSPLTISB:
> +    case ALTIVEC_BUILTIN_VSPLTISH:
> +    case ALTIVEC_BUILTIN_VSPLTISW:
> +      {
> +        arg0 = gimple_call_arg (stmt, 0);
> +        lhs = gimple_call_lhs (stmt);
> +        /* Only fold the vec_splat_*() if arg0 is constant.  */
> +        if ( TREE_CODE (arg0) != INTEGER_CST)
> +          return false;

Is there a reason to not do this for non-constants?  (even not for
float constants?)
You should probably double-check there is a LHS, folding runs before DCE.

> +        tree splat_value = build_int_cst (TREE_TYPE (TREE_TYPE (lhs)),
> +                                          TREE_INT_CST_LOW (arg0));
> +        vec<constructor_elt, va_gc> *ctor_elts = NULL;
> +        unsigned int n_elts = TYPE_VECTOR_SUBPARTS (TREE_TYPE (lhs));
> +        for (unsigned int i=0; i < n_elts ; i++)
> +          CONSTRUCTOR_APPEND_ELT (ctor_elts, NULL_TREE, splat_value);
> +        tree splat_tree = build_constructor (TREE_TYPE (lhs), ctor_elts);

Just use

           tree slat_tree = build_vector_from_val (splat_value);

that would also work for non-constants btw.

> +        g = gimple_build_assign (lhs, splat_tree);
> +        gimple_set_location (g, gimple_location (stmt));
> +        gsi_replace (gsi, g, true);
> +        return true;
> +      }
> +
>      default:
>        if (TARGET_DEBUG_BUILTIN)
>         fprintf (stderr, "gimple builtin intrinsic not matched:%d %s %s\n",
>                  fn_code, fn_name1, fn_name2);
>        break;
> diff --git a/gcc/testsuite/gcc.target/powerpc/fold-vec-splat-misc-invalid.c b/gcc/testsuite/gcc.target/powerpc/fold-vec-splat-misc-invalid.c
> new file mode 100644
> index 0000000..20f5b05
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/powerpc/fold-vec-splat-misc-invalid.c
> @@ -0,0 +1,33 @@
> +/* Verify that overloaded built-ins for vec_splat_s8 and vec_splat_s16
> +   generate errors as expected when we attempt to use invalid inputs.  */
> +
> +/* { dg-do compile } */
> +/* { dg-require-effective-target powerpc_vsx_ok } */
> +/* { dg-options "-mvsx -O2" } */
> +
> +#include <altivec.h>
> +
> +vector signed short
> +testss_1 (unsigned int ui)
> +{
> +  return vec_splat_s16 (ui);/* { dg-error "argument 1 must be a 5-bit signed literal" } */
> +}
> +
> +vector unsigned short
> +testss_2 (signed int si)
> +{
> +  return vec_splat_u16 (si);/* { dg-error "argument 1 must be a 5-bit signed literal" } */
> +}
> +
> +vector signed char
> +testsc_1 (unsigned int ui)
> +{
> +  return vec_splat_s8 (ui); /* { dg-error "argument 1 must be a 5-bit signed literal" } */
> +}
> +
> +vector unsigned char
> +testsc_2 (signed int si)
> +{
> +  return vec_splat_u8 (si);/* { dg-error "argument 1 must be a 5-bit signed literal" } */
> +}
> +
>
>


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