[PATCH] VEC_COND_EXPR: fix ICE in gimple_expand_vec_cond_expr

Richard Biener richard.guenther@gmail.com
Mon Aug 31 08:01:22 GMT 2020


On Fri, Aug 28, 2020 at 4:18 PM Martin Liška <mliska@suse.cz> wrote:
>
> Hey.
>
> The patch is about VEC_COND_EXP comparison of a SSA_NAME with a constant
> that is artifact of -fno-tree-ccp.
>
> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
>
> Ready to be installed?

Err, no - we shouldn't do this at RTL expansion time.  And piecewise
expansion is gross - in this the case is a constant boolean vector IIRC
(not sure what mode?) and ISEL only tries matching up with
a comparison operand.  But ISEL should also handle matching up with
a constant "boolean vector" ("boolean vector"s are artifacts of VEC_COND_EXPRs,
but some targets allow bitwise arithmetic on them...).  So the compensation
needs to happen in ISEL, recognizing

 _1 = {0}
 _2 = _1 ? ...;

as

 _2 = .VCOND (0 == 0, ...)

or so.

Richard.

> Thanks,
> Martin
>
> gcc/ChangeLog:
>
>         PR tree-optimization/96466
>         * gimple-fold.c (expand_cmp_piecewise): New.
>         * gimple-fold.h (nunits_for_known_piecewise_op): New.
>         (expand_cmp_piecewise): Moved from ...
>         * tree-vect-generic.c (expand_vector_comparison): ... here.
>         (nunits_for_known_piecewise_op): Moved to gimple-fold.h.
>         * gimple-isel.cc (gimple_expand_vec_cond_expr): Use
>         expand_cmp_piecewise fallback for constants.
>
> gcc/testsuite/ChangeLog:
>
>         PR tree-optimization/96466
>         * gcc.dg/vect/pr96466.c: New test.
> ---
>   gcc/gimple-fold.c                   | 28 ++++++++++++++++++++
>   gcc/gimple-fold.h                   | 14 ++++++++++
>   gcc/gimple-isel.cc                  | 10 ++++---
>   gcc/testsuite/gcc.dg/vect/pr96466.c | 18 +++++++++++++
>   gcc/tree-vect-generic.c             | 41 ++---------------------------
>   5 files changed, 69 insertions(+), 42 deletions(-)
>   create mode 100644 gcc/testsuite/gcc.dg/vect/pr96466.c
>
> diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
> index dcc1b56a273..86d5d0ed7d8 100644
> --- a/gcc/gimple-fold.c
> +++ b/gcc/gimple-fold.c
> @@ -8056,3 +8056,31 @@ gimple_stmt_integer_valued_real_p (gimple *stmt, int depth)
>         return false;
>       }
>   }
> +
> +tree
> +expand_cmp_piecewise (gimple_stmt_iterator *gsi, tree type, tree op0, tree op1)
> +{
> +  tree inner_type = TREE_TYPE (TREE_TYPE (op0));
> +  tree part_width = vector_element_bits_tree (TREE_TYPE (op0));
> +  tree index = bitsize_int (0);
> +  int nunits = nunits_for_known_piecewise_op (TREE_TYPE (op0));
> +  int prec = GET_MODE_PRECISION (SCALAR_TYPE_MODE (type));
> +  tree ret_type = build_nonstandard_integer_type (prec, 1);
> +  tree ret_inner_type = boolean_type_node;
> +  int i;
> +  tree t = build_zero_cst (ret_type);
> +
> +  if (TYPE_PRECISION (ret_inner_type) != 1)
> +    ret_inner_type = build_nonstandard_integer_type (1, 1);
> +  for (i = 0; i < nunits;
> +       i++, index = int_const_binop (PLUS_EXPR, index, part_width))
> +    {
> +      tree a = tree_vec_extract (gsi, inner_type, op0, part_width, index);
> +      tree b = tree_vec_extract (gsi, inner_type, op1, part_width, index);
> +      tree result = gimplify_build2 (gsi, NE_EXPR, ret_inner_type, a, b);
> +      t = gimplify_build3 (gsi, BIT_INSERT_EXPR, ret_type, t, result,
> +                          bitsize_int (i));
> +    }
> +
> +  return gimplify_build1 (gsi, VIEW_CONVERT_EXPR, type, t);
> +}
> diff --git a/gcc/gimple-fold.h b/gcc/gimple-fold.h
> index 0ed1d1ffe83..7e843b34f53 100644
> --- a/gcc/gimple-fold.h
> +++ b/gcc/gimple-fold.h
> @@ -147,6 +147,20 @@ gimple_build_vector (gimple_seq *seq, tree_vector_builder *builder)
>   extern bool gimple_stmt_nonnegative_warnv_p (gimple *, bool *, int = 0);
>   extern bool gimple_stmt_integer_valued_real_p (gimple *, int = 0);
>
> +/* Return the number of elements in a vector type TYPE that we have
> +   already decided needs to be expanded piecewise.  We don't support
> +   this kind of expansion for variable-length vectors, since we should
> +   always check for target support before introducing uses of those.  */
> +
> +static inline unsigned int
> +nunits_for_known_piecewise_op (const_tree type)
> +{
> +  return TYPE_VECTOR_SUBPARTS (type).to_constant ();
> +}
> +
> +extern tree expand_cmp_piecewise (gimple_stmt_iterator *gsi, tree lhs,
> +                                 tree op0, tree op1);
> +
>   /* In gimple-match.c.  */
>   extern tree gimple_simplify (enum tree_code, tree, tree,
>                              gimple_seq *, tree (*)(tree));
> diff --git a/gcc/gimple-isel.cc b/gcc/gimple-isel.cc
> index b330cf4c20e..32e3bc31f7f 100644
> --- a/gcc/gimple-isel.cc
> +++ b/gcc/gimple-isel.cc
> @@ -33,8 +33,8 @@ along with GCC; see the file COPYING3.  If not see
>   #include "gimplify-me.h"
>   #include "gimplify.h"
>   #include "tree-cfg.h"
> -#include "bitmap.h"
>   #include "tree-ssa-dce.h"
> +#include "gimple-fold.h"
>
>   /* Expand all VEC_COND_EXPR gimple assignments into calls to internal
>      function based on type of selected expansion.  */
> @@ -119,8 +119,12 @@ gimple_expand_vec_cond_expr (gimple_stmt_iterator *gsi,
>         /* Fake op0 < 0.  */
>         else
>         {
> -         gcc_assert (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (op0)))
> -                     == MODE_VECTOR_INT);
> +         if (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (op0))) != MODE_VECTOR_INT)
> +           {
> +             tree t = expand_cmp_piecewise (gsi, TREE_TYPE (lhs), op0, op1);
> +             return gimple_build_assign (lhs, NOP_EXPR, t);
> +           }
> +
>           op0a = op0;
>           op0b = build_zero_cst (TREE_TYPE (op0));
>           tcode = LT_EXPR;
> diff --git a/gcc/testsuite/gcc.dg/vect/pr96466.c b/gcc/testsuite/gcc.dg/vect/pr96466.c
> new file mode 100644
> index 00000000000..8cca5e12ff2
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/vect/pr96466.c
> @@ -0,0 +1,18 @@
> +/* PR tree-optimization/96466 */
> +/* { dg-do compile } */
> +/* { dg-options "-Og -finline-functions-called-once -fno-tree-ccp" } */
> +
> +typedef unsigned long __attribute__ ((__vector_size__ (8))) V;
> +
> +V
> +bar (unsigned long x, V v)
> +{
> +  v &= x >= v;
> +  return (V) v;
> +}
> +
> +V
> +foo (void)
> +{
> +  return bar (5, (V) 4441221375);
> +}
> diff --git a/gcc/tree-vect-generic.c b/gcc/tree-vect-generic.c
> index 6d5d65195ae..b01aa301baa 100644
> --- a/gcc/tree-vect-generic.c
> +++ b/gcc/tree-vect-generic.c
> @@ -42,20 +42,11 @@ along with GCC; see the file COPYING3.  If not see
>   #include "insn-config.h"
>   #include "tree-ssa-dce.h"
>   #include "recog.h"            /* FIXME: for insn_data */
> +#include "gimple-fold.h"
>
>
>   static void expand_vector_operations_1 (gimple_stmt_iterator *, bitmap);
>
> -/* Return the number of elements in a vector type TYPE that we have
> -   already decided needs to be expanded piecewise.  We don't support
> -   this kind of expansion for variable-length vectors, since we should
> -   always check for target support before introducing uses of those.  */
> -static unsigned int
> -nunits_for_known_piecewise_op (const_tree type)
> -{
> -  return TYPE_VECTOR_SUBPARTS (type).to_constant ();
> -}
> -
>   /* Return true if TYPE1 has more elements than TYPE2, where either
>      type may be a vector or a scalar.  */
>
> @@ -427,35 +418,7 @@ expand_vector_comparison (gimple_stmt_iterator *gsi, tree type, tree op0,
>                        TYPE_VECTOR_SUBPARTS (type)
>                        * GET_MODE_BITSIZE (SCALAR_TYPE_MODE
>                                                 (TREE_TYPE (type)))))
> -       {
> -         tree inner_type = TREE_TYPE (TREE_TYPE (op0));
> -         tree part_width = vector_element_bits_tree (TREE_TYPE (op0));
> -         tree index = bitsize_int (0);
> -         int nunits = nunits_for_known_piecewise_op (TREE_TYPE (op0));
> -         int prec = GET_MODE_PRECISION (SCALAR_TYPE_MODE (type));
> -         tree ret_type = build_nonstandard_integer_type (prec, 1);
> -         tree ret_inner_type = boolean_type_node;
> -         int i;
> -         location_t loc = gimple_location (gsi_stmt (*gsi));
> -         t = build_zero_cst (ret_type);
> -
> -         if (TYPE_PRECISION (ret_inner_type) != 1)
> -           ret_inner_type = build_nonstandard_integer_type (1, 1);
> -         warning_at (loc, OPT_Wvector_operation_performance,
> -                     "vector operation will be expanded piecewise");
> -         for (i = 0; i < nunits;
> -              i++, index = int_const_binop (PLUS_EXPR, index, part_width))
> -           {
> -             tree a = tree_vec_extract (gsi, inner_type, op0, part_width,
> -                                        index);
> -             tree b = tree_vec_extract (gsi, inner_type, op1, part_width,
> -                                        index);
> -             tree result = gimplify_build2 (gsi, code, ret_inner_type, a, b);
> -             t = gimplify_build3 (gsi, BIT_INSERT_EXPR, ret_type, t, result,
> -                                  bitsize_int (i));
> -           }
> -         t = gimplify_build1 (gsi, VIEW_CONVERT_EXPR, type, t);
> -       }
> +       t = expand_cmp_piecewise (gsi, type, op0, op1);
>         else
>         t = expand_vector_piecewise (gsi, do_compare, type,
>                                      TREE_TYPE (TREE_TYPE (op0)), op0, op1,
> --
> 2.28.0
>


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