[PATCH] teach phi-opt to produce -(a COND b)

[Richard Guenther]

On Fri, 27 Apr 2012, Paolo Bonzini wrote:

> This patch teaches phiopt to look at phis whose arguments are -1 and 0,
> and produce negated setcc statements.
> 
> Bootstrapped/regtested x86_64-pc-linux-gnu, together with the patch
> for pr53138.  Ok for mainline?

Ok.

Thanks,
Richard.

> Paolo
> 
> 2012-04-27  Paolo Bonzini  <bonzini@gnu.org>
> 
>         * tree-ssa-phiopt.c (conditional_replacement): Replace PHIs
> 	whose arguments are -1 and 0, by negating the result of the
> 	conditional.
> 
> 2012-04-27  Paolo Bonzini  <bonzini@gnu.org>
> 
>         * gcc.c-torture/execute/20120427-2.c: New testcase.
>         * gcc.dg/tree-ssa/phi-opt-10.c: New testcase.
> 
> 
> Index: tree-ssa-phiopt.c
> ===================================================================
> --- tree-ssa-phiopt.c	(revisione 186859)
> +++ tree-ssa-phiopt.c	(copia locale)
> @@ -536,17 +536,21 @@
>    gimple_stmt_iterator gsi;
>    edge true_edge, false_edge;
>    tree new_var, new_var2;
> +  bool neg;
>  
>    /* FIXME: Gimplification of complex type is too hard for now.  */
>    if (TREE_CODE (TREE_TYPE (arg0)) == COMPLEX_TYPE
>        || TREE_CODE (TREE_TYPE (arg1)) == COMPLEX_TYPE)
>      return false;
>  
> -  /* The PHI arguments have the constants 0 and 1, then convert
> -     it to the conditional.  */
> +  /* The PHI arguments have the constants 0 and 1, or 0 and -1, then
> +     convert it to the conditional.  */
>    if ((integer_zerop (arg0) && integer_onep (arg1))
>        || (integer_zerop (arg1) && integer_onep (arg0)))
> -    ;
> +    neg = false;
> +  else if ((integer_zerop (arg0) && integer_all_onesp (arg1))
> +	   || (integer_zerop (arg1) && integer_all_onesp (arg0)))
> +    neg = true;
>    else
>      return false;
>  
> @@ -558,7 +562,7 @@
>       falls through into BB.
>  
>       There is a single PHI node at the join point (BB) and its arguments
> -     are constants (0, 1).
> +     are constants (0, 1) or (0, -1).
>  
>       So, given the condition COND, and the two PHI arguments, we can
>       rewrite this PHI into non-branching code:
> @@ -585,12 +589,20 @@
>       edge so that we know when to invert the condition below.  */
>    extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
>    if ((e0 == true_edge && integer_zerop (arg0))
> -      || (e0 == false_edge && integer_onep (arg0))
> +      || (e0 == false_edge && !integer_zerop (arg0))
>        || (e1 == true_edge && integer_zerop (arg1))
> -      || (e1 == false_edge && integer_onep (arg1)))
> +      || (e1 == false_edge && !integer_zerop (arg1)))
>      cond = fold_build1_loc (gimple_location (stmt),
> -			    TRUTH_NOT_EXPR, TREE_TYPE (cond), cond);
> +                            TRUTH_NOT_EXPR, TREE_TYPE (cond), cond);
>  
> +  if (neg)
> +    {
> +      cond = fold_convert_loc (gimple_location (stmt),
> +                               TREE_TYPE (result), cond);
> +      cond = fold_build1_loc (gimple_location (stmt),
> +                              NEGATE_EXPR, TREE_TYPE (cond), cond);
> +    }
> +
>    /* Insert our new statements at the end of conditional block before the
>       COND_STMT.  */
>    gsi = gsi_for_stmt (stmt);
> Index: testsuite/gcc.c-torture/execute/20120427-2.c
> ===================================================================
> --- testsuite/gcc.c-torture/execute/20120427-2.c	(revisione 0)
> +++ testsuite/gcc.c-torture/execute/20120427-2.c	(revisione 0)
> @@ -0,0 +1,38 @@
> +typedef struct sreal
> +{
> +  unsigned sig;		/* Significant.  */
> +  int exp;		/* Exponent.  */
> +} sreal;
> +
> +sreal_compare (sreal *a, sreal *b)
> +{
> +  if (a->exp > b->exp)
> +    return 1;
> +  if (a->exp < b->exp)
> +    return -1;
> +  if (a->sig > b->sig)
> +    return 1;
> +  if (a->sig < b->sig)
> +    return -1;
> +  return 0;
> +}
> +
> +sreal a[] = {
> +   { 0, 0 },
> +   { 1, 0 },
> +   { 0, 1 },
> +   { 1, 1 }
> +};
> +
> +int main()
> +{
> +  int i, j;
> +  for (i = 0; i <= 3; i++) {
> +    for (j = 0; j < 3; j++) {
> +      if (i < j && sreal_compare(&a[i], &a[j]) != -1) abort();
> +      if (i == j && sreal_compare(&a[i], &a[j]) != 0) abort();
> +      if (i > j && sreal_compare(&a[i], &a[j]) != 1) abort();
> +    }
> +  }
> +  return 0;
> +}
> Index: testsuite/gcc.dg/tree-ssa/phi-opt-10.c
> ===================================================================
> --- testsuite/gcc.dg/tree-ssa/phi-opt-10.c	(revisione 0)
> +++ testsuite/gcc.dg/tree-ssa/phi-opt-10.c	(revisione 0)
> @@ -0,0 +1,11 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -fdump-tree-optimized" } */
> +
> +int nem1_phi (unsigned long a) { return a ? -1 : 0; }
> +int eqm1_phi (unsigned long a) { return a ? 0 : -1; }
> +
> +int spaceship1 (long a) { return a > 0 ? 1 : a < 0 ? -1 : 0; }
> +int spaceship2 (long a) { return a > 0 ? 1 : a == 0 ? 0 : -1; }
> +
> +/* { dg-final { scan-tree-dump-times " = -D" 4 "optimized"} } */
> +/* { dg-final { cleanup-tree-dump "optimized" } } */
> 
> 

-- 
Richard Guenther <rguenther@suse.de>
SUSE / SUSE Labs
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