Re: [PATCH] reassoc: Fold some statements [PR108819]

[Richard Biener via Gcc-patches]

> Am 18.02.2023 um 11:41 schrieb Jakub Jelinek via Gcc-patches 
> <gcc-patches@gcc.gnu.org>:
> 
> Hi!
> 
> This spot in update_ops can replace one or both of the assign operands with
> constants, creating 1 & 1 and similar expressions which can confuse later
> passes until they are folded.  Rather than folding both constants by hand
> and also handling swapping of operands for commutative ops if the first one
> is constant and second one is not, the following patch just uses
> fold_stmt_inplace to do that.  I think we shouldn't fold more than the
> single statement because that could screw up the rest of the pass, we'd have
> to mark all those with uids, visited and the like.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

Ok

Richard 
> 2023-02-18  Jakub Jelinek  <ja...@redhat.com>
> 
>    PR tree-optimization/108819
>    * tree-ssa-reassoc.cc (update_ops): Fold new stmt in place.
> 
>    * gcc.dg/pr108819.c: New test.
> 
> --- gcc/tree-ssa-reassoc.cc.jj    2023-02-16 10:41:11.000000000 +0100
> +++ gcc/tree-ssa-reassoc.cc    2023-02-17 22:43:18.949984553 +0100
> @@ -4687,6 +4687,9 @@ update_ops (tree var, enum tree_code cod
>       gimple_set_uid (g, gimple_uid (stmt));
>       gimple_set_visited (g, true);
>       gsi_insert_before (&gsi, g, GSI_SAME_STMT);
> +      gimple_stmt_iterator gsi2 = gsi_for_stmt (g);
> +      if (fold_stmt_inplace (&gsi2))
> +    update_stmt (g);
>     }
>   return var;
> }
> --- gcc/testsuite/gcc.dg/pr108819.c.jj    2023-02-17 17:50:10.084914418 +0100
> +++ gcc/testsuite/gcc.dg/pr108819.c    2023-02-17 17:48:30.765369964 +0100
> @@ -0,0 +1,19 @@
> +/* PR tree-optimization/108819 */
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -fno-tree-ccp -fno-tree-forwprop" } */
> +
> +int a, b;
> +
> +int
> +main ()
> +{
> +  int d = 1;
> +  for (; b; b++)
> +    if (a < 1)
> +      while (d <= a && a <= 0UL)
> +    {
> +      int *e = &d;
> +      *e = 0;
> +    }
> +  return 0;
> +}
> 
>    Jakub
>