Re: [PATCH] if-to-switch: fix matching of negative conditions

["Martin Liška" <mliska@suse.cz>]

Whoops, sorry, bad mailing list.

On 12/8/20 2:22 PM, Martin Liška wrote:
> We must be careful which edge we follow for conditions
> of a negative form (index != 2).
> 
> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
> 
> Ready to be installed?
> Thanks,
> Martin
> 
> gcc/ChangeLog:
> 
>      PR tree-optimization/98182
>      * gimple-if-to-switch.cc (pass_if_to_switch::execute): Request
>      chain linkage through false edges only.
> 
> gcc/testsuite/ChangeLog:
> 
>      PR tree-optimization/98182
>      * gcc.dg/tree-ssa/if-to-switch-10.c: New test.
>      * gcc.dg/tree-ssa/pr98182.c: New test.
> ---
>   gcc/gimple-if-to-switch.cc                    |  6 +++
>   .../gcc.dg/tree-ssa/if-to-switch-10.c         | 44 +++++++++++++++++++
>   gcc/testsuite/gcc.dg/tree-ssa/pr98182.c       | 18 ++++++++
>   3 files changed, 68 insertions(+)
>   create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/if-to-switch-10.c
>   create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr98182.c
> 
> diff --git a/gcc/gimple-if-to-switch.cc b/gcc/gimple-if-to-switch.cc
> index 8e1043ae7c4..311f6f6ac97 100644
> --- a/gcc/gimple-if-to-switch.cc
> +++ b/gcc/gimple-if-to-switch.cc
> @@ -522,6 +522,12 @@ pass_if_to_switch::execute (function *fun)
>             if (!info2 || info->m_ranges[0].exp != info2->m_ranges[0].exp)
>           break;
> 
> +          /* It is important that the blocks are linked through FALSE_EDGE.
> +         For an expression of index != VALUE, true and false edges
> +         are flipped.  */
> +          if (info2->m_false_edge != e)
> +        break;
> +
>             chain->m_entries.safe_push (info2);
>             bitmap_set_bit (seen_bbs, e->src->index);
>             info = info2;
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/if-to-switch-10.c b/gcc/testsuite/gcc.dg/tree-ssa/if-to-switch-10.c
> new file mode 100644
> index 00000000000..7b8da1c9f3c
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/if-to-switch-10.c
> @@ -0,0 +1,44 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-iftoswitch-optimized" } */
> +
> +int global;
> +int foo ();
> +
> +int main(int argc, char **argv)
> +{
> +  if (argc != 1)
> +    {
> +      if (argc != 2)
> +    {
> +      if (argc == 3)
> +        {
> +          foo ();
> +          foo ();
> +        }
> +      else if (argc == 4)
> +        {
> +          foo ();
> +        }
> +      else if (argc == 5)
> +        {
> +          global = 2;
> +        }
> +      else
> +        global -= 123;
> +    }
> +      else
> +    {
> +      global += 1;
> +    }
> +    }
> +  else
> +    foo ();
> +
> +
> +  global -= 12;
> +  return 0;
> +}
> +
> +/* { dg-final { scan-tree-dump "Canonical GIMPLE case clusters: 1 2 3 4 5" "iftoswitch" } } */
> +/* { dg-final { scan-tree-dump "Condition chain with \[^\n\r]\* BBs transformed into a switch statement." "iftoswitch" } } */
> +
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr98182.c b/gcc/testsuite/gcc.dg/tree-ssa/pr98182.c
> new file mode 100644
> index 00000000000..29a547e3788
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr98182.c
> @@ -0,0 +1,18 @@
> +/* PR tree-optimization/98182 */
> +/* { dg-do compile } */
> +/* { dg-options "-O1 --param case-values-threshold=1 -fdump-tree-iftoswitch-optimized" } */
> +
> +int global;
> +int foo ();
> +
> +int main(int argc, char **argv)
> +{
> +  if (argc != 1)
> +    __builtin_abort ();
> +  else if (argc != 2)
> +    __builtin_abort ();
> +  else
> +    return 0;
> +}
> +
> +/* { dg-final { scan-tree-dump-not "Condition chain" "iftoswitch" } } */