Re: [PATCH] ivopts: Fix IP_END handling for asm goto [PR107997]

[Richard Biener via Gcc-patches]

> Am 10.12.2022 um 10:40 schrieb Jakub Jelinek via Gcc-patches 
> <gcc-patches@gcc.gnu.org>:
> 
> Hi!
> 
> The following testcase ICEs, because the latch bb ends with
> asm goto which has both fallthrough to the header and one or more labels
> in the header too.  In that case there is just a single edge out of the
> latch block, but still the asm goto is stmt_ends_bb_p statement, yet
> ivopts decides to emit an IV bump at the IP_END position and inserts
> it into the same bb as the asm goto after it, which then fails verification
> (control flow in the middle of bb).
> 
> The following patch fixes it by splitting the latch -> header edge in that
> case and inserting into the newly created bb, where split_edge ->
> redirect_edge_and_branch is able to deal with this case correctly.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

Ok,

Richard 


> 2022-12-10  Jakub Jelinek  <ja...@redhat.com>
> 
>    PR tree-optimization/107997
>    * tree-ssa-loop-ivopts.cc: Include cfganal.h.
>    (create_new_iv) <case IP_END>: If ip_end_pos bb is non-empty and ends
>    with a stmt which ends bb, instead of adding iv update after it split
>    the latch edge and insert iterator into the new latch bb.
> 
>    * gcc.c-torture/compile/pr107997.c: New test.
> 
> --- gcc/tree-ssa-loop-ivopts.cc.jj    2022-12-05 11:10:37.786670489 +0100
> +++ gcc/tree-ssa-loop-ivopts.cc    2022-12-09 14:42:24.722896379 +0100
> @@ -131,6 +131,7 @@ along with GCC; see the file COPYING3.
> #include "builtins.h"
> #include "tree-vectorizer.h"
> #include "dbgcnt.h"
> +#include "cfganal.h"
> 
> /* For lang_hooks.types.type_for_mode.  */
> #include "langhooks.h"
> @@ -7235,6 +7236,12 @@ create_new_iv (struct ivopts_data *data,
>     case IP_END:
>       incr_pos = gsi_last_bb (ip_end_pos (data->current_loop));
>       after = true;
> +      if (!gsi_end_p (incr_pos) && stmt_ends_bb_p (gsi_stmt (incr_pos)))
> +    {
> +      edge e = find_edge (gsi_bb (incr_pos), data->current_loop->header);
> +      incr_pos = gsi_after_labels (split_edge (e));
> +      after = false;
> +    }
>       break;
> 
>     case IP_AFTER_USE:
> --- gcc/testsuite/gcc.c-torture/compile/pr107997.c.jj    2022-12-09 
> 14:45:29.458160841 +0100
> +++ gcc/testsuite/gcc.c-torture/compile/pr107997.c    2022-12-09 
> 14:45:12.290415073 +0100
> @@ -0,0 +1,23 @@
> +/* PR tree-optimization/107997 */
> +
> +int a, b;
> +void bar (int);
> +int baz (void);
> +
> +void *
> +foo (int x, void *y)
> +{
> +  asm goto ("" : : "r" (x || !a) : : l);
> +l:
> +  if (y)
> +    return 0;
> +  bar (b ? b : x);
> +  while (x--)
> +    {
> +      if (!baz ())
> +    baz ();
> +      asm goto ("" : : : : l2);
> +    l2:;
> +    }
> +  return y;
> +}
> 
>    Jakub
>