[2/3] PHIOPT: Loop over calling factor_out_conditional_conversion

After adding diamond shaped bb support to factor_out_conditional_conversion,
we can get a case where we have two conversions that needs factored out
and then would have another phiopt happen.
An example is:
```
static inline unsigned long long g(int t)
{
  unsigned t1 = t;
  return t1;
}
unsigned long long f(int c, int d, int e)
{
  unsigned long long t;
  if (c > d)
    t = g(c);
  else
    t = g(d);
  return t;
}
```
In this case we should get a MAX_EXPR in phiopt1 with two casts.
Before this patch, we would just factor out the outer cast and then
wait till phiopt2 to factor out the inner cast.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

gcc/ChangeLog:

	* tree-ssa-phiopt.cc (pass_phiopt::execute): Loop
	over factor_out_conditional_conversion.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/minmax-17.c: New test.
---
 gcc/testsuite/gcc.dg/tree-ssa/minmax-17.c | 21 ++++++++++++++++++
 gcc/tree-ssa-phiopt.cc                    | 27 +++++++++++++----------
 2 files changed, 36 insertions(+), 12 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/minmax-17.c

On Sun, May 7, 2023 at 6:45 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> After adding diamond shaped bb support to factor_out_conditional_conversion,
> we can get a case where we have two conversions that needs factored out
> and then would have another phiopt happen.
> An example is:
> ```
> static inline unsigned long long g(int t)
> {
>   unsigned t1 = t;
>   return t1;
> }
> unsigned long long f(int c, int d, int e)
> {
>   unsigned long long t;
>   if (c > d)
>     t = g(c);
>   else
>     t = g(d);
>   return t;
> }
> ```
> In this case we should get a MAX_EXPR in phiopt1 with two casts.
> Before this patch, we would just factor out the outer cast and then
> wait till phiopt2 to factor out the inner cast.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

OK.

Thanks,
Richard.

> gcc/ChangeLog:
>
>         * tree-ssa-phiopt.cc (pass_phiopt::execute): Loop
>         over factor_out_conditional_conversion.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.dg/tree-ssa/minmax-17.c: New test.
> ---
>  gcc/testsuite/gcc.dg/tree-ssa/minmax-17.c | 21 ++++++++++++++++++
>  gcc/tree-ssa-phiopt.cc                    | 27 +++++++++++++----------
>  2 files changed, 36 insertions(+), 12 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/minmax-17.c
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-17.c b/gcc/testsuite/gcc.dg/tree-ssa/minmax-17.c
> new file mode 100644
> index 00000000000..bd737e6b4cb
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-17.c
> @@ -0,0 +1,21 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O -fdump-tree-phiopt1-details" } */
> +
> +static inline unsigned long long g(int t)
> +{
> +  unsigned t1 = t;
> +  return t1;
> +}
> +unsigned long long test_max(int c, int d, int e)
> +{
> +  unsigned long long t;
> +  if (c > d)
> +    t = g(c);
> +  else
> +    t = g(d);
> +  return t;
> +}
> +
> +/* We should figure out that test_max has an MAX_EXPR in it. */
> +/* { dg-final { scan-tree-dump " = MAX_EXPR" "phiopt1"} } */
> +/* { dg-final { scan-tree-dump-times "changed to factor conversion out from" 2 "phiopt1"} } */
> diff --git a/gcc/tree-ssa-phiopt.cc b/gcc/tree-ssa-phiopt.cc
> index 41fea78dc8d..7fe088b13ff 100644
> --- a/gcc/tree-ssa-phiopt.cc
> +++ b/gcc/tree-ssa-phiopt.cc
> @@ -4085,20 +4085,23 @@ pass_phiopt::execute (function *)
>           node.  */
>        gcc_assert (arg0 != NULL_TREE && arg1 != NULL_TREE);
>
> -      gphi *newphi;
>        if (single_pred_p (bb1)
> -         && EDGE_COUNT (merge->preds) == 2
> -         && (newphi = factor_out_conditional_conversion (e1, e2, phi,
> -                                                         arg0, arg1,
> -                                                         cond_stmt)))
> +         && EDGE_COUNT (merge->preds) == 2)
>         {
> -         phi = newphi;
> -         /* factor_out_conditional_conversion may create a new PHI in
> -            BB2 and eliminate an existing PHI in BB2.  Recompute values
> -            that may be affected by that change.  */
> -         arg0 = gimple_phi_arg_def (phi, e1->dest_idx);
> -         arg1 = gimple_phi_arg_def (phi, e2->dest_idx);
> -         gcc_assert (arg0 != NULL_TREE && arg1 != NULL_TREE);
> +         gphi *newphi = phi;
> +         while (newphi)
> +           {
> +             phi = newphi;
> +             /* factor_out_conditional_conversion may create a new PHI in
> +                BB2 and eliminate an existing PHI in BB2.  Recompute values
> +                that may be affected by that change.  */
> +             arg0 = gimple_phi_arg_def (phi, e1->dest_idx);
> +             arg1 = gimple_phi_arg_def (phi, e2->dest_idx);
> +             gcc_assert (arg0 != NULL_TREE && arg1 != NULL_TREE);
> +             newphi = factor_out_conditional_conversion (e1, e2, phi,
> +                                                         arg0, arg1,
> +                                                         cond_stmt);
> +           }
>         }
>
>        /* Do the replacement of conditional if it can be done.  */
> --
> 2.31.1
>