Re: [PATCH] MATCH: Move `a <= CST1 ? MAX<a, CST2> : a` optimization to match

[Richard Biener <richard.guenther@gmail.com>]

On Mon, May 8, 2023 at 12:21 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This moves the `a <= CST1 ? MAX<a, CST2> : a` optimization
> from phiopt to match. It just adds a new pattern to match.pd.
>
> There is one more change needed before being able to remove
> minmax_replacement from phiopt.
>
> A few notes on the testsuite changes:
> * phi-opt-5.c is now able to optimize at phiopt1 so remove
> the xfail.
> * pr66726-4.c can be optimized during fold before phiopt1
> so need to change the scanning.
> * pr66726-5.c needs two phiopt passes currently to optimize
> to the right thing, it needed 2 phiopt passes before, the cast
> from int to unsigned char is the reason.
> * pr66726-6.c is what the original pr66726-4.c was testing
> before the fold was able to optimize it.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu.

OK.

> gcc/ChangeLog:
>
>         * match.pd (`(a CMP CST1) ? max<a,CST2> : a`): New
>         pattern.
>
> gcc/testsuite/ChangeLog:
>
>         * gcc.dg/tree-ssa/phi-opt-5.c: Remove last xfail.
>         * gcc.dg/tree-ssa/pr66726-4.c: Change how scanning
>         works.
>         * gcc.dg/tree-ssa/pr66726-5.c: New test.
>         * gcc.dg/tree-ssa/pr66726-6.c: New test.
> ---
>  gcc/match.pd                              | 18 +++++++++++++++
>  gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c |  2 +-
>  gcc/testsuite/gcc.dg/tree-ssa/pr66726-4.c |  5 +++-
>  gcc/testsuite/gcc.dg/tree-ssa/pr66726-5.c | 28 +++++++++++++++++++++++
>  gcc/testsuite/gcc.dg/tree-ssa/pr66726-6.c | 17 ++++++++++++++
>  5 files changed, 68 insertions(+), 2 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr66726-5.c
>  create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr66726-6.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index ceae1c34abc..a55ede838cd 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -4954,6 +4954,24 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>       (if (code == MAX_EXPR)
>        (minmax (max @1 @2) @4)))))))
>
> +/* Optimize (a CMP CST1) ? max<a,CST2> : a */
> +(for cmp    (gt  ge  lt  le)
> +     minmax (min min max max)
> + (simplify
> +  (cond (cmp @0 @1) (minmax:c@2 @0 @3) @4)
> +   (with
> +    {
> +      tree_code code = minmax_from_comparison (cmp, @0, @1, @0, @4);
> +    }
> +    (if ((cmp == LT_EXPR || cmp == LE_EXPR)
> +        && code == MIN_EXPR
> +         && integer_nonzerop (fold_build2 (LE_EXPR, boolean_type_node, @3, @1)))
> +     (min @2 @4)
> +     (if ((cmp == GT_EXPR || cmp == GE_EXPR)
> +         && code == MAX_EXPR
> +          && integer_nonzerop (fold_build2 (GE_EXPR, boolean_type_node, @3, @1)))
> +      (max @2 @4))))))
> +
>  /* X != C1 ? -X : C2 simplifies to -X when -C1 == C2.  */
>  (simplify
>   (cond (ne @0 INTEGER_CST@1) (negate@3 @0) INTEGER_CST@2)
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c
> index 5f78a1ba6dc..e78d9d8b83d 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/phi-opt-5.c
> @@ -39,7 +39,7 @@ float repl2 (float vary)
>
>  /* phiopt1 confused by predictors.  */
>  /* { dg-final { scan-tree-dump "vary.*MAX_EXPR.*0\\.0" "phiopt1" } } */
> -/* { dg-final { scan-tree-dump "vary.*MIN_EXPR.*1\\.0" "phiopt1" { xfail *-*-* } } } */
> +/* { dg-final { scan-tree-dump "vary.*MIN_EXPR.*1\\.0" "phiopt1" } } */
>  /* { dg-final { scan-tree-dump "vary.*MAX_EXPR.*0\\.0" "phiopt2"} } */
>  /* { dg-final { scan-tree-dump "vary.*MIN_EXPR.*1\\.0" "phiopt2"} } */
>
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr66726-4.c b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-4.c
> index 4e43522f3a3..930ad5fb79f 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/pr66726-4.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-4.c
> @@ -9,4 +9,7 @@ foo (unsigned char *p, int i)
>    *p = SAT (i);
>  }
>
> -/* { dg-final { scan-tree-dump-times "COND_EXPR .*and PHI .*converted to straightline code" 1 "phiopt1" } } */
> +/* fold could optimize SAT before phiopt1 so only match on the
> +   MIN/MAX here.  */
> +/* { dg-final { scan-tree-dump-times "= MIN_EXPR" 1 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "= MAX_EXPR" 1 "phiopt1" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr66726-5.c b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-5.c
> new file mode 100644
> index 00000000000..4b5066cdb6b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-5.c
> @@ -0,0 +1,28 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-phiopt1-details -fdump-tree-phiopt2-details -fdump-tree-optimized" } */
> +
> +#define SAT(x) (x < 0 ? 0 : (x > 255 ? 255 : x))
> +
> +unsigned char
> +foo (unsigned char *p, int i)
> +{
> +  if (i < 0)
> +    return 0;
> +  {
> +    int t;
> +    if (i > 255)
> +      t = 255;
> +    else
> +      t = i;
> +    return t;
> +  }
> +}
> +
> +/* Because of the way PHIOPT works, it only does the merging of BBs after it is done so we get the case were we can't
> +   optimize the above until phiopt2 right now.  */
> +/* { dg-final { scan-tree-dump-times "COND_EXPR .*and PHI .*converted to straightline code" 2 "phiopt1" { xfail *-*-* } } } */
> +/* { dg-final { scan-tree-dump-times "COND_EXPR .*and PHI .*converted to straightline code" 0 "phiopt2" { xfail *-*-* } } } */
> +/* { dg-final { scan-tree-dump-times "= MIN_EXPR" 1 "phiopt1" } } */
> +/* { dg-final { scan-tree-dump-times "= MAX_EXPR" 1 "phiopt1" { xfail *-*-* } } } */
> +/* { dg-final { scan-tree-dump-times "= MIN_EXPR" 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "= MAX_EXPR" 1 "optimized"  } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr66726-6.c b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-6.c
> new file mode 100644
> index 00000000000..5c6b4992608
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/pr66726-6.c
> @@ -0,0 +1,17 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-phiopt1-details" } */
> +
> +
> +unsigned char
> +foo1 (unsigned char *p, int i)
> +{
> +  if (i < 0)
> +    return 0;
> +  {
> +    int t = i > 255 ? 255 : i;
> +    return t;
> +  }
> +}
> +/* testing to see if moving the cast out of the conditional. */
> +
> +/* { dg-final { scan-tree-dump-times "COND_EXPR .*and PHI .*converted to straightline code" 1 "phiopt1" } } */
> --
> 2.31.1
>