On Fri, Jul 21, 2023 at 6:06 AM Andrew Pinski via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This adds a simple match pattern to simplify
> `max<max<a,b>,a>` to `max<a,b>`. Reassociation handles
> this already (r0-77700-ge969dbde29bfd396259357) but
> seems like we should be able to handle this even before
> reassociation.
>
> This fixes part of PR tree-optimization/80574 but more
> work is needed fix it the rest of the way. The original
> testcase there is fixed but the RTL level is what fixes
> it the rest of the way.
>
> OK? Bootstrapped and tested on x86_64-linux-gnu.
>
> gcc/ChangeLog:
>
> * match.pd (minmax<minmax<a,b>,a>->minmax<a,b>): New
> transformation.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.dg/tree-ssa/reassoc-12.c: Disable all of
> the passes that enables match-and-simplify.
maybe turn it into a GIMPLE testcase instead ...
In any case OK.
Thanks,
Richard.
> * gcc.dg/tree-ssa/minmax-23.c: New test.
> ---
> gcc/match.pd | 6 +++++-
> gcc/testsuite/gcc.dg/tree-ssa/minmax-23.c | 22 ++++++++++++++++++++++
> gcc/testsuite/gcc.dg/tree-ssa/reassoc-12.c | 3 ++-
> 3 files changed, 29 insertions(+), 2 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/minmax-23.c
>
> diff --git a/gcc/match.pd b/gcc/match.pd
> index 4dfe92623f7..bfd15d6cd4a 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -3503,7 +3503,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (for minmax (min max)
> (simplify
> (minmax @0 @0)
> - @0))
> + @0)
> +/* max(max(x,y),x) -> max(x,y) */
> + (simplify
> + (minmax:c (minmax:c@2 @0 @1) @0)
> + @2))
> /* For fmin() and fmax(), skip folding when both are sNaN. */
> (for minmax (FMIN_ALL FMAX_ALL)
> (simplify
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-23.c
> b/gcc/testsuite/gcc.dg/tree-ssa/minmax-23.c
> new file mode 100644
> index 00000000000..0b7e51bb97e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-23.c
> @@ -0,0 +1,22 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O1 -fno-tree-reassoc -fdump-tree-optimized" } */
> +
> +
> +#define MAX(a,b) (a)>=(b) ? (a) : (b)
> +
> +#define MIN(a,b) (a)<=(b) ? (a) : (b)
> +
> +int test1(int a, int b)
> +{
> + int d = MAX(a,b);
> + return MAX(a,d);
> +}
> +int test2(int a, int b)
> +{
> + int d = MIN(a,b);
> + return MIN(a,d);
> +}
> +
> +/* We should be optimize these two functions even without reassociation. */
> +/* { dg-final { scan-tree-dump-times "MAX_EXPR " 1 "optimized"} } */
> +/* { dg-final { scan-tree-dump-times "MIN_EXPR " 1 "optimized"} } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/reassoc-12.c
> b/gcc/testsuite/gcc.dg/tree-ssa/reassoc-12.c
> index 9a138ebcf70..2238147de19 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/reassoc-12.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/reassoc-12.c
> @@ -1,5 +1,6 @@
> /* { dg-do compile } */
> -/* { dg-options "-O2 -fdump-tree-reassoc1-details" } */
> +/* Match-and-simplify can handle now MAX<MAX<a,b>,a>->MAX<a,b>, disable all
> of the passes that uses that. */
> +/* { dg-options "-O1 -fdump-tree-reassoc1-details -fno-tree-ccp
> -fno-tree-ccp -fno-tree-forwprop -fno-tree-fre" } */
> int f(int a, int b)
> {
> /* MAX_EXPR <a, a> should cause it to be equivalent to a. */
> --
> 2.31.1
>
