Thank you for the review Jeff. I don't need to look at the opcode to know the result. The pattern will be matched only in these 4 cases:
X <= MAX(X, Y) -> true
X > MAX(X, Y) -> false
X >= MIN(X, Y) -> true
X < MIN(X, Y) -> false
So, the result will be true for GE_EXPR and LE_EXPR and false otherwise.
I added two test files: one for positive cases and one for negative cases. The
updated patch is attached.
Thanks,
Eugene
-----Original Message-----
From: Jeff Law <l...@redhat.com>
Sent: Monday, November 30, 2020 9:51 AM
To: Eugene Rozenfeld <eugene.rozenf...@microsoft.com>; gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] [tree-optimization] Optimize max/min pattern with
comparison
On 11/25/20 3:04 PM, Eugene Rozenfeld via Gcc-patches wrote:
> Make the following simplifications:
> X <= MAX(X, Y) -> true
> X > MAX(X, Y) -> false
> X >= MIN(X, Y) -> true
> X < MIN(X, Y) -> false
>
> This fixes PR96708.
>
> Tested on x86_64-pc-linux-gnu.
>
> bool f(int a, int b)
> {
> int tmp = (a < b) ? b : a;
> return tmp >= a;
> }
>
> Code without the patch:
>
> vmovd xmm0,edi
> vmovd xmm1,esi
> vpmaxsd xmm0,xmm0,xmm1
> vmovd eax,xmm0
> cmp eax,edi
> setge al
> ret
>
> Code with the patch:
>
> mov eax,0x1
> ret
>
> Eugene
>
> 0001-Optimize-max-pattern-with-comparison.patch
>
> From f6391c197b670b516238ac7707512c1358336520 Mon Sep 17 00:00:00 2001
> From: Eugene Rozenfeld <ero...@microsoft.com>
> Date: Sat, 21 Nov 2020 01:08:50 -0800
> Subject: [PATCH] Optimize max pattern with comparison
>
> Make the following simplifications:
> X <= MAX(X, Y) -> true
> X > MAX(X, Y) -> false
> X >= MIN(X, Y) -> true
> X < MIN(X, Y) -> false
>
> This fixes PR96708.
>
> gcc/
> * match.pd : New patterns.
> ---
> gcc/match.pd | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/gcc/match.pd b/gcc/match.pd index
> cbb4bf0b32d..75237741946 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -2851,6 +2851,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> (cmp (minmax @0 INTEGER_CST@1) INTEGER_CST@2)
> (comb (cmp @0 @2) (cmp @1 @2))))
>
> +/* X <= MAX(X, Y) -> true
> + X > MAX(X, Y) -> false
> + X >= MIN(X, Y) -> true
> + X < MIN(X, Y) -> false */
> +(for minmax (min min max max )
> + cmp (ge lt le gt )
> + (simplify
> + (cmp @0 (minmax:c @0 @1))
> + { constant_boolean_node (cmp == GE_EXPR || cmp == LE_EXPR, type); }
> +))
Don't you need to look at the opcode (MIN vs MAX) vs CMP to know the result?Â
I'd really like to see some tests for the testsuite.   In particular I'd
like to see positive tests where we should apply the optimization and negative
tests when we should not apply the optimization.
I also wonder if there's value in handling this in Ranger and/or DOM. Though
I'd probably wait to see if fixing in match.pd is sufficient to cover the cases
I'm thinking of in Ranger & DOM.
Jeff
0001-Optimize-min-and-max-patterns-with-comparison.patch
Description: 0001-Optimize-min-and-max-patterns-with-comparison.patch
