RE: [PATCH v4] [tree-optimization/110279] Consider FMA in get_reassociation_width

[Di Zhao OS <dizhao@os.amperecomputing.com>]

[-- Attachment #1: Type: text/plain, Size: 6905 bytes --]

Updated the fix in attachment.

Is it OK for trunk?

Tested on aarch64-unknown-linux-gnu and x86_64-pc-linux-gnu.

Thanks,
Di Zhao

> -----Original Message-----
> From: Di Zhao OS <dizhao@os.amperecomputing.com>
> Sent: Sunday, December 17, 2023 8:31 PM
> To: Thomas Schwinge <thomas@codesourcery.com>; gcc-patches@gcc.gnu.org
> Cc: Richard Biener <richard.guenther@gmail.com>
> Subject: RE: [PATCH v4] [tree-optimization/110279] Consider FMA in
> get_reassociation_width
> 
> Hello Thomas,
> 
> > -----Original Message-----
> > From: Thomas Schwinge <thomas@codesourcery.com>
> > Sent: Friday, December 15, 2023 5:46 PM
> > To: Di Zhao OS <dizhao@os.amperecomputing.com>; gcc-patches@gcc.gnu.org
> > Cc: Richard Biener <richard.guenther@gmail.com>
> > Subject: RE: [PATCH v4] [tree-optimization/110279] Consider FMA in
> > get_reassociation_width
> >
> > Hi!
> >
> > On 2023-12-13T08:14:28+0000, Di Zhao OS <dizhao@os.amperecomputing.com>
> wrote:
> > > --- /dev/null
> > > +++ b/gcc/testsuite/gcc.dg/pr110279-2.c
> > > @@ -0,0 +1,41 @@
> > > +/* PR tree-optimization/110279 */
> > > +/* { dg-do compile } */
> > > +/* { dg-options "-Ofast --param tree-reassoc-width=4 --param fully-
> > pipelined-fma=1 -fdump-tree-reassoc2-details -fdump-tree-optimized" } */
> > > +/* { dg-additional-options "-march=armv8.2-a" { target aarch64-*-* } } */
> > > +
> > > +#define LOOP_COUNT 800000000
> > > +typedef double data_e;
> > > +
> > > +#include <stdio.h>
> > > +
> > > +__attribute_noinline__ data_e
> > > +foo (data_e in)
> >
> > Pushed to master branch commit 91e9e8faea4086b3b8aef2355fc12c1559d425f6
> > "Fix 'gcc.dg/pr110279-2.c' syntax error due to '__attribute_noinline__'",
> > see attached.
> >
> > However:
> >
> > > +{
> > > +  data_e a1, a2, a3, a4;
> > > +  data_e tmp, result = 0;
> > > +  a1 = in + 0.1;
> > > +  a2 = in * 0.1;
> > > +  a3 = in + 0.01;
> > > +  a4 = in * 0.59;
> > > +
> > > +  data_e result2 = 0;
> > > +
> > > +  for (int ic = 0; ic < LOOP_COUNT; ic++)
> > > +    {
> > > +      /* Test that a complete FMA chain with length=4 is not broken.  */
> > > +      tmp = a1 + a2 * a2 + a3 * a3 + a4 * a4 ;
> > > +      result += tmp - ic;
> > > +      result2 = result2 / 2 - tmp;
> > > +
> > > +      a1 += 0.91;
> > > +      a2 += 0.1;
> > > +      a3 -= 0.01;
> > > +      a4 -= 0.89;
> > > +
> > > +    }
> > > +
> > > +  return result + result2;
> > > +}
> > > +
> > > +/* { dg-final { scan-tree-dump-not "was chosen for reassociation"
> > "reassoc2"} } */
> > > +/* { dg-final { scan-tree-dump-times {\.FMA } 3 "optimized"} } */
> 
> Thank you for the fix.
> 
> > ..., I still see these latter two tree dump scans FAIL, for GCN:
> >
> >     $ grep -C2 'was chosen for reassociation' pr110279-2.c.197t.reassoc2
> >       2 *: a3_40
> >       2 *: a2_39
> >     Width = 4 was chosen for reassociation
> >     Transforming _15 = powmult_1 + powmult_3;
> >      into _63 = powmult_1 + a1_38;
> >     $ grep -F .FMA pr110279-2.c.265t.optimized
> >       _63 = .FMA (a2_39, a2_39, a1_38);
> >       _64 = .FMA (a3_40, a3_40, powmult_5);
> >
> > ..., nvptx:
> >
> >     $ grep -C2 'was chosen for reassociation' pr110279-2.c.197t.reassoc2
> >       2 *: a3_40
> >       2 *: a2_39
> >     Width = 4 was chosen for reassociation
> >     Transforming _15 = powmult_1 + powmult_3;
> >      into _63 = powmult_1 + a1_38;
> >     $ grep -F .FMA pr110279-2.c.265t.optimized
> >       _63 = .FMA (a2_39, a2_39, a1_38);
> >       _64 = .FMA (a3_40, a3_40, powmult_5);
> 
> For these 2 targets, the reassoc_width for FMUL is 1 (default value),
> While the testcase assumes that to be 4. The bug was introduced when I
> updated the patch but forgot to update the testcase.
> 
> > ..., but also x86_64-pc-linux-gnu:
> >
> >     $  grep -C2 'was chosen for reassociation' pr110279-2.c.197t.reassoc2
> >       2 *: a3_40
> >       2 *: a2_39
> >     Width = 2 was chosen for reassociation
> >     Transforming _15 = powmult_1 + powmult_3;
> >      into _63 = powmult_1 + powmult_3;
> >     $ grep -cF .FMA pr110279-2.c.265t.optimized
> >     0
> 
> For x86_64 this needs "-mfma". Sorry the compile options missed that.
> Can the change below fix these issues? I moved them into
> testsuite/gcc.target/aarch64, since they rely on tunings.
> 
> Tested on aarch64-unknown-linux-gnu.
> 
> >
> > Grüße
> >  Thomas
> >
> >
> > -----------------
> > Siemens Electronic Design Automation GmbH; Anschrift: Arnulfstraße 201,
> 80634
> > München; Gesellschaft mit beschränkter Haftung; Geschäftsführer: Thomas
> > Heurung, Frank Thürauf; Sitz der Gesellschaft: München; Registergericht
> > München, HRB 106955
> 
> Thanks,
> Di Zhao
> 
> ---
>  gcc/testsuite/{gcc.dg => gcc.target/aarch64}/pr110279-1.c | 3 +--
>  gcc/testsuite/{gcc.dg => gcc.target/aarch64}/pr110279-2.c | 3 +--
>  2 files changed, 2 insertions(+), 4 deletions(-)
>  rename gcc/testsuite/{gcc.dg => gcc.target/aarch64}/pr110279-1.c (83%)
>  rename gcc/testsuite/{gcc.dg => gcc.target/aarch64}/pr110279-2.c (78%)
> 
> diff --git a/gcc/testsuite/gcc.dg/pr110279-1.c
> b/gcc/testsuite/gcc.target/aarch64/pr110279-1.c
> similarity index 83%
> rename from gcc/testsuite/gcc.dg/pr110279-1.c
> rename to gcc/testsuite/gcc.target/aarch64/pr110279-1.c
> index f25b6aec967..97d693f56a5 100644
> --- a/gcc/testsuite/gcc.dg/pr110279-1.c
> +++ b/gcc/testsuite/gcc.target/aarch64/pr110279-1.c
> @@ -1,6 +1,5 @@
>  /* { dg-do compile } */
> -/* { dg-options "-Ofast --param avoid-fma-max-bits=512 --param tree-reassoc-
> width=4 -fdump-tree-widening_mul-details" } */
> -/* { dg-additional-options "-march=armv8.2-a" { target aarch64-*-* } } */
> +/* { dg-options "-Ofast -mcpu=generic --param avoid-fma-max-bits=512 --param
> tree-reassoc-width=4 -fdump-tree-widening_mul-details" } */
> 
>  #define LOOP_COUNT 800000000
>  typedef double data_e;
> diff --git a/gcc/testsuite/gcc.dg/pr110279-2.c
> b/gcc/testsuite/gcc.target/aarch64/pr110279-2.c
> similarity index 78%
> rename from gcc/testsuite/gcc.dg/pr110279-2.c
> rename to gcc/testsuite/gcc.target/aarch64/pr110279-2.c
> index b6b69969c6b..a88cb361fdc 100644
> --- a/gcc/testsuite/gcc.dg/pr110279-2.c
> +++ b/gcc/testsuite/gcc.target/aarch64/pr110279-2.c
> @@ -1,7 +1,6 @@
>  /* PR tree-optimization/110279 */
>  /* { dg-do compile } */
> -/* { dg-options "-Ofast --param tree-reassoc-width=4 --param fully-pipelined-
> fma=1 -fdump-tree-reassoc2-details -fdump-tree-optimized" } */
> -/* { dg-additional-options "-march=armv8.2-a" { target aarch64-*-* } } */
> +/* { dg-options "-Ofast -mcpu=generic --param tree-reassoc-width=4 --param
> fully-pipelined-fma=1 -fdump-tree-reassoc2-details -fdump-tree-optimized" } */
> 
>  #define LOOP_COUNT 800000000
>  typedef double data_e;
> --
> 2.25.1

[-- Attachment #2: 0001-Fix-compile-options-of-pr110279-1.c-and-pr110279-2.c.patch --]
[-- Type: application/octet-stream, Size: 2606 bytes --]

From 216976028c4d5d66b1666fe501abb869d480c214 Mon Sep 17 00:00:00 2001
From: "dzhao.ampere" <di.zhao@amperecomputing.com>
Date: Sun, 17 Dec 2023 19:33:42 +0800
Subject: [PATCH] Fix compile options of pr110279-1.c and pr110279-2.c

The two testcases are for targets that support FMA. And
pr110279-2.c assumes reassoc_width of FMUL to be 4.

This patch adds missing options, to fix regression test failures
on nvptx/GCN (default reassoc_width of FMUL is 1) and x86_64
(need "-mfma").

gcc/testsuite/ChangeLog:

        * gcc.dg/pr110279-1.c: Add "-mcpu=generic" for aarch64; add
	"-mfma" for x86_64.
        * gcc.dg/pr110279-2.c: Replace "-march=armv8.2-a" with
	"-mcpu=generic"; limit the check to be on aarch64.
---
 gcc/testsuite/gcc.dg/pr110279-1.c | 3 ++-
 gcc/testsuite/gcc.dg/pr110279-2.c | 6 +++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/pr110279-1.c b/gcc/testsuite/gcc.dg/pr110279-1.c
index f25b6aec967..c2737418afe 100644
--- a/gcc/testsuite/gcc.dg/pr110279-1.c
+++ b/gcc/testsuite/gcc.dg/pr110279-1.c
@@ -1,6 +1,7 @@
 /* { dg-do compile } */
 /* { dg-options "-Ofast --param avoid-fma-max-bits=512 --param tree-reassoc-width=4 -fdump-tree-widening_mul-details" } */
-/* { dg-additional-options "-march=armv8.2-a" { target aarch64-*-* } } */
+/* { dg-additional-options "-mfma" { target i?86-*-* x86_64-*-* } } */
+/* { dg-additional-options "-mcpu=generic" { target aarch64*-*-* } } */
 
 #define LOOP_COUNT 800000000
 typedef double data_e;
diff --git a/gcc/testsuite/gcc.dg/pr110279-2.c b/gcc/testsuite/gcc.dg/pr110279-2.c
index b6b69969c6b..135e64882d1 100644
--- a/gcc/testsuite/gcc.dg/pr110279-2.c
+++ b/gcc/testsuite/gcc.dg/pr110279-2.c
@@ -1,7 +1,7 @@
 /* PR tree-optimization/110279 */
 /* { dg-do compile } */
 /* { dg-options "-Ofast --param tree-reassoc-width=4 --param fully-pipelined-fma=1 -fdump-tree-reassoc2-details -fdump-tree-optimized" } */
-/* { dg-additional-options "-march=armv8.2-a" { target aarch64-*-* } } */
+/* { dg-additional-options "-mcpu=generic" { target aarch64*-*-* } } */
 
 #define LOOP_COUNT 800000000
 typedef double data_e;
@@ -35,5 +35,5 @@ foo (data_e in)
   return result + result2;
 }
 
-/* { dg-final { scan-tree-dump-not "was chosen for reassociation" "reassoc2"} } */
-/* { dg-final { scan-tree-dump-times {\.FMA } 3 "optimized"} } */
\ No newline at end of file
+/* { dg-final { scan-tree-dump-not "was chosen for reassociation" "reassoc2" { target aarch64*-*-* }} } */
+/* { dg-final { scan-tree-dump-times {\.FMA } 3 "optimized" { target aarch64*-*-* }} } */
\ No newline at end of file
-- 
2.25.1