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

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

> Am 22.12.2023 um 16:05 schrieb Di Zhao OS <dizhao@os.amperecomputing.com>:
> 
> Updated the fix in attachment.
> 
> Is it OK for trunk?

Ok

> 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
> <0001-Fix-compile-options-of-pr110279-1.c-and-pr110279-2.c.patch>