From: Umesh Kalappa <umesh.kalappa0@gmail.com>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Andrew Pinski <pinskia@gmail.com>,
Nicholas Piggin <npiggin@gmail.com>,
linuxppc-dev@lists.ozlabs.org, gcc@gcc.gnu.org,
libc-alpha@sourceware.org, Michael Ellerman <mpe@ellerman.id.au>,
Paul E Murphy <murphyp@linux.ibm.com>
Subject: Re: Passing the complex args in the GPR's
Date: Tue, 6 Jun 2023 22:37:19 +0530 [thread overview]
Message-ID: <CAGfacvQ7qE4S-U=XLVRdZmitWJiCcppWH+VscpKz4piDYWwp=w@mail.gmail.com> (raw)
In-Reply-To: <20230606164256.GQ19790@gate.crashing.org>
Hi Segher ,
>>What did you expect, what happened instead?
For example the complex args are passed in GPR's for cexp in the case
GCC and Clang uses caller memory .
for reference : https://godbolt.org/z/MfMz3cTe7
We have cross tools like some of libraries built using the GCC and
some use Clang .
We approached Clang developers on this behaviour (Why stack , not the
FPR's registers like PPC64) and they are not going to change this
behaviour, and asked us to refer back to GCC ,hence this email thread.
Question is : Why does GCC choose to use GPR's here and have any
reference to support this decision ?
Thank you
~Umesh
On Tue, Jun 6, 2023 at 10:16 PM Segher Boessenkool
<segher@kernel.crashing.org> wrote:
>
> Hi!
>
> On Tue, Jun 06, 2023 at 08:35:22PM +0530, Umesh Kalappa wrote:
> > Hi Adnrew,
> > Thank you for the quick response and for PPC64 too ,we do have
> > mismatches in ABI b/w complex operations like
> > https://godbolt.org/z/bjsYovx4c .
> >
> > Any reason why GCC chose to use GPR 's here ?
>
> What did you expect, what happened instead? Why did you expect that,
> and why then is it an error what did happen?
>
> You used -O0. As long as the code works, all is fine. But unoptimised
> code frequently is hard to read, please use -O2 instead?
>
> As Andrew says, why did you use -m32 for GCC but -m64 for LLVM? It is
> hard to compare those at all! 32-bit PowerPC Linux ABI (based on 32-bit
> PowerPC ELF ABI from 1995, BE version) vs. 64-bit ELFv2 ABI from 2015
> (LE version).
>
>
> Segher
next prev parent reply other threads:[~2023-06-06 17:07 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-24 9:38 [PATCH Linux] powerpc: add documentation for HWCAPs Nicholas Piggin
2022-05-24 9:52 ` Florian Weimer
2022-05-24 18:32 ` Segher Boessenkool
2022-07-15 1:17 ` Nicholas Piggin
2022-07-15 14:35 ` Segher Boessenkool
2022-05-24 17:38 ` Segher Boessenkool
2022-07-15 1:00 ` Nicholas Piggin
2023-06-06 14:49 ` Passing the complex args in the GPR's Umesh Kalappa
2023-06-06 14:58 ` Andrew Pinski
2023-06-06 15:05 ` Umesh Kalappa
2023-06-06 15:16 ` Andrew Pinski
2023-06-06 16:42 ` Segher Boessenkool
2023-06-06 17:07 ` Umesh Kalappa [this message]
2023-06-06 17:33 ` David Edelsohn
2023-06-07 13:17 ` Michael Matz
2023-06-06 17:18 ` Joseph Myers
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