From: Bruce Richardson <bruce.richardson@intel.com>
To: "Stanisław Kardach" <kda@semihalf.com>
Cc: David Christensen <drc@linux.vnet.ibm.com>,
David Marchand <david.marchand@redhat.com>, dev <dev@dpdk.org>,
upstream@semihalf.com, Aaron Conole <aconole@redhat.com>,
"Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
"Ruifeng Wang (Arm Technology China)" <ruifeng.wang@arm.com>,
Jerin Jacob Kollanukkaran <jerinj@marvell.com>
Subject: Re: [PATCH 0/3] Fix xmm_t to rte_xmm_t scalar conversion
Date: Tue, 21 Jun 2022 10:38:47 +0100 [thread overview]
Message-ID: <YrGRp5QfOaMsjhkF@bricha3-MOBL.ger.corp.intel.com> (raw)
In-Reply-To: <CALVGJW+86cUbfx0nKJMvwXcD0+sFBStFiWXjtMXnzrYC7Oe4fA@mail.gmail.com>
On Tue, Jun 21, 2022 at 11:30:32AM +0200, Stanisław Kardach wrote:
> On Tue, Jun 21, 2022 at 12:54 AM David Christensen
> <drc@linux.vnet.ibm.com> wrote:
> >
> > > On Thu, Jun 9, 2022 at 2:17 PM Stanislaw Kardach <kda@semihalf.com> wrote:
> > >>
> > >> As David noticed in [1] there is an issue with C++ compilation of the
> > >> rte_vect.h header in RISC-V. Upon closer inspection, the problem appears on
> > >> all architectures due to the type conversion rules in C++.
> > >> More precisely a union type rte_xmm_t requires a conversion constructor
> > >> from xmm_t type.
> > >> The most obvious fix is to use a structure initializer for such copies
> > >> (since rte_xmm_t union contains xmm_t anyway). The generated assembly
> > >> at -O2 is exactly the same, so there's no real impact.
> > >>
> > >> The bigger question is whether accessing bits of the architecture specific
> > >> xmm_t type in an array fashion is always correct? All current architectures
> > >> define rte_xmm_t in the same manner implying that.
> > >
> > > Copying other arch maintainers.
> >
> > My read of the Altivec vector layout for LE systems says the existing
> > union operator rte_xmm_t is correct, though my C++ experience is
> > limited. How can I generate an error with C++ to expose this issue?
> >
> > Dave
> To replicate this issue:
> 1. Apply the patch below. In essence it forces the use of scalar lpm
> and changes C++ compiler to g++ so that meson properly detects it.
> Otherwise C++ checks won't be generated.
> 2. Configure build with: meson build-ppc64le --werror --cross-file
> config/ppc/ppc64le-power8-linux-gcc-ubuntu -Dcheck_includes=true
> 3. Build with: ninja -C build-ppc64le buildtools/chkincs/chkincs-cpp
>
> Note that the build target only gets generated if C++ compiler is
> properly discovered by meson. To be honest I'm not sure why
> powerpc64le-linux-gnu-cpp doesn't get properly picked up by meson.
Generally the "cpp" binary is not the c-plus-plus one, but the C
preprocessor one. Perhaps the original files are incorrect here, and should
all refer to g++.
/Bruce
next prev parent reply other threads:[~2022-06-21 9:39 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-09 12:16 Stanislaw Kardach
2022-06-09 12:16 ` [PATCH 1/3] eal/riscv: fix xmm_t casting for C++ Stanislaw Kardach
2022-06-13 9:29 ` David Marchand
2022-06-09 12:17 ` [PATCH 2/3] lpm: fix xmm_t casting for C++ in scalar version Stanislaw Kardach
2022-06-13 9:29 ` David Marchand
2022-06-09 12:17 ` [PATCH 3/3] ci: use crossbuild-essential-riscv64 for compiling Stanislaw Kardach
2022-06-13 9:29 ` David Marchand
2022-06-14 12:31 ` Aaron Conole
2022-06-15 7:25 ` [PATCH 0/3] Fix xmm_t to rte_xmm_t scalar conversion David Marchand
2022-06-20 22:54 ` David Christensen
2022-06-21 9:30 ` Stanisław Kardach
2022-06-21 9:38 ` Bruce Richardson [this message]
2022-06-21 9:42 ` Stanisław Kardach
2022-06-21 9:49 ` Bruce Richardson
2022-06-21 10:22 ` Thomas Monjalon
2022-06-21 11:05 ` Stanisław Kardach
2022-06-21 11:53 ` Thomas Monjalon
2022-06-21 12:37 ` Stanisław Kardach
2022-06-21 14:20 ` Bruce Richardson
2022-06-21 19:48 ` Tyler Retzlaff
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