Re: Do not perform tests that are not supported by the CPU.

[Jonathan Wakely <jwakely.gcc@gmail.com>]

On Fri, 22 Apr 2022 at 16:34, sajcho via Gcc-help <gcc-help@gcc.gnu.org> wrote:
>
> On 22-04-22 15:32:07, Jonathan Wakely wrote:
> > On Fri, 22 Apr 2022 at 14:18, sajcho via Gcc-help <gcc-help@gcc.gnu.org> wrote:
> > >
> > > Hi.
> > >
> > > lscpu output:
> > >
> > > Architecture:            aarch64
> > >   CPU op-mode(s):        32-bit, 64-bit
> > >   Byte Order:            Little Endian
> > > CPU(s):                  6
> > >   On-line CPU(s) list:   0,3-5
> > >   Off-line CPU(s) list:  1,2
> > > Vendor ID:               ARM
> > >   Model name:            Cortex-A57
> > >     Model:               3
> > >     Thread(s) per core:  1
> > >     Core(s) per cluster: 4
> > >     Socket(s):           -
> > >     Cluster(s):          1
> > >     Stepping:            r1p3
> > >     CPU max MHz:         2035,2000
> > >     CPU min MHz:         960,0000
> > >     BogoMIPS:            62.50
> > >     Flags:               fp asimd evtstrm aes pmull sha1 sha2 crc32 cpuid
> > > Caches (sum of all):
> > >   L1d:                   128 KiB (4 instances)
> > >   L1i:                   192 KiB (4 instances)
> > >   L2:                    2 MiB (1 instance)
> > > NUMA:
> > >   NUMA node(s):          1
> > >   NUMA node0 CPU(s):     0,3-5
> > > Vulnerabilities:
> > >   Itlb multihit:         Not affected
> > >   L1tf:                  Not affected
> > >   Mds:                   Not affected
> > >   Meltdown:              Mitigation; PTI
> > >   Spec store bypass:     Not affected
> > >   Spectre v1:            Mitigation; __user pointer sanitization
> > >   Spectre v2:            Mitigation; Branch predictor hardening, BHB
> > >   Srbds:                 Not affected
> > >   Tsx async abort:       Not affected
> > >
> > > ../configure --prefix=/usr --libexecdir=/usr/lib --enable-languages=c,c++,fortran,lto --enable-threads=posix --enable-__cxa_atexit --enable-default-pie --enable-default-ssp --enable-linker-build-id --enable-initfini-array --enable-link-serialization=1 --enable-gnu-indirect-function --enable-plugin --disable-nls --disable-multilib --disable-sjlj-exceptions --disable-libunwind-exceptions --disable-libquadmath-support --disable-libquadmath --with-system-zlib --with-linker-hash-style=gnu --with-build-config=bootstrap-lto --with-pkgversion=SAUX-Aarch64 --build=aarch64-unknown-linux-gnu --host=aarch64-unknown-linux-gnu
> > >
> > > make profiledbootstrap
> > >
> > > This is where my question begins.
> > > Is there any easy way to avoid tests (sve, sve2, aapcs ....) that are not supported by this cpu?
> >
> > In theory you shouldn't need to do anything. Tests that use those
> > features should be restricted to only run when the CPU supports them,
> > via https://gcc.gnu.org/onlinedocs/gccint/Effective-Target-Keywords.html#AArch64-specific-attributes
> >
> > In practice, some tests might not use the correct keywords to ensure
> > that happens.
> >
> > Have you tried it?
> >
>
> He didn't try. I'm confused.
>
> These attributes are specified in lib/target-supports.exp.
> I don't know how to use them.
>
> I don't think my knowledge is sufficient.

You don't use them, the GCC tests use them to say things like "this
test requires sve hardware", which causes the testsuite framework to
skip those tests if the hardware support is absent.