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

[sajcho <saux.aarch64@gmail.com>]

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.


---
Remember, no question is too stupid and no problem too small
            *** We've all been beginners ***