sysdeps/powerpc/powerpc32/power7/memset.S used by sysdeps/powerpc/powerpc32/power4/multiarch/memset-power7.S also assumes dcbz to cover 128 bytes at a time. This breaks memset() for normal (non-rtld) case.

AFAICS, powerpc 7450 can't run POWER4 code.  So, this processor shouldn't be running POWER4 or POWER7 code.
The question that needs to be answered is: why is your build getting them?

I tried to reproduce your build, but I did not get any POWER4 files:
configure --host=powerpc-linux-gnu --prefix=/usr CC="powerpc-linux-gnu-gcc" CFLAGS="-O2 -ggdb3 -mcpu=7450"

$ grep submachine config.log 
libc_cv_cc_submachine=''
submachine=''

I used commit ID 756c306502498f999fdd494477b9cea1b45e4faf.

What are you getting in your config.log?

Created attachment 12793 [details]
ppc7450-config.log

ppc7450-config.log is a config.log from

    ../glibc /configure --host=powerpc-unknown-linux-gnu --prefix=/usr \
        CC="powerpc-unknown-linux-gnu-gcc -mcpu=7450" \
        CFLAGS="-O2 -ggdb3 -mcpu=7450"

(In reply to Tulio Magno Quites Machado Filho from comment #2)
> AFAICS, powerpc 7450 can't run POWER4 code.  So, this processor shouldn't be
> running POWER4 or POWER7 code.
> The question that needs to be answered is: why is your build getting them?

Oh, I had no idea.

Mechanically power7 is detected at sysdeps/powerpc/preconfigure.ac:

$ echo 'int foo () { return 0; }' | powerpc-unknown-linux-gnu-gcc-10.2.0 -S -frecord-gcc-switches -xc -o - - | fgrep machine
        .machine ppc
$ echo 'int foo () { return 0; }' | powerpc-unknown-linux-gnu-gcc-10.2.0 -mcpu=7450 -S -frecord-gcc-switches -xc -o - - | fgrep machine
        .machine power7

Is it a gcc bug?

> I tried to reproduce your build, but I did not get any POWER4 files:
> configure --host=powerpc-linux-gnu --prefix=/usr CC="powerpc-linux-gnu-gcc"
> CFLAGS="-O2 -ggdb3 -mcpu=7450"
> 
> $ grep submachine config.log 
> libc_cv_cc_submachine=''
> submachine=''

For me -mcpu=7450 enabled mutilarch as well. Do you get it as well?

> I used commit ID 756c306502498f999fdd494477b9cea1b45e4faf.
> 
> What are you getting in your config.log?

Attached https://sourceware.org/bugzilla/attachment.cgi?id=12793, should be done against the same commit.

(In reply to Sergei Trofimovich from comment #4)
> (In reply to Tulio Magno Quites Machado Filho from comment #2)
> > AFAICS, powerpc 7450 can't run POWER4 code.  So, this processor shouldn't be
> > running POWER4 or POWER7 code.
> > The question that needs to be answered is: why is your build getting them?
> 
> Oh, I had no idea.
> 
> Mechanically power7 is detected at sysdeps/powerpc/preconfigure.ac:
> 
> $ echo 'int foo () { return 0; }' | powerpc-unknown-linux-gnu-gcc-10.2.0 -S
> -frecord-gcc-switches -xc -o - - | fgrep machine
>         .machine ppc
> $ echo 'int foo () { return 0; }' | powerpc-unknown-linux-gnu-gcc-10.2.0
> -mcpu=7450 -S -frecord-gcc-switches -xc -o - - | fgrep machine
>         .machine power7
> 
> Is it a gcc bug?

CCing gcc power maintainers.

My naive grep suggests -mcpu=7450 should be ppc+altivec only and not power7:

gcc/config/rs6000/driver-rs6000.c:

"""
    { "7450",   "-mppc %{!mvsx:%{!maltivec:-maltivec}}" },
""

gcc/config/rs6000/rs6000.c derives '.machine' as:

"""
#ifdef USING_ELFOS_H
const char *rs6000_machine;

const char *
rs6000_machine_from_flags (void)
{
  HOST_WIDE_INT flags = rs6000_isa_flags;

  /* Disable the flags that should never influence the .machine selection.  */
  flags &= ~(OPTION_MASK_PPC_GFXOPT | OPTION_MASK_PPC_GPOPT);

  if ((flags & (ISA_3_1_MASKS_SERVER & ~ISA_3_0_MASKS_SERVER)) != 0)
    return "power10";
  if ((flags & (ISA_3_0_MASKS_SERVER & ~ISA_2_7_MASKS_SERVER)) != 0)
    return "power9";
  if ((flags & (ISA_2_7_MASKS_SERVER & ~ISA_2_6_MASKS_SERVER)) != 0)
    return "power8";
  if ((flags & (ISA_2_6_MASKS_SERVER & ~ISA_2_5_MASKS_SERVER)) != 0)
    return "power7";
  if ((flags & (ISA_2_5_MASKS_SERVER & ~ISA_2_4_MASKS)) != 0)
    return "power6";
  if ((flags & (ISA_2_4_MASKS & ~ISA_2_1_MASKS)) != 0)
    return "power5";
  if ((flags & ISA_2_1_MASKS) != 0)
    return "power4";
  if ((flags & OPTION_MASK_POWERPC64) != 0)
    return "ppc64";
  return "ppc";
}

void
emit_asm_machine (void)
{
  fprintf (asm_out_file, "\t.machine %s\n", rs6000_machine);
}
#endif
"""

"power7" is selected because (ISA_2_6_MASKS_SERVER & ~ISA_2_5_MASKS_SERVER) contains OPTION_MASK_ALTIVEC, and mcpu=7450 adds OPTION_MASK_ALTIVEC to rs6000_isa_flags.  The whole logic in rs6000_machine_from_flags is busted.  It should check that _all_ flags are present.  Please file a bug with gcc.

(In reply to Andreas Schwab from comment #6)
> "power7" is selected because (ISA_2_6_MASKS_SERVER & ~ISA_2_5_MASKS_SERVER)
> contains OPTION_MASK_ALTIVEC, and mcpu=7450 adds OPTION_MASK_ALTIVEC to
> rs6000_isa_flags.  The whole logic in rs6000_machine_from_flags is busted. 
> It should check that _all_ flags are present.  Please file a bug with gcc.

Sounds good. What should '.machine' contain for -mcpu=7450? 'ppc'?

I'm asking because I'm not sure what '.machine' means for gas: upper bound on available ISA or lower bound?

.machine sets the upper bound accepted by the assembler.  It should match the mapping in the asm_names table in driver-rs6000.c.

Nice catch!
This is only happening with GCC 10:

$ gcc-10 -S -m32 -mcpu=7450 -frecord-gcc-switches -xc -o - - < /dev/null | grep -E 'mcpu|machine'
        .machine power7
        .ascii  "-mcpu=7450"
$ gcc-9 -S -m32 -mcpu=7450 -frecord-gcc-switches -xc -o - - < /dev/null | grep -E 'mcpu|machine'
        .ascii  "-mcpu=7450"

This is gcc.gnu.org/PR96786 now.  Thanks!