optimize sort by inlining comparison functions

[xenu]

This makes special-cased forms such as sort { $b <=> $a }
even faster.

Also, since this commit removes PL_sort_RealCmp, it fixes the
issue with nested sort calls mentioned in #16129

PS. Because of b578cab commit (normalize indentation), I recommend using "hide whitespace changes" when reviewing.

[xenu]

Some benchmarks (the source code is here), "fastblead" is the one with my changes:

Key:
    Ir   Instruction read
    Dr   Data read
    Dw   Data write
    COND conditional branches
    IND  indirect branches
    _m   branch predict miss
    _m1  level 1 cache miss
    _mm  last cache (e.g. L3) miss
    -    indeterminate percentage (e.g. 1/0)

The numbers represent relative counts per loop iteration, compared to
/home/xenu/blead/bin/perl5.31.10 at 100.0%.
Higher is better: for example, using half as many instructions gives 200%,
while using twice as many gives 50%.

nsort_asc
numeric sort ascending

       /home/xenu/blead/bin/perl5.31.10 /home/xenu/fastblead/bin/perl5.31.10
       -------------------------------- ------------------------------------
    Ir                           100.00                               115.45
    Dr                           100.00                               113.63
    Dw                           100.00                               139.99
  COND                           100.00                               100.00
   IND                           100.00                           1000090.00

COND_m                           100.00                                88.89
 IND_m                           100.00                               100.00

 Ir_m1                           100.00                               100.00
 Dr_m1                           100.00                               100.00
 Dw_m1                           100.00                               100.00

 Ir_mm                           100.00                               100.00
 Dr_mm                           100.00                               100.00
 Dw_mm                           100.00                               100.00

nsort_desc
numeric sort descending

       /home/xenu/blead/bin/perl5.31.10 /home/xenu/fastblead/bin/perl5.31.10
       -------------------------------- ------------------------------------
    Ir                           100.00                               119.64
    Dr                           100.00                               120.00
    Dw                           100.00                               153.32
  COND                           100.00                               104.97
   IND                           100.00                           2000080.00

COND_m                           100.00                               100.00
 IND_m                           100.00                               100.00

 Ir_m1                           100.00                               100.00
 Dr_m1                           100.00                               100.00
 Dw_m1                           100.00                               100.00

 Ir_mm                           100.00                               100.00
 Dr_mm                           100.00                               100.00
 Dw_mm                           100.00                               100.00

ssort_asc
string sort ascending

       /home/xenu/blead/bin/perl5.31.10 /home/xenu/fastblead/bin/perl5.31.10
       -------------------------------- ------------------------------------
    Ir                           100.00                               100.00
    Dr                           100.00                               101.25
    Dw                           100.00                               100.00
  COND                           100.00                               100.00
   IND                           100.00                               150.00

COND_m                           100.00                               100.00
 IND_m                           100.00                               100.00

 Ir_m1                           100.00                               100.00
 Dr_m1                           100.00                               100.00
 Dw_m1                           100.00                               100.00

 Ir_mm                           100.00                               100.00
 Dr_mm                           100.00                               100.00
 Dw_mm                           100.00                               100.00

ssort_desc
string sort descending

       /home/xenu/blead/bin/perl5.31.10 /home/xenu/fastblead/bin/perl5.31.10
       -------------------------------- ------------------------------------
    Ir                           100.00                               103.35
    Dr                           100.00                               106.23
    Dw                           100.00                               106.06
  COND                           100.00                               100.00
   IND                           100.00                               200.00

COND_m                           100.00                                99.99
 IND_m                           100.00                               100.00

 Ir_m1                           100.00                               100.00
 Dr_m1                           100.00                               100.00
 Dw_m1                           100.00                               100.00

 Ir_mm                           100.00                               100.00
 Dr_mm                           100.00                               100.00
 Dw_mm                           100.00                               100.00

AVERAGE

       /home/xenu/blead/bin/perl5.31.10 /home/xenu/fastblead/bin/perl5.31.10
       -------------------------------- ------------------------------------
    Ir                           100.00                               109.00
    Dr                           100.00                               109.82
    Dw                           100.00                               120.87
  COND                           100.00                               101.20
   IND                           100.00                               342.82

COND_m                           100.00                                96.97
 IND_m                           100.00                               100.00

 Ir_m1                           100.00                               100.00
 Dr_m1                           100.00                               100.00
 Dw_m1                           100.00                               100.00

 Ir_mm                           100.00                               100.00
 Dr_mm                           100.00                               100.00
 Dw_mm                           100.00                               100.00

[xenu]

Here are some non-scientific benchmarks of numeric sort (source code):

> time ~/blead/bin/perl5.31.10 num_sort.pl

real    0m2.988s
user    0m2.875s
sys     0m0.047s
> time ~/blead/bin/perl5.31.10 num_sort.pl

real    0m2.984s
user    0m2.922s
sys     0m0.047s
> time ~/blead/bin/perl5.31.10 num_sort.pl

real    0m2.982s
user    0m2.953s
sys     0m0.000s

> time ~/fastblead/bin/perl5.31.10 num_sort.pl

real    0m2.485s
user    0m2.453s
sys     0m0.016s
> time ~/fastblead/bin/perl5.31.10 num_sort.pl

real    0m2.481s
user    0m2.406s
sys     0m0.047s
> time ~/fastblead/bin/perl5.31.10 num_sort.pl

real    0m2.519s
user    0m2.438s
sys     0m0.047s

and reverse numeric sort (source code):

> time ~/blead/bin/perl5.31.10 reverse_num_sort.pl

real    0m3.198s
user    0m3.141s
sys     0m0.016s
> time ~/blead/bin/perl5.31.10 reverse_num_sort.pl

real    0m3.206s
user    0m3.172s
sys     0m0.016s
> time ~/blead/bin/perl5.31.10 reverse_num_sort.pl

real    0m3.197s
user    0m3.156s
sys     0m0.016s

> time ~/fastblead/bin/perl5.31.10 reverse_num_sort.pl

real    0m2.578s
user    0m2.516s
sys     0m0.047s
> time ~/fastblead/bin/perl5.31.10 reverse_num_sort.pl

real    0m2.577s
user    0m2.531s
sys     0m0.016s
> time ~/fastblead/bin/perl5.31.10 reverse_num_sort.pl

real    0m2.566s
user    0m2.484s
sys     0m0.063s

As you can see, on my machine the optimized numeric sort is ~15% faster and reverse numeric sort is ~20% faster.

[xenu]

I force pushed to improve a comment in embed.fnc.

[khwilliamson]

LGTM

[khwilliamson]

I think here and another place, the attribute__always_inline is a relic of an earlier version, and is generated by the macro. Most functions declared as such in this file don't have an attribute specified explicitly

[xenu]

I've added sortsv_flags_impl to embed.fnc and removed the attribute from its definition but I would rather not do the same for dynprep().

dynprep() takes arguments of types that exist only inside pp_sort.c, so I'd have to either move the typedefs to perl.h (which is an obfuscation) or remove them (which is beyond the scope of this PR).

[dur-randir]

I observe ~5% overall improvement, which is very nice for such a used function.

[hvds]

@xenu I note that this is now generating warning: unused parameter 'flags' on the renamed S_sortsv_flags_impl. It is not immediately clear to me whether it just wants a PERL_UNUSED_ARG or whether the interface should actually remove flags from _impl and all the specific sort functions.

[jkeenan]

@xenu I note that this is now generating warning: unused parameter 'flags' on the renamed S_sortsv_flags_impl. It is not immediately clear to me whether it just wants a PERL_UNUSED_ARG or whether the interface should actually remove flags from _impl and all the specific sort functions.

As reported in #17632