So I converted a small string/grammar parser, from pure perl, to XS. And benchmarked it. I was surprised, the old pure perl optree implementation, is only 30% of the speed of XS C code (3/11=%30). A string parser written in C with memcmp() vs PurePerl's eq, 3x slower. Not bad.

More interesting is, I decided as a crazy C/XS guts hack, to have a Perl XSUB, calling another Perl XSUB, C function to C function. And it was FOUR TIMES FASTER. 4x!!!!

Just by getting rid of the PP for() loop and the internal Perl_call_sv() and Perl_pp_entersub() overhead, and totally removing the the Perl 5 engine/API/interpretor, between 2 Perl 5 XSUBs (C functions), it made things FOUR TIMES FASTER.

So &$xs('__stdcall') for(0..1000);

vs

for(i=0;i<1000;i++) {/*removd*/XS_Local__C_calltype_to_num_xs(aTHX_ cv);/*removd*/}

these 2 for() loops, one in Perl 5, the other in C99, had a 4x faster difference in speed.

C compiler was -O2 MSVC 2022 x64 on a Intel Core I5-2520M 2.5ghz. 

         Rate   pp   xs
pp  3159521/s   -- -73%
xs 11612872/s 268%   --
      Rate    pp    xs   xs2
pp   333/s    --  -72%  -93%
xs  1192/s  258%    --  -74%
xs2 4516/s 1255%  279%    --

[download]


BEGIN {
    sub APICONTROL_CC_STD    () { 0 }
    sub APICONTROL_CC_C    () { 1 }
}
sub calltype_to_num {
    my $type = shift;

    if (!$type || $type eq "__stdcall" || $type eq "WINAPI" || $type e
+q "NTAPI"
        || $type eq "CALLBACK"  ) {
        return APICONTROL_CC_STD;
    }
    elsif ($type eq "_cdecl" || $type eq "__cdecl" || $type eq "WINAPI
+V") {
        return APICONTROL_CC_C;
    }
    else {
        warn "unknown calling convention: '$type'";
        return APICONTROL_CC_STD;
    }
}

[download]


I32
calltype_to_num_xs(type)
    SV* type
PREINIT:
    const char * p;
    I32 l;
CODE:
    SvGETMAGIC(type);
    if(!SvPOK(type)) {
        if(!SvOK(type) || (SvIOK(type) && !SvIVX(type)) || !sv_true(ty
+pe)) {
            RETVAL = APICONTROL_CC_STD;
        } else {
            unk:
            warn("unknown calling convention: '" SVf "'", type);
            RETVAL = APICONTROL_CC_STD;
        }
    } else {
        p = SvPVX(type);
        l = (U32)SvCUR(type);
        switch(l) {
            case STRLENs(""):
                if(memEQs(p,l,"")){RETVAL = APICONTROL_CC_STD;break;}
                else goto unk;
            case STRLENs("CDECL"):
                if(memEQs(p,l,"CDECL")){RETVAL = APICONTROL_CC_C;break
+;}
                else if(memEQs(p,l,"NTAPI")){RETVAL = APICONTROL_CC_ST
+D;break;}
                else if(memEQs(p,l,"cdecl")){RETVAL = APICONTROL_CC_C;
+break;}
                else goto unk;
            case STRLENs("PASCAL"):
                if(memEQs(p,l,"PASCAL")){RETVAL = APICONTROL_CC_STD;br
+eak;}
                else if(memEQs(p,l,"WINAPI")){RETVAL = APICONTROL_CC_S
+TD;break;}
                else if(memEQs(p,l,"WMIAPI")){RETVAL = APICONTROL_CC_S
+TD;break;}
                else if(memEQs(p,l,"pascal")){RETVAL = APICONTROL_CC_S
+TD;break;}
                else if(memEQs(p,l,"_cdecl")){RETVAL = APICONTROL_CC_C
+;break;}
                else goto unk;
            case STRLENs("WINAPIV"):
                if(memEQs(p,l,"WINAPIV")){RETVAL = APICONTROL_CC_C;bre
+ak;}
                else if(memEQs(p,l,"__cdecl")){RETVAL = APICONTROL_CC_
+C;break;}
                else goto unk;
            case STRLENs("APIENTRY"):
                if(memEQs(p,l,"APIENTRY")){RETVAL = APICONTROL_CC_STD;
+break;}
                else if(memEQs(p,l,"CALLBACK")){RETVAL = APICONTROL_CC
+_STD;break;}
                else if(memEQs(p,l,"IMAGEAPI")){RETVAL = APICONTROL_CC
+_STD;break;}
                else goto unk;
            case STRLENs("__CRTDECL"):
                if(memEQs(p,l,"__CRTDECL")){RETVAL = APICONTROL_CC_C;b
+reak;}
                else if(memEQs(p,l,"__stdcall")){RETVAL = APICONTROL_C
+C_STD;break;}
                else goto unk;
            case STRLENs("__fastcall"):
                if(memEQs(p,l,"__fastcall")){goto unk;RETVAL = APICONT
+ROL_CC_FC;break;}
                else if(memEQs(p,l,"__thiscall")){goto unk;RETVAL = AP
+ICONTROL_CC_TC;break;}
                else if(memEQs(p,l,"APIPRIVATE")){RETVAL = APICONTROL_
+CC_STD;break;}
                else goto unk;
            case STRLENs("__vectorcall"):
                if(memEQs(p,l,"__vectorcall")){goto unk;RETVAL = APICO
+NTROL_CC_VC;break;}
                else goto unk;
            case STRLENs("STDAPICALLTYPE"):
                if(memEQs(p,l,"STDAPICALLTYPE")){RETVAL = APICONTROL_C
+C_STD;break;}
                else goto unk;
            case STRLENs("STDAPIVCALLTYPE"):
                if(memEQs(p,l,"STDAPIVCALLTYPE")){RETVAL = APICONTROL_
+CC_C;break;}
                else goto unk;
            case STRLENs("STDMETHODCALLTYPE"):
                if(memEQs(p,l,"STDMETHODCALLTYPE")){RETVAL = APICONTRO
+L_CC_STD;break;}
                else goto unk;
            case STRLENs("STDMETHODVCALLTYPE"):
                if(memEQs(p,l,"STDMETHODVCALLTYPE")){RETVAL = APICONTR
+OL_CC_C;break;}
                else goto unk;
            default: goto unk;
        }
    }
OUTPUT:
    RETVAL

void
calltype_to_num_xs2(intype)
INPUT:
    SV* intype
PREINIT:
    SV* sv = sv_2mortal(newSVpvs("__stdcall"));
    int i;
PPCODE:
    SP = &(ST(-1));
    for(i=0;i<1000;i++) {
        PUSHMARK(SP);
        PUSHs(sv);
        PUTBACK;
        XS_Local__C_calltype_to_num_xs(aTHX_ cv);
        SPAGAIN;
        SP = &(ST(-1));
    }
    PUTBACK;

[download]


use Local::C;
use Benchmark qw(cmpthese :hireswallclock);

{   my ($pp, $xs, $xs2, $cctype) = (\&Local::C::calltype_to_num, \&Loc
+al::C::calltype_to_num_xs, 
\&Local::C::calltype_to_num_xs2);
    cmpthese( -1, {
        pp => sub{&$pp('__stdcall');}, 
        xs => sub{&$xs('__stdcall');}
    });
    cmpthese( -1, {
        pp => sub{&$pp('__stdcall') for(0..10000);}, 
    xs => sub{&$xs('__stdcall') for(0..10000);},
    xs2 => sub{&$xs2('__stdcall') for(0..10);}
    });
exit;
}

[download]

In reply to benchmarks, PurePerl vs Perl XS, Only!!! 3x slower, PerlXS C vs Real C, 4x slower by bulk88

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