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I backed away from this when I saw you weren't using an MS compiler, as I've no experience of gcc/mingw, but it seems to me that this will remain a mystery until you start inspecting the generated code. With MS CL adding /link /FAs to the compiler options cause it to output a .asm file.

When I run the following:

#! perl -slw use strict; use Config; print $Config{ ccflags }; use Inline C => Config => BUILD_NOISY => 1, CCFLAGS => $Config{ ccflag +s } . "/link /FAs"; use Inline C => <<'END_C', NAME => '_junk', CLEAN_AFTER_BUILD =>0; int i = 0; void test( SV *sv ) { ++i; return; } int check( SV *sv ) { return i; } END_C use Time::HiRes qw[ time ]; our $N //= 1e6; my $start = time; my $i = 0; $i = test( 1 ) for 1 .. $N; printf "Took %fseconds\n", time() - $start; print check( 1 )

The assembly code produced for test() is pretty much exactly what you'd expect:

PUBLIC test ; Function compile flags: /Ogtpy _TEXT SEGMENT sv$ = 8 test PROC ; 10 : ++i; inc DWORD PTR i ; 11 : return; ; 12 : } ret 0 test ENDP _TEXT ENDS

But then you have to look at the Perl callable wrapper function to see all the overhead that Perl-callability adds:

_TEXT SEGMENT my_perl$ = 48 cv$ = 56 XS_main_test PROC ; 174 : { mov QWORD PTR [rsp+8], rbx mov QWORD PTR [rsp+16], rsi push rdi sub rsp, 32 ; 00000020H mov rdi, rdx ; 175 : dVAR; dXSARGS; call Perl_get_context mov rcx, rax call Perl_Istack_sp_ptr mov rbx, QWORD PTR [rax] call Perl_get_context mov rcx, rax call Perl_Imarkstack_ptr_ptr mov rcx, QWORD PTR [rax] add rcx, -4 movsxd rsi, DWORD PTR [rcx+4] mov QWORD PTR [rax], rcx call Perl_get_context mov rcx, rax call Perl_Istack_base_ptr mov rax, QWORD PTR [rax] lea rdx, QWORD PTR [rax+rsi*8] inc esi sub rbx, rdx sar rbx, 3 ; 176 : if (items != 1) cmp ebx, 1 je SHORT $LN8@XS_main_te ; 177 : croak_xs_usage(cv, "sv"); call Perl_get_context lea r8, OFFSET FLAT:??_C@_02CPGMCOJE@sv?$AA@ mov rdx, rdi mov rcx, rax call Perl_croak_xs_usage $LN8@XS_main_te: ; 178 : PERL_UNUSED_VAR(ax); /* -Wall */ ; 179 : SP -= items; ; 180 : { ; 181 : SV * sv = ST(0) ; 182 : ; call Perl_get_context mov rcx, rax call Perl_Istack_base_ptr ; File c:\test\_inline\build\_junk\_junk.xs ; 30 : temp = PL_markstack_ptr++; call Perl_get_context mov rcx, rax call Perl_Imarkstack_ptr_ptr ; 31 : test(sv); inc DWORD PTR i mov rbx, QWORD PTR [rax] lea rcx, QWORD PTR [rbx+4] mov QWORD PTR [rax], rcx ; 32 : if (PL_markstack_ptr != temp) { call Perl_get_context mov rcx, rax call Perl_Imarkstack_ptr_ptr cmp QWORD PTR [rax], rbx je SHORT $LN4@XS_main_te ; 33 : /* truly void, because dXSARGS not invoked */ ; 34 : PL_markstack_ptr = temp; call Perl_get_context mov rcx, rax call Perl_Imarkstack_ptr_ptr mov QWORD PTR [rax], rbx ; 35 : XSRETURN_EMPTY; /* return empty stack */ call Perl_get_context mov rcx, rax call Perl_Istack_base_ptr movsxd rcx, esi mov rax, QWORD PTR [rax] lea rbx, QWORD PTR [rax+rcx*8-8] call Perl_get_context mov rcx, rax call Perl_Istack_sp_ptr mov QWORD PTR [rax], rbx $LN4@XS_main_te: ; File c:\test\_inline\build\_junk\_junk.c ; 200 : } mov rbx, QWORD PTR [rsp+48] mov rsi, QWORD PTR [rsp+56] add rsp, 32 ; 00000020H pop rdi ret 0 XS_main_test ENDP _TEXT ENDS

And the real eye-opener comes when start looking at the code behind those call Perl_xxx; littered all over the place. (Why is it necessary to call Perl_get_context() 9 times for EVERY CALL to such a simple function?)

If you assume that your original empty C stub is actually causing code to be generated and run -- and I don't; I think your call to the empty function is being optimised away --then it would be instructive to see the difference in the code that is being called.


With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority". The enemy of (IT) success is complexity.
In the absence of evidence, opinion is indistinguishable from prejudice. Suck that fhit

In reply to Re^5: Inline::C on Windows: how to improve performance of compiled code? by BrowserUk
in thread Inline::C on Windows: how to improve performance of compiled code? by vr

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