BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Code Optimization Stack Pointer Manipulation Goto page 1, 2, 3  Next          BorlandTalk.com Forum Index -> Delphi Language BASM View previous topic :: View next topic   Author Message Dennis Guest Posted: Tue Oct 04, 2005 9:29 am    Post subject: Code Optimization Stack Pointer Manipulation Hi Can anybody tell me why the compiler emits this code pop ecx pop ecx and not add esp,8 ? The pop ecx /pop ecx code looks weird and slow to me while add esp,8 is very natural fast and simple. popping a register involves a copy of data from the stack into the register. This is repeated twice and is slower and bigger than just one add. Best regards Dennis Back to top Per Larsen Guest Posted: Tue Oct 04, 2005 9:41 am    Post subject: Re: Code Optimization Stack Pointer Manipulation The double-pop is one byte shorter than the add - my guess is that's the reason and that there wasn't any significant difference in speed when this was originally done. I agree that it looks weird, FWIW. - Per Back to top Dennis Guest Posted: Tue Oct 04, 2005 9:48 am    Post subject: Re: Code Optimization Stack Pointer Manipulation Hi Per Thanks for explaining. Should we recommend it being changed? Best regards Dennis Back to top Per Larsen Guest Posted: Tue Oct 04, 2005 1:11 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation "Dennis" <marianndkc (AT) home3 (DOT) gvdnet.dk> wrote Quote: Hi Per Thanks for explaining. Should we recommend it being changed? If we can prove it's significantly faster, yes - otherwise no. - Per Back to top Dennis Guest Posted: Tue Oct 04, 2005 1:21 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation Hi Per I will do some benchmarking but I do not think that it is significant slower. I any circumstances it is an "Extreme cornercase" priority report - if made. Best regards Dennis Back to top Dennis Guest Posted: Tue Oct 04, 2005 1:32 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation Hi Somebody help me benchmark function FirstOrderPolynomialBASM1(X : Double) : Double; const A : Double = 2; B : Double = 3; asm add esp,-$08 //Result := A*X + B; fld A fmul qword ptr [ebp+$08] fadd B fstp qword ptr [ebp-$08] wait fld qword ptr [ebp-$08] pop ecx pop ecx end; versus function FirstOrderPolynomialBASM2(X : Double) : Double; const A : Double = 2; B : Double = 3; asm add esp,-$08 //Result := A*X + B; fld A fmul qword ptr [ebp+$08] fadd B fstp qword ptr [ebp-$08] wait fld qword ptr [ebp-$08] //pop ecx //pop ecx add esp,$08 end; I use this simple benchmark procedure TTimingForm.Button1Click(Sender: TObject); var StartTime, EndTime, RunTime : TDateTime; I : Integer; Y, X : Double; const MAX : Integer = 1700000000; begin X := 5; StartTime := Time; for I := 1 to MAX do begin Y := FirstOrderPolynomialBASM1(X); //Y := FirstOrderPolynomialBASM2(X); end; EndTime := Time; RunTime := EndTime - StartTime; RunTimeEdit.Text := TimeToStr(RunTime); YEdit.Text := FloatToStr(Y); end; Best regards Dennis Back to top Dennis Guest Posted: Tue Oct 04, 2005 1:37 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation Hi I get FirstOrderPolynomialBASM1 // 53 sec FirstOrderPolynomialBASM2 // 44 sec On Opteron 240. But we should not jump to any conclusion until we have more benchmark results. The benchmark does not take care of branch target alignment or data alignment. More compilations and runs are needed. Best regards Dennis Back to top Dennis Guest Posted: Tue Oct 04, 2005 1:42 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation I get FirstOrderPolynomialBASM1 // 31 sec FirstOrderPolynomialBASM2 // 27 sec On Dothan 1733. Best regards Dennis Back to top Florent Ouchet Guest Posted: Tue Oct 04, 2005 4:38 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation Hi, I get FirstOrderPolynomialBASM1 // 1 min 18 FirstOrderPolynomialBASM2 // 1 min 19 on a P3M @ 866MHz Results are really close. Regards, Florent Back to top Dennis Guest Posted: Tue Oct 04, 2005 6:10 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation Hi Florent Could you upload your exe's to attachments? And the source. Then I will try run them here too. Best regards Dennis Back to top Florent Ouchet Guest Posted: Tue Oct 04, 2005 6:59 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation Dennis wrote: Quote: Could you upload your exe's to attachments? And the source. I use the one you provided, will little modifications. this simple benchmark is really easy to use. I don't take care of function alignment. Adding the SetThreadPriority increases the differencies : 25s for add 27s for pop pop (I reduced the number of loop). Regards, Florent Back to top Dennis Guest Posted: Tue Oct 04, 2005 7:37 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation Hi Florent I would like the exe's. They migth be aligned diffrently from the ones I made. Best regards Dennis Back to top Dennis Guest Posted: Tue Oct 04, 2005 7:40 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation Just found it. 14 versus 14 seconds on my Opteron. Best regards Dennis Back to top Florent Ouchet Guest Posted: Tue Oct 04, 2005 7:45 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation Dennis wrote: Quote: I would like the exe's. They migth be aligned diffrently from the ones I made. There are big differences between benchmarking using the debug and debugging in release. That is the only idea that comes to me. The exe is not difficult to find I inserted exe and project/source files in the zip file. Florent Back to top Dennis Guest Posted: Tue Oct 04, 2005 7:49 pm    Post subject: Re: Code Optimization Stack Pointer Manipulation Hi Florent Yes, but you did not write here that you uploaded anything ;-) I think we need a better benchmark. I will try to make one tomorrow based on our Fastcode Template B&V. 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