On Tue, Dec 28, 2021 at 1:09 PM Juha Manninen via lazarus <lazarus@lists.lazarus-ide.org> wrote:
> I confess I didn't remember what PopCnt does. I checked from the net. > FPC implements it as internproc. > function PopCnt(Const AValue : QWord): QWord;[internproc:fpc_in_popcnt_x]; > I guess it translates to one x86_64 instruction. > Is it implemented for all CPUs? I found this: > https://gitlab.com/freepascal.org/fpc/source/-/issues/38729 I just tested PopCnt vs Multiplication on win32 and win64. The version with PopCnt is appr. 3 times slower on both 32 and 64 bit! C:\Users\Bart\LazarusProjecten\bugs\Utf8\ulenfast>fpc ulen.lpr Free Pascal Compiler version 3.3.1 [2021/12/08] for i386 Copyright (c) 1993-2021 by Florian Klaempfl and others Target OS: Win32 for i386 C:\Users\Bart\LazarusProjecten\bugs\Utf8\ulenfast>ulen Unsigned version with multiplication: 1344 Unsigned version with PopCnt : 3563 C:\Users\Bart\LazarusProjecten\bugs\Utf8\ulenfast>fpc ulen.lpr -Px86_64 Free Pascal Compiler version 3.3.1 [2021/12/08] for x86_64 Copyright (c) 1993-2021 by Florian Klaempfl and others Target OS: Win64 for x64 C:\Users\Bart\LazarusProjecten\bugs\Utf8\ulenfast>ulen Unsigned version with multiplication: 656 Unsigned version with PopCnt : 3797 It looks like PopCnt on these platforms at least calls the generic version (/rtl/inc/generic.inc). -- Bart -- _______________________________________________ lazarus mailing list lazarus@lists.lazarus-ide.org https://lists.lazarus-ide.org/listinfo/lazarus
