DOS ain't dead

rebuilding NASM 0.98.39 (without MMX/3DNOW/686/SSE) (Developers)

posted by Rugxulo , Usono, 13.04.2020, 07:16

> > > The 486 and 586 didn't add much (not counting MMX, 3DNow!), so I felt
> > > I should keep those. But everything else (Cyrix, MMX, 3DNow!, P6, IA64
> > > [JMPE], SSE[123]) I deleted.
> >
> > (P6 has a highly useful cmov that reduces branching, and is a substitute
> > for a branch instruction and a mov. IIRC it is 3 bytes and replaces a
> > one byte branch and two bytes mov. (in both cases + size of imm),
> > equal size, better performance)
>
> I did double-check for you. Not counting Cyrix, P6 only is 35 instructions.
> So it's only an extra 2 kb of space used, so it probably wouldn't hurt
> to include here

So I refreshed "nasmlite". But sometimes it's hard to know what really helps or not (especially for old cpus I don't have on hand to test). I did enable support for P6 instructions, though (but easily disabled via makefile, if needed).

"-a" enables word alignment and didn't hurt size at all, so that's a no-brainer, but it's still of questionable benefit (without further testing). "-G' speed optimization (vs. size) would've taken 6 kb extra, and I didn't even bother because I can't prove it actually helps at all. (I need to compare "-S" assembly output, but even that's probably targeting truly ancient cpus. "-S" also ran out of memory on preproc.c, so that's fun.)

I still need to read the compiler manuals in more detail. There's plenty of other options and miscellaneous trivia.

Complete thread:

• rebuilding NASM 0.98.39 (2005) for 16-bit 8086 host - Rugxulo, 14.03.2020, 08:13 (Developers)
  • rebuilding NASM 0.98.39 (2005) for 16-bit 8086 host - Rugxulo, 16.03.2020, 01:24
    • rebuilding NASM 0.98.39 (2005) for 16-bit 8086 host - rr, 16.03.2020, 15:22
      • rebuilding NASM 0.98.39 (without MMX/3DNOW/686/SSE) - Rugxulo, 17.03.2020, 05:20
        • rebuilding NASM 0.98.39 (without MMX/3DNOW/686/SSE) - ecm, 17.03.2020, 06:58
          • rebuilding NASM 0.98.39 (without MMX/3DNOW/686/SSE) - Rugxulo, 22.03.2020, 00:48
            • rebuilding NASM 0.98.39 (without MMX/3DNOW/686/SSE) - ecm, 22.03.2020, 10:13
              • rebuilding NASM 2.09 and NASM compatibility - ecm, 22.03.2020, 11:45
            • rebuilding NASM 0.98.39 (without MMX/3DNOW/686/SSE) - ecm, 06.09.2020, 23:09
        • rebuilding NASM 0.98.39 (without MMX/3DNOW/686/SSE) - Rugxulo, 22.03.2020, 00:42
          • rebuilding NASM 0.98.39 (without MMX/3DNOW/686/SSE) - marcov, 22.03.2020, 13:08
            • CMOV - ecm, 22.03.2020, 14:26
              • CMOV - marcov, 22.03.2020, 18:32
                • CMOV - marcov, 23.03.2020, 12:52
            • rebuilding NASM 0.98.39 (without MMX/3DNOW/686/SSE) - Rugxulo, 23.03.2020, 04:27
              • NASM 0.98.39 (MSC 7, "286", not full instruction support) - Rugxulo, 24.03.2020, 20:36
                • NASM 0.98.39 (not full instruction support) - Rugxulo, 24.03.2020, 21:16
                  • NASM 0.98.39 (not full instruction support) - ecm, 24.03.2020, 22:55
                    • NASM 0.98.39 (not full instruction support) - Rugxulo, 24.03.2020, 23:17
                  • NASM 0.98.39 (not full instruction support) ... LOADALL - Rugxulo, 31.03.2020, 20:07
              • rebuilding NASM 0.98.39 (without MMX/3DNOW/686/SSE) - Rugxulo, 13.04.2020, 07:16
            • deprecated MMX and obsolete 3DNow! - Rugxulo, 24.03.2020, 17:54