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Ask SN: When Is Assembly Worth It?

posted by Cactus on Saturday March 08 2014, @03:30AM   Printer-friendly
from the don't-tell-me-upgrade-PCs dept.

Subsentient writes:

"I'm a C programmer and Linux enthusiast. For some time, I've had it on my agenda to build the new version of my i586/Pentium 1 compatible distro, since I have a lot of machines that aren't i686 that are still pretty useful.

Let me tell you, since I started working on this, I've been in hell these last few days! The Pentium Pro was the first chip to support CMOV (Conditional move), and although that was many years ago, lots of chips were still manufactured that didn't support this (or had it broken), including many semi-modern VIA chips, and the old AMD K6.

Just about every package that has to deal with multimedia has lots of inline assembler, and most of it contains CMOV. Most packages let you disable it, either with a switch like ./configure --disable-asm or by tricking it into thinking your chip doesn't support it, but some of them (like MPlayer, libvpx/vp9) do NOT. This means, that although my machines are otherwise full blown, good, honest x86-32 chips, I cannot use that software at all, because it always builds in bad instructions, thanks to these huge amounts of inline assembly!

Of course, then there's the fact that these packages, that could otherwise possibly build and work on all types of chips, are now limited to what's usually the ARM/PPC/x86 triumvirate (sorry, no SPARC Linux!), and the small issue that inline assembly is not actually supported by the C standard.

Is assembly worth it for the handicaps and trouble that it brings? Personally I am a language lawyer/standard Nazi, so inline ASM doesn't sit well with me for additional reasons."

 
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  • (Score: 1) by jackb_guppy on Saturday March 08 2014, @12:51PM

    by jackb_guppy (3560) on Saturday March 08 2014, @12:51PM (#13223)

    The idea of higher languages is to remove the hardware from coding question. This allows for portability between different systems and OS. Now if language can be independent of the OS, would be more good.

    ASM/machine level coding is there to meet special needs. It is more a "business" function and less like a design consideration.

    Year ago I was supporting a hotel system, written in RPG (language on IBM midrange machines mainly) with ASM objects that where linked at compile time to handle date conversions and currency formatting. The business need of for functionality and speed where more important that easy of transporting it the code another platform. Later we also wrote ASM routines to handle B-trees, inventory and room searches. These high level functions became the new bottle neck in the system preventing better use of the underlying hardware and price point of equipment.

    Yes, we could have done the job without ASM, but the price point would be higher and along with maintenance costs. But we gave up portability.