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Explaining my fast 6502 code generator

pubby.games

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Re: Explaining my fast 6502 code generator

#11

Post by ajross »

iainmerrick wrote: post #9
ajross wrote: post #8

Bookmarked this to read about optimizers, because it looks great. That said, I clicked on the link because it had "6502" in the title. And... this isn't very interesting as a retrocomputing activity. To be blunt: there's absolutely no way in hell a compiler architecture like that is ever going to be self-hosting in 64k of memory space.

Not interesting to you, but other people may differ! A cross-compiler targeting the 6502 is still interesting to some. As the article notes, these compiler techniques weren’t invented in the 70s because computers weren’t powerful enough to make good use of them. What’s wrong with exploring what the original hardware is capable of when freed from those restrictions?

There's nothing "wrong" with it. I'm just saying that if I'm going to read an article about fun 6502 activities, I want to see it hosted on an Apple II. If I want to read about compiler techniques, I'd prefer to see it targetting a more orthogonal (or less weird, anyway) architecture.

Re: Explaining my fast 6502 code generator

#12

Post by pubby »

billyjobob wrote: post #10

All the other compilers in the comparison are C compilers, right? Whereas this compiler is compiling its own home made language? So not sure how the comparison can be valid.

FWIW the custom language is very close to C, and the examples are pretty much a 1-1 transposition.

I agree with you though on a different note. It's dubious to compare compilers by benchmarking them, because tests are highly arbitrary and are won/lost based on single weak links. It's not really an exact science, but rather something you can start with to figure out how things are behaving. I mostly base my opinions by looking at the assembly code each compiler generates, but a single bar graph is a better presentation for articles.

Re: Explaining my fast 6502 code generator

#13

Post by ecpottinger »

iainmerrick wrote: post #9
ajross wrote: post #8

Bookmarked this to read about optimizers, because it looks great. That said, I clicked on the link because it had "6502" in the title. And... this isn't very interesting as a retrocomputing activity. To be blunt: there's absolutely no way in hell a compiler architecture like that is ever going to be self-hosting in 64k of memory space.

Not interesting to you, but other people may differ! A cross-compiler targeting the 6502 is still interesting to some. As the article notes, these compiler techniques weren’t invented in the 70s because computers weren’t powerful enough to make good use of them. What’s wrong with exploring what the original hardware is capable of when freed from those restrictions?

It is my understanding the the GEOS system was developed on a more powerful machine than the C64/Atari computers it was used on. This let then have the entire code in memory and then processed for common functions. They could not do this on the the 64K-8 bit computers at the time.

Re: Explaining my fast 6502 code generator

#14

Post by troad »

ajross wrote: post #8

Bookmarked this to read about optimizers, because it looks great. That said, I clicked on the link because it had "6502" in the title. And... this isn't very interesting as a retrocomputing activity. To be blunt: there's absolutely no way in hell a compiler architecture like that is ever going to be self-hosting in 64k of memory space.

I don't think of retro-computing as an activity limited solely to the hardware and software that existed at a given time, that's far too restrictive for me.

6502 is an architecture, not a specific machine, nor even the set of machines that supported that architecture in the past. The architecture is and remains interesting on its own! (6502 assembly remains a really good intro to assembly, for instance, even for people that have never even seen a C64.)

There is absolutely scope for people to do fun things with 6502 that could never run on a C64 or an Apple II. The vast majority of 6502 code today runs in emulation, so there's really no reason to artificially gimp it to ape the limitations of any given machine. (Unless emulating that specific machine of course!)

Re: Explaining my fast 6502 code generator

#15

Post by mmphosis »

billyjobob wrote: post #10

All the other compilers in the comparison are C compilers, right? Whereas this compiler is compiling its own home made language? So not sure how the comparison can be valid.

I think NESFab is a medium level programming language targeting the NES 6502. On NES, the Decimal flag has no effect.

GNU Compiler Collection no longer targets 6502, but an older version of the GNU C Compiler could. LLVM targeting 6502 is limited. There is also the cc65 cross compiler. [1]

LLVM [2] and GCC [3] are compiler and toolchain technologies. The name Low Level Virtual Machine (LLVM) is no longer officially an acronym, and the GNU C Compiler is now the GNU Compiler Collection (GCC).

[1] https://www.cc65.org/ [2] https://www.llvm.org/ [3] https://gcc.gnu.org/

Re: Explaining my fast 6502 code generator

#17

Post by ajross »

troad wrote: post #14
ajross wrote: post #8

Bookmarked this to read about optimizers, because it looks great. That said, I clicked on the link because it had "6502" in the title. And... this isn't very interesting as a retrocomputing activity. To be blunt: there's absolutely no way in hell a compiler architecture like that is ever going to be self-hosting in 64k of memory space.

I don't think of retro-computing as an activity limited solely to the hardware and software that existed at a given time, that's far too restrictive for me. 6502 is an architecture, not a specific machine, nor even the set of machines that supported that architecture in the past. The architecture is and remains interesting on its own! (6502 assembly remains a really good intro to assembly, for instance, even for peop…

> 6502 assembly remains a really good intro to assembly

It... really is not, though. It doesn't teach you macro assemblers as they exist in the modern world. It doesn't teach you interaction with the linker except in the simplest ways.

And while the instruction set is "simple" in the sense that it can be understood on a page of paper, lots of critically important ideas don't exist in a meaningful way. Modern techniques like register assignment aren't possible given the limitations and non-orthogonality of the CPU state. There's no "ABI" equivalent you can use to call a standard function, and even something as foundational as "passing arguments" to a function isn't directly expressible, because the "stack pointer" isn't actually a pointer. In point (heh) of fact, no pointers are pointers because the 6502 doesn't actually have an abstraction for a memory address!

Everyone should learn to hack on an Apple II (and good grief, not a Commodore unless you are trying to learn VIC-II or SID hardware), but not to teach themselves "assembly" as a skill they might apply elsewhere.

In fact it's almost the same argument used for why we teach new kids Python and not BASIC. The latter just isn't a useful tool for expressing the concepts you need to learn.

Re: Explaining my fast 6502 code generator

#18

Post by Luc »

ajross wrote: post #17
troad wrote: post #14

Earlier quoted context omitted.

I don't think of retro-computing as an activity limited solely to the hardware and software that existed at a given time, that's far too restrictive for me. 6502 is an architecture, not a specific machine, nor even the set of machines that supported that architecture in the past. The architecture is and remains interesting on its own! (6502 assembly remains a really good intro to assembly, for instance, even for peop…

> 6502 assembly remains a really good intro to assembly It... really is not, though. It doesn't teach you macro assemblers as they exist in the modern world. It doesn't teach you interaction with the linker except in the simplest ways. And while the instruction set is "simple" in the sense that it can be understood on a page of paper, lots of critically important ideas don't exist in a meaningful way. Modern techniqu…

Wow you really are into telling people what they should do.

Re: Explaining my fast 6502 code generator

#19

Post by ajross »

Luc wrote: post #18
ajross wrote: post #17

Earlier quoted context omitted.

> 6502 assembly remains a really good intro to assembly It... really is not, though. It doesn't teach you macro assemblers as they exist in the modern world. It doesn't teach you interaction with the linker except in the simplest ways. And while the instruction set is "simple" in the sense that it can be understood on a page of paper, lots of critically important ideas don't exist in a meaningful way. Modern techniqu…

Wow you really are into telling people what they should do.

> Wow you really are into telling people what they should do.

Saying "6502 is not a good platform for learning assembly" is simply not the same thing as saying "you should not learn assembly language with a 6502 assembler", and I don't understand how you're interpreting it that way.

It's just giving you my opinion and advice. By your own logic, you are now trying to censor my ability to give that opinion and advice. That's bad too, right? Why are you "telling me what to do"?

Chill. Opinions are OK. If you don't agree, that's fine. But a better response is a reasoned counter argument and not "don't say that".

Re: Explaining my fast 6502 code generator

#20

Post by Someone »

troad wrote: post #14
ajross wrote: post #8

Bookmarked this to read about optimizers, because it looks great. That said, I clicked on the link because it had "6502" in the title. And... this isn't very interesting as a retrocomputing activity. To be blunt: there's absolutely no way in hell a compiler architecture like that is ever going to be self-hosting in 64k of memory space.

I don't think of retro-computing as an activity limited solely to the hardware and software that existed at a given time, that's far too restrictive for me. 6502 is an architecture, not a specific machine, nor even the set of machines that supported that architecture in the past. The architecture is and remains interesting on its own! (6502 assembly remains a really good intro to assembly, for instance, even for peop…

> The vast majority of 6502 code today runs in emulation

Emulating a 6502 isn’t that popular, so _if_ there’s even a single commercial product still using a 6502, I would guess that could easily run more 6502 cycles in total than are getting emulated.

Now, are there any? I wouldn’t know, but

- it seems you can still buy new (they’re RoHS compliant, so I don’t think they have stocks going back decades that they’re selling) 6502 CPUs (https://www.westerndesigncenter.com/wdc/HowToOrder.php)

- It was true during the Tamagotchi craze (https://hackaday.com/2013/05/24/tamagotchi-rom-dump-and-reve...: “it was a huge chore just to figure out what processor this uses. It turned out to be a 6502 core with a few other things built in”), but that’s over 20 years ago.

So, where, if anywhere, are these things being used?

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