Explaining my fast 6502 code generator
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Explaining my fast 6502 code generator
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Re: Explaining my fast 6502 code generator
#2> my compiler generates faster code than GCC, LLVM, and every other compiler I compared it to
GCC and LLVM can target the 6502?!?
Re: Explaining my fast 6502 code generator
#3> my compiler generates faster code than GCC, LLVM, and every other compiler I compared it to GCC and LLVM can target the 6502?!?
For LLVM, I don’t think it’s in the official repo, but yes:
Re: Explaining my fast 6502 code generator
#4This is a Massalin superoptimizer.
Re: Explaining my fast 6502 code generator
#5> my compiler generates faster code than GCC, LLVM, and every other compiler I compared it to GCC and LLVM can target the 6502?!?
GCC: Via an old, unofficial port: https://github.com/itszor/gcc-6502
Re: Explaining my fast 6502 code generator
#6This is a Massalin superoptimizer.
From a quick skim of Massalin's paper, they seem similar in how they generate combinations of instructions and prune, but different in other areas. Superoptimizer spews out every combination of instruction (even invalid ones) in a search for true optimality, and uses boolean logic + emulation to determine equivalent code sequences to prune. 6502 algorithm only generates combinations it knows will work, and uses a symbolic approach to determine equivalence. Its results are not always optimal, and portions like the PBQP stuff is obviously different.
Re: Explaining my fast 6502 code generator
#7This does far more than I did back in my PET and then Amiga days, but one thing I did was write a multi-pass compiler. Each pass at first found ways to make the come better (usually smaller so it ran faster). Even simple code I wrote could see a 10-20% improvement.
Of-course, this is because the original code was quick and dirty. I wonder what improvement modern compilers could have added.
Re: Explaining my fast 6502 code generator
#8Bookmarked 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.
Re: Explaining my fast 6502 code generator
#9Bookmarked 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?
Re: Explaining my fast 6502 code generator
#10All 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.