5 ms·

Since Xbox360 is PPC, does this convert to x86_64?

• monocasa 3y ago
  Yes, it recompiles.
• deaddodo 3y ago
  The main README explains their approach. It disassembles PPC, generates equivalent C++ and compiles that into the target ISA (amd64).
  • stavros 3y ago
    Is it not completely crazy that this is even possible? This sounds like wizardry to me.
    • anthk 3y ago
      Qemu does something similar. And Box86 does that while keeping 3D acceleration on converting X86->ARM linux binaries. https://github.com/ptitSeb/box86 https://github.com/ptitSeb/box86
      • actionfromafar 3y ago
        It also depends on how strictly you want preserve the behaviour of the asm.
    • ilyt 3y ago
      It's quite common way to get good performance out of emulated code, althought usually it's JIT. But yeah, it is crazy complex
    • Gordonjcp 3y ago
      Well, think about it this way - suppose you have a block of C code and you compile it to object code, like: if (hitByMissile == True) { lives--; if (lives == 0) playing = False; } ; next address is 0x8f02 it might turn into: ld a, (4011h) jr z, 8f02h ld a, (4020h) dec a ld (4020h), a jr z, 8f02h xor a, a ld (0x4021h), a ; next address is 8f02h That might disassemble back to C as: if (var4011 != 0) { var4020--; if (var4020 == 0) { var4021 == 0; } } like that. Less readable, because we have no variable names, and not identical to the source code but probably close enough, but the important thing is we don't care if we understand it or not. If we declare a variable that our original code stores at 4020h in a 16-bit address space, but it ends up somewhere wildly different in our 32-bit address space because we're recompiling on a newer machine, we don't care - we just care that the name gets used consistently. If you then read through the disassembled source you could start to piece together what the variables are, though.
      • stavros 3y ago
        It's not so much the variables, but that compilation must be a lossy process. There may be many ways to interpret the assembly, and the compiler might generate different asm than the one that was decompiled.
        • jacquesm 3y ago
          Much less lossy than you probably would think if you've never dug through what your typical compiler outputs. There usually aren't that many ways to interpret the assembly and it doesn't matter whether it generates different assembly as long as it does the same thing. The typical code generator for a compiler uses all kinds of boilerplate for common constructs (loops, function calls, data access) and once you know about these you can usually recognize them on sight.
          • stavros 3y ago
            Hmm, that's interesting, thanks Jaques.
            • jacquesm 3y ago
              np Optimizing compilers can make this quite a bit harder by the way, extra passes that do all kinds of reshuffling to get rid of instructions, to combine them and to move things from memory into registers. You can usually tell compilers to output assembly code, doing that for a program that you wrote yourself is a good exercise to see how your high level code translates into lower level code. And with optimization off all you see is the code generator's output.
              • Gordonjcp 3y ago
                Yeah this is where you start to see decompilers outputting C code that just looks like assembler written out as C. There was one I used to use years ago - can't remember the name, some odd commercial thing from one of the many commercial C products that never really took off - that would do a good job *mostly* but at some point start outputting blocks of code with lots of `register` variables in, and you knew it had gone out to lunch on that bit.
    • dagmx 3y ago
      In addition to the examples other commenters have given, it’s also how Rosetta 2 works to translate x86_64 to arm64 for supporting Intel binaries on M1/M2 Macs
    • foobiekr 3y ago
      Moore's law has blessed all of us with nearly infinite compute relative to systems from a decade ago. Now, that we've relentlessly squandered all of it, well, that's on us.
      • stavros 3y ago
        Cries in Electron
  • eltoto 3y ago
    What is PPC please ? Can't find anything
    • wahahah 3y ago
      Add "computing" to your query to disambiguate.
    • recrof 3y ago
      PowerPC
    • ThePowerOfFuet 3y ago
      PowerPC
• stevefan1999 3y ago
  By using C++ as a pseudo-optimal intermediate representation. I mean, at this point, I rather decompile back to LLVM yo.