4 ms·

Something like "(x3+(y/20)5)" will generate a few lines of assembly (about 3 to 5 in this case, assuming registers are pre-loaded). But usually no, there won't

by gens 10y ago

Something like "(x3+(y/20)5)" will generate a few lines of assembly (about 3 to 5 in this case, assuming registers are pre-loaded). But usually no, there won't be much more code. For example "while(1){..." equals just one instruction, and "for(x=10, x<0, x--){..." is 2-3 instructions. edit: idk how to put a asterisk up there in the example above I have no idea where people get the idea that one line of C equals 10 lines of asm. PS Assembly is not hard at all, and is good to understand/read assembly when coding C. The only thing is that it is a bit rough to start coding in it (no good tutorials is one of the two-three difficulties).

mschuster91 10y ago
> I have no idea where people get the idea that one line of C equals 10 lines of asm. Because coding in asm takes more than just the raw instructions. x86 doesn't have many registers so you're shifting around stuff across registers and memory all the time, not to mention stack setup/teardown and the error checking (e.g. div0, overflow) you are supposed to do after operations.
- gens 10y ago
  C doesn't check for overflows.. I also disagree with "shifting around stuff across registers and memory all the time". An "average" function doesn't really have all that many variables and x86 has 8 GP registers (16 on amd64). You don't even have to declare variables, you just take a register (and/or a location in memory) and use it as you wish. I'm now sitting here thinking what can be done in C that would end up being a lot of instructions, and i can't think of anything. Going over an array does not, neither does recursion (recursion is just syntactic sugar in the end). What else.. i can't think of anything. Macros ? But macros are cheating in this comparison (not to mention that the flat assembler has actual macros, that are extremely powerful)
  - userbinator 10y ago
    C doesn't check for overflows.. This is one of the things where (x86) Asm is definitely easier: divide overflows naturally cause an exception which will get handled automatically, and add/subtract/multiply overflows can be checked with one extra (JO or JC) instruction. In C, this is all undefined behaviour. I'm now sitting here thinking what can be done in C that would end up being a lot of instructions, and i can't think of anything. Crypto algorithms come to mind, but like you said, macros can take care of that easily... and on this page is an AES-256 CFB implementation in Asm that is around the same size of source as others in C (but much smaller binary): http://reimagery.com/fsfd/encrypt.htm http://reimagery.com/fsfd/encrypt.htm

by gens 10y ago

mschuster91 10y ago

> I have no idea where people get the idea that one line of C equals 10 lines of asm. Because coding in asm takes more than just the raw instructions. x86 doesn't have many registers so you're shifting around stuff across registers and memory all the time, not to mention stack setup/teardown and the error checking (e.g. div0, overflow) you are supposed to do after operations.

gens 10y ago
C doesn't check for overflows.. I also disagree with "shifting around stuff across registers and memory all the time". An "average" function doesn't really have all that many variables and x86 has 8 GP registers (16 on amd64). You don't even have to declare variables, you just take a register (and/or a location in memory) and use it as you wish. I'm now sitting here thinking what can be done in C that would end up being a lot of instructions, and i can't think of anything. Going over an array does not, neither does recursion (recursion is just syntactic sugar in the end). What else.. i can't think of anything. Macros ? But macros are cheating in this comparison (not to mention that the flat assembler has actual macros, that are extremely powerful)
- userbinator 10y ago
  C doesn't check for overflows.. This is one of the things where (x86) Asm is definitely easier: divide overflows naturally cause an exception which will get handled automatically, and add/subtract/multiply overflows can be checked with one extra (JO or JC) instruction. In C, this is all undefined behaviour. I'm now sitting here thinking what can be done in C that would end up being a lot of instructions, and i can't think of anything. Crypto algorithms come to mind, but like you said, macros can take care of that easily... and on this page is an AES-256 CFB implementation in Asm that is around the same size of source as others in C (but much smaller binary): http://reimagery.com/fsfd/encrypt.htm http://reimagery.com/fsfd/encrypt.htm