13 ms·

What I get in these article is that the original intent on C language stands true. Use C as a common platform denominator without crazy optimizations (like tcc

What I get in these article is that the original intent on C language stands true. Use C as a common platform denominator without crazy optimizations (like tcc). If you need performance, specialize, C gives you the tools to call assembly (or use compiler some intrinsic or even inline assembly). Complex compiler doing crazy optimizations, in my opinion, is not worth it.

eru 9mo ago
Well, C is a lie anyway: it's not how computers work any more (and I'm not sure it's how they ever worked).
- woooooo 9mo ago
  Assembly isnt how they work under the hood, but its the highest fidelity interface we have. C as "portable assembler" is targeting the surface that chip designers give us and the one that they try to make fast via all their microcode tricks.
kergonath 9mo ago
> Complex compiler doing crazy optimizations, in my opinion, is not worth it. For these optimisations that are in the back-end, they are used for other languages that can be higher-level or that cannot drop to assembler as easily. C is just one of the front-ends of modern compiler suites.
- ziml77 9mo ago
  Some of them even give you access to this stuff. C# has Vector<T> which picks implementations of various operations based on the current CPU's capabilities. But they also let you have complete control if you want by providing functions in the System.Runtime.Instrinsics namespace.
vjerancrnjak 9mo ago
I remember being quite surprised that my implementation which uses manual stack updates is much slower than what compiler had with recursion. Turns out, I was pushing and popping from stack on every conceptual "recursive call", but compiler figured out it can keep 2-3 recursive levels in registers and pop/push 30% of the time, had more stuff in memory than my version as well. Even when I reduced memory read/writes to ~50% of the recursive program, kept most of the state in registers, the recursive program was faster anyway due to just using more registers than me. I realized then that I cannot reason about the microoptimizations at all if I'm coding in a high-level language like C or C++. Hard to predict the CPU pipeline, sometimes profile guided optimization gets me there faster than my own silliness of assuming I can reason about it.

eru 9mo ago

Well, C is a lie anyway: it's not how computers work any more (and I'm not sure it's how they ever worked).

woooooo 9mo ago
Assembly isnt how they work under the hood, but its the highest fidelity interface we have. C as "portable assembler" is targeting the surface that chip designers give us and the one that they try to make fast via all their microcode tricks.

kergonath 9mo ago

> Complex compiler doing crazy optimizations, in my opinion, is not worth it. For these optimisations that are in the back-end, they are used for other languages that can be higher-level or that cannot drop to assembler as easily. C is just one of the front-ends of modern compiler suites.

ziml77 9mo ago
Some of them even give you access to this stuff. C# has Vector<T> which picks implementations of various operations based on the current CPU's capabilities. But they also let you have complete control if you want by providing functions in the System.Runtime.Instrinsics namespace.

vjerancrnjak 9mo ago

I remember being quite surprised that my implementation which uses manual stack updates is much slower than what compiler had with recursion. Turns out, I was pushing and popping from stack on every conceptual "recursive call", but compiler figured out it can keep 2-3 recursive levels in registers and pop/push 30% of the time, had more stuff in memory than my version as well. Even when I reduced memory read/writes to ~50% of the recursive program, kept most of the state in registers, the recursive program was faster anyway due to just using more registers than me. I realized then that I cannot reason about the microoptimizations at all if I'm coding in a high-level language like C or C++. Hard to predict the CPU pipeline, sometimes profile guided optimization gets me there faster than my own silliness of assuming I can reason about it.