C++ with assembly

[Red Squirrel]

I know assembly can be used right within C++. I've never tried it as I don't know much about assembly but I did research it a bit out of curiosity.

What would be the advantages of using assembly in C++? Is there any performance advantage or does the optimizer take care of that with regular C++ code?

I may possibly be writing a very large scale game server application and if assembly can increase performance I might start learning it and throw that in where some very fast calculations need to be done in batches. -O3 optimization is very fast but if I can get faster, then even better.

 

[degibson]

Inline ASM is most useful for invoking ISA functionality that isn't directly exposed by the language, e.g. atomic fetch-and-add, SSE extensions, popcount, etc. Compilers are good at optimizing, but sometimes can't quite understand when to use, say SSE instructions, and certainly there isn't a good 'language only' way to tell a compiler to use HW atomic operations.

In general, prefer the following options:
1) Language endemics
2) Compiler macros
3) Inline ASM
4) External ASM function calls

 

[Absolution75]

If you are using visual studio, it only uses up to SSE3 for optimization. Using SSE4.x is useful in certain situations.

If you compile with intel's compiler, it may automatically optimize using higher level SSE instruction sets (not sure on that).