Using Assembly Language in C/C++

Question

I remember reading somewhere that to really optimize & speed up certain section of the code, programmers write that section in Assembly language. My questions are -

Answer 1

On some embedded devices (phones and PDAs), it's useful because the compilers are not terribly mature, and can generate extremely slow and even incorrect code. I have personally had to work around, or write assembly code to fix, the buggy output of several different compilers for ARM-based embedded platforms.

Answer 2

First of all, you need to profile your program. Then you optimize the most used paths in C or C++ code. Unless advantages are clear you don't rewrite in assembler. Using assembler makes your code harder to maintain and much less portable - it is not worth it except in very rare situations.