When is assembly faster than C?

Question

One of the stated reasons for knowing assembler is that, on occasion, it can be employed to write code that will be more performant than writing that code in a higher-level

Answer 1

More often than you think, C needs to do things that seem to be unneccessary from an Assembly coder's point of view just because the C standards say so.

Integer promotion, for example. If you want to shift a char variable in C, one would usually expect that the code would do in fact just that, a single bit shift.

The standards, however, enforce the compiler to do a sign extend to int before the shift and truncate the result to char afterwards which might complicate code depending on the target processor's architecture.