As I just posted, any speed comparison needs to be based on specific implementations (compiler A vs compiler B), not languages.

When it comes to assembly, the "compiler" is the person writing the code, and while assembly gives you the maximum flexibility to potentially equal or outperform any compiler for any language, there are not too many people with the skill to do that, especially when writing large programs (which due to the effort required are rarely written in assembler). In general there is much more potential for improving the speed of programs by changing the design and using better algorithms, which is where high level languages offer a big benefit by making this easier.