Is < faster than <=?

Question

Is if( a < 901 ) faster than if( a <= 900 ).

Not exactly as in this simple example, but there are slight performance changes on loop

Answer 1

TL;DR answer

For most combinations of architecture, compiler and language, < will not be faster than <=.

Full answer

Other answers have concentrated on x86 architecture, and I don't know the ARM architecture (which your example assembler seems to be) well enough to comment specifically on the code generated, but this is an example of a micro-optimisation which is very architecture specific, and is as likely to be an anti-optimisation as it is to be an optimisation.

As such, I would suggest that this sort of micro-optimisation is an example of cargo cult programming rather than best software engineering practice.

Counterexample

There are probably some architectures where this is an optimisation, but I know of at least one architecture where the opposite may be true. The venerable Transputer architecture only had machine code instructions for equal to and greater than or equal to, so all comparisons had to be built from these primitives.

Even then, in almost all cases, the compiler could order the evaluation instructions in such a way that in practice, no comparison had any advantage over any other. Worst case though, it might need to add a reverse instruction (REV) to swap the top two items on the operand stack. This was a single byte instruction which took a single cycle to run, so had the smallest overhead possible.

Summary

Whether or not a micro-optimisation like this is an optimisation or an anti-optimisation depends on the specific architecture you are using, so it is usually a bad idea to get into the habit of using architecture specific micro-optimisations, otherwise you might instinctively use one when it is inappropriate to do so, and it looks like this is exactly what the book you are reading is advocating.