Comment by o11c

Decent intro, though nothing new.

A couple useful points it lacks:

* `switch` statements can be lowered in two different ways: using a jump table (an indirect branch, only possible when values are adjacent; requires a highly-predictable branch to check the range first), or using a binary search (multiple direct branches). Compilers have heuristics to determine which should be used, but I haven't played with them.

* You may be able to turn an indirect branch into a direct branch using code like the following:

  if (function_pointer == expected_function)
    expected_function();
  else
    (*function_pointer)();

* It's generally easy to turn tail recursion into a loop, but it takes effort to design your code to make that possible in the first place. The usual Fibonacci example is a good basic intro; tree-walking is a good piece of homework.

* `cmov` can be harmful (since it has to compute both sides) if branch is even moderately predictable and/or if the less-likely side has too many instructions. That said, from my tests, compilers are still too hesitant to use `cmov` even for cases where yes I really know dammit. OoO CPUs are weird to reason about but I've found that due to dependencies between other instructions, there's often some execution ports to spare for the other side of the branch.