Re: Why Plan 9 C compilers don't have asm("")

[Cort Dougan]

I'm talking about _modern_ processors, not processors that dominate the
modern age.  This isn't x86.  I don't believe that even aggressive
re-ordering will cause a serious hit in performance on function calls.
Unconditional branches are definitely predictable so icache pre-fetches are
not more complicated that straight-line code.

Measurement is more important, though.  I've rejected a number of
optimizations from people (including many of my own) that were "obvious
enhancements" because of what they showed in real-world measurements.  If
it doesn't run faster, despite the theory being "right", it's worthless.