On 4/9/12 4:21 AM, Manu wrote:
After thinking on it a bit, I'm becoming a little worried about this
move for 2 rarely considered reasons:
Using lowering to a template, debug(/unoptimised) performance will
probably get a lot slower, which is really annoying. And
debugging/stepping might become considerably more annoying too, if every
time I press F11 (step in) over a function call that happens to receive
an arg from an array, the debugger then steps into the array templates
index operator... We'd be no better off than with STL, unless the
language has clever ways of hiding this magic from the debugger too, and
optimising/inlining the index even in debug builds...? But this is the
built-in array, and not a library we can optionally not use.
I agree. So we have the counterarguments:
1. Lowering would treat array primitives as sheer D code, subject to
refusal of inlining. That means worse performance.
2. Unless the compiler takes special measures, source-level debuggers
will trace through core, uninteresting code for array operations.
3. There are patterns that attempt to optimize by e.g. using .ptr, but
end up pessimizing code because they trigger multiple memory allocations.
Andrei
