dsimcha wrote:
== Quote from Walter Bright (newshou...@digitalmars.com)'s article
bearophile wrote:
Bekenn:
The use of ref introduces a level of indirection.
This is correct. But a minimally decent compiler must be able to remove this
indirection where possible, like here, and produce efficient code.
Having the optimizer remove indirection is rarely possible in C or C++, due to
aliasing.
I'm sure there are tons of nitty-gritty details in implementing something like
this properly, but **in principle**, can't the compiler put a runtime check in
for
aliasing and select the code path based on whether aliasing is present or not?
Essentially, you'd have two generated functions, one that handles the aliasing
case and one that handles the no-aliasing case.
The check will cost you more than you win!
But even a check is rarely even possible. Call any function in C/C++, and the
optimizer has to throw in the towel on the values of any indirect references.
Even if the optimizer can do interprocedural analysis, the source of that
function may not be available to the compiler, or the function may be a virtual
call.
D has a number of characteristics which can permit much more aggressive
optimization, but the opportunity is unrealized.
