On Thursday, 28 February 2013 at 07:22:53 UTC, Walter Bright
wrote:
On 2/27/2013 10:02 PM, deadalnix wrote:
On Thursday, 28 February 2013 at 05:28:47 UTC, Walter Bright
wrote:
On 2/27/2013 9:20 PM, deadalnix wrote:
If the range define empty with something like front ==
sentinel, the inliner
should kick in a reduce the whole stuff to only one read, no
?
auto c = front;
if (c == sentinel || c == XX)
is two reads. This may not seem important, but when you want
high speed, it
can halve it.
Don't you have to check for both all the time ? You have to
check for the
sentinel anyway.
I suggest again taking a look at the dmd source lexer.c for how
to do it. There is no extra check.
I did, in fact I know it for quite a while.
It does check for sentinel in many places (and it has to). How is
it better than a empty property defined as front == sentinel ?
For instance,
if(!r.empty) {
switch(r.front) {
// cases
}
// somecode
} else {
// error code
}
Will be optimized by adding a case for the sentinel in the switch
(if dmd don't, then it has to be fixed, LLVM is definitively able
to do stuff like that, and I didn't checked, but I'd bet that GCC
can do it as well) in the given way :
switch(r.front) {
case sentinel :
// error code
goto Label;
// cases
}
// somecode
Label:
I don't see how defining a specific sentinel range here helps.
