Should the comma operator be removed in D2?

[Robert Jacques]

On Tue, 17 Nov 2009 18:34:32 -0500, retard <re at tard.com.invalid> wrote:

> Tue, 17 Nov 2009 15:04:01 -0800, Bill Baxter wrote:
>
>> On Tue, Nov 17, 2009 at 2:53 PM, Robert Jacques <sandford at jhu.edu>
>>> *sigh* The reason the compiler would have to create a temporary struct,
>>> is because that's what a tuple is at runtime. Tuples need to be compact
>>> (like structs) so that they can be passed to functions, etc.
>>
>> Sigh back at ya.  I think all of us are just assuming that the compiler
>> will be smart enough to realize that the tuple value is not being used
>> and optimize it away.
>> It should be fairly trivial to detect and handle appropriately.  At
>> least in the case of that for loop there.  I think unused value
>> elimination is probably one of the first things you study in compiler
>> classes on optimization.  It must be because even *I* know about it and
>> I've only taken one compiler class that barely touched on optimization
>> at all.  :-)
>
> Elimination of unused values has been one of the basic optimizations in C
> compilers for decades. E.g. gcc 4.4 does tremendous amounts of
> optimizations and the constant folding logic might even optimize away the
> whole 'for' loop, the function containing the for loop or even the whole
> object file containing the function.
>
> If this kind of argumentation is used against new features, almost every
> high level feature in D should be shaved off - classes, scope statements,
> all literals etc. There is a serious amount of extra code those produce
> compared to a hand crafted asm version of the program.

Yes, I know all this. But, before Bill, no-one seemed be cognizant of it  
(either the optimization or the representation). Also, all those well  
known optimizations don't magically work for structs: I've seen modern  
compilers do some pretty stupid things when structs and temporary values  
are involved.