checkedint call removal

[bearophile via Digitalmars-d]

Walter:

>Instead of adding more language features,<

Perhaps you can't solve this problem in a sufficiently clean way 
without adding language features (and a assume() is not the 
solution, see below).

---------------------

Ola Fosheim:

> Conflating run time debug checks with programmer provided 
> guarantees sounds dangerous. Call it "assume" not "assert" then.

But this still missed the point. I am not interested in 
annotations, in this thread I am not asking for a built-in 
assume() (or for some weird kind kind of assert() that is much 
worse).

Let's go back to the second example I've shown:

void main() {
     import std.stdio, core.checkedint;
	
     ubyte x = 100;
     ubyte y = 200;	

     bool overflow = false;
     immutable result = muls(x, y, overflow);
     assert(!overflow);
     writeln("Product: ", result);
}


Here I am not willing to add an assume(). Here at the call point 
of muls() x and y have a full range of ubytes, so the range 
analysis tell the compiler their product will not overflow, so it 
can replace the muls() with a regular product and leave overflow 
untouched. This is faster.

The same kind of optimization is desired for a SInt or other 
library-defined types. So the point of this discussion is how to 
do this. The problem is that the compiler has some static 
information about ranges, but to optimize away user-defined types 
such information needs to be read and given to "static ifs" to 
replace the calls to muls() to calls to regular operations.

Bye,
bearophile