checkedint call removal

[David Bregman via Digitalmars-d]

On Wednesday, 30 July 2014 at 14:51:34 UTC, Andrei Alexandrescu 
wrote:
>> If assert degenerates to assume in release mode, any bugs in 
>> the program
>> could potentially cause a lot more brittleness and 
>> unexpected/undefined
>> behavior than they otherwise would have. In particular, code 
>> generation
>> based on invalid assumptions could be memory unsafe.
>
> I think gcc does that.

It makes more sense in C because it's not memory safe anyways. In 
D, assume would not be @safe, so to have asserts become assumes 
in release mode seems problematic. Perhaps the assume could be 
omitted in safe code, similar to how bounds checks are retained 
for safe code even in release.

> Also, it's unclear to me what the optimizer would be supposed 
> to do if an assumption turns out to be false.
>

One example is a switch statement, if we hint to the compiler 
(via assume) that the default case is unreachable, the compiler 
can potentially generate something like a jump table with no 
bounds check. To generate memory safe code, the compiler needs to 
insert the bounds check even though the assume says it's not 
needed.