dmd foreach loops throw exceptions on invalid UTF sequences, use replacementDchar instead

[deadalnix]

On Saturday, 6 November 2021 at 01:55:47 UTC, deadalnix wrote:
> On Saturday, 6 November 2021 at 00:40:41 UTC, Andrei 
> Alexandrescu wrote:
>> Turns out the EH code is very well separated. Gcc goes so far 
>> as to generate two separate functions, one for hot and one for 
>> cold. Clang also does a good job separating the paths.
>>
>
> You bet, I wrote the code that separates the two :)
>

To expand on that, I also wrote code that send all the exception 
handling code in a cold section in the executable (and if PGO is 
enabled, also really cold codepath). This impact on benchmark was 
fairly minimal, so this ended up not being merged.