Inline Assembler bug fixes

[Stefan Koch]

On Saturday, 29 August 2020 at 06:36:03 UTC, Walter Bright wrote:
> The inline assembler is a surprisingly compact piece of code 
> for what it does, but is overly complex. It's also not used 
> that much, so it has tended to be neglected, and bug reports 
> have slowly accumulated for it. Some were 10 years old.
>
> [...]

Please fix this one as well:
https://issues.dlang.org/show_bug.cgi?id=18826