Compiler optimization breaks multi-threaded code

[Sean Kelly]

Kagamin <spam at here.lot> wrote:
> Sean Kelly Wrote:
> 
>>> shared uint cnt;
>>> void atomicInc  ( ) { uint o; while ( !cas( &cnt, o, o + 1 ) ) o =
> > > cnt; }
>>> 
>>> is compiled with dmd -O to something like:
>>> 
>>> shared uint cnt;
>>> void atomicInc  ( ) { while ( !cas( &cnt, cnt, cnt + 1 ) ) { } }
>> What a mess.  DMD isn't supposed to optimize across asm blocks.
> 
> There're no asm blocks in the code. It's a violated contract of shared
> data access.

cas() contains an asm block. Though I guess in this case the compiler
isn't actually optimizing across it. Does atomic!"+="(&cnt, 1) work
correctly?  I know the issue with shared would still have to be fixed,
but that code uses asm for the load as well, so it probably won't be
optimized the same way.