From: pkk@spth.de   
      
   Am 30.11.25 um 12:28 schrieb David Brown:   
   >>   
   >> I see two implementation strategies:   
   >>   
   >> * Just ignore the values of the padding bits. You don't need to and or   
   >> anything after arithmetic operations. Makes arithmetic as fast as   
   >> possible. But you need special handling at comparisons and casts.   
   >>   
   >> * Always keep the padding bits in line with the value, i.e. and after   
   >> arithemetic operations for unsigned, copy value of sign bit for   
   >> signed. Extra effort at arithmetic operations, but no extra effort at   
   >> casts and comparisons.   
   >>   
   >   
   > That sounds about right.  It's much the same as the implementation of   
   > _Bool.  You either ignore the padding bits while doing the calculations   
   > and filter them out when they later get in the way, or you keep them   
   > neat and consistent (signed or unsigned extended, as appropriate) during   
   > calculations and it's all fine for other operations.  I have no idea   
   > what might be the most efficient choice overall - it could vary by   
   > application, but I expect implementations to have one fixed strategy.   
   >   
      
   _Bool is a bit different, since it promotes to int, so we don't really   
   have arithemetic directly on _Bool: I can definitely see an   
   implementation going one way for _BitInt, and the other for _Bool.   
      
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