BITS_PER_UNIT larger than 8 -- word addressing

[Boris Boesler]

On 2007-11-27 18:29, Michael Eager wrote:
 > Joseph S. Myers wrote:
 > > On Tue, 27 Nov 2007, Michael Eager wrote:
 > >
 > >> I think that there is a pervasive understanding that SImode is
 > >> single precision integer, 32-bits long.
 > >
 > > Only among contributors not considering non-8-bit bytes.  SImode  
is 4
 > > times QImode, 4*BITS_PER_UNIT bits, and may not exist (or at  
least not be
 > > particularly usable, much like the limitations on TImode on 32-bit
 > > targets) with large BITS_PER_UNIT.
 >
 > I think you just described the majority of contributors.  :-)
 >
 > It's human nature not to recognize one's tacit assumptions or their
 > consequences.

  I assume that GCC internals assume that memory can be byte (8 bits)  
addressed - for historical reasons. Therefore, the sizes of all types  
are multiples of a byte. The same is true for addressing values in  
memory. (Sizes of types and their addresses must be separated more  
precisely. A 32 bit value could be on a 4 bit boundary!) But this is  
changing. Addressable units are on 32 bit boundaries or even on 4 bit  
boundaries today. Well, this is the problem I'm running in right now.

Boris