memcpy to an unaligned address

[Mike Stump]

On Aug 2, 2005, at 1:45 PM, Ian Lance Taylor wrote:
> That argument doesn't make sense to me.  memcpy takes a void*
> argument, which has no presumed alignment.

The memcpy builtin uses the static type of the actual argument  
(before conversion to void*), to gain hints about the alignments of  
the data coming in.  This is so that we can producing nice fast code  
for 1-16 bytes objects.  This is actually good.  The real problem is  
formation of the address of the member doesn't produce a pointer to  
unaligned type, but rather a pointer to aligned type, this is the  
part that is wrong.  We'd have to add pointers to unaligned data to  
our type system to fix it.  That should be done, but is a hard/big  
job, and no one has stepped forward to do it.