Bit-field patch, resurrected

[Jim Wilson]

Joseph S. Myers wrote:
> Here at last is the resurrected bit-field patch to give bit-fields in
> C their proper types (integer types of the specified signedness and
> width, as required by the C standard, rather than the declared types);

Another issue to consider is the interaction with tree-ssa here. 
tree-ssa adds a lot of optimizations passes in between c-typeck.c and 
expr.c.

If you perform the REDUCE_BIT_FIELD stuff in c-typeck.c, tree-ssa will 
be aware of it, and optimize appropriately.

If you perform the REDUCE_BIT_FIELD stuff in expr.c, it will occur after 
tree-ssa.  This means that tree-ssa will not have the opportunity to 
optimize away unnecesssary REDUCE_BIT_FIELD operations.  It means that 
tree-ssa may perform inappropriate transformations because it isn't 
aware that C99 operations may have bit-field result types, unlike C89 
and C90.
-- 
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com