optimizing bitfield compilation

[Xingzhi Pan]

Hi folks,

I'm studying gcc's source code (4.4.3 for now) to learn how to
optimize bitfield compilation.  Currently I'm using C as an example.
Since gcc is so big I need some guide here.  So my questions are:

1. Does gcc compile C bitfields into some intermediate representation (IR)?
2. If so, does the optimization happen BEFORE or AFTER the IR?  Or both?
3. Where can I find relevant source code?  I already did a find+grep
in gcc-4.4.3/gcc directory but I lack the general knowledge of the
overall structure of gcc so the result didn't help much.
4. Is there any special flags for this feature?

I hope I'm sending to the right list.  If not please tell me where to
go.  Thanks in advance.

Harry