[LLVMdev] [PATCH] - Union types, attempt 2
clattner at apple.com
Fri Jan 15 10:11:44 PST 2010
On Jan 13, 2010, at 12:11 PM, Talin wrote:
> It depends on whether or not unions can be passed around as SSA
> values or not. I can think of situations where you would want to.
> In particular, GEP is useful because you can avoid the bitcast above
> - GEP to element 0 if you want an int (in the example above), or to
> element 1 if you want a double.
> Also, I'm thinking that insertvalue might be the best way to
> construct a constant union. Right now there's a bit of a problem in
> that the data type of a constant must match exactly the declared
> type; However in the case of a union what we want is for the data
> type of the initializer to exactly match the type of one of the
> union members. I thought this would be relatively easy to do, but
> it's a little trickier than I realized.
I think it is useful to support insert/extract on unions just for
orthogonality alone. Stuff that works on structs should generally
work on unions too.
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