[LLVMdev] vaargs and backwards compatibility

Andrew Lenharth alenhar2 at cs.uiuc.edu
Tue Mar 29 10:56:53 PST 2005

So Alpha and some other potential targets (amd64?) use structs for
va_list.  This is very much at odds with the current instructions and

So the question for the community is how much backwards compatibility
should be maintained for vaargs?  Essentially the behavior needs to be
reverted to LLVM 1.0 semantics for vaarg instructions.  Currently there
is conversion code to convert the old behavior to the new behavior. 
However, converting from the current behavior to the old behavior is
very non-trivial.

Is bytecode compatibility for this feature important enough to try to do
the automatic coversion (if even possible?).  And given that, can the
1.0 conversion code be dropped?


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