[LLVMdev] C embedded extensions and LLVM

Christopher Lamb
Sun, 11 Nov 2007 07:07:05 -0000

I've been playing around with clang/LLVM looking at adding partial
support for the draft technical report for embedded C extensions
(TR18037, http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1169.pdf),
specifically named address spaces.

Named address spaces need to be tracked in LLVM in essentially all
the same places that alignment is tracked, which necessitates adding
the information to the .bc format. Given the Apple has shipped .bc
files I'm guessing that backwards compatibility is very important.
Given this and the work I see happening on using the newish serialize/
deserialize infrastructure what is the pattern for extending the .bc
format in a backwards compatible way? Is it safe to add records to
the writer for an instruction and predicate parts of the reader based
on the number of records present so that old .bc files with fewer
records for that entry should still be able to be read?

--
Christopher Lamb



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