[LLVMdev] Debug information and bitcode linking patch

[Richard Pennington]

Hi,

The enclosed patch preserves debug information about compilation units, 
functions, and line number information when doing bitcode linking. I'm 
not easily able to try this for non-bitcode linking. Could someone 
familiar with debug info take a look and tell me if it appears to be benign?

The rational is that formerly the compile units and subprogram 
definitions were made into a single occurrence after linking, which 
really messed up the debug info. This patch keeps them separate, as they 
should be.

This is a fix for http://llvm.org/bugs/show_bug.cgi?id=4530

-Rich