[LLVMbugs] [Bug 3749] New: linker adds spurious use to appending globals

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=3749

           Summary: linker adds spurious use to appending globals
           Product: new-bugs
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Keywords: miscompilation
          Severity: major
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: kamm-removethis at incasoftware.de
                CC: llvmbugs at cs.uiuc.edu


When linking two modules containing appending globals with uses=0 with
llvm::Linker, the resulting global will have a uses count of one.

The cause for the extra use is found in LinkModules.cpp:1168, where a
ConstantExpr::getBitCast(NG, G1->getType()) is created as a replacement for
previous uses of G1 - even if there weren't any.

This bug is significant as the nonzero use count stops LLVM from processing
magic global constants such as llvm.global_ctors.


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