[LLVMbugs] [Bug 5263] New: bugpoint: should be able to reduce linker bugs

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.org/bugs/show_bug.cgi?id=5263

           Summary: bugpoint: should be able to reduce linker bugs
           Product: new-bugs
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: new bugs
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: edwintorok at gmail.com
                CC: llvmbugs at cs.uiuc.edu


When reducing a bug in llvm-ld there are 2 things missing:
1. bugpoint doesn't support -l<libraryname>, where <libraryname> is a .a file
containing bitcode files (llvm-ld does support this, llvm-link again doesn't).

This can be worked around by doing llvm-ld -disable-opt -o foo.bc, then
reducing foo.bc with bugpoint. UNLESS the bug is in the linker itself, then you
have to extract each .a file by hand, and link all the .o files. That takes us
to the next problem:

2. bugpoint should be able to reduce the linker command-line, when the bug is
in the linker (i.e. the linked file doesn't pass -verify). It should do a
binary search, trying to figure out which files need to be linked to reproduce
the bug.
It should then also try to start deleting functions/types/globals to create an
even more minimal testcase (similar to multidelta, except not reduce in-place).

This could then be used to reduce performance bugs (like linking itself taking
way too much time, or memory).

3. bugpoint should be able to find out if any of its input bitcodes doesn't
pass -verify, and give a message about it.
This has happened with llvm-gcc -O2, see PR5262.


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