[llvm-bugs] [Bug 27553] New: A lto build of clang with lld has 2624 more symbols than with gold

via llvm-bugs llvm-bugs at lists.llvm.org
Thu Apr 28 08:31:32 PDT 2016


https://llvm.org/bugs/show_bug.cgi?id=27553

            Bug ID: 27553
           Summary: A lto build of clang with lld has 2624 more symbols
                    than with gold
           Product: lld
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: rafael.espindola at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

The problem is the handling of linkonce_odr.

The problem is that we set CanOmitFromDynSym for each file. This is a really
nice pattern that would extend naturally to having the same feature in ELF.

The issue is that with lazy loading of bitcode it has to be conservative since
it has not seen all the uses.

The gold plugin solves this problem by instead:
* Storing the name of every potential candidate.
* Checking if there are uses in the merged bitcode.

Probably the nicest way of solving this is adding an attribute that says that
the address of a GV is not taken.

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