[llvm-bugs] [Bug 26502] New: LLVM ERROR: unable to evaluate offset to undefined symbol

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=26502

            Bug ID: 26502
           Summary: LLVM ERROR: unable to evaluate offset to undefined
                    symbol
           Product: libraries
           Version: 3.8
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: jholajter at arxan.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 15840
  --> https://llvm.org/bugs/attachment.cgi?id=15840&action=edit
Bitcode file that reproduces the issue

The following IR is causing a failure in llc when lowering to an object file:

; RUN: llc double-alias.bc -filetype=obj -o double-alias.o 
@bar = global i32 0
@foo2 = alias i32, i32* @bar
@foo3 = alias i32, i32* @foo2
@baz = global i32* @foo3

Is redirection through multiple aliases supposed to work? If @baz is modified
to reference @foo2 instead of @foo3, the IR lowers to an object file
successfully.

Without asserts enabled, the following error is seen:
LLVM ERROR: unable to evaluate offset to undefined symbol '_foo2'

With asserts enabled, the following assert is seen:
Assertion failed: ((SymbolContents == SymContentsUnset || SymbolContents ==
SymContentsOffset) && "Cannot get offset for a common/variable symbol"),
function getOffset, file /llvm-3.8-rc1/src/include/llvm/MC/MCSymbol.h, line
317.
0  llc                      0x00000001111c2a5e
llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 46
1  llc                      0x00000001111c2e99
PrintStackTraceSignalHandler(void*) + 25
2  llc                      0x00000001111bf729 llvm::sys::RunSignalHandlers() +
425
3  llc                      0x00000001111c31e2 SignalHandler(int) + 354
4  libsystem_platform.dylib 0x00007fff885c2eaa _sigtramp + 26
5  llc                      0x0000000111e06635 ErrorCategory + 87253
6  llc                      0x00000001111c2ebb raise + 27
7  llc                      0x00000001111c2f62 abort + 18
8  llc                      0x00000001111c2f4e __assert_rtn + 126
9  llc                      0x0000000110bb988e llvm::MCSymbol::getOffset()
const + 126
10 llc                      0x0000000110bbc25d getLabelOffset(llvm::MCAsmLayout
const&, llvm::MCSymbol const&, bool, unsigned long long&) + 221
11 llc                      0x0000000110bba362
getSymbolOffsetImpl(llvm::MCAsmLayout const&, llvm::MCSymbol const&, bool,
unsigned long long&) + 322
12 llc                      0x0000000110bba456
llvm::MCAsmLayout::getSymbolOffset(llvm::MCSymbol const&) const + 38
13 llc                      0x0000000110b82f21
llvm::MCAssembler::evaluateFixup(llvm::MCAsmLayout const&, llvm::MCFixup
const&, llvm::MCFragment const*, llvm::MCValue&, unsigned long long&) const +
625
14 llc                      0x0000000110b85036
llvm::MCAssembler::handleFixup(llvm::MCAsmLayout const&, llvm::MCFragment&,
llvm::MCFixup const&) + 182
15 llc                      0x0000000110b85a7f
llvm::MCAssembler::layout(llvm::MCAsmLayout&) + 2223
16 llc                      0x0000000110b85f33 llvm::MCAssembler::Finish() + 83
17 llc                      0x0000000110bd07ff
llvm::MCObjectStreamer::FinishImpl() + 191
18 llc                      0x0000000110bc2017 (anonymous
namespace)::MCMachOStreamer::FinishImpl() + 807
19 llc                      0x0000000110bdba35 llvm::MCStreamer::Finish() + 149
20 llc                      0x0000000110296a21
llvm::AsmPrinter::doFinalization(llvm::Module&) + 5425
21 llc                      0x0000000110a4e5d4
llvm::FPPassManager::doFinalization(llvm::Module&) + 84
22 llc                      0x0000000110a4f7f3 (anonymous
namespace)::MPPassManager::runOnModule(llvm::Module&) + 3603
23 llc                      0x0000000110a4e766
llvm::legacy::PassManagerImpl::run(llvm::Module&) + 342
24 llc                      0x0000000110a4fd81
llvm::legacy::PassManager::run(llvm::Module&) + 33
25 llc                      0x000000010eece223 compileModule(char**,
llvm::LLVMContext&) + 19363
26 llc                      0x000000010eec9621 main + 225
27 libdyld.dylib            0x00007fff85f6a5ad start + 1
28 libdyld.dylib            0x0000000000000005 start + 2047433305
Stack dump:
0.
Program arguments: /llvm-3.8-rc1/build/bin/llc double-alias.ll -filetype=obj -o
double-alias.o 
Illegal instruction: 4

The attached bc and ll files are for LLVM-3.8 RC2, but this is reproducible on
older versions of LLVM as well.

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