[llvm-bugs] [Bug 26680] New: bad alignment for xmm constants due to conflicting COMDATs

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=26680

            Bug ID: 26680
           Summary: bad alignment for xmm constants due to conflicting
                    COMDATs
           Product: new-bugs
           Version: 3.8
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: r.sagitario at gmx.de
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

With LLVM 3.8 for Win64, compile these three files with optimizations:

// a.cpp
double fun(double x)
{
    return x > 1.0 ? 2.0 : 3.0;
}

// b.cpp
double goo(double* x)
{
    x[0] += 3.0;
    x[1] += 2.0;
    return x[0] + x[1];
}

// m.cpp
double fun(double);
double goo(double*);

int main()
{
    fun(1);
    double x[2] = { 0, 0 };
    return goo(x) > 0;
}


with "clang -O -m64 m.cpp a.cpp b.cpp".

The resulting executable crashes due to bad alignment for the
__xmm at 40000000000000004008000000000000 constant. Both a.obj and b.obj define
the COMDAT. a.obj only requires alignment 8, but b.obj needs 16 byte alignment
for the 'addpd' instruction. The linker picks the one from a.obj.

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