[llvm-bugs] [Bug 38385] New: Segmentation fault using -mcmodel=large -fpic options after r337740

via llvm-bugs llvm-bugs at lists.llvm.org
Tue Jul 31 06:25:55 PDT 2018


https://bugs.llvm.org/show_bug.cgi?id=38385

            Bug ID: 38385
           Summary: Segmentation fault using -mcmodel=large -fpic options
                    after r337740
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: ilia.taraban at intel.com
                CC: llvm-bugs at lists.llvm.org

This test fails with Segmentation fault after r337740:

================= nice.c ==============
int main ()
{
    unsigned int a [100] = {0};
    return 0;
}
=======================================

>>> clang -v
clang version 7.0.0 (trunk 338366)
Target: x86_64-unknown-linux-gnu
Thread model: posix
...

>>> clang -O0 -o nice.exe nice.c
>>> nice.exe

>>> clang -O0  -mcmodel=large -fpic  -o nice.exe nice.c
>>> nice.exe 
Segmentation fault (core dumped)

Started failing after 
------------------------------------------------------------------------
r337740 | rnk | 2018-07-23 23:14:35 +0200 (Mon, 23 Jul 2018) | 9 lines

Re-land r335297 "[X86] Implement more of x86-64 large and medium PIC code
models"

Don't try to generate large PIC code for non-ELF targets. Neither COFF
nor MachO have relocations for large position independent code, and
users have been using "large PIC" code models to JIT 64-bit code for a
while now. With this change, if they are generating ELF code, their
JITed code will truly be PIC, but if they target MachO or COFF, it will
contain 64-bit immediates that directly reference external symbols. For
a JIT, that's perfectly fine.
------------------------------------------------------------------------

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