[llvm-bugs] [Bug 34169] New: LTO seems to be optimizing away calls to compiler generated symbols

Sat Aug 12 01:22:36 PDT 2017

https://bugs.llvm.org/show_bug.cgi?id=34169

            Bug ID: 34169
           Summary: LTO seems to be optimizing away calls to compiler
                    generated symbols
           Product: tools
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: release blocker
          Priority: P
         Component: lto
          Assignee: unassignedbugs at nondot.org
          Reporter: phosek at chromium.org
                CC: llvm-bugs at lists.llvm.org

We're seeing this issue when building our kernel and low-level libraries (below
libc) with LTO. This appears to be a recent regression, we don't see these
issues with our Clang build from April.

https://storage.googleapis.com/fuchsia-build/lld/libuserboot.cpio

/usr/local/google/home/phosek/clang-llvm/llvm/out/lld/bin/ld.lld: error:
undefined symbol: memmove
>>> referenced by ld-temp.o
>>>               lto.tmp:(bootstrap)

/usr/local/google/home/phosek/clang-llvm/llvm/out/lld/bin/ld.lld: error:
undefined symbol: memcpy
>>> referenced by ld-temp.o
>>>               lto.tmp:(bootstrap)

https://storage.googleapis.com/fuchsia-build/lld/libmagenta.cpio

/usr/local/google/home/phosek/clang-llvm/llvm/out/lld/bin/ld.lld: error:
undefined symbol: __stack_chk_fail                                             

                                >>> referenced by acpi.cpp:54
(kernel/platform/pc/acpi.cpp:54)                                               

                                                                           >>> 
             lto.tmp:(platform_init_acpi_tables)

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