[llvm-bugs] [Bug 27836] New: Segfault of __thread varaible in Linux/ARM due to bug of LLVM ARM code generation

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=27836

            Bug ID: 27836
           Summary: Segfault of __thread varaible in Linux/ARM due to bug
                    of LLVM ARM code generation
           Product: libraries
           Version: 3.6
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: ARM
          Assignee: unassignedbugs at nondot.org
          Reporter: leemgs at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 16399
  --> https://llvm.org/bugs/attachment.cgi?id=16399&action=edit
ARM: don't attempt to merge litpools referencing different PC-anchors.

There are four thread local storage (TLS) models in Clang/LLVM as following:
1) global-dynamic TLS model
2) local-dynamic TLS model
3) local-exec TLS model
4) initial-exec TLS model
and emulated-TLS (for Android S/W platform)??

Even though, We can build run normally with the static relocation method by
selecting the initial-exec TLS model instead of global-dynamic TLS model (by
default) , We need to run the clang application code with global-dynamic (or
local-dynamic) TLS model in order that we support some applications is working
with dlopen(3) library call.

We have found the appropriate solution for some clang/LLVM applications
including 1) __thread variables and 2) -O2/-O3 of the clang language. Could you
apply this patch to Ubuntu 14.04 LTS and Ubuntu 16.04 LTS repository?

* LLVM: Revision 268662 (ARM: don't attempt to merge litpools referencing
different PC-anchors.)
http://llvm.org/viewvc/llvm-project?view=revision&revision=268662

Below is the mailing list discussed to fix this issue.
http://lists.llvm.org/pipermail/llvm-dev/2016-May/098974.html
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160502/353476.html
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160509/355091.html
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160516/356679.html

* Before r268662:
  ubuntu at raspberrypi2#> ./corerun ./hello.exe (with -O2/-O3)
  Segmentation Fault

* After r268662:
  ubuntu at raspberrypi2#> ./corerun ./hello.exe (with -O2/-O3)
  Hello!!! Welcome to .NET Core (CoreCLR) world.!!!

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