Bug#999474: llvm-13: segmentation fault (and corrupted stack) while compiling some OpenCL kernel with pocl on i386

[Andreas Beckmann]

Package: llvm-13
Version: 1:13.0.0-9
Severity: important

This bug is also reproducible with llvm-9/11/12, and probably with
older versions, too.

This bug is a bit tricky to reproduce as it will need a version of pocl
built with a different target cpu than what is uploaded in the archive.

In an i386 chroot ...

Get the pocl source package, unpack and apply patches.
Install the pocl build-depends.
Install clang-13 libclang-13-dev libclang-cpp13-dev llvm-13-dev
(or the corresponding packages of any other llvm version).
In debian/control set the llvm version in the clang/llvm B-D to
the version you want to use. (d/rules parses the version from there)
In debian/rules set
	LLVM_ARCH-i386                   = x86-64
(instead of LLVM_ARCH-i386 = i686)
(anything like pentium4 or newer would work to reproduce the bug,
only when targeting the really old CPUs like i686 it works fine)
Build the package: debian/rules build
This will abort with some failing tests ...

Now we can reproduce the segmentation fault:

# cd obj-i686-linux-gnu
# POCL_DEVICES=basic POCL_BUILDING=1 OCL_ICD_VENDORS="$(pwd)/ocl-vendors" ./tests/kernel/kernel test_ilogb
Running test test_ilogb...
Segmentation fault (core dumped)

retry in gdb:

# POCL_DEVICES=basic POCL_BUILDING=1 OCL_ICD_VENDORS="$(pwd)/ocl-vendors" gdb --args ./tests/kernel/kernel test_ilogb
GNU gdb (Debian 10.1-2) 10.1.90.20210103-git
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "i686-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
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For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./tests/kernel/kernel...
(gdb) run
Starting program: /pocl-1.8/obj-i686-linux-gnu/tests/kernel/kernel test_ilogb
Running test test_ilogb...
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/i386-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
0xf05c7d22 in ?? () from /usr/lib/llvm-13/lib/libLLVM-13.so.1
(gdb) bt
#0  0xf05c7d22 in ?? () from /usr/lib/llvm-13/lib/libLLVM-13.so.1
#1  0x5655d210 in ?? ()
Backtrace stopped: previous frame inner to this frame (corrupt stack?)


I had tried to install the relevant -dbgsym packages, but the
backtrace didn't get better.

If there is anything I can do to help you debug this?


Andreas