https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111611
Bug ID: 111611
Summary: Auto-Vectorize Compiler Optimization Causing Exception
/ Crash
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: markus.verv...@x41-dsec.de
Target Milestone: ---
Created attachment 56001
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56001&action=edit
poc for a crash due to unaligned memory
The gcc compiler produces a binary that crashes with a segmentation fault due
to unaligned memory access in a vector instruction when using the compiler
flags `-fmarch=native -ftree-slp-vectorize`.
On a system with a i7-1255U CPU, a crash can be reproduced reliably when
compiling and executing the attached test program with the following command:
gcc -Wall -Wextra -O1 -march=native -ftree-slp-vectorize rbtdb.c -o test
&& ./test
It was found that an unaligned pointer is used in a x86_64 vector
instruction:
vmovdqa ymmword ptr [rbx + 0x20], ymm0
Further investigation reveals that this seems to be caused by a miscompilation
due to automatic vectorization optimizations caused by the flags -march=native
-ftree-slp-vectorize, which cause the compiler to use the native instruction
set of the detected architecture and to apply auto-vectorization24 performance
optimizations.
Hardware: 12th Gen Intel(R) Core(TM) i7-12700H
System: Debian Linux 11
Output of `gcc -v`:
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/10/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa:hsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 10.2.1-6'
--with-bugurl=file:///usr/share/doc/gcc-10/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr
--with-gcc-major-version-only --program-suffix=-10
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib
--enable-libphobos-checking=release --with-target-system-zlib=auto
--enable-objc-gc=auto --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib
--with-tune=generic
--enable-offload-targets=nvptx-none=/build/gcc-10-Km9U7s/gcc-10-10.2.1/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-10-Km9U7s/gcc-10-10.2.1/debian/tmp-gcn/usr,hsa
--without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
--with-build-config=bootstrap-lto-lean --enable-link-mutex
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.2.1 20210110 (Debian 10.2.1-6)
