[Bug other/77769] New: function generated for OpenMP region uses wrong instruction set

["yzhang1985 at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77769

            Bug ID: 77769
           Summary: function generated for OpenMP region uses wrong
                    instruction set
           Product: gcc
           Version: 6.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: other
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yzhang1985 at gmail dot com
  Target Milestone: ---

Created attachment 39707
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39707&action=edit
compilation will fail with "target specific option mismatch"

Greetings, I'm trying write AVX2 SIMD intrinsics code that will be dynamically
dispatched at runtime through a function pointer. The code has to work for
vanilla x86_64 processors, so I can't use -mavx2.

Instead, I use #pragma GCC target("avx2") to target AVX2 for selected
functions. The bug is that whenever I call AVX or AVX2 intrinsics inside an
OpenMP region, I get the error, "target specific option mismatch"

If I move the intrinsics code to another function, it can compile, but if I
mark that function with __attribute__((always_inline)), the compilation fails
with the same error.

So, my conclusion is that the OpenMP code generator is still targeting vanilla
x86_64, instead of AVX2. Appreciate it if someone can work on fixing this.

command line:
g++ -O3 -fopenmp openmp_wrong_target_isa.cpp


Sorry, I couldn't include the preprocessed file as requested - exceeds upload
limit.

gcc -v output:

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/6/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 6.2.0-4'
--with-bugurl=file:///usr/share/doc/gcc-6/README.Bugs
--enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-6 --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 --with-sysroot=/
--enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-libmpx --enable-plugin --with-system-zlib
--disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-6-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-6-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --with-arch-32=i686 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 6.2.0 20160914 (Debian 6.2.0-4)