[Bug target/70733] New: Wrong code with nested structs and bit field.

[vsevolod.livinskij at frtk dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70733

            Bug ID: 70733
           Summary: Wrong code with nested structs and bit field.
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vsevolod.livinskij at frtk dot ru
  Target Milestone: ---

Created attachment 38314
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38314&action=edit
Reproducer.

Test case produces incorrect result.

Output:
> clang++ repr.cpp; ./a.out
-4
> g++ repr.cpp; ./a.out
137438953468

GCC version:
> g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/export/users/vlivinsk/gcc-trunk/bin/libexec/gcc/x86_64-pc-linux-gnu/7.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /export/users/vlivinsk/gcc-trunk/gcc/configure
--with-arch=corei7 --with-cpu=corei7 --enable-clocale=gnu --with-system-zlib
--enable-shared --with-demangler-in-ld --enable-cloog-backend=isl
--with-fpmath=sse --enable-checking=release --enable-languages=c,c++,lto
--with-gmp=/export/users/vlivinsk/gcc-trunk/gmp-6.1.0/bin
--with-mpfr=/export/users/vlivinsk/gcc-trunk/mpfr-3.1.3/bin
--with-mpc=/export/users/vlivinsk/gcc-trunk/mpc-1.0.3/bin
--prefix=/export/users/vlivinsk/gcc-trunk/bin
Thread model: posix
gcc version 7.0.0 20160418 (experimental) (Revision=235129)

Test:
#include <iostream>

struct A {
    unsigned long member : 37;
};

struct B {
    A member;
} b;

long a;

int main() {
    b.member.member = 4;
    a = -b.member.member;
    if (a != 4)
        abort();
}