[Bug rtl-optimization/28611] New: wrong code generated when cast to union is used

["awit at po dot opole dot pl" <gcc-bugzilla at gcc dot gnu dot org>]

source code:

typedef union {
    int word;
    char byte[2];
} Union;

int proc(int l)
{
    if (l < 0 )
        ((Union)l).byte[0] = 0;
    return l;
}

command line for avr:

avr-gcc -mmcu=atmega8 -S -Os test.c

Procedure proc is compiled to single ret instruction.

command line for i586:

gcc -c -Os test.c

Procedure proc is compiled to frame initialization code and ret instruction.

For casting to union used in conditionaly expression :

    if (((Union)l).byte[1] & 0x80) 
        l = 0;

corect code is genereted.

System SUSE 10.1

avr-gcc onfigured with: ../configure --prefix=/opt/cross
--with-local-prefix=/usr/local --infodir=/opt/cross/share/info
--mandir=/opt/cross/share/man --libdir=/opt/cross/lib
--libexecdir=/opt/cross/lib --enable-languages=c,c++ --enable-checking=release
--with-gxx-include-dir=/usr/include/c++/4.1.0 --enable-ssp --disable-libssp
--disable-libgcj --with-slibdir=/lib --with-system-zlib --enable-shared
--enable-__cxa_atexit --enable-libstdcxx-allocator=new --target=avr
--disable-nls --disable-shared --host=i586-suse-linux

i586 gcc configured with: ../configure --enable-threads=posix --prefix=/usr
--with-local-prefix=/usr/local --infodir=/usr/share/info
--mandir=/usr/share/man --libdir=/usr/lib --libexecdir=/usr/lib
--enable-languages=c,c++,objc,fortran,java,ada --enable-checking=release
--with-gxx-include-dir=/usr/include/c++/4.1.0 --enable-ssp --disable-libssp
--enable-java-awt=gtk --enable-gtk-cairo --disable-libjava-multilib
--with-slibdir=/lib --with-system-zlib --enable-shared --enable-__cxa_atexit
--enable-libstdcxx-allocator=new --without-system-libunwind --with-cpu=generic
--host=i586-suse-linux


-- 
           Summary: wrong code generated when cast to union is used
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: awit at po dot opole dot pl
  GCC host triplet: i586-suse-linux
GCC target triplet: avr, i586-suse-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28611