[Bug optimization/13373] New: optimization with -frerun-cse-after-loop -fexpensive-optimizations produces wrong code on mcore

["olaf at bonorden dot de" <gcc-bugzilla at gcc dot gnu dot org>]

Compilation of a crc8 faild: 
 
source: 
unsigned short Calc_crc8(unsigned char data, unsigned short crc ) 
{ 
        unsigned char i,x16,carry; 
 
        for (i = 0; i < 8; i++) 
    { 
                x16 = (unsigned char)((data & 1) ^ ((unsigned char)crc & 1)); 
                data >>= 1; 
                if (x16 == 1) 
                { 
                   crc ^= 0x4002; 
                   carry = 1; 
                } 
                else carry = 0; 
                crc >>= 1; 
                if (carry) 
                   crc |= 0x8000; 
                else 
                   crc &= 0x7fff; 
    } 
        return crc; 
} 
----------- 
Compilation with "mcore-be-elf-gcc -mbig-endian -O0 -frerun-cse-after-loop 
crc.c -S" is ok, 
with "mcore-be-elf-gcc -mbig-endian -O0 -frerun-cse-after-loop 
-fexpensive-optimizations crc.c -S" the code is not correct. 
 
Part in the produced assembler code: 
first version: 
        ld.h    r7,(r8,2) 
        bgeni   r6,14 
        addi    r6,2    // 16386 0x4002 
        xor     r7,r6 
        st.h    r7,(r8,2) 
        ldw     r6,(r8,8) 
        st.b    r6,(r8,6) 
wrong second version: 
        ld.h    r7,(r8,2) 
        st.h    r7,(r8,2) 
        ldw     r7,(r8,8) 
        st.b    r7,(r8,6) 
The xor part is removed :-( 
 
Compiler without optimization is nearly useless.

-- 
           Summary: optimization with -frerun-cse-after-loop -fexpensive-
                    optimizations produces wrong code on mcore
           Product: gcc
           Version: 3.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: olaf at bonorden dot de
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: mcore-be-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13373