[Bug rtl-optimization/26069] New: Runtime endian-ness check is no longer optimized out.

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

bool tell_endian() {
  unsigned x = 1;
  return *(char*)&x;
}

g++ 3.4.2 produces:

00000000 <_Z11tell_endianv>:
    0:   55                      push   %ebp
    1:   89 e5                   mov    %esp,%ebp
    3:   b8 01 00 00 00          mov    $0x1,%eax
    8:   c9                      leave
    9:   c3                      ret

g++ 4.0.0 produces:

    0:   55                      push   %ebp
    1:   89 e5                   mov    %esp,%ebp
    3:   83 ec 10                sub    $0x10,%esp
    6:   c7 45 fc 01 00 00 00    movl   $0x1,0xfffffffc(%ebp)
    d:   31 c0                   xor    %eax,%eax
    f:   80 7d fc 00             cmpb   $0x0,0xfffffffc(%ebp)
   13:   0f 95 c0                setne  %al
   16:   c9                      leave
   17:   c3                      ret

compile line:
g++ -O3 -c -o endian_test.o endian_test.cpp


-- 
           Summary: Runtime endian-ness check is no longer optimized out.
           Product: gcc
           Version: 4.0.2
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: atgraham at gmail dot com
  GCC host triplet: linux-x86-elf
GCC target triplet: linux-x86-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26069