[Bug tree-optimization/23429] New: Operations involving unsigneds could be simplified

[tkoenig at gcc dot gnu dot org]

This could just return 1.

$ cat unsigned-arith.c
int foo(unsigned int *a, unsigned int *b, unsigned int *c)
{
    unsigned int s1, s2;

    s1 = *a + *b;
    s2 = *c + *b;

    return s1 + *c == s2 + *a;
}
$ gcc -O3 -S unsigned-arith.c
$ cat unsigned-arith.s
        .file   "unsigned-arith.c"
        .text
        .p2align 4,,15
.globl foo
        .type   foo, @function
foo:
        pushl   %ebp
        movl    %esp, %ebp
        movl    8(%ebp), %eax
        pushl   %ebx
        movl    (%eax), %ecx
        movl    12(%ebp), %eax
        movl    (%eax), %ebx
        movl    16(%ebp), %eax
        movl    (%eax), %eax
        leal    (%ebx,%eax), %edx
        leal    (%ecx,%edx), %edx
        addl    %ebx, %ecx
        popl    %ebx
        addl    %ecx, %eax
        cmpl    %eax, %edx
        popl    %ebp
        sete    %al
        movzbl  %al, %eax
        ret
        .size   foo, .-foo
        .ident  "GCC: (GNU) 4.1.0 20050815 (experimental)"
        .section        .note.GNU-stack,"",@progbits
$ gfortran -v
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ../gcc-4.1/configure --prefix=/home/ig25 
--enable-languages=c,f95
Thread model: posix
gcc version 4.1.0 20050815 (experimental)

-- 
           Summary: Operations involving unsigneds could be simplified
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P2
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tkoenig at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23429