[Bug tree-optimization/65461] -Warray-bounds warnings in the linux kernel (free_area_init_nodes)

["slash.tmp at free dot fr" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65461

Mason <slash.tmp at free dot fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |msebor at gcc dot gnu.org,
                   |                            |slash.tmp at free dot fr

--- Comment #3 from Mason <slash.tmp at free dot fr> ---
Here is a reduced test case:

extern void foo(int *p);
extern int array[2];
void func(void)
{
    int i;

    for (i = 1; i < 2; i++) {
        if (i == 1) continue;
        array[i-1] = 0;
    }

    foo(&i);
}

$ gcc-7 -O3 -Wall -S testcase5.c 
testcase5.c: In function 'func':
testcase5.c:9:14: warning: array subscript is below array bounds
[-Warray-bounds]
         array[i-1] = 0;
         ~~~~~^~~~~

It is obvious that the loop is a NOP (other than setting i to 2)
(start at 1, skip that index, move to 2, exit loop)
And gcc figures it out, but only after issuing a spurious warning.

func:
        subq    $24, %rsp       # allocate space on the stack
        leaq    12(%rsp), %rdi  # copy &i to rdi
        movl    $2, 12(%rsp)    # i = 2
        call    foo             # foo(&i)
        addq    $24, %rsp       # clean up stack
        ret