[Bug c/37569] Loop incorrectly optimized to endless loop with -Os/-O2/-O3

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #7 from rguenth at gcc dot gnu dot org  2008-09-18 08:57 -------
Well ... VRP validly asserts that i_7 is not NULL after dereferencing it:

<bb 3>:
  # i_2 = PHI <4094B(2), i_20(8)>
  # sum_1 = PHI <0(2), sum_9(8)>
  i_7 = i_2 + -4;
  D.1209_8 = *i_7;
  i_20 = ASSERT_EXPR <i_7, i_7 != 0B>;
  sum_9 = D.1209_8 + sum_1;
  if (i_20 != 0B)
    goto <bb 8>;
  else
    goto <bb 4>;

<bb 8>:
  goto <bb 3>;


which makes it optimize the check for i_20 != NULL to true.

You can work around this with -fno-delete-null-pointer-checks, but frankly
in a hosted i686-pc-cygwin environment the code is just broken.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37569