> >> diff -u gcc/tree-ssa-loop-niter.c (working copy) gcc/tree-ssa-loop-niter.c > >> (working copy) > >> --- gcc/tree-ssa-loop-niter.c (working copy) > >> +++ gcc/tree-ssa-loop-niter.c (working copy) > >> @@ -2875,6 +2875,16 @@ > >> low = lower_bound_in_type (type, type); > >> high = upper_bound_in_type (type, type); > >> > >> + /* In C, pointer arithmetic p + 1 cannot use a NULL pointer, and p - 1 > >> cannot > >> + produce a NULL pointer. The contrary would mean NULL points to an > >> object, > >> + while NULL is supposed to compare unequal with the address of all > >> objects. > >> + Furthermore, p + 1 cannot produce a NULL pointer and p - 1 cannot > >> use a > >> + NULL pointer since that would mean wrapping, which we assume here > >> not to > >> + happen. So, we can exclude NULL from the valid range of pointer > >> + arithmetic. */ > >> + if (int_cst_value (low) == 0) > >> + low = build_int_cstu (TREE_TYPE (low), TYPE_ALIGN_UNIT (TREE_TYPE > >> (type))); > >> + > >> record_nonwrapping_iv (loop, base, step, stmt, low, high, false, true); > >> } > > > > OK, > > I think this is only valid for !flag_delete_null_pointer_checks, on > architectures where that isn't the default we have to assume that > NULL may point to an object.
agreed. Thanks for the correction. Zdenek
