c39cb6bf83
If on &base->member the offset isn't constant or isn't zero and
-fdelete-null-pointer-checks and not -fwrapv-pointer and base has a range
that doesn't include NULL, we return the range of the base.
Usually it isn't a big deal, because for most pointers we just use
varying, range_zero and range_nonzero ranges and nothing beyond that,
but if a pointer is initialized from a constant, we actually track the
exact range and in that case this causes miscompilation.
As discussed on IRC, I think doing something like:
offset_int off2;
if (off_cst && off.is_constant (&off2))
{
tree cst = wide_int_to_tree (sizetype, off2 / BITS_PER_UNIT);
// adjust range r with POINTER_PLUS_EXPR cst
if (!range_includes_zero_p (&r))
return true;
}
// Fallback
r = range_nonzero (TREE_TYPE (gimple_assign_rhs1 (stmt)));
return true;
could work, given that most of the pointer ranges are just the simple ones
perhaps it is too much for little benefit.
2021-11-17 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/103255
* gimple-range-fold.cc (fold_using_range::range_of_address): Return
range_nonzero rather than unadjusted base's range. Formatting fixes.
* gcc.c-torture/execute/pr103255.c: New test.
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