I tracked it down to this:
/* Allow conversions between integral types and pointers only if
there is no sign or zero extension involved. */
if (((POINTER_TYPE_P (type) && INTEGRAL_TYPE_P (TREE_TYPE (op)))
|| (POINTER_TYPE_P (TREE_TYPE (op)) && INTEGRAL_TYPE_P (type)))
&& TYPE_PRECISION (type) == TYPE_PRECISION (TREE_TYPE (op)))
return false;
The code does not do what the comment says. It also requires that
there be no truncation.
However, of course, other parts of the compiler complain about
truncation as well.
The root cause is this:
ptr = fold_build2 (POINTER_PLUS_EXPR, TREE_TYPE (ptr), ptr,
fold_convert (sizetype, vtable));
We fold_convert to sizetype, without regard for whether it's the same
precision as TREE_TYPE (ptr). vtable is the right size, ptr is the
right size, but we're creating an intermediate that's the wrong size.
Can we put in a calculate-unsigned-for-type call here? That should be
sizetype for everyone else, but the special type for m32c.
