lowerbitint: Fix 2 bitint lowering bugs [PR111625]

lowerbitint: Fix 2 bitint lowering bugs [PR111625]

This patch fixes 2 issues.  One is when we want to get address of
an uninitialized large/huge bitint SSA_NAME for multiplication/division/modulo
or conversion to floating point (binary or decimal), the code just creates
an uninitialized limb sized variable and passes address of that, but I forgot
to initialize *prec in that case, so it invoked UB at compile time rather
than at runtime.  As it is UB, we could use anything valid as precision there,
say 2 bits for signed, 1 bit for unsigned as smallest possible set of values,
or full bitint precision as full random value.  Though, because we only pass
address to a single limb, I think it is best to pass the bitsize of the limb.

And the other issue is that when ranger in range_to_prec finds some range
is undefined_p (), it will assert {lower,upper}_bound () method isn't called
on it, but we were.  So, the patch adjusts range_to_proc to treat it like
the !optimized case, full bitint precision.

2023-09-30  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/111625
	PR middle-end/111637
	* gimple-lower-bitint.cc (range_to_prec): Use prec or -prec if
	r.undefined_p ().
	(bitint_large_huge::handle_operand_addr): For uninitialized operands
	use limb_prec or -limb_prec precision.