lower-bitint: Fix up handling of uninitialized large/huge _BitInt call arguments...

lower-bitint: Fix up handling of uninitialized large/huge _BitInt call arguments [PR113316]

The code to assign large/huge _BitInt SSA_NAMEs to partitions intentionally
ignores uninitialized SSA_NAMEs:
          /* Also ignore uninitialized uses.  */
          if (SSA_NAME_IS_DEFAULT_DEF (s)
              && (!SSA_NAME_VAR (s) || VAR_P (SSA_NAME_VAR (s))))
            continue;
because there is no need to store them into memory, all we need is when
trying to extract some limb from them use uninitialized SSA_NAME for the
limb.

The following testcase shows this is a problem for call arguments though,
for those we need to create replacement SSA_NAMEs which are loaded from
the underlying variable.  For uninitialized SSA_NAMEs because we didn't
create underlying variable for them var_to_partition doesn't work, the
following patch handles it by just creating an uninitialized replacement
SSA_NAME.

2024-01-12  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/113316
	* gimple-lower-bitint.cc (bitint_large_huge::lower_call): Handle
	uninitialized large/huge _BitInt arguments to calls.

	* gcc.dg/bitint-67.c: New test.