bitint: Handle m_bitfld_load cast in outer m_cast_conditional [PR114555]

bitint: Handle m_bitfld_load cast in outer m_cast_conditional [PR114555]

We ICE on the following testcase, because we use result of a PHI node
which is only conditional because of a m_cast_conditional on the outermost
loops PHI node argument and so is invalid SSA form.

The following patch fixes it like similar cases elsewhere by adding
needed intervening PHI(s).

2024-04-04  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/114555
	* gimple-lower-bitint.cc (bitint_large_huge::handle_cast): For
	m_bitfld_load and save_cast_conditional add any needed PHIs
	and adjust t4 accordingly.

	* gcc.dg/bitint-103.c: New test.
	* gcc.dg/bitint-104.c: New test.