analyzer: add src_region param to region_model::check_for_poison [PR106479]

analyzer: add src_region param to region_model::check_for_poison [PR106479]

PR analyzer/106479 notes that we don't always show the region-creation
event for a memmove from an uninitialized stack region.  This occurs
when using kf_memcpy_memmove.  Fix by passing a src_region hint to
region_model::check_for_poison.

gcc/analyzer/ChangeLog:
	PR analyzer/106479
	* kf.cc (kf_memcpy_memmove::impl_call_pre): Pass in source region
	to region_model::check_for_poison.
	* region-model-asm.cc (region_model::on_asm_stmt): Pass NULL
	region to region_model::check_for_poison.
	* region-model.cc (region_model::check_for_poison): Add
	"src_region" param, and pass it to poisoned_value_diagnostic.
	(region_model::on_assignment): Pass NULL region to
	region_model::check_for_poison.
	(region_model::get_rvalue): Likewise.
	* region-model.h (region_model::check_for_poison): Add
	"src_region" param.
	* sm-fd.cc (fd_state_machine::on_accept): Pass in source region
	to region_model::check_for_poison.
	* varargs.cc (kf_va_copy::impl_call_pre): Pass NULL region to
	region_model::check_for_poison.
	(kf_va_arg::impl_call_pre): Pass in source region to
	region_model::check_for_poison.

gcc/testsuite/ChangeLog:
	PR analyzer/106479
	* gcc.dg/analyzer/pr104308.c (test_memmove_within_uninit): Remove
	xfail on region creation event.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>