analyzer: fix uninit false +ves [PR108664,PR108666,PR108725]

analyzer: fix uninit false +ves [PR108664,PR108666,PR108725]

This patch updates poisoned_value_diagnostic so that, where possible,
it checks to see if the value is still poisoned along the execution
path seen during feasibility analysis, rather than just that seen
in the exploded graph.

Integration testing shows this reduction in the number of
false positives:
  -Wanalyzer-use-of-uninitialized-value: 191 -> 153 (-38)
where the changes happen in:
      coreutils-9.1: 34 -> 20 (-14)
         qemu-7.2.0: 78 -> 54 (-24)

gcc/analyzer/ChangeLog:
	PR analyzer/108664
	PR analyzer/108666
	PR analyzer/108725
	* diagnostic-manager.cc (epath_finder::get_best_epath): Add
	"target_stmt" param.
	(epath_finder::explore_feasible_paths): Likewise.
	(epath_finder::process_worklist_item): Likewise.
	(saved_diagnostic::calc_best_epath): Pass m_stmt to
	epath_finder::get_best_epath.
	* engine.cc (feasibility_state::maybe_update_for_edge): Move
	per-stmt logic to...
	(feasibility_state::update_for_stmt): ...this new function.
	* exploded-graph.h (feasibility_state::update_for_stmt): New decl.
	* feasible-graph.cc (feasible_node::get_state_at_stmt): New.
	* feasible-graph.h: Include "analyzer/exploded-graph.h".
	(feasible_node::get_state_at_stmt): New decl.
	* infinite-recursion.cc
	(infinite_recursion_diagnostic::check_valid_fpath_p): Update for
	vfunc signature change.
	* pending-diagnostic.h (pending_diagnostic::check_valid_fpath_p):
	Convert first param to a reference.  Add stmt param.
	* region-model.cc: Include "analyzer/feasible-graph.h".
	(poisoned_value_diagnostic::poisoned_value_diagnostic): Add
	"check_expr" param.
	(poisoned_value_diagnostic::check_valid_fpath_p): New.
	(poisoned_value_diagnostic::m_check_expr): New field.
	(region_model::check_for_poison): Attempt to supply a check_expr
	to the diagnostic
	(region_model::deref_rvalue): Add NULL for new check_expr param
	of poisoned_value_diagnostic.
	(region_model::get_or_create_region_for_heap_alloc): Don't reuse
	regions that are marked as TOUCHED.

gcc/testsuite/ChangeLog:
	PR analyzer/108664
	PR analyzer/108666
	PR analyzer/108725
	* gcc.dg/analyzer/coreutils-cksum-pr108664.c: New test.
	* gcc.dg/analyzer/coreutils-sum-pr108666.c: New test.
	* gcc.dg/analyzer/torture/uninit-pr108725.c: New test.

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