analyzer: bitfield fixes [PR99212]

This patch verifies the previous fix for bitfield sizes by implementing
enough support for bitfields in the analyzer to get the test cases to pass.

The patch implements support in the analyzer for reading from a
BIT_FIELD_REF, and support for folding BIT_AND_EXPR of a mask, to handle
the cases generated in tests.

The existing bitfields tests in data-model-1.c turned out to rely on
undefined behavior, in that they were assigning values to a signed
bitfield that were outside of the valid range of values.  I believe that
that's why we were seeing target-specific differences in the test
results (PR analyzer/99212).  The patch updates the test to remove the
undefined behaviors.

gcc/analyzer/ChangeLog:
	PR analyzer/99212
	* region-model-manager.cc
	(region_model_manager::maybe_fold_binop): Add support for folding
	BIT_AND_EXPR of compound_svalue and a mask constant.
	* region-model.cc (region_model::get_rvalue_1): Implement
	BIT_FIELD_REF in terms of...
	(region_model::get_rvalue_for_bits): New function.
	* region-model.h (region_model::get_rvalue_for_bits): New decl.
	* store.cc (bit_range::from_mask): New function.
	(selftest::test_bit_range_intersects_p): New selftest.
	(selftest::assert_bit_range_from_mask_eq): New.
	(ASSERT_BIT_RANGE_FROM_MASK_EQ): New macro.
	(selftest::assert_no_bit_range_from_mask_eq): New.
	(ASSERT_NO_BIT_RANGE_FROM_MASK): New macro.
	(selftest::test_bit_range_from_mask): New selftest.
	(selftest::analyzer_store_cc_tests): Call the new selftests.
	* store.h (bit_range::intersects_p): New.
	(bit_range::from_mask): New decl.
	(concrete_binding::get_bit_range): New accessor.
	(store_manager::get_concrete_binding): New overload taking
	const bit_range &.

gcc/testsuite/ChangeLog:
	PR analyzer/99212
	* gcc.dg/analyzer/bitfields-1.c: New test.
	* gcc.dg/analyzer/data-model-1.c (struct sbits): Make bitfields
	explicitly signed.
	(test_44): Update test values assigned to the bits to ones that
	fit in the range of the bitfield type.  Remove xfails.
	(test_45): Remove xfails.

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

1 files changed, 18 insertions, 0 deletions

diff --git a/gcc/analyzer/store.h b/gcc/analyzer/store.h
index be09b42..7bd2824 100644
--- a/gcc/analyzer/store.h
+++ b/gcc/analyzer/store.h
@@ -297,8 +297,16 @@ struct bit_range
 	    && m_size_in_bits == other.m_size_in_bits);
   }
 
+  bool intersects_p (const bit_range &other) const
+  {
+    return (get_start_bit_offset () < other.get_next_bit_offset ()
+	    && other.get_start_bit_offset () < get_next_bit_offset ());
+  }
+
   static int cmp (const bit_range &br1, const bit_range &br2);
 
+  static bool from_mask (unsigned HOST_WIDE_INT mask, bit_range *out);
+
   bit_offset_t m_start_bit_offset;
   bit_size_t m_size_in_bits;
 };
@@ -338,6 +346,8 @@ public:
   const concrete_binding *dyn_cast_concrete_binding () const FINAL OVERRIDE
   { return this; }
 
+  const bit_range &get_bit_range () const { return m_bit_range; }
+
   bit_offset_t get_start_bit_offset () const
   {
     return m_bit_range.m_start_bit_offset;
@@ -739,6 +749,14 @@ public:
   get_concrete_binding (bit_offset_t start_bit_offset,
 			bit_offset_t size_in_bits,
 			enum binding_kind kind);
+  const concrete_binding *
+  get_concrete_binding (const bit_range &bits,
+			enum binding_kind kind)
+  {
+    return get_concrete_binding (bits.get_start_bit_offset (),
+				 bits.m_size_in_bits,
+				 kind);
+  }
   const symbolic_binding *
   get_symbolic_binding (const region *region,
 			enum binding_kind kind);