[PATCH 05/15] Add selftests to fold-const.c

[David Malcolm <dmalcolm at redhat dot com>]

Jeff approved an older version of this (as a separate
unittests/test-folding.c):
 https://gcc.gnu.org/ml/gcc-patches/2015-10/msg03305.html
> OK if/when prereqs are approved. Minor twiddling if we end up
> moving it elsewhere or standardizing/reducing header files
> is pre-approved.

gcc/ChangeLog:
	* fold-const.c: Include "selftest.h".
	(class tree_folding_test): New test subclass.
	(tree_folding_test, arithmetic_folding): New selftest.
---
 gcc/fold-const.c | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 698062e..27c9216 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -74,6 +74,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-into-ssa.h"
 #include "md5.h"
 #include "case-cfn-macros.h"
+#include "selftest.h"
 
 #ifndef LOAD_EXTEND_OP
 #define LOAD_EXTEND_OP(M) UNKNOWN
@@ -14423,3 +14424,68 @@ c_getstr (tree src)
 
   return TREE_STRING_POINTER (src) + tree_to_uhwi (offset_node);
 }
+
+#if CHECKING_P
+
+namespace {
+
+/* A test fixture for writing tests of folding trees.  */
+class tree_folding_test : public ::selftest::test
+{
+ protected:
+  void
+  assert_binop_folds_to_const (tree lhs, enum tree_code code, tree rhs,
+			       tree constant)
+  {
+    EXPECT_EQ (constant, fold_build2 (code, TREE_TYPE (lhs), lhs, rhs));
+  }
+
+  void
+  assert_binop_folds_to_nonlvalue (tree lhs, enum tree_code code, tree rhs,
+				   tree wrapped_expr)
+  {
+    tree result = fold_build2 (code, TREE_TYPE (lhs), lhs, rhs);
+    EXPECT_NE (wrapped_expr, result);
+    EXPECT_EQ (NON_LVALUE_EXPR, TREE_CODE (result));
+    EXPECT_EQ (wrapped_expr, TREE_OPERAND (result, 0));
+  }
+};
+
+TEST_F (tree_folding_test, arithmetic_folding)
+{
+  tree type = integer_type_node;
+  tree x = create_tmp_var_raw (type, "x");
+  tree zero = build_zero_cst (type);
+  tree one = build_int_cst (type, 1);
+
+  /* Addition.  */
+  /* 1 <-- (0 + 1) */
+  assert_binop_folds_to_const (zero, PLUS_EXPR, one,
+			       one);
+  assert_binop_folds_to_const (one, PLUS_EXPR, zero,
+			       one);
+
+  /* (nonlvalue)x <-- (x + 0) */
+  assert_binop_folds_to_nonlvalue (x, PLUS_EXPR, zero,
+				   x);
+
+  /* Subtraction.  */
+  /* 0 <-- (x - x) */
+  assert_binop_folds_to_const (x, MINUS_EXPR, x,
+			       zero);
+  assert_binop_folds_to_nonlvalue (x, MINUS_EXPR, zero,
+				   x);
+
+  /* Multiplication.  */
+  /* 0 <-- (x * 0) */
+  assert_binop_folds_to_const (x, MULT_EXPR, zero,
+			       zero);
+
+  /* (nonlvalue)x <-- (x * 1) */
+  assert_binop_folds_to_nonlvalue (x, MULT_EXPR, one,
+				   x);
+}
+
+}  // anon namespace
+
+#endif /* CHECKING_P */
-- 
1.8.5.3