[PATCH 02/14] Support for adding and stripping location_t wrapper nodes

[David Malcolm <dmalcolm@redhat.com>]

This patch provides a mechanism in tree.c for adding a wrapper node
for expressing a location_t, for those nodes for which
!CAN_HAVE_LOCATION_P, along with a new method of cp_expr.

It's called in later patches in the kit via that new method.

In this version of the patch, I use NON_LVALUE_EXPR for wrapping
constants, and VIEW_CONVERT_EXPR for other nodes.

I also turned off wrapper nodes for EXCEPTIONAL_CLASS_P, for the sake
of keeping the patch kit more minimal.

The patch also adds a STRIP_ANY_LOCATION_WRAPPER macro for stripping
such nodes, used later on in the patch kit.

gcc/ChangeLog:
	PR c++/43486
	* tree.c (maybe_wrap_with_location): New function.
	* tree.h (STRIP_ANY_LOCATION_WRAPPER): New macro.
	(maybe_wrap_with_location): New decl.
	(location_wrapper_p): New inline function.

gcc/cp/ChangeLog:
	PR c++/43486
	* cp-tree.h (cp_expr::maybe_add_location_wrapper): New method.
---
 gcc/cp/cp-tree.h |  6 ++++++
 gcc/tree.c       | 27 +++++++++++++++++++++++++++
 gcc/tree.h       | 26 ++++++++++++++++++++++++++
 3 files changed, 59 insertions(+)

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 874cbcb..726b6f5 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -93,6 +93,12 @@ public:
     set_location (make_location (m_loc, start, finish));
   }
 
+  cp_expr& maybe_add_location_wrapper ()
+  {
+    m_value = maybe_wrap_with_location (m_value, m_loc);
+    return *this;
+  }
+
  private:
   tree m_value;
   location_t m_loc;
diff --git a/gcc/tree.c b/gcc/tree.c
index 28e157f..50c818c 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -13747,6 +13747,33 @@ set_source_range (tree expr, source_range src_range)
   return adhoc;
 }
 
+/* Return EXPR, potentially wrapped with a LOCATION_WRAPPER_EXPR node
+   at LOC, if !CAN_HAVE_LOCATION_P (expr).  */
+
+tree
+maybe_wrap_with_location (tree expr, location_t loc)
+{
+  if (expr == NULL)
+    return NULL;
+  if (loc == UNKNOWN_LOCATION)
+    return expr;
+  if (CAN_HAVE_LOCATION_P (expr))
+    return expr;
+  /* We should only be adding wrappers for constants and for decls,
+     or for some exceptional tree nodes (e.g. BASELINK in the C++ FE).  */
+  gcc_assert (CONSTANT_CLASS_P (expr)
+	      || DECL_P (expr)
+	      || EXCEPTIONAL_CLASS_P (expr));
+
+  if (EXCEPTIONAL_CLASS_P (expr))
+    return expr;
+
+  if (CONSTANT_CLASS_P (expr))
+    return build1_loc (loc, NON_LVALUE_EXPR, TREE_TYPE (expr), expr);
+  else
+    return build1_loc (loc, VIEW_CONVERT_EXPR, TREE_TYPE (expr), expr);
+}
+
 /* Return the name of combined function FN, for debugging purposes.  */
 
 const char *
diff --git a/gcc/tree.h b/gcc/tree.h
index 277aa91..fb45a8d 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -483,6 +483,15 @@ extern void omp_clause_range_check_failed (const_tree, const char *, int,
 #define STRIP_USELESS_TYPE_CONVERSION(EXP) \
   (EXP) = tree_ssa_strip_useless_type_conversions (EXP)
 
+/* Remove any VIEW_CONVERT_EXPR or NON_LVALUE_EXPR that's purely
+   in use to provide a location_t.  */
+
+#define STRIP_ANY_LOCATION_WRAPPER(EXP) \
+  do {					\
+    if (location_wrapper_p (EXP))	\
+      (EXP) = TREE_OPERAND ((EXP), 0);	\
+  } while (0)
+
 /* Nonzero if TYPE represents a vector type.  */
 
 #define VECTOR_TYPE_P(TYPE) (TREE_CODE (TYPE) == VECTOR_TYPE)
@@ -1147,6 +1156,8 @@ get_expr_source_range (tree expr)
 
 extern void protected_set_expr_location (tree, location_t);
 
+extern tree maybe_wrap_with_location (tree, location_t);
+
 /* In a TARGET_EXPR node.  */
 #define TARGET_EXPR_SLOT(NODE) TREE_OPERAND_CHECK_CODE (NODE, TARGET_EXPR, 0)
 #define TARGET_EXPR_INITIAL(NODE) TREE_OPERAND_CHECK_CODE (NODE, TARGET_EXPR, 1)
@@ -3637,6 +3648,21 @@ id_equal (const char *str, const_tree id)
   return !strcmp (str, IDENTIFIER_POINTER (id));
 }
 
+/* Test if EXP is merely a wrapper node, added to express a location_t
+   on behalf of its child.  */
+
+inline bool location_wrapper_p (const_tree exp)
+{
+  if (((TREE_CODE (exp) == NON_LVALUE_EXPR
+	&& CONSTANT_CLASS_P (TREE_OPERAND (exp, 0)))
+       || (TREE_CODE (exp) == VIEW_CONVERT_EXPR
+	   && !CONSTANT_CLASS_P (TREE_OPERAND (exp, 0))))
+      && (TREE_TYPE (exp)
+	  == TREE_TYPE (TREE_OPERAND (exp, 0))))
+    return true;
+  return false;
+}
+
 #define error_mark_node			global_trees[TI_ERROR_MARK]
 
 #define intQI_type_node			global_trees[TI_INTQI_TYPE]
-- 
1.8.5.3