Add support for the rust offset intrinsic

This patch adds the initial support for generic intrinsics these are do not
map directly to GCC builtins and need to be substited with their specificed
types. This patch allows for custom implementation body for these functions
by specifying handler functions which will generate the applicable
intrinsic when asked for.

Addresses #658

1 files changed, 18 insertions, 0 deletions

diff --git a/gcc/rust/backend/rust-tree.cc b/gcc/rust/backend/rust-tree.cc
index 8e39408..6f7614d 100644
--- a/gcc/rust/backend/rust-tree.cc
+++ b/gcc/rust/backend/rust-tree.cc
@@ -17,6 +17,7 @@
 // <http://www.gnu.org/licenses/>.
 
 #include "rust-tree.h"
+#include "fold-const.h"
 #include "stringpool.h"
 #include "attribs.h"
 #include "escaped_string.h"
@@ -656,4 +657,21 @@ get_fndecl_from_callee (tree fn)
   return NULL_TREE;
 }
 
+tree
+pointer_offset_expression (tree base_tree, tree index_tree, location_t location)
+{
+  tree element_type_tree = TREE_TYPE (TREE_TYPE (base_tree));
+  if (base_tree == error_mark_node || TREE_TYPE (base_tree) == error_mark_node
+      || index_tree == error_mark_node || element_type_tree == error_mark_node)
+    return error_mark_node;
+
+  tree element_size = TYPE_SIZE_UNIT (element_type_tree);
+  index_tree = fold_convert_loc (location, sizetype, index_tree);
+  tree offset
+    = fold_build2_loc (location, MULT_EXPR, sizetype, index_tree, element_size);
+
+  return fold_build2_loc (location, POINTER_PLUS_EXPR, TREE_TYPE (base_tree),
+			  base_tree, offset);
+}
+
 } // namespace Rust