[ISan] Workaround for SAVE_EXPRsandbox/denis13/isan_fix

Change-Id: Iac55ab97fae23b9046bb40b4556cb85b24c278bf

3 files changed, 53 insertions, 2 deletions

diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 5e8bb742bf4..e6daeac26a8 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -34,6 +34,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimplify.h"
 #include "attribs.h"
 
+extern tree isan_expr (tree expr);
 static tree bot_manip (tree *, int *, void *);
 static tree bot_replace (tree *, int *, void *);
 static hashval_t list_hash_pieces (tree, tree, tree);
@@ -4057,6 +4058,16 @@ cp_save_expr (tree expr)
   return save_expr (expr);
 }
 
+/* Workaround for isan and save_expr.  */
+
+tree
+cp_isan_expr (tree expr)
+{
+  if (processing_template_decl)
+    return expr;
+  return isan_expr (expr);
+}
+
 /* Initialize tree.c.  */
 
 void
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 458baa70539..5e5cd6407e7 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -37,6 +37,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "c-family/c-ubsan.h"
 #include "params.h"
 
+extern tree cp_isan_expr (tree expr);
 static tree cp_build_addr_expr_strict (tree, tsubst_flags_t);
 static tree cp_build_function_call (tree, tree, tsubst_flags_t);
 static tree pfn_from_ptrmemfunc (tree);
@@ -5173,9 +5174,9 @@ cp_build_binary_op (location_t location,
 	 How to get actual value from SAVE_EXPR ?
 	 FIXME: use SAVE_EXPR.   */
 
+      op0 = cp_isan_expr (op0);
+      op1 = cp_isan_expr (op1);
       /*
-      op0 = cp_save_expr (op0);
-      op1 = cp_save_expr (op1);
       op0 = fold_non_dependent_expr (op0);
       op1 = fold_non_dependent_expr (op1);
       */
diff --git a/gcc/tree.c b/gcc/tree.c
index 7ce14c93663..64327099909 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -3375,6 +3375,45 @@ save_expr (tree expr)
   return t;
 }
 
+/* Workaround for isan and save_expr.  */
+
+tree
+isan_expr (tree expr)
+{
+  tree t = fold (expr);
+  tree inner;
+
+  /* If the tree evaluates to a constant, then we don't want to hide that
+     fact (i.e. this allows further folding, and direct checks for constants).
+     However, a read-only object that has side effects cannot be bypassed.
+     Since it is no problem to reevaluate literals, we just return the
+     literal node.  */
+  inner = skip_simple_arithmetic (t);
+  if (TREE_CODE (inner) == ERROR_MARK)
+    return inner;
+
+  if (tree_invariant_p_1 (inner))
+    return t;
+
+  /* If INNER contains a PLACEHOLDER_EXPR, we must evaluate it each time, since
+     it means that the size or offset of some field of an object depends on
+     the value within another field.
+
+     Note that it must not be the case that T contains both a PLACEHOLDER_EXPR
+     and some variable since it would then need to be both evaluated once and
+     evaluated more than once.  Front-ends must assure this case cannot
+     happen by surrounding any such subexpressions in their own SAVE_EXPR
+     and forcing evaluation at the proper time.  */
+  if (contains_placeholder_p (inner))
+    return t;
+
+  /* This expression might be placed ahead of a jump to ensure that the
+     value was computed on both sides of the jump.  So make sure it isn't
+     eliminated as dead.  */
+  TREE_SIDE_EFFECTS (t) = 1;
+  return t;
+}
+
 /* Look inside EXPR into any simple arithmetic operations.  Return the
    outermost non-arithmetic or non-invariant node.  */