PR sanitizer/58413

c-family/
	* c-ubsan.c (ubsan_instrument_shift): Don't instrument
	an expression if we can prove it is correct.
	(ubsan_instrument_division): Likewise.  Remove unnecessary
	check.
testsuite/
	* c-c++-common/ubsan/shift-5.c: New test.
	* c-c++-common/ubsan/shift-6.c: New test.
	* c-c++-common/ubsan/div-by-zero-5.c: New test.
	* gcc.dg/ubsan/c-shift-1.c: New test.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@202886 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 10 insertions, 8 deletions

diff --git a/gcc/c-family/c-ubsan.c b/gcc/c-family/c-ubsan.c
index 9f43f6d55b8..0bfc660cdd5 100644
--- a/gcc/c-family/c-ubsan.c
+++ b/gcc/c-family/c-ubsan.c
@@ -51,14 +51,6 @@ ubsan_instrument_division (location_t loc, tree op0, tree op1)
   if (TREE_CODE (type) != INTEGER_TYPE)
     return NULL_TREE;
 
-  /* If we *know* that the divisor is not -1 or 0, we don't have to
-     instrument this expression.
-     ??? We could use decl_constant_value to cover up more cases.  */
-  if (TREE_CODE (op1) == INTEGER_CST
-      && integer_nonzerop (op1)
-      && !integer_minus_onep (op1))
-    return NULL_TREE;
-
   t = fold_build2 (EQ_EXPR, boolean_type_node,
 		    op1, build_int_cst (type, 0));
 
@@ -74,6 +66,11 @@ ubsan_instrument_division (location_t loc, tree op0, tree op1)
       t = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, t, x);
     }
 
+  /* If the condition was folded to 0, no need to instrument
+     this expression.  */
+  if (integer_zerop (t))
+    return NULL_TREE;
+
   /* In case we have a SAVE_EXPR in a conditional context, we need to
      make sure it gets evaluated before the condition.  */
   t = fold_build2 (COMPOUND_EXPR, TREE_TYPE (t), op0, t);
@@ -138,6 +135,11 @@ ubsan_instrument_shift (location_t loc, enum tree_code code,
       tt = fold_build2 (TRUTH_OR_EXPR, boolean_type_node, x, tt);
     }
 
+  /* If the condition was folded to 0, no need to instrument
+     this expression.  */
+  if (integer_zerop (t) && (tt == NULL_TREE || integer_zerop (tt)))
+    return NULL_TREE;
+
   /* In case we have a SAVE_EXPR in a conditional context, we need to
      make sure it gets evaluated before the condition.  */
   t = fold_build2 (COMPOUND_EXPR, TREE_TYPE (t), op0, t);