From: Richard Sandiford <richard.sandiford@arm.com>
Date: Thu, 18 Apr 2019 12:30:36 +0000 (+0000)
Subject: Fix UB in int_const_binop
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=714996e2c2e1fd788c87b3a87648977468ad4251;p=gcc.git

Fix UB in int_const_binop

When testing PR 85164, the baseline bootstrap-ubsan results had
a lot of failures from int_const_binop.  This is because with the
new overflow handling we can sometimes do:

      poly_res = res;

on an uninitialised res.

2019-04-18  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* fold-const.c (int_const_binop): Return early on failure.

From-SVN: r270443
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8dba1ed7bf3..5b8c5acb076 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2019-04-18  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* fold-const.c (int_const_binop): Return early on failure.
+
 2019-04-18  Richard Sandiford  <richard.sandiford@arm.com>
 
 	PR middle-end/85164
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index c2884a67519..c4257721cfe 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -1173,7 +1173,6 @@ tree
 int_const_binop (enum tree_code code, const_tree arg1, const_tree arg2,
 		 int overflowable)
 {
-  bool success = false;
   poly_wide_int poly_res;
   tree type = TREE_TYPE (arg1);
   signop sign = TYPE_SIGN (type);
@@ -1183,17 +1182,18 @@ int_const_binop (enum tree_code code, const_tree arg1, const_tree arg2,
     {
       wide_int warg1 = wi::to_wide (arg1), res;
       wide_int warg2 = wi::to_wide (arg2, TYPE_PRECISION (type));
-      success = wide_int_binop (res, code, warg1, warg2, sign, &overflow);
+      if (!wide_int_binop (res, code, warg1, warg2, sign, &overflow))
+	return NULL_TREE;
       poly_res = res;
     }
-  else if (poly_int_tree_p (arg1) && poly_int_tree_p (arg2))
-    success = poly_int_binop (poly_res, code, arg1, arg2, sign, &overflow);
-  if (success)
-    return force_fit_type (type, poly_res, overflowable,
-			   (((sign == SIGNED || overflowable == -1)
-			     && overflow)
-			    | TREE_OVERFLOW (arg1) | TREE_OVERFLOW (arg2)));
-  return NULL_TREE;
+  else if (!poly_int_tree_p (arg1)
+	   || !poly_int_tree_p (arg2)
+	   || !poly_int_binop (poly_res, code, arg1, arg2, sign, &overflow))
+    return NULL_TREE;
+  return force_fit_type (type, poly_res, overflowable,
+			 (((sign == SIGNED || overflowable == -1)
+			   && overflow)
+			  | TREE_OVERFLOW (arg1) | TREE_OVERFLOW (arg2)));
 }
 
 /* Return true if binary operation OP distributes over addition in operand