PR tree-optimization/59124 (bogus -Warray-bounds warning)

gcc/ChangeLog:

	PR tree-optimization/59124
	* tree-vrp.c (register_edge_assert_for_2): For NAME != CST1
	where NAME = A +- CST2 add the assertion A != (CST1 -+ CST2).

gcc/testsuite/ChangeLog:

	PR tree-optimization/59124
	* gcc.dg/Warray-bounds-19.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@234544 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9d5b011..af1b6c2 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2016-03-30  Patrick Palka  <ppalka@gcc.gnu.org>
+
+       PR tree-optimization/59124
+       * tree-vrp.c (register_edge_assert_for_2): For NAME != CST1
+       where NAME = A +- CST2 add the assertion A != (CST1 -+ CST2).
+
 2016-03-29  Jeff Law  <law@redhat.com>
 
        * tree-ssa-coalesce.c (struct ssa_conflicts): Fix typo in

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index fd0dc5d..2d0ecda 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-03-30  Patrick Palka  <ppalka@gcc.gnu.org>
+
+       PR tree-optimization/59124
+       * gcc.dg/Warray-bounds-19.c: New test.
+
 2016-03-29  Zachary T Welch <zwelch@codesourcery.com>
 
        * lib/prune.exp (escape_regex_chars): New.

diff --git a/gcc/testsuite/gcc.dg/Warray-bounds-19.c b/gcc/testsuite/gcc.dg/Warray-bounds-19.c
new file mode 100644 (file)
index 0000000..e2f9661
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Warray-bounds-19.c
@@ -0,0 +1,17 @@
+/* PR tree-optimization/59124 */
+/* { dg-options "-O3 -Warray-bounds" } */
+
+unsigned baz[6];
+
+void foo(unsigned *bar, unsigned n)
+{
+  unsigned i, j;
+
+  if (n > 6)
+    n = 6;
+
+  for (i = 1; i < n; i++)
+    for (j = i - 1; j > 0; j--)
+      bar[j - 1] = baz[j - 1];
+}
+

diff --git a/gcc/tree-vrp.c b/gcc/tree-vrp.c
index b5654c5..bbdf9ce 100644 (file)
--- a/gcc/tree-vrp.c
+++ b/gcc/tree-vrp.c
@@ -5310,6 +5310,27 @@ register_edge_assert_for_2 (tree name, edge e, gimple_stmt_iterator bsi,
       if (is_gimple_assign (def_stmt))
        rhs_code = gimple_assign_rhs_code (def_stmt);
 
+      /* In the case of NAME != CST1 where NAME = A +- CST2 we can
+         assert that A != CST1 -+ CST2.  */
+      if ((comp_code == EQ_EXPR || comp_code == NE_EXPR)
+         && (rhs_code == PLUS_EXPR || rhs_code == MINUS_EXPR))
+       {
+         tree op0 = gimple_assign_rhs1 (def_stmt);
+         tree op1 = gimple_assign_rhs2 (def_stmt);
+         if (TREE_CODE (op0) == SSA_NAME
+             && TREE_CODE (op1) == INTEGER_CST
+             && live_on_edge (e, op0)
+             && !has_single_use (op0))
+           {
+             enum tree_code reverse_op = (rhs_code == PLUS_EXPR
+                                          ? MINUS_EXPR : PLUS_EXPR);
+             op1 = int_const_binop (reverse_op, val, op1);
+             if (TREE_OVERFLOW (op1))
+               op1 = drop_tree_overflow (op1);
+             register_new_assert_for (op0, op0, comp_code, op1, NULL, e, bsi);
+           }
+       }
+
       /* Add asserts for NAME cmp CST and NAME being defined
         as NAME = (int) NAME2.  */
       if (!TYPE_UNSIGNED (TREE_TYPE (val))