c-common.c (warn_tautological_cmp): Bail for float types.

	* c-common.c (warn_tautological_cmp): Bail for float types.

	* c-c++-common/Wtautological-compare-3.c: New test.

From-SVN: r226388

gcc/c-family/ChangeLog

+2015-07-30  Marek Polacek  <polacek@redhat.com>
+
+	* c-common.c (warn_tautological_cmp): Bail for float types.
+
 2015-07-27  Marek Polacek  <polacek@redhat.com>
 
 	PR bootstrap/67030

gcc/c-family/c-common.c

@@ -1910,6 +1910,12 @@ warn_tautological_cmp (location_t loc, enum tree_code code, tree lhs, tree rhs)
       || (CONVERT_EXPR_P (rhs) || TREE_CODE (rhs) == NON_LVALUE_EXPR))
     return;
 
+  /* Don't warn if either LHS or RHS has an IEEE floating-point type.
+     It could be a NaN, and NaN never compares equal to anything, even
+     itself.  */
+  if (FLOAT_TYPE_P (TREE_TYPE (lhs)) || FLOAT_TYPE_P (TREE_TYPE (rhs)))
+    return;
+
   if (operand_equal_p (lhs, rhs, 0))
     {
       /* Don't warn about array references with constant indices;

gcc/testsuite/ChangeLog

+2015-07-30  Marek Polacek  <polacek@redhat.com>
+
+	* c-c++-common/Wtautological-compare-3.c: New test.
+
 2015-07-29  Alan Lawrence  <alan.lawrence@arm.com>
 
 	* gcc.target/aarch64/vld1_lane.c (main): Remove unused test data.

gcc/testsuite/c-c++-common/Wtautological-compare-3.c

+/* { dg-do compile } */
+/* { dg-options "-Wtautological-compare" } */
+/* Test we don't warn for floats.  */
+
+struct S { double d; float f; };
+
+void
+fn1 (int i, float f, double d, struct S *s, float *fp)
+{
+  if (f == f);
+  if (f != f);
+  if (d == d);
+  if (d != d);
+  if (fp[i] == fp[i]);
+  if (fp[i] != fp[i]);
+  if (s->f == s->f);
+  if (s->f != s->f);
+  if (s->d == s->d);
+  if (s->d != s->d);
+}