C++ PATCHes for bootstrap/68346, 68361

[Jason Merrill <jason at redhat dot com>]

A couple of bootstrap issues on some targets:

68346: My earlier change to avoid folding the arguments to 
warn_tautological_cmp wasn't quite right, either.  This patch folds 
within the function, at the place where we are interested in a constant 
value.

68361: The way we were trying to suppress -Wparentheses before wasn't 
effective enough.  Let's actually turn off the flag around the relevant 
convert call.

Tested x86_64-pc-linux-gnu, applying to trunk.

commit 56ca181e3d438fb9b95c865fde6e77f5335c791a
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Nov 17 10:51:24 2015 -0500

    	PR bootstrap/68361
    	* cvt.c (cp_convert_and_check): Use warning_sentinel to suppress
    	-Wparentheses.

diff --git a/gcc/cp/cvt.c b/gcc/cp/cvt.c
index 0231efc..ebca004 100644
--- a/gcc/cp/cvt.c
+++ b/gcc/cp/cvt.c
@@ -644,7 +644,7 @@ cp_convert_and_check (tree type, tree expr, tsubst_flags_t complain)
       else
 	{
 	  /* Avoid bogus -Wparentheses warnings.  */
-	  TREE_NO_WARNING (folded) = true;
+	  warning_sentinel w (warn_parentheses);
 	  folded_result = cp_convert (type, folded, tf_none);
 	}
       folded_result = fold_simple (folded_result);
diff --git a/gcc/testsuite/g++.dg/warn/Wparentheses-28.C b/gcc/testsuite/g++.dg/warn/Wparentheses-28.C
new file mode 100644
index 0000000..f6636cb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wparentheses-28.C
@@ -0,0 +1,14 @@
+// PR bootstrap/68361
+// { dg-options -Wparentheses }
+
+struct A
+{
+  int p: 2;
+};
+
+A a, b;
+
+int main()
+{
+  bool t = (a.p = b.p);
+}

commit 7489a9400cffa4c1010debaf2d86dcd286ce1cfd
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Nov 17 12:56:00 2015 -0500

    	PR bootstrap/68346
    
    	* c-common.c (warn_tautological_cmp): Fold before checking for
    	constants.

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 06d857c..f50ca48 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -1924,7 +1924,7 @@ warn_tautological_cmp (location_t loc, enum tree_code code, tree lhs, tree rhs)
 
   /* We do not warn for constants because they are typical of macro
      expansions that test for features, sizeof, and similar.  */
-  if (CONSTANT_CLASS_P (lhs) || CONSTANT_CLASS_P (rhs))
+  if (CONSTANT_CLASS_P (fold (lhs)) || CONSTANT_CLASS_P (fold (rhs)))
     return;
 
   /* Don't warn for e.g.
diff --git a/gcc/testsuite/g++.dg/warn/Wtautological-compare2.C b/gcc/testsuite/g++.dg/warn/Wtautological-compare2.C
new file mode 100644
index 0000000..9d9060d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wtautological-compare2.C
@@ -0,0 +1,11 @@
+// PR bootstrap/68346
+// { dg-options -Wtautological-compare }
+
+#define INVALID_REGNUM			(~(unsigned int) 0)
+#define PIC_OFFSET_TABLE_REGNUM INVALID_REGNUM
+
+int main()
+{
+  if ((unsigned) PIC_OFFSET_TABLE_REGNUM != INVALID_REGNUM)
+    __builtin_abort();
+}