PR c++/86586 - -fcompare-debug=-Wsign-compare.

This patch limits constexpr folding for -Wsign-compare to only cases that we
would warn for without considering constant values, avoiding the folding in
the testcase in question.

gcc/c-family/
	* c-warn.c (warn_for_sign_compare): Call fold_for_warn.
gcc/cp/
	* typeck.c (cp_build_binary_op): Don't fold for -Wsign-compare.

From-SVN: r270136

gcc/c-family/ChangeLog

+2019-04-03  Jason Merrill  <jason@redhat.com>
+
+	PR c++/86586 - -fcompare-debug=-Wsign-compare.
+	* c-warn.c (warn_for_sign_compare): Call fold_for_warn.
+
 2019-04-01  Martin Sebor  <msebor@redhat.com>
 
 	PR c/89685

gcc/c-family/c-warn.c

@@ -2073,6 +2073,9 @@ warn_for_sign_compare (location_t location,
       else
 	sop = orig_op1, uop = orig_op0;
 
+      sop = fold_for_warn (sop);
+      uop = fold_for_warn (uop);
+
       STRIP_TYPE_NOPS (sop);
       STRIP_TYPE_NOPS (uop);
       base_type = (TREE_CODE (result_type) == COMPLEX_TYPE

gcc/cp/ChangeLog

 2019-04-03  Jason Merrill  <jason@redhat.com>
 
+	PR c++/86586 - -fcompare-debug=-Wsign-compare.
+	* typeck.c (cp_build_binary_op): Don't fold for -Wsign-compare.
+
 	PR c++/89331 - ICE with offsetof in incomplete class.
 	* semantics.c (finish_offsetof): Handle error_mark_node.
 	* typeck.c (build_class_member_access_expr): Call

gcc/cp/typeck.c

@@ -5486,14 +5486,7 @@ cp_build_binary_op (const op_location_t &location,
 	  && !enum_cast_to_int (orig_op0)
 	  && !enum_cast_to_int (orig_op1))
 	{
-	  tree oop0 = maybe_constant_value (orig_op0);
-	  tree oop1 = maybe_constant_value (orig_op1);
-
-	  if (TREE_CODE (oop0) != INTEGER_CST)
-	    oop0 = cp_fully_fold (orig_op0);
-	  if (TREE_CODE (oop1) != INTEGER_CST)
-	    oop1 = cp_fully_fold (orig_op1);
-	  warn_for_sign_compare (location, oop0, oop1, op0, op1, 
+	  warn_for_sign_compare (location, orig_op0, orig_op1, op0, op1,
 				 result_type, resultcode);
 	}
     }

gcc/testsuite/g++.target/i386/mv1.C

 /* Test case to check if Multiversioning works.  */
 /* { dg-do run } */
 /* { dg-require-ifunc "" }  */
-/* { dg-options "-O2 -fPIC" } */
+/* { dg-options "-O2 -fPIC -fcompare-debug=-Wsign-compare" } */
 
 #include <assert.h>