From 0f57194bfccc05e07b48e8ccd60d3653c6d65c9a Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Tue, 6 Dec 2016 10:24:36 +0100
Subject: [PATCH] re PR c++/71537 (GCC rejects consetxpr boolean conversions
 and comparisons on the result of pointer arithmetic.)

	PR c++/71537
	* fold-const.c (fold_comparison): Assume CONSTANT_CLASS_P (base0)
	plus offset is non-zero.  For maybe_nonzero_address decl base0,
	require indirect_base0.

	* g++.dg/cpp0x/constexpr-71537.C: New test.

From-SVN: r243286
---
 gcc/ChangeLog                                |  5 +++++
 gcc/fold-const.c                             | 18 ++++++++++--------
 gcc/testsuite/ChangeLog                      |  3 +++
 gcc/testsuite/g++.dg/cpp0x/constexpr-71537.C | 18 ++++++++++++++++++
 4 files changed, 36 insertions(+), 8 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-71537.C

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9ed8f5f8295..aef86e3566c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,10 @@
 2016-12-06  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/71537
+	* fold-const.c (fold_comparison): Assume CONSTANT_CLASS_P (base0)
+	plus offset is non-zero.  For maybe_nonzero_address decl base0,
+	require indirect_base0.
+
 	PR c++/71537
 	* fold-const-call.c (fold_const_call_1): Remove memchr handling here.
 	(fold_const_call) <case CFN_BUILT_IN_STRNCMP,
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 6517188c4c6..c649e547ead 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -8419,14 +8419,16 @@ fold_comparison (location_t loc, enum tree_code code, tree type,
 	 below follow the C++ rules with the additional property that
 	 every object pointer compares greater than a null pointer.
       */
-      else if (DECL_P (base0)
-	       && maybe_nonzero_address (base0) > 0
-	       /* Avoid folding references to struct members at offset 0 to
-		  prevent tests like '&ptr->firstmember == 0' from getting
-		  eliminated.  When ptr is null, although the -> expression
-		  is strictly speaking invalid, GCC retains it as a matter
-		  of QoI.  See PR c/44555. */
-	       && (offset0 == NULL_TREE && bitpos0 != 0)
+      else if (((DECL_P (base0)
+		 && maybe_nonzero_address (base0) > 0
+		 /* Avoid folding references to struct members at offset 0 to
+		    prevent tests like '&ptr->firstmember == 0' from getting
+		    eliminated.  When ptr is null, although the -> expression
+		    is strictly speaking invalid, GCC retains it as a matter
+		    of QoI.  See PR c/44555. */
+		 && (offset0 == NULL_TREE && bitpos0 != 0))
+		|| CONSTANT_CLASS_P (base0))
+	       && indirect_base0
 	       /* The caller guarantees that when one of the arguments is
 		  constant (i.e., null in this case) it is second.  */
 	       && integer_zerop (arg1))
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index b44993b956b..7aa429fca28 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2016-12-06  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/71537
+	* g++.dg/cpp0x/constexpr-71537.C: New test.
+
 	PR c++/71537
 	* g++.dg/cpp0x/constexpr-memchr.C: New test.
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-71537.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-71537.C
new file mode 100644
index 00000000000..3d5ac349225
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-71537.C
@@ -0,0 +1,18 @@
+// PR c++/71537
+// { dg-do compile { target c++11 } }
+
+constexpr int n[42] = {1};
+constexpr int x1 = n ? 1 : 0;
+constexpr int x2 = n + 1 ? 1 : 0;
+constexpr int x3 = "abc" ? 1 : 0;
+constexpr int x4 = "abc" + 1 ? 1 : 0;
+constexpr bool x5 = "abc" + 1;
+constexpr bool x6 = "abc" + 4;
+constexpr bool x7 = n + 42;
+static_assert (x1 == 1, "");
+static_assert (x2 == 1, "");
+static_assert (x3 == 1, "");
+static_assert (x4 == 1, "");
+static_assert (x5, "");
+static_assert (x6, "");
+static_assert (x7, "");
-- 
2.30.2