From d61d2a5f3ce9238bad7cbd7733d90c6ec7ae5fbc Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@acm.org>
Date: Thu, 14 Jan 2021 05:15:33 -0800
Subject: [PATCH] c++: Fix erroneous parm comparison logic [PR 98372]

I flubbed an application of De Morgan's law.  Let's just express the
logic directly and let the compiler figure it out.  This bug made it
look like pr52830 was fixed, but it is not.

	PR c++/98372
	gcc/cp/
	* tree.c (cp_tree_equal): Correct map_context logic.
	gcc/testsuite/
	* g++.dg/cpp0x/constexpr-52830.C: Restore dg-ice
	* g++.dg/template/pr98372.C: New.
---
 gcc/cp/tree.c                                |  4 ++--
 gcc/testsuite/g++.dg/cpp0x/constexpr-52830.C |  1 +
 gcc/testsuite/g++.dg/template/pr98372.C      | 28 ++++++++++++++++++++++++++++
 3 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/pr98372.C

diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index d339036..3a9a86d 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -3841,8 +3841,8 @@ cp_tree_equal (tree t1, tree t2)
 	  /* Module duplicate checking can have t1 = new, t2 =
 	     existing, and they should be considered matching at this
 	     point.  */
-	  && (DECL_CONTEXT (t1) != map_context_from
-	      && DECL_CONTEXT (t2) != map_context_to))
+	  && !(DECL_CONTEXT (t1) == map_context_from
+	       && DECL_CONTEXT (t2) == map_context_to))
 	/* When comparing hash table entries, only an exact match is
 	   good enough; we don't want to replace 'this' with the
 	   version from another function.  But be more flexible
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-52830.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-52830.C
index 04f039f..2c9d2f9 100644
--- a/gcc/testsuite/g++.dg/cpp0x/constexpr-52830.C
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-52830.C
@@ -1,5 +1,6 @@
 // PR c++/52830
 // { dg-do compile { target c++11 } }
+// { dg-ice "comptypes" }
 
 template<bool b> struct eif { typedef void type; };
 template<>       struct eif<false> {};
diff --git a/gcc/testsuite/g++.dg/template/pr98372.C b/gcc/testsuite/g++.dg/template/pr98372.C
new file mode 100644
index 0000000..f1e8b0f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/pr98372.C
@@ -0,0 +1,28 @@
+// PR 98372 ICE due to incorrect type compare
+// { dg-do compile { target c++11 } }
+
+template <typename _Tp> using remove_pointer_t = typename _Tp ::type;
+template <bool> struct enable_if;
+template <bool _Cond, typename>
+using enable_if_t = typename enable_if<_Cond>::type;
+template <typename> bool is_convertible_v;
+template <typename, unsigned long = 0> class Span;
+template <typename T, unsigned long> class Span {
+  using element_type = T;
+  template <unsigned long N>
+  Span(element_type (&arr)[N],
+       enable_if_t<is_convertible_v<remove_pointer_t<decltype(data(arr))>>,
+                   decltype(nullptr)>);
+};
+template <typename T> class Span<T> {
+  using element_type = T;
+  template <unsigned long N>
+  Span(element_type (&arr)[N],
+       enable_if_t<is_convertible_v<remove_pointer_t<decltype(data(arr))>>,
+                   decltype(nullptr)>);
+};
+
+struct aaa
+{
+  Span<char> data0;
+};
-- 
2.7.4