From 7b3a85be33a118ca58e07f172a8f4de4af84934d Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Sun, 27 Feb 2011 12:11:19 -0500
Subject: [PATCH] re PR c++/47904 (ICE with DECL_PARM_INDEX (this) in
 cp_tree_equal)

	PR c++/47904
	* tree.c (cp_tree_equal) [PARM_DECL]: Don't crash on
	DECL_ARTIFICIAL parms.

From-SVN: r170544
---
 gcc/cp/ChangeLog                           |  6 ++++++
 gcc/cp/tree.c                              | 18 +++++++++++------
 gcc/testsuite/ChangeLog                    |  4 ++++
 gcc/testsuite/g++.dg/template/this-targ1.C | 23 ++++++++++++++++++++++
 4 files changed, 45 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/template/this-targ1.C

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index ac768737bd18..663d4caaaa6f 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2011-02-26  Jason Merrill  <jason@redhat.com>
+
+	PR c++/47904
+	* tree.c (cp_tree_equal) [PARM_DECL]: Don't crash on
+	DECL_ARTIFICIAL parms.
+
 2010-12-16  Release Manager
 
 	* GCC 4.5.2 released.
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 54b76a850307..994056d9ca3d 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -2089,12 +2089,18 @@ cp_tree_equal (tree t1, tree t2)
 
     case PARM_DECL:
       /* For comparing uses of parameters in late-specified return types
-	 with an out-of-class definition of the function.  */
-      if (same_type_p (TREE_TYPE (t1), TREE_TYPE (t2))
-	  && DECL_PARM_INDEX (t1) == DECL_PARM_INDEX (t2))
-	return true;
-      else
-	return false;
+	 with an out-of-class definition of the function, but can also come
+	 up for expressions that involve 'this' in a member function
+	 template.  */
+      if (same_type_p (TREE_TYPE (t1), TREE_TYPE (t2)))
+	{
+	  if (DECL_ARTIFICIAL (t1) ^ DECL_ARTIFICIAL (t2))
+	    return false;
+	  if (DECL_ARTIFICIAL (t1)
+	      || DECL_PARM_INDEX (t1) == DECL_PARM_INDEX (t2))
+	    return true;
+	}
+      return false;
 
     case VAR_DECL:
     case CONST_DECL:
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ccda4effcd00..5055e516c98c 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2011-02-26  Jason Merrill  <jason@redhat.com>
+
+	* g++.dg/template/this-targ1.C: New.
+
 2011-02-19  Alexandre Oliva  <aoliva@redhat.com>
 
 	PR tree-optimization/46620
diff --git a/gcc/testsuite/g++.dg/template/this-targ1.C b/gcc/testsuite/g++.dg/template/this-targ1.C
new file mode 100644
index 000000000000..6864be5abbc3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/this-targ1.C
@@ -0,0 +1,23 @@
+// PR c++/47904
+
+template <bool>
+struct S
+{
+};
+
+template <class T>
+class U
+{
+  T t;
+  int foo () const
+  {
+    S <sizeof (t) == 1> s;
+    return 1;
+  }
+  int bar () const
+  {
+    S <sizeof (t) == 1> s;
+    return 1;
+  }
+};
+
-- 
2.47.2