c++: import/export NTTP objects

[Nathan Sidwell <nathan@acm.org>]

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This adds smarts to the module machinery to handle NTTP object
VAR_DECLs.  Like typeinfo objects, these must be ignored in the symbol
table, streamed specially and recreated on stream in.

Patrick, thanks for the testcase, I don't know how to attribute that to 
you in the changelog anymore.

nathan

-- 
Nathan Sidwell

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From a1f7f9541c2b20eb44750b9c15cd831c62d67f21 Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@acm.org>
Date: Wed, 28 Sep 2022 09:21:14 -0700
Subject: [PATCH] c++: import/export NTTP objects

This adds smarts to the module machinery to handle NTTP object
VAR_DECLs.  Like typeinfo objects, these must be ignored in the symbol
table, streamed specially and recreated on stream in.

	gcc/cp/
	PR c++/100616
	* module.cc (enum tree_tag): Add tt_nttp_var.
	(trees_out::decl_node): Handle NTTP objects.
	(trees_in::tree_node): Handle tt_nttp_var.
	(depset::hash::add_binding_entry): Skip NTTP objects.

	gcc/testsuite/
	PR c++/100616
	* g++.dg/modules/100616_a.H: New.
	* g++.dg/modules/100616_b.C: New.
	* g++.dg/modules/100616_c.C: New.
	* g++.dg/modules/100616_d.C: New.
---
 gcc/cp/module.cc                        | 35 +++++++++++++++++++++++++
 gcc/testsuite/g++.dg/modules/100616_a.H |  5 ++++
 gcc/testsuite/g++.dg/modules/100616_b.C |  7 +++++
 gcc/testsuite/g++.dg/modules/100616_c.C |  7 +++++
 gcc/testsuite/g++.dg/modules/100616_d.C | 10 +++++++
 5 files changed, 64 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/modules/100616_a.H
 create mode 100644 gcc/testsuite/g++.dg/modules/100616_b.C
 create mode 100644 gcc/testsuite/g++.dg/modules/100616_c.C
 create mode 100644 gcc/testsuite/g++.dg/modules/100616_d.C

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index d965017940a..cbf3a77de01 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -2737,6 +2737,7 @@ enum tree_tag {
   tt_tinfo_var,		/* Typeinfo object. */
   tt_tinfo_typedef,	/* Typeinfo typedef.  */
   tt_ptrmem_type,	/* Pointer to member type.  */
+  tt_nttp_var,		/* NTTP_OBJECT VAR_DECL.  */
 
   tt_parm,		/* Function parameter or result.  */
   tt_enum_value,	/* An enum value.  */
@@ -8548,6 +8549,21 @@ trees_out::decl_node (tree decl, walk_kind ref)
 	    }
 	  return false;
 	}
+
+      if (DECL_NTTP_OBJECT_P (decl))
+	{
+	  /* A NTTP parm object.  */
+	  if (streaming_p ())
+	    i (tt_nttp_var);
+	  tree_node (tparm_object_argument (decl));
+	  tree_node (DECL_NAME (decl));
+	  int tag = insert (decl);
+	  if (streaming_p ())
+	    dump (dumper::TREE)
+	      && dump ("Wrote nttp object:%d %N", tag, DECL_NAME (decl));
+	  return false;
+	}
+
       break;
 
     case TYPE_DECL:
@@ -9627,6 +9643,21 @@ trees_in::tree_node (bool is_use)
       }
       break;
 
+    case tt_nttp_var:
+      /* An NTTP object. */
+      {
+	tree init = tree_node ();
+	tree name = tree_node ();
+	if (!get_overrun ())
+	  {
+	    res = get_template_parm_object (init, name);
+	    int tag = insert (res);
+	    dump (dumper::TREE)
+	      && dump ("Created nttp object:%d %N", tag, name);
+	  }
+      }
+      break;
+
     case tt_enum_value:
       /* An enum const value.  */
       {
@@ -12760,6 +12791,10 @@ depset::hash::add_binding_entity (tree decl, WMB_Flags flags, void *data_)
 	/* Ignore TINFO things.  */
 	return false;
 
+      if (TREE_CODE (decl) == VAR_DECL && DECL_NTTP_OBJECT_P (decl))
+	/* Ignore NTTP objects.  */
+	return false;
+
       if (!(flags & WMB_Using) && CP_DECL_CONTEXT (decl) != data->ns)
 	{
 	  /* A using that lost its wrapper or an unscoped enum
diff --git a/gcc/testsuite/g++.dg/modules/100616_a.H b/gcc/testsuite/g++.dg/modules/100616_a.H
new file mode 100644
index 00000000000..9bc42bcc05b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/100616_a.H
@@ -0,0 +1,5 @@
+// { dg-additional-options {-std=c++20 -fmodule-header} }
+// { dg-module-cmi {} }
+
+template<auto> struct C { };
+struct A { };
diff --git a/gcc/testsuite/g++.dg/modules/100616_b.C b/gcc/testsuite/g++.dg/modules/100616_b.C
new file mode 100644
index 00000000000..416fd524b2c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/100616_b.C
@@ -0,0 +1,7 @@
+// { dg-additional-options {-std=c++20 -fmodules-ts} }
+
+export module pr100616_b;
+// { dg-module-cmi pr100616_b }
+
+import "100616_a.H";
+export C<A{}> c1;
diff --git a/gcc/testsuite/g++.dg/modules/100616_c.C b/gcc/testsuite/g++.dg/modules/100616_c.C
new file mode 100644
index 00000000000..5c79f5eef68
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/100616_c.C
@@ -0,0 +1,7 @@
+// { dg-additional-options {-std=c++20 -fmodules-ts} }
+
+export module pr100616_c;
+// { dg-module-cmi pr100616_c }
+
+import "100616_a.H";
+export C<A{}> c2;
diff --git a/gcc/testsuite/g++.dg/modules/100616_d.C b/gcc/testsuite/g++.dg/modules/100616_d.C
new file mode 100644
index 00000000000..d9515db1140
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/100616_d.C
@@ -0,0 +1,10 @@
+// { dg-additional-options {-std=c++20 -fmodules-ts} }
+
+import "100616_a.H";
+import pr100616_b;
+import pr100616_c;
+
+C<A{}> c0;
+using type = decltype(c0);
+using type = decltype(c1);
+using type = decltype(c2); // bogus error: types of c1 and c2 don't match
-- 
2.30.2