ipcp don't propagate where not needed

This patch disables propagation of ipcp information into partitions
where all instances of the node are marked to be inlined.

Motivation:
Incremental LTO needs stable values between compilations to be
effective. This requirement fails with following example:

void heavily_used_function(int);
...
heavily_used_function(__LINE__);

Ipcp creates long list of all __LINE__ arguments, and then
propagates it with every function clone, even though for inlined
functions this information is not useful.

gcc/ChangeLog:

	* ipa-prop.cc (write_ipcp_transformation_info): Disable
	uneeded value propagation.
	* lto-cgraph.cc (lto_symtab_encoder_encode): Default values.
	(lto_symtab_encoder_always_inlined_p): New.
	(lto_set_symtab_encoder_not_always_inlined): New.
	(add_node_to): Set always inlined.
	* lto-streamer.h (struct lto_encoder_entry): New field.
	(lto_symtab_encoder_always_inlined_p): New.

gcc/ipa-prop.cc

@@ -5405,9 +5405,15 @@ write_ipcp_transformation_info (output_block *ob, cgraph_node *node,
       streamer_write_bitpack (&bp);
     }
 
-  streamer_write_uhwi (ob, vec_safe_length (ts->m_vr));
-  for (const ipa_vr &parm_vr : ts->m_vr)
-    parm_vr.streamer_write (ob);
+  /* If all instances of this node are inlined, ipcp info is not useful.  */
+  if (!lto_symtab_encoder_only_for_inlining_p (encoder, node))
+    {
+      streamer_write_uhwi (ob, vec_safe_length (ts->m_vr));
+      for (const ipa_vr &parm_vr : ts->m_vr)
+	parm_vr.streamer_write (ob);
+    }
+  else
+    streamer_write_uhwi (ob, 0);
 }
 
 /* Stream in the aggregate value replacement chain for NODE from IB.  */

gcc/lto-cgraph.cc

@@ -113,7 +113,7 @@ lto_symtab_encoder_encode (lto_symtab_encoder_t encoder,
 
   if (!encoder->map)
     {
-      lto_encoder_entry entry = {node, false, false, false};
+      lto_encoder_entry entry (node);
 
       ref = encoder->nodes.length ();
       encoder->nodes.safe_push (entry);
@@ -123,7 +123,7 @@ lto_symtab_encoder_encode (lto_symtab_encoder_t encoder,
   size_t *slot = encoder->map->get (node);
   if (!slot || !*slot)
     {
-      lto_encoder_entry entry = {node, false, false, false};
+      lto_encoder_entry entry (node);
       ref = encoder->nodes.length ();
       if (!slot)
         encoder->map->put (node, ref + 1);
@@ -168,6 +168,15 @@ lto_symtab_encoder_delete_node (lto_symtab_encoder_t encoder,
   return true;
 }
 
+/* Return TRUE if the NODE and its clones are always inlined.  */
+
+bool
+lto_symtab_encoder_only_for_inlining_p (lto_symtab_encoder_t encoder,
+					struct cgraph_node *node)
+{
+  int index = lto_symtab_encoder_lookup (encoder, node);
+  return encoder->nodes[index].only_for_inlining;
+}
 
 /* Return TRUE if we should encode the body of NODE (if any).  */
 
@@ -179,17 +188,6 @@ lto_symtab_encoder_encode_body_p (lto_symtab_encoder_t encoder,
   return encoder->nodes[index].body;
 }
 
-/* Specify that we encode the body of NODE in this partition.  */
-
-static void
-lto_set_symtab_encoder_encode_body (lto_symtab_encoder_t encoder,
-				    struct cgraph_node *node)
-{
-  int index = lto_symtab_encoder_encode (encoder, node);
-  gcc_checking_assert (encoder->nodes[index].node == node);
-  encoder->nodes[index].body = true;
-}
-
 /* Return TRUE if we should encode initializer of NODE (if any).  */
 
 bool
@@ -797,13 +795,28 @@ output_refs (lto_symtab_encoder_t encoder)
 
 static void
 add_node_to (lto_symtab_encoder_t encoder, struct cgraph_node *node,
-	     bool include_body)
+	     bool include_body, bool not_inlined)
 {
   if (node->clone_of)
-    add_node_to (encoder, node->clone_of, include_body);
+    add_node_to (encoder, node->clone_of, include_body, not_inlined);
+
+  int index = lto_symtab_encoder_encode (encoder, node);
+  gcc_checking_assert (encoder->nodes[index].node == node);
+
   if (include_body)
-    lto_set_symtab_encoder_encode_body (encoder, node);
-  lto_symtab_encoder_encode (encoder, node);
+    encoder->nodes[index].body = true;
+  if (not_inlined)
+    encoder->nodes[index].only_for_inlining = false;
+}
+
+/* Add NODE into encoder as well as nodes it is cloned from.
+   Do it in a way so clones appear first.  */
+
+static void
+add_node_to (lto_symtab_encoder_t encoder, struct cgraph_node *node,
+	     bool include_body)
+{
+  add_node_to (encoder, node, include_body, include_body && !node->inlined_to);
 }
 
 /* Add all references in NODE to encoders.  */

gcc/lto-streamer.h

@@ -443,12 +443,21 @@ struct lto_stats_d
 /* Entry of LTO symtab encoder.  */
 struct lto_encoder_entry
 {
+  /* Constructors.  */
+  lto_encoder_entry () {}
+  lto_encoder_entry (symtab_node* n)
+    : node (n), in_partition (false), body (false), only_for_inlining (true),
+      initializer (false)
+  {}
+
   symtab_node *node;
   /* Is the node in this partition (i.e. ltrans of this partition will
      be responsible for outputting it)? */
   unsigned int in_partition:1;
   /* Do we encode body in this partition?  */
   unsigned int body:1;
+  /* Do we stream this node only for inlining?  */
+  unsigned int only_for_inlining:1;
   /* Do we encode initializer in this partition?
      For example the readonly variable initializers are encoded to aid
      constant folding even if they are not in the partition.  */
@@ -911,6 +920,8 @@ void lto_symtab_encoder_delete (lto_symtab_encoder_t);
 bool lto_symtab_encoder_delete_node (lto_symtab_encoder_t, symtab_node *);
 bool lto_symtab_encoder_encode_body_p (lto_symtab_encoder_t,
 				       struct cgraph_node *);
+bool lto_symtab_encoder_only_for_inlining_p (lto_symtab_encoder_t,
+					     struct cgraph_node *);
 bool lto_symtab_encoder_in_partition_p (lto_symtab_encoder_t,
 					symtab_node *);
 void lto_set_symtab_encoder_in_partition (lto_symtab_encoder_t,