[1/2] analyzer: diagnostic_path: avoid printing redundant data

diff --git a/gcc/diagnostic-format-json.cc b/gcc/diagnostic-format-json.cc
index 60363348a92e..181ba8a65afc 100644
--- a/gcc/diagnostic-format-json.cc
+++ b/gcc/diagnostic-format-json.cc
@@ -295,7 +295,9 @@  diagnostic_output_format_init (diagnostic_context *context,
 	context->begin_group_cb = json_begin_group;
 	context->end_group_cb =  json_end_group;
 	context->final_cb =  json_final_cb;
-	context->print_path = NULL; /* handled in json_end_diagnostic.  */
+	/* Handled in json_end_diagnostic:  */
+	delete context->m_path_printer;
+	context->m_path_printer = NULL;
 
 	/* The metadata is handled in JSON format, rather than as text.  */
 	context->show_cwe = false;
diff --git a/gcc/diagnostic-show-locus.c b/gcc/diagnostic-show-locus.c
index 3208d99c3451..055a264ae01c 100644
--- a/gcc/diagnostic-show-locus.c
+++ b/gcc/diagnostic-show-locus.c
@@ -2570,6 +2570,13 @@  diagnostic_show_locus (diagnostic_context * context,
 
   context->last_location = loc;
 
+  /* If we have a path that which when printed would make printing
+     RICHLOC redundant, then print that now instead.  */
+  if (context->m_path_printer)
+    if (context->m_path_printer->maybe_print_path_rather_than_richloc
+	  (context, *richloc))
+      return;
+
   layout layout (context, richloc, diagnostic_kind);
   for (int line_span_idx = 0; line_span_idx < layout.get_num_line_spans ();
        line_span_idx++)
diff --git a/gcc/diagnostic.c b/gcc/diagnostic.c
index 52d5ffbfb4a0..fe540d9a133d 100644
--- a/gcc/diagnostic.c
+++ b/gcc/diagnostic.c
@@ -210,6 +210,8 @@  diagnostic_initialize (diagnostic_context *context, int n_opts)
   context->get_option_url = NULL;
   context->last_location = UNKNOWN_LOCATION;
   context->last_module = 0;
+  context->m_path_printer = NULL;
+  context->make_json_for_path = NULL;
   context->x_data = NULL;
   context->lock = 0;
   context->inhibit_notes_p = false;
@@ -287,6 +289,9 @@  diagnostic_finish (diagnostic_context *context)
   XDELETE (context->printer);
   context->printer = NULL;
 
+  delete context->m_path_printer;
+  context->m_path_printer = NULL;
+
   if (context->edit_context_ptr)
     {
       delete context->edit_context_ptr;
@@ -673,8 +678,8 @@  diagnostic_show_any_path (diagnostic_context *context,
   if (!path)
     return;
 
-  if (context->print_path)
-    context->print_path (context, path);
+  if (context->m_path_printer)
+    context->m_path_printer->print_path (context, *diagnostic->richloc);
 }
 
 /* Return true if the events in this path involve more than one
@@ -694,6 +699,40 @@  diagnostic_path::interprocedural_p () const
   return false;
 }
 
+/* Return true if it would be redundant to print this rich_location with
+   diagnostic_show_locus if we were to also then print the path of this
+   rich_location.
+
+   Specifically return true if this rich_location has a single location,
+   and a path, no fix-it hints or labels, and the single location is
+   within the path.
+
+   Implemented here as libcpp has only a forward decl of diagnostic_path.  */
+
+bool
+rich_location::path_makes_location_redundant_p () const
+{
+  if (m_path == NULL)
+    return false;
+  if (get_num_locations () != 1)
+    return false;
+
+  /* Must be no fix-it hints or labels. */
+  if (get_num_fixit_hints () > 0)
+    return false;
+  const location_range *lr = get_range (0);
+  if (lr->m_label)
+    return false;
+
+  /* Check if primary location is within path.  */
+  location_t loc = get_loc ();
+  const unsigned num = m_path->num_events ();
+  for (unsigned i = 0; i < num; i++)
+    if (m_path->get_event (i).get_location () == loc)
+      return true;
+  return false;
+}
+
 void
 default_diagnostic_starter (diagnostic_context *context,
 			    diagnostic_info *diagnostic)
diff --git a/gcc/diagnostic.h b/gcc/diagnostic.h
index 2e42d95752fc..7691a8b1d114 100644
--- a/gcc/diagnostic.h
+++ b/gcc/diagnostic.h
@@ -99,6 +99,38 @@  typedef void (*diagnostic_finalizer_fn) (diagnostic_context *,
 class edit_context;
 namespace json { class value; }
 
+/* Abstract base class for printing diagnostic_paths, to isolate
+   the path-printing code (which uses tree and thus is in OBJS) from the
+   core diagnostic machinery (which is in OBJS-libcommon).
+
+   Concrete implementation is in tree-diagnostic-path.cc.
+
+   Implemented as a pair of calls, and thus as a pair of vfuncs, rather than
+   a pair of callbacks.
+
+   This is done to allow -fdiagnostics-path-format=inline-events to
+   consolidate and print less for, the common case where the path contains the
+   rich_location, and hence the rich_location can be elided when it is
+   redundant.  */
+
+class path_printer
+{
+public:
+  static path_printer *make_tree_default ();
+  virtual ~path_printer () {}
+
+  /* Vfunc called by diagnostic_show_locus: potentially print the path
+     as inline events if the rest of the rich_location is redundant,
+     returning true if this is the case.  */
+  virtual bool maybe_print_path_rather_than_richloc (diagnostic_context *,
+						     const rich_location &) = 0;
+
+  /* Vfunc called after the call to diagnostic_show_locus: print the path, if
+     it wasn't printed already.  */
+  virtual void print_path (diagnostic_context *,
+			   const rich_location &) = 0;
+};
+
 /* This data structure bundles altogether any information relevant to
    the context of a diagnostic message.  */
 struct diagnostic_context
@@ -232,8 +264,10 @@  struct diagnostic_context
      particular option.  */
   char *(*get_option_url) (diagnostic_context *, int);
 
-  void (*print_path) (diagnostic_context *, const diagnostic_path *);
-  json::value *(*make_json_for_path) (diagnostic_context *, const diagnostic_path *);
+  /* Client hooks for working with diagnostic_paths.  */
+  path_printer *m_path_printer;
+  json::value *(*make_json_for_path) (diagnostic_context *,
+				      const diagnostic_path *);
 
   /* Auxiliary data for client.  */
   void *x_data;
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index dc6d5a14ed41..c471a602d23a 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -4177,27 +4177,24 @@  test.c:29:5: note: (3) when calling 'PyList_Append', passing NULL from (1) as ar
 @samp{inline-events} means to print the events ``inline'' within the source
 code.  This view attempts to consolidate the events into runs of
 sufficiently-close events, printing them as labelled ranges within the source.
-
 For example, the same events as above might be printed as:
 
 @smallexample
-  'test': events 1-3
-    |
-    |   25 |   list = PyList_New(0);
-    |      |          ^~~~~~~~~~~~~
-    |      |          |
-    |      |          (1) when 'PyList_New' fails, returning NULL
-    |   26 |
-    |   27 |   for (i = 0; i < count; i++) @{
-    |      |   ~~~
-    |      |   |
-    |      |   (2) when 'i < count'
-    |   28 |     item = PyLong_FromLong(random());
-    |   29 |     PyList_Append(list, item);
-    |      |     ~~~~~~~~~~~~~~~~~~~~~~~~~
-    |      |     |
-    |      |     (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
-    |
+test.c:29:5: error: passing NULL as argument 1 to 'PyList_Append' which requires a non-NULL parameter
+   25 |   list = PyList_New(0);
+      |          ^~~~~~~~~~~~~
+      |          |
+      |          (1) when 'PyList_New' fails, returning NULL
+   26 |
+   27 |   for (i = 0; i < count; i++) @{
+      |   ~~~
+      |   |
+      |   (2) when 'i < count'
+   28 |     item = PyLong_FromLong(random());
+   29 |     PyList_Append(list, item);
+      |     ~~~~~~~~~~~~~~~~~~~~~~~~~
+      |     |
+      |     (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
 @end smallexample
 
 Interprocedural control flow is shown by grouping the events by stack frame,
@@ -4251,13 +4248,17 @@  For example:
 (etc)
 @end smallexample
 
+If the location of the diagnostic is contained within the path and there are
+no fix-it hints or other complications, the source code for the location
+is elided and just the path is printed.
+
 @item -fdiagnostics-show-path-depths
 @opindex fdiagnostics-show-path-depths
 This option provides additional information when printing control-flow paths
 associated with a diagnostic.
 
 If this is option is provided then the stack depth will be printed for
-each run of events within @option{-fdiagnostics-path-format=separate-events}.
+each run of events within @option{-fdiagnostics-path-format=inline-events}.
 
 This is intended for use by GCC developers and plugin developers when
 debugging diagnostics that report interprocedural control flow.
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-default.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-default.c
index 5712dbd64725..d0ad8d6b987d 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-default.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-default.c
@@ -12,8 +12,6 @@  void wrapped_free (void *ptr)
 {
   free (ptr); /* { dg-warning "double-free of 'ptr' \\\[CWE-415\\]" } */
   /* { dg-begin-multiline-output "" }
-   free (ptr);
-   ^~~~~~~~~~
   'test': events 1-2
     |
     | {
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-1.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-1.c
index 430d81737718..5fc005a767b3 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-1.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-1.c
@@ -12,8 +12,6 @@  void wrapped_free (void *ptr)
 {
   free (ptr); /* { dg-warning "double-free of 'ptr' \\\[CWE-415\\]" } */
   /* { dg-begin-multiline-output "" }
-   free (ptr);
-   ^~~~~~~~~~
   'test': events 1-2
     |
     | {
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-2.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-2.c
index c2bfabec9101..7072308185cd 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-2.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-2.c
@@ -17,8 +17,6 @@  void wrapped_free (void *ptr)
 {
   free (ptr); /* { dg-warning "double-free of 'ptr' \\\[CWE-415\\]" } */
   /* { dg-begin-multiline-output "" }
-   free (ptr);
-   ^~~~~~~~~~
   'test': events 1-2
     |
     | {
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-3.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-3.c
index 5e7b099f7273..fa346628b14c 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-3.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-path-format-inline-events-3.c
@@ -16,8 +16,6 @@  void wrapped_free (void *ptr)
 {
   free (ptr); /* { dg-warning "double-free of 'ptr' \\\[CWE-415\\]" } */
   /* { dg-begin-multiline-output "" }
-   NN |   free (ptr);
-      |   ^~~~~~~~~~
   'test': events 1-2
     |
     |   NN | {
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-2.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-2.c
index 391aeb9ec30f..d436b0e5d6cf 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-2.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-2.c
@@ -33,24 +33,19 @@  make_a_list_of_random_ints_badly(PyObject *self,
 
   /* { dg-error "passing NULL as argument 1 to 'PyList_Append' which requires a non-NULL parameter" "" { target *-*-* } PyList_Append } */
   /* { dg-begin-multiline-output "" }
+   25 |   list = PyList_New(0);
+      |          ^~~~~~~~~~~~~
+      |          |
+      |          (1) when 'PyList_New' fails, returning NULL
+   26 | 
+   27 |   for (i = 0; i < count; i++) {
+      |   ~~~     
+      |   |
+      |   (2) when 'i < count'
+   28 |     item = PyLong_FromLong(random());
    29 |     PyList_Append(list, item);
-      |     ^~~~~~~~~~~~~~~~~~~~~~~~~
-  'make_a_list_of_random_ints_badly': events 1-3
-    |
-    |   25 |   list = PyList_New(0);
-    |      |          ^~~~~~~~~~~~~
-    |      |          |
-    |      |          (1) when 'PyList_New' fails, returning NULL
-    |   26 | 
-    |   27 |   for (i = 0; i < count; i++) {
-    |      |   ~~~     
-    |      |   |
-    |      |   (2) when 'i < count'
-    |   28 |     item = PyLong_FromLong(random());
-    |   29 |     PyList_Append(list, item);
-    |      |     ~~~~~~~~~~~~~~~~~~~~~~~~~
-    |      |     |
-    |      |     (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
-    |
+      |     ~~~~~~~~~~~~~~~~~~~~~~~~~
+      |     |
+      |     (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
      { dg-end-multiline-output "" } */
 }
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-2a.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-2a.c
new file mode 100644
index 000000000000..e8dc5bf82155
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-2a.c
@@ -0,0 +1,58 @@ 
+/* Example of a path that can't elide its richloc, due to a label.  */
+
+/* { dg-do compile } */
+/* { dg-options "-fdiagnostics-show-caret -fdiagnostics-show-line-numbers -fplugin-arg-diagnostic_plugin_test_paths-dummy_label" } */
+
+#include <stddef.h>
+#include <stdlib.h>
+
+/* Minimal reimplementation of cpython API.  */
+typedef struct PyObject {} PyObject;
+extern int PyArg_ParseTuple (PyObject *args, const char *fmt, ...);
+extern PyObject *PyList_New (int);
+extern PyObject *PyLong_FromLong(long);
+extern void PyList_Append(PyObject *list, PyObject *item);
+
+PyObject *
+make_a_list_of_random_ints_badly (PyObject *self,
+				  PyObject *args)
+{
+  PyObject *list, *item;
+  long count, i;
+
+  if (!PyArg_ParseTuple(args, "i", &count)) {
+    return NULL;
+  }
+
+  list = PyList_New(0); /* { dg-line PyList_New } */
+	
+  for (i = 0; i < count; i++) {
+    item = PyLong_FromLong(random());
+    PyList_Append(list, item); /* { dg-line PyList_Append } */
+  }
+  
+  return list;
+
+  /* { dg-error "passing NULL as argument 1 to 'PyList_Append' which requires a non-NULL parameter" "" { target *-*-* } PyList_Append } */
+  /* { dg-begin-multiline-output "" }
+   31 |     PyList_Append(list, item);
+      |     ^~~~~~~~~~~~~~~~~~~~~~~~~
+      |     |
+      |     dummy label
+  events 1-3
+   27 |   list = PyList_New(0);
+      |          ^~~~~~~~~~~~~
+      |          |
+      |          (1) when 'PyList_New' fails, returning NULL
+   28 | 
+   29 |   for (i = 0; i < count; i++) {
+      |   ~~~     
+      |   |
+      |   (2) when 'i < count'
+   30 |     item = PyLong_FromLong(random());
+   31 |     PyList_Append(list, item);
+      |     ~~~~~~~~~~~~~~~~~~~~~~~~~
+      |     |
+      |     (3) when calling 'PyList_Append', passing NULL from (1) as argument 1
+     { dg-end-multiline-output "" } */
+}
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-4.c b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-4.c
index 41cbaaaaa976..5f1648b0fbce 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-4.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic-test-paths-4.c
@@ -29,8 +29,6 @@  void test (void)
 }
 
 /* { dg-begin-multiline-output "" }
-   NN |   fprintf(stderr, "LOG: %s", msg);
-      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   'test': events 1-2
     |
     |   NN | {
diff --git a/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_paths.c b/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_paths.c
index cf05ca3a5d32..fa075057d504 100644
--- a/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_paths.c
+++ b/gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_paths.c
@@ -57,7 +57,7 @@  const pass_data pass_data_test_show_path =
 class pass_test_show_path : public ipa_opt_pass_d
 {
 public:
-  pass_test_show_path(gcc::context *ctxt)
+  pass_test_show_path(gcc::context *ctxt, bool dummy_label)
     : ipa_opt_pass_d (pass_data_test_show_path, ctxt,
 		      NULL, /* generate_summary */
 		      NULL, /* write_summary */
@@ -67,13 +67,16 @@  public:
 		      NULL, /* stmt_fixup */
 		      0, /* function_transform_todo_flags_start */
 		      NULL, /* function_transform */
-		      NULL) /* variable_transform */
+		      NULL), /* variable_transform */
+    m_dummy_label (dummy_label)
   {}
 
   /* opt_pass methods: */
   bool gate (function *) { return true; }
   virtual unsigned int execute (function *);
 
+  bool m_dummy_label;
+
 }; // class pass_test_show_path
 
 /* Determine if STMT is a call with NUM_ARGS arguments to a function
@@ -110,7 +113,7 @@  check_for_named_call (gimple *stmt,
 /* Example 1: a purely intraprocedural path.  */
 
 static void
-example_1 ()
+example_1 (bool dummy_label)
 {
   gimple_stmt_iterator gsi;
   basic_block bb;
@@ -146,6 +149,13 @@  example_1 ()
     {
       auto_diagnostic_group d;
       gcc_rich_location richloc (gimple_location (call_to_PyList_Append));
+
+      text_range_label label ("dummy label");
+      if (dummy_label)
+	richloc.add_range (gimple_location (call_to_PyList_Append),
+			   SHOW_RANGE_WITHOUT_CARET,
+			   &label);
+
       simple_diagnostic_path path (global_dc->printer);
       diagnostic_event_id_t alloc_event_id
 	= path.add_event (gimple_location (call_to_PyList_New),
@@ -424,19 +434,13 @@  example_3 ()
 unsigned int
 pass_test_show_path::execute (function *)
 {
-  example_1 ();
+  example_1 (m_dummy_label);
   example_2 ();
   example_3 ();
 
   return 0;
 }
 
-static opt_pass *
-make_pass_test_show_path (gcc::context *ctxt)
-{
-  return new pass_test_show_path (ctxt);
-}
-
 int
 plugin_init (struct plugin_name_args *plugin_info,
 	     struct plugin_gcc_version *version)
@@ -449,7 +453,14 @@  plugin_init (struct plugin_name_args *plugin_info,
   if (!plugin_default_version_check (version, &gcc_version))
     return 1;
 
-  pass_info.pass = make_pass_test_show_path (g);
+  bool dummy_label = false;
+  for (int i = 0; i < argc; i++)
+    {
+      if (strcmp (argv[i].key, "dummy_label") == 0)
+	dummy_label = true;
+    }
+
+  pass_info.pass = new pass_test_show_path (g, dummy_label);
   pass_info.reference_pass_name = "whole-program";
   pass_info.ref_pass_instance_number = 1;
   pass_info.pos_op = PASS_POS_INSERT_BEFORE;
diff --git a/gcc/testsuite/gcc.dg/plugin/plugin.exp b/gcc/testsuite/gcc.dg/plugin/plugin.exp
index c380ac942bd9..65d34625a1ce 100644
--- a/gcc/testsuite/gcc.dg/plugin/plugin.exp
+++ b/gcc/testsuite/gcc.dg/plugin/plugin.exp
@@ -98,6 +98,7 @@  set plugin_test_list [list \
     { diagnostic_plugin_test_paths.c \
 	  diagnostic-test-paths-1.c \
 	  diagnostic-test-paths-2.c \
+	  diagnostic-test-paths-2a.c \
 	  diagnostic-test-paths-3.c \
 	  diagnostic-test-paths-4.c \
 	  diagnostic-path-format-default.c \
diff --git a/gcc/tree-diagnostic-path.cc b/gcc/tree-diagnostic-path.cc
index 32dc054519b7..da7d4893a2d5 100644
--- a/gcc/tree-diagnostic-path.cc
+++ b/gcc/tree-diagnostic-path.cc
@@ -211,11 +211,13 @@  class path_summary
  public:
   path_summary (const diagnostic_path &path, bool check_rich_locations);
 
-  void print (diagnostic_context *dc, bool show_depths) const;
+  void print (diagnostic_context *dc, bool show_depths,
+	      bool need_event_header = true) const;
 
   unsigned get_num_ranges () const { return m_ranges.length (); }
 
  private:
+  const diagnostic_path &m_path;
   auto_delete_vec <event_range> m_ranges;
 };
 
@@ -223,6 +225,7 @@  class path_summary
 
 path_summary::path_summary (const diagnostic_path &path,
 			    bool check_rich_locations)
+: m_path (path)
 {
   const unsigned num_events = path.num_events ();
 
@@ -272,34 +275,42 @@  print_fndecl (pretty_printer *pp, tree fndecl, bool quoted)
    descriptions within calls to diagnostic_show_locus, using labels to
    show the events:
 
-   'foo' (events 1-2)
+   'foo': events 1-2
      | NN |
      |    |
-     +--> 'bar' (events 3-4)
+     +--> 'bar': events 3-4
             | NN |
             |    |
-            +--> 'baz' (events 5-6)
+            +--> 'baz': events 5-6
                    | NN |
                    |    |
      <------------ +
      |
-   'foo' (events 7-8)
+   'foo': events 7-8
      | NN |
      |    |
-     +--> 'bar' (events 9-10)
+     +--> 'bar': events 9-10
             | NN |
             |    |
-            +--> 'baz' (events 11-12)
+            +--> 'baz': events 11-12
                    | NN |
                    |    |
 
    If SHOW_DEPTHS is true, append " (depth N)" to the header of each run
    of events.
 
-   For events with UNKNOWN_LOCATION, print a summary of each the event.  */
+   For events with UNKNOWN_LOCATION, print a summary of each the event.
+
+   If the path is purely intraprocedural, don't print the function name
+   or the left-hand stack-depth lines.
+
+   If NEED_EVENT_HEADER is true, then a header is printed for every run
+   of events.  Otherwise, headers are only printed if there is more than
+   one run of events.  */
 
 void
-path_summary::print (diagnostic_context *dc, bool show_depths) const
+path_summary::print (diagnostic_context *dc,  bool show_depths,
+		     bool need_event_header) const
 {
   pretty_printer *pp = dc->printer;
 
@@ -317,6 +328,8 @@  path_summary::print (diagnostic_context *dc, bool show_depths) const
   typedef int_hash <int, EMPTY, DELETED> vbar_hash;
   hash_map <vbar_hash, int> vbar_column_for_depth;
 
+  const bool interprocedural = m_path.interprocedural_p ();
+
   /* Print the ranges.  */
   const int base_indent = 2;
   int cur_indent = base_indent;
@@ -324,67 +337,77 @@  path_summary::print (diagnostic_context *dc, bool show_depths) const
   event_range *range;
   FOR_EACH_VEC_ELT (m_ranges, i, range)
     {
-      write_indent (pp, cur_indent);
-      if (i > 0)
+      /* Write the header line for a run of events.  */
+      if (m_ranges.length () > 1 || need_event_header)
 	{
-	  const path_summary::event_range *prev_range
-	    = m_ranges[i - 1];
-	  if (range->m_stack_depth > prev_range->m_stack_depth)
+	  write_indent (pp, cur_indent);
+	  if (i > 0)
 	    {
-	      /* Show pushed stack frame(s).  */
-	      const char *push_prefix = "+--> ";
-	      pp_string (pp, start_line_color);
-	      pp_string (pp, push_prefix);
-	      pp_string (pp, end_line_color);
-	      cur_indent += strlen (push_prefix);
+	      const path_summary::event_range *prev_range
+		= m_ranges[i - 1];
+	      if (range->m_stack_depth > prev_range->m_stack_depth)
+		{
+		  /* Show pushed stack frame(s).  */
+		  const char *push_prefix = "+--> ";
+		  pp_string (pp, start_line_color);
+		  pp_string (pp, push_prefix);
+		  pp_string (pp, end_line_color);
+		  cur_indent += strlen (push_prefix);
+		}
 	    }
+	  if (interprocedural && range->m_fndecl)
+	    {
+	      print_fndecl (pp, range->m_fndecl, true);
+	      pp_string (pp, ": ");
+	    }
+	  if (range->m_start_idx == range->m_end_idx)
+	    pp_printf (pp, "event %i",
+		       range->m_start_idx + 1);
+	  else
+	    pp_printf (pp, "events %i-%i",
+		       range->m_start_idx + 1, range->m_end_idx + 1);
+	  if (show_depths)
+	    pp_printf (pp, " (depth %i)", range->m_stack_depth);
+	  pp_newline (pp);
 	}
-      if (range->m_fndecl)
-	{
-	  print_fndecl (pp, range->m_fndecl, true);
-	  pp_string (pp, ": ");
-	}
-      if (range->m_start_idx == range->m_end_idx)
-	pp_printf (pp, "event %i",
-		   range->m_start_idx + 1);
-      else
-	pp_printf (pp, "events %i-%i",
-		   range->m_start_idx + 1, range->m_end_idx + 1);
-      if (show_depths)
-	pp_printf (pp, " (depth %i)", range->m_stack_depth);
-      pp_newline (pp);
 
       /* Print a run of events.  */
       {
-	write_indent (pp, cur_indent + per_frame_indent);
-	pp_string (pp, start_line_color);
-	pp_string (pp, "|");
-	pp_string (pp, end_line_color);
-	pp_newline (pp);
+	if (interprocedural)
+	  {
+	    write_indent (pp, cur_indent + per_frame_indent);
+	    pp_string (pp, start_line_color);
+	    pp_string (pp, "|");
+	    pp_string (pp, end_line_color);
+	    pp_newline (pp);
+	  }
 
 	char *saved_prefix = pp_take_prefix (pp);
 	char *prefix;
-	{
-	  pretty_printer tmp_pp;
-	  write_indent (&tmp_pp, cur_indent + per_frame_indent);
-	  pp_string (&tmp_pp, start_line_color);
-	  pp_string (&tmp_pp, "|");
-	  pp_string (&tmp_pp, end_line_color);
-	  prefix = xstrdup (pp_formatted_text (&tmp_pp));
-	}
-	pp_set_prefix (pp, prefix);
-	pp_prefixing_rule (pp) = DIAGNOSTICS_SHOW_PREFIX_EVERY_LINE;
+	if (interprocedural)
+	  {
+	    pretty_printer tmp_pp;
+	    write_indent (&tmp_pp, cur_indent + per_frame_indent);
+	    pp_string (&tmp_pp, start_line_color);
+	    pp_string (&tmp_pp, "|");
+	    pp_string (&tmp_pp, end_line_color);
+	    prefix = xstrdup (pp_formatted_text (&tmp_pp));
+	    pp_set_prefix (pp, prefix);
+	    pp_prefixing_rule (pp) = DIAGNOSTICS_SHOW_PREFIX_EVERY_LINE;
+	  }
 	range->print (dc);
-	pp_set_prefix (pp, saved_prefix);
-
-	write_indent (pp, cur_indent + per_frame_indent);
-	pp_string (pp, start_line_color);
-	pp_string (pp, "|");
-	pp_string (pp, end_line_color);
-	pp_newline (pp);
+	if (interprocedural)
+	  {
+	    pp_set_prefix (pp, saved_prefix);
+	    write_indent (pp, cur_indent + per_frame_indent);
+	    pp_string (pp, start_line_color);
+	    pp_string (pp, "|");
+	    pp_string (pp, end_line_color);
+	    pp_newline (pp);
+	  }
       }
 
-      if (i < m_ranges.length () - 1)
+      if (interprocedural && i < m_ranges.length () - 1)
 	{
 	  const path_summary::event_range *next_range
 	    = m_ranges[i + 1];
@@ -441,51 +464,116 @@  path_summary::print (diagnostic_context *dc, bool show_depths) const
     }
 }
 
-} /* end of anonymous namespace for path-printing code.  */
+/* Concrete implementation of path_printer.
 
-/* Print PATH to CONTEXT, according to CONTEXT's path_format.  */
+   Putting this here isolates the path-printing code (which uses tree and
+   thus is in OBJS) from the core diagnostic machinery (which is in
+   OBJS-libcommon).  */
 
-void
-default_tree_diagnostic_path_printer (diagnostic_context *context,
-				      const diagnostic_path *path)
+class impl_path_printer : public path_printer
 {
-  gcc_assert (path);
-
-  const unsigned num_events = path->num_events ();
-
-  switch (context->path_format)
-    {
-    case DPF_NONE:
-      /* Do nothing.  */
-      return;
-
-    case DPF_SEPARATE_EVENTS:
+public:
+  bool maybe_print_path_rather_than_richloc (diagnostic_context *context,
+					     const rich_location &richloc)
+    FINAL OVERRIDE
+  {
+    switch (context->path_format)
       {
-	/* A note per event.  */
-	for (unsigned i = 0; i < num_events; i++)
-	  {
-	    const diagnostic_event &event = path->get_event (i);
-	    label_text event_text (event.get_desc (false));
-	    gcc_assert (event_text.m_buffer);
-	    diagnostic_event_id_t event_id (i);
-	    inform (event.get_location (),
-		    "%@ %s", &event_id, event_text.m_buffer);
-	    event_text.maybe_free ();
-	  }
+      default:
+	gcc_unreachable ();
+      case DPF_NONE:
+      case DPF_SEPARATE_EVENTS:
+	return false;
+
+      case DPF_INLINE_EVENTS:
+	{
+	  /* If we can, then print the path here, rather than RICHLOC. */
+	  if (richloc.path_makes_location_redundant_p ())
+	    {
+	      impl_print_path (context, richloc, false);
+	      return true;
+	    }
+	  return false;
+	}
       }
-      break;
+  }
 
-    case DPF_INLINE_EVENTS:
+  void print_path (diagnostic_context *context,
+		   const rich_location &richloc) FINAL OVERRIDE
+  {
+    switch (context->path_format)
       {
-	/* Consolidate related events.  */
-	path_summary summary (*path, true);
-	char *saved_prefix = pp_take_prefix (context->printer);
-	pp_set_prefix (context->printer, NULL);
-	summary.print (context, context->show_path_depths);
-	pp_flush (context->printer);
-	pp_set_prefix (context->printer, saved_prefix);
+      default:
+	gcc_unreachable ();
+      case DPF_NONE:
+	break;
+      case DPF_SEPARATE_EVENTS:
+	{
+	  const diagnostic_path *path = richloc.get_path ();
+	  gcc_assert (path);
+
+	  const unsigned num_events = path->num_events ();
+
+	  /* A note per event.  */
+	  for (unsigned i = 0; i < num_events; i++)
+	    {
+	      const diagnostic_event &event = path->get_event (i);
+	      label_text event_text (event.get_desc (false));
+	      gcc_assert (event_text.m_buffer);
+	      diagnostic_event_id_t event_id (i);
+	      inform (event.get_location (),
+		      "%@ %s", &event_id, event_text.m_buffer);
+	      event_text.maybe_free ();
+	    }
+	}
+	break;
+
+      case DPF_INLINE_EVENTS:
+	{
+	  if (richloc.path_makes_location_redundant_p ())
+	    {
+	      /* Then we already printed the path during diagnostic_show_locus
+		 on RICHLOC; nothing left to do.  */
+	      return;
+	    }
+	  /* Otherwise, print the path.  We have also printed RICHLOC
+	     via diagnostic_show_locus, so we must print event headers, to
+	     stop the path following on directly from the diagnostic_show_locus
+	     call.  */
+	  impl_print_path (context, richloc, true);
+	}
       }
-    }
+  }
+
+  void impl_print_path (diagnostic_context *context,
+			const rich_location &richloc,
+			bool need_event_header)
+  {
+    const diagnostic_path *path = richloc.get_path ();
+    gcc_assert (path);
+
+    /* Consolidate related events.  */
+    path_summary summary (*path, true);
+    char *saved_prefix = pp_take_prefix (context->printer);
+    pp_set_prefix (context->printer, NULL);
+    summary.print (context, context->show_path_depths,
+		   need_event_header);
+    pp_flush (context->printer);
+    pp_set_prefix (context->printer, saved_prefix);
+  }
+};
+
+} /* end of anonymous namespace for path-printing code.  */
+
+/* class path_printer.  */
+
+/* Make a concrete path_printer instance.
+   The caller is reponsible for deleting it.  */
+
+path_printer *
+path_printer::make_tree_default ()
+{
+  return new impl_path_printer ();
 }
 
 /* This has to be here, rather than diagnostic-format-json.cc,
@@ -591,14 +679,21 @@  test_intraprocedural_path (pretty_printer *event_pp)
   path_summary summary (path, false);
   ASSERT_EQ (summary.get_num_ranges (), 1);
 
-  test_diagnostic_context dc;
-  summary.print (&dc, true);
-  ASSERT_STREQ ("  `foo': events 1-2 (depth 0)\n"
-		"    |\n"
-		"    | (1): first `free'\n"
-		"    | (2): double `free'\n"
-		"    |\n",
-		pp_formatted_text (dc.printer));
+  {
+    test_diagnostic_context dc;
+    summary.print (&dc, true, false);
+    ASSERT_STREQ (" (1): first `free'\n"
+		  " (2): double `free'\n",
+		  pp_formatted_text (dc.printer));
+  }
+  {
+    test_diagnostic_context dc;
+    summary.print (&dc, true, true);
+    ASSERT_STREQ ("  events 1-2 (depth 0)\n"
+		  " (1): first `free'\n"
+		  " (2): double `free'\n",
+		  pp_formatted_text (dc.printer));
+  }
 }
 
 /* Verify that print_path_summary works on an interprocedural path.  */
diff --git a/gcc/tree-diagnostic.c b/gcc/tree-diagnostic.c
index d5f2f9e7e2d7..b8b78f5ea279 100644
--- a/gcc/tree-diagnostic.c
+++ b/gcc/tree-diagnostic.c
@@ -312,6 +312,6 @@  tree_diagnostics_defaults (diagnostic_context *context)
   diagnostic_starter (context) = default_tree_diagnostic_starter;
   diagnostic_finalizer (context) = default_diagnostic_finalizer;
   diagnostic_format_decoder (context) = default_tree_printer;
-  context->print_path = default_tree_diagnostic_path_printer;
+  context->m_path_printer = path_printer::make_tree_default ();
   context->make_json_for_path = default_tree_make_json_for_path;
 }
diff --git a/gcc/tree-diagnostic.h b/gcc/tree-diagnostic.h
index d97a97380245..e9a119273a0c 100644
--- a/gcc/tree-diagnostic.h
+++ b/gcc/tree-diagnostic.h
@@ -57,8 +57,6 @@  void tree_diagnostics_defaults (diagnostic_context *context);
 bool default_tree_printer (pretty_printer *, text_info *, const char *,
 			   int, bool, bool, bool, bool *, const char **);
 
-extern void default_tree_diagnostic_path_printer (diagnostic_context *,
-						  const diagnostic_path *);
 extern json::value *default_tree_make_json_for_path (diagnostic_context *,
 						     const diagnostic_path *);
 
diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index eaddcb64bc67..229806fd4984 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -1732,6 +1732,8 @@  class rich_location
   const diagnostic_path *get_path () const { return m_path; }
   void set_path (const diagnostic_path *path) { m_path = path; }
 
+  bool path_makes_location_redundant_p () const;
+
 private:
   bool reject_impossible_fixit (location_t where);
   void stop_supporting_fixits ();