[lto] Add streamer hooks for emitting location_t (issue5249058)

diff --git a/gcc/lto-streamer-in.c b/gcc/lto-streamer-in.c
index d4e80c7..f18b944 100644
--- a/gcc/lto-streamer-in.c
+++ b/gcc/lto-streamer-in.c
@@ -50,6 +50,7 @@  along with GCC; see the file COPYING3.  If not see
 #include "lto-streamer.h"
 #include "tree-streamer.h"
 #include "tree-pass.h"
+#include "streamer-hooks.h"
 
 /* The table to hold the file names.  */
 static htab_t file_name_hash_table;
@@ -180,15 +181,23 @@  lto_input_location_bitpack (struct data_in *data_in, struct bitpack_d *bp)
 }
 
 
-/* Read a location from input block IB.  */
+/* Read a location from input block IB.
+   If the input_location streamer hook exists, call it.
+   Otherwise, proceed with reading the location from the
+   expanded location bitpack.  */
 
 location_t
 lto_input_location (struct lto_input_block *ib, struct data_in *data_in)
 {
-  struct bitpack_d bp;
+  if (streamer_hooks.input_location)
+    return streamer_hooks.input_location (ib, data_in);
+  else
+    {
+      struct bitpack_d bp;
 
-  bp = streamer_read_bitpack (ib);
-  return lto_input_location_bitpack (data_in, &bp);
+      bp = streamer_read_bitpack (ib);
+      return lto_input_location_bitpack (data_in, &bp);
+    }
 }
 
 
diff --git a/gcc/lto-streamer-out.c b/gcc/lto-streamer-out.c
index c14b3a9..4d88f62 100644
--- a/gcc/lto-streamer-out.c
+++ b/gcc/lto-streamer-out.c
@@ -172,15 +172,21 @@  lto_output_location_bitpack (struct bitpack_d *bp,
 
 
 /* Emit location LOC to output block OB.
-   When bitpack is handy, it is more space effecient to call
+   If the output_location streamer hook exists, call it.
+   Otherwise, when bitpack is handy, it is more space efficient to call
    lto_output_location_bitpack with existing bitpack.  */
 
 void
 lto_output_location (struct output_block *ob, location_t loc)
 {
-  struct bitpack_d bp = bitpack_create (ob->main_stream);
-  lto_output_location_bitpack (&bp, ob, loc);
-  streamer_write_bitpack (&bp);
+  if (streamer_hooks.output_location)
+    streamer_hooks.output_location (ob, loc);
+  else
+    {
+      struct bitpack_d bp = bitpack_create (ob->main_stream);
+      lto_output_location_bitpack (&bp, ob, loc);
+      streamer_write_bitpack (&bp);
+    }
 }
 
 
diff --git a/gcc/streamer-hooks.h b/gcc/streamer-hooks.h
index b4c6562..0c1d483 100644
--- a/gcc/streamer-hooks.h
+++ b/gcc/streamer-hooks.h
@@ -51,6 +51,16 @@  struct streamer_hooks {
      and descriptors needed by the unpickling routines.  It returns the
      tree instantiated from the stream.  */
   tree (*read_tree) (struct lto_input_block *, struct data_in *);
+
+  /* [OPT] Called by lto_input_location to retrieve the source location of the
+     tree currently being read. If this hook returns NULL, lto_input_location
+     defaults to calling lto_input_location_bitpack.  */
+  location_t (*input_location) (struct lto_input_block *, struct data_in *);
+
+  /* [OPT] Called by lto_output_location to write the source_location of the
+     tree currently being written. If this hook returns NULL,
+     lto_output_location defaults to calling lto_output_location_bitpack.  */
+  void (*output_location) (struct output_block *, location_t);
 };
 
 #define stream_write_tree(OB, EXPR, REF_P) \