[gcc r10-11039] lto/106540 - fix LTO tree input wrt dwarf2out_register_external_die

[gcc r10-11039] lto/106540 - fix LTO tree input wrt dwarf2out_register_external_die

[Richard Biener]

https://gcc.gnu.org/g:d2fa5521282cc7b5510e1e2c431a56d12693d74f

commit r10-11039-gd2fa5521282cc7b5510e1e2c431a56d12693d74f
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Aug 8 09:07:23 2022 +0200

    lto/106540 - fix LTO tree input wrt dwarf2out_register_external_die
    
    I've revisited the earlier two workarounds for dwarf2out_register_external_die
    getting duplicate entries.  It turns out that r11-525-g03d90a20a1afcb
    added dref_queue pruning to lto_input_tree but decl reading uses that
    to stream in DECL_INITIAL even when in the middle of SCC streaming.
    When that SCC then gets thrown away we can end up with debug nodes
    registered which isn't supposed to happen.  The following adjusts
    the DECL_INITIAL streaming to go the in-SCC way, using lto_input_tree_1,
    since no SCCs are expected at this point, just refs.
    
            PR lto/106540
            PR lto/106334
            * lto-streamer-in.c (lto_read_tree_1): Use lto_input_tree_1
            to input DECL_INITIAL, avoiding to commit drefs.
    
    (cherry picked from commit 4769ac6c5dfde2810a0266fe388211edc644e623)

Diff:
---
 gcc/lto-streamer-in.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/gcc/lto-streamer-in.c b/gcc/lto-streamer-in.c
index d5f581439fb..b0f8407a1d7 100644
--- a/gcc/lto-streamer-in.c
+++ b/gcc/lto-streamer-in.c
@@ -1689,11 +1689,14 @@ lto_read_tree_1 (class lto_input_block *ib, class data_in *data_in, tree expr)
   /* Read all the pointer fields in EXPR.  */
   streamer_read_tree_body (ib, data_in, expr);
 
-  /* Read any LTO-specific data not read by the tree streamer.  */
+  /* Read any LTO-specific data not read by the tree streamer.  Do not use
+     stream_read_tree here since that flushes the dref_queue in mids of
+     SCC reading.  */
   if (DECL_P (expr)
       && TREE_CODE (expr) != FUNCTION_DECL
       && TREE_CODE (expr) != TRANSLATION_UNIT_DECL)
-    DECL_INITIAL (expr) = stream_read_tree (ib, data_in);
+    DECL_INITIAL (expr)
+      = lto_input_tree_1 (ib, data_in, streamer_read_record_start (ib), 0);
 
   /* Stream references to early generated DIEs.  Keep in sync with the
      trees handled in dwarf2out_register_external_die.  */