[binutils-gdb] gdb/dwarf: return dwarf2_cu from load_full_{comp, type}_unit

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=0826b7b7f8527c065ab573bd67ac691654339f03

commit 0826b7b7f8527c065ab573bd67ac691654339f03
Author: Simon Marchi <[email protected]>
Date:   Sat Feb 21 15:07:29 2026 -0500

    gdb/dwarf: return dwarf2_cu from load_full_{comp,type}_unit
    
    Make load_full_{comp,type}_unit return a non-owning reference to the
    created dwarf2_cu.  The functions still install the dwarf2_cu in
    dwarf2_per_objfile::m_dwarf2_cus with dwarf2_per_objfile::set_cu.
    
    Make dwarf2_per_objfile::set_cu return a non-owning reference as well,
    for convenience.  This makes things easier to follow, and reduces the
    number of calls of unnecessary dwarf2_per_objfile::get_cu calls (i.e.
    map lookups).
    
    Change-Id: I51ed32585521cad0b89a4ca398915d7e0c1141e1
    Approved-By: Tom Tromey <[email protected]>

Diff:
---
 gdb/dwarf2/read.c | 59 ++++++++++++++++++++++++++++++-------------------------
 gdb/dwarf2/read.h |  6 ++++--
 2 files changed, 36 insertions(+), 29 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index b40cc52024c..42b04c90785 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -889,8 +889,8 @@ static struct type *get_DW_AT_signature_type (struct die_info *,
 					      const struct attribute *,
 					      struct dwarf2_cu *);
 
-static void load_full_type_unit (signatured_type *sig_type,
-				  dwarf2_per_objfile *per_objfile);
+static dwarf2_cu *load_full_type_unit (signatured_type *sig_type,
+				       dwarf2_per_objfile *per_objfile);
 
 static int attr_to_dynamic_prop (const struct attribute *attr,
 				 struct die_info *die, struct dwarf2_cu *cu,
@@ -914,10 +914,9 @@ static void dwarf2_symbol_mark_computed (const struct attribute *attr,
 static struct type *set_die_type (struct die_info *, struct type *,
 				  struct dwarf2_cu *, bool = false);
 
-static void load_full_comp_unit (dwarf2_per_cu *per_cu,
-				 dwarf2_per_objfile *per_objfile,
-				 bool skip_partial,
-				 std::optional<language> pretend_language);
+static dwarf2_cu *load_full_comp_unit
+  (dwarf2_per_cu *per_cu, dwarf2_per_objfile *per_objfile,
+   bool skip_partial, std::optional<language> pretend_language);
 
 static compunit_symtab *process_full_comp_unit (dwarf2_cu *cu);
 
@@ -1569,13 +1568,14 @@ static dwarf2_cu *
 load_cu (dwarf2_per_cu *per_cu, dwarf2_per_objfile *per_objfile,
 	 bool skip_partial)
 {
+  dwarf2_cu *cu;
+
   if (signatured_type *sig_type = per_cu->as_signatured_type ();
       sig_type != nullptr)
-    load_full_type_unit (sig_type, per_objfile);
+    cu = load_full_type_unit (sig_type, per_objfile);
   else
-    load_full_comp_unit (per_cu, per_objfile, skip_partial, std::nullopt);
+    cu = load_full_comp_unit (per_cu, per_objfile, skip_partial, std::nullopt);
 
-  dwarf2_cu *cu = per_objfile->get_cu (per_cu);
   if (cu == nullptr)
     return nullptr;  /* Dummy CU.  */
 
@@ -4055,9 +4055,12 @@ process_queue (dwarf2_per_objfile *per_objfile)
   dwarf_read_debug_printf ("Done expanding %u symtabs.", expanded_count);
 }
 
-/* Load the DIEs associated with PER_CU into memory.  */
+/* Load the DIEs associated with PER_CU into memory.
 
-static void
+   Return the new dwarf2_cu.  This function may return nullptr, if the unit is
+   dummy.  */
+
+static dwarf2_cu *
 load_full_comp_unit (dwarf2_per_cu *this_cu, dwarf2_per_objfile *per_objfile,
 		     bool skip_partial,
 		     std::optional<language> pretend_language)
@@ -4069,13 +4072,13 @@ load_full_comp_unit (dwarf2_per_cu *this_cu, dwarf2_per_objfile *per_objfile,
   cutu_reader reader (*this_cu, *per_objfile, nullptr, skip_partial,
 		      pretend_language, abbrev_table_cache);
   if (reader.is_dummy ())
-    return;
+    return nullptr;
 
   reader.read_all_dies ();
 
   /* Save this dwarf2_cu in the per_objfile.  The per_objfile owns it
      now.  */
-  per_objfile->set_cu (this_cu, reader.release_cu ());
+  return &per_objfile->set_cu (this_cu, reader.release_cu ());
 }
 
 /* Add a DIE to the delayed physname list.  */
@@ -17535,9 +17538,12 @@ get_DW_AT_signature_type (struct die_info *die, const struct attribute *attr,
 
 /* Read in a signatured type and build its CU and DIEs.
    If the type is a stub for the real type in a DWO file,
-   read in the real type from the DWO file as well.  */
+   read in the real type from the DWO file as well.
 
-static void
+   Return the new dwarf2_cu.  This function may return nullptr, if the unit is
+   dummy.  */
+
+static dwarf2_cu *
 load_full_type_unit (signatured_type *sig_type,
 		     dwarf2_per_objfile *per_objfile)
 {
@@ -17547,17 +17553,16 @@ load_full_type_unit (signatured_type *sig_type,
   abbrev_table_cache abbrev_table_cache;
   cutu_reader reader (*sig_type, *per_objfile, nullptr, false,
 		      std::nullopt, abbrev_table_cache);
+  sig_type->tu_read = 1;
 
-  if (!reader.is_dummy ())
-    {
-      reader.read_all_dies ();
+  if (reader.is_dummy ())
+    return nullptr;
 
-      /* Save this dwarf2_cu in the per_objfile.  The per_objfile owns it
-	 now.  */
-      per_objfile->set_cu (sig_type, reader.release_cu ());
-    }
+  reader.read_all_dies ();
 
-  sig_type->tu_read = 1;
+  /* Save this dwarf2_cu in the per_objfile.  The per_objfile owns it
+     now.  */
+  return &per_objfile->set_cu (sig_type, reader.release_cu ());
 }
 
 /* See read.h.  */
@@ -18301,12 +18306,12 @@ dwarf2_per_objfile::get_cu (dwarf2_per_cu *per_cu)
 
 /* See read.h.  */
 
-void
+dwarf2_cu &
 dwarf2_per_objfile::set_cu (dwarf2_per_cu *per_cu, dwarf2_cu_up cu)
 {
-  gdb_assert (this->get_cu (per_cu) == nullptr);
-
-  m_dwarf2_cus[per_cu] = std::move (cu);
+  auto [it, inserted] = m_dwarf2_cus.try_emplace (per_cu, std::move (cu));
+  gdb_assert (inserted);
+  return *it->second;
 }
 
 /* See read.h.  */
diff --git a/gdb/dwarf2/read.h b/gdb/dwarf2/read.h
index e9874ce1fab..761a6cadefb 100644
--- a/gdb/dwarf2/read.h
+++ b/gdb/dwarf2/read.h
@@ -935,8 +935,10 @@ struct dwarf2_per_objfile
   /* Get the dwarf2_cu matching PER_CU for this objfile.  */
   dwarf2_cu *get_cu (dwarf2_per_cu *per_cu);
 
-  /* Set the dwarf2_cu matching PER_CU for this objfile.  */
-  void set_cu (dwarf2_per_cu *per_cu, dwarf2_cu_up cu);
+  /* Set the dwarf2_cu matching PER_CU for this objfile.
+
+     Return a non-owning reference to the dwarf2_cu.  */
+  dwarf2_cu &set_cu (dwarf2_per_cu *per_cu, dwarf2_cu_up cu);
 
   /* Remove/free the dwarf2_cu matching PER_CU for this objfile.  */
   void remove_cu (dwarf2_per_cu *per_cu);