[review v3] Precompute hash value for symbol_set_names

["Christian Biesinger (Code Review)" <gerrit@gnutoolchain-gerrit.osci.io>]

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/307
......................................................................

Precompute hash value for symbol_set_names

We can also compute the hash for the mangled name on a background
thread so make this function even faster (about a 7% speedup).

gdb/ChangeLog:

2019-10-03  Christian Biesinger  <cbiesinger@google.com>

	* minsyms.c (minimal_symbol_reader::install): Also compute the hash
	of the mangled name on the background thread.
	* symtab.c (symbol_set_names): Allow passing in the hash of the
	linkage_name.
	* symtab.h (symbol_set_names): Likewise.

Change-Id: I044449e7eb60cffc1c43efd3412f2b485bd9faac
---
M gdb/minsyms.c
M gdb/symtab.c
M gdb/symtab.h
3 files changed, 30 insertions(+), 6 deletions(-)



diff --git a/gdb/minsyms.c b/gdb/minsyms.c
index f9d1172..d2d8bf5 100644
--- a/gdb/minsyms.c
+++ b/gdb/minsyms.c
@@ -1258,6 +1258,12 @@
     }
 }
 
+struct computed_hash_values
+{
+  size_t name_length;
+  hashval_t mangled_name_hash;
+};
+
 /* Build (or rebuild) the minimal symbol hash tables.  This is necessary
    after compacting or sorting the table since the entries move around
    thus causing the internal minimal_symbol pointers to become jumbled.  */
@@ -1370,6 +1376,8 @@
       std::mutex demangled_mutex;
 #endif
 
+      std::vector<computed_hash_values> hash_values (mcount);
+
       msymbols = m_objfile->per_bfd->msymbols.get ();
       gdb::parallel_for_each
 	(&msymbols[0], &msymbols[mcount],
@@ -1377,6 +1385,8 @@
 	 {
 	   for (minimal_symbol *msym = start; msym < end; ++msym)
 	     {
+	       size_t idx = msym - msymbols;
+	       hash_values[idx].name_length = strlen (msym->name);
 	       if (!msym->name_set)
 		 {
 		   /* This will be freed later, by symbol_set_names.  */
@@ -1386,6 +1396,9 @@
 		     (msym, demangled_name,
 		      &m_objfile->per_bfd->storage_obstack);
 		   msym->name_set = 1;
+
+		   hash_values[idx].mangled_name_hash
+		     = fast_hash (msym->name, hash_values[idx].name_length);
 		 }
 	     }
 	   {
@@ -1396,8 +1409,14 @@
 #endif
 	     for (minimal_symbol *msym = start; msym < end; ++msym)
 	       {
-		 symbol_set_names (msym, msym->name, false,
-				   m_objfile->per_bfd);
+		 size_t idx = msym - msymbols;
+		 symbol_set_names
+		   (msym,
+		    gdb::string_view(msym->name,
+				     hash_values[idx].name_length),
+		    false,
+		    m_objfile->per_bfd,
+		    hash_values[idx].mangled_name_hash);
 	       }
 	   }
 	 });
diff --git a/gdb/symtab.c b/gdb/symtab.c
index 3502827..f5a759d 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -825,7 +825,8 @@
 void
 symbol_set_names (struct general_symbol_info *gsymbol,
 		  gdb::string_view linkage_name, bool copy_name,
-		  struct objfile_per_bfd_storage *per_bfd)
+		  struct objfile_per_bfd_storage *per_bfd,
+		  gdb::optional<hashval_t> hash)
 {
   struct demangled_name_entry **slot;
 
@@ -853,9 +854,11 @@
     create_demangled_names_hash (per_bfd);
 
   struct demangled_name_entry entry (linkage_name);
+  if (!hash.has_value ())
+    hash = hash_demangled_name_entry (&entry);
   slot = ((struct demangled_name_entry **)
-	  htab_find_slot (per_bfd->demangled_names_hash.get (),
-			  &entry, INSERT));
+          htab_find_slot_with_hash (per_bfd->demangled_names_hash.get (),
+				    &entry, *hash, INSERT));
 
   /* If this name is not in the hash table, add it.  */
   if (*slot == NULL
diff --git a/gdb/symtab.h b/gdb/symtab.h
index 4172a25..fe74204 100644
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -522,7 +522,9 @@
 		    (objfile)->per_bfd)
 extern void symbol_set_names (struct general_symbol_info *symbol,
 			      gdb::string_view linkage_name, bool copy_name,
-			      struct objfile_per_bfd_storage *per_bfd);
+			      struct objfile_per_bfd_storage *per_bfd,
+			      gdb::optional<hashval_t> hash
+			        = gdb::optional<hashval_t> ());
 
 /* Now come lots of name accessor macros.  Short version as to when to
    use which: Use SYMBOL_NATURAL_NAME to refer to the name of the

-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: I044449e7eb60cffc1c43efd3412f2b485bd9faac
Gerrit-Change-Number: 307
Gerrit-PatchSet: 3
Gerrit-Owner: Christian Biesinger <cbiesinger@google.com>
Gerrit-Reviewer: Tom Tromey <tromey@sourceware.org>
Gerrit-MessageType: newpatchset