[binutils-gdb] Add a fast_hash function in common-utils

[gdb-buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 1a6ff1a96b302283d517b3cdeae7310adecbe859 ***

commit 1a6ff1a96b302283d517b3cdeae7310adecbe859
Author:     Christian Biesinger <cbiesinger@google.com>
AuthorDate: Fri Sep 27 13:08:25 2019 -0500
Commit:     Christian Biesinger <cbiesinger@google.com>
CommitDate: Tue Oct 22 11:26:17 2019 -0500

    Add a fast_hash function in common-utils
    
    Also updates a caller in symtab.c. For now this just calls htab_hash_string
    but the next patch will change it to xxhash, if available.
    
    gdb/ChangeLog:
    
    2019-10-22  Christian Biesinger  <cbiesinger@google.com>
    
            * utils.h (fast_hash): New function.
            * symtab.c (hash_demangled_name_entry): Call new function
            fast_hash.
    
    Change-Id: I77cac0d9aa78fc65316a2af449f52edcae72dc9b

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index d271330400..bbf5d0897d 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2019-10-22  Christian Biesinger  <cbiesinger@google.com>
+
+	* utils.h (fast_hash): New function.
+	* symtab.c (hash_demangled_name_entry): Call new function
+	fast_hash.
+
 2019-10-22  Christian Biesinger  <cbiesinger@google.com>
 
 	* symtab.c (struct demangled_name_entry): Change type of mangled
diff --git a/gdb/symtab.c b/gdb/symtab.c
index 567d09d355..dff92ca203 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -70,6 +70,7 @@
 #include <algorithm>
 #include "gdbsupport/gdb_string_view.h"
 #include "gdbsupport/pathstuff.h"
+#include "gdbsupport/common-utils.h"
 
 /* Forward declarations for local functions.  */
 
@@ -727,7 +728,7 @@ hash_demangled_name_entry (const void *data)
   const struct demangled_name_entry *e
     = (const struct demangled_name_entry *) data;
 
-  return iterative_hash (e->mangled.data (), e->mangled.length (), 0);
+  return fast_hash (e->mangled.data (), e->mangled.length ());
 }
 
 /* Equality function for the demangled name hash.  */
diff --git a/gdb/utils.h b/gdb/utils.h
index af8b461b6e..478c485e66 100644
--- a/gdb/utils.h
+++ b/gdb/utils.h
@@ -567,4 +567,14 @@ extern void copy_bitwise (gdb_byte *dest, ULONGEST dest_offset,
 			  const gdb_byte *source, ULONGEST source_offset,
 			  ULONGEST nbits, int bits_big_endian);
 
+/* A fast hashing function.  This can be used to hash strings in a fast way
+   when the length is known.  If no fast hashing library is available, falls
+   back to iterative_hash from libiberty.  */
+
+static inline unsigned int
+fast_hash (const char* str, size_t len)
+{
+  return iterative_hash (str, len, 0);
+}
+
 #endif /* UTILS_H */