Re: [RFA 2/2] Simplify the psymbol hash function

[Tom Tromey <tom@tromey.com>]

>>>>> "Tom" == Tom Tromey <tom@tromey.com> writes:

Tom> I can add comments to the psymbol hash and comparison functions to
Tom> mention this.

How's this?

Tom

commit a042125cb391b1b489f272353a4c90068fc92954
Author: Tom Tromey <tom@tromey.com>
Date:   Thu Nov 2 12:48:44 2017 -0600

    Simplify the psymbol hash function
    
    This patch simplifies the psymbol_hash function, by changing it not to
    examine the contents of the symbol's name.  This change just mirrors
    what psymbol_compare already does -- it is checking for name equality,
    which is ok because symbol names are interned in symbol_set_names.
    
    This change speeds up psymbol reading.  "gdb -nx -batch gdb"
    previously took ~1.8 seconds on my machine, and with this patch it now
    takes ~1.7 seconds.
    
    gdb/ChangeLog
    2017-11-09  Tom Tromey  <tom@tromey.com>
    
            * psymtab.c (psymbol_hash): Do not hash string contents.
            (psymbol_compare): Add comment.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 03ccf9d57c..014ae04a3d 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2017-11-09  Tom Tromey  <tom@tromey.com>
+
+	* psymtab.c (psymbol_hash): Do not hash string contents.
+	(psymbol_compare): Add comment.
+
 2017-11-04  Tom Tromey  <tom@tromey.com>
 
 	* dictionary.c (dict_hash): Move "TKB" check into the "switch".
diff --git a/gdb/psymtab.c b/gdb/psymtab.c
index 29d40dcc04..06a65bf26e 100644
--- a/gdb/psymtab.c
+++ b/gdb/psymtab.c
@@ -1548,7 +1548,9 @@ psymbol_hash (const void *addr, int length)
   h = hash_continue (&lang, sizeof (unsigned int), h);
   h = hash_continue (&domain, sizeof (unsigned int), h);
   h = hash_continue (&theclass, sizeof (unsigned int), h);
-  h = hash_continue (psymbol->ginfo.name, strlen (psymbol->ginfo.name), h);
+  /* Note that psymbol names are interned via symbol_set_names, so
+     there's no need to hash the contents of the name here.  */
+  h = hash_continue (&psymbol->ginfo.name, sizeof (psymbol->ginfo.name), h);
 
   return h;
 }
@@ -1568,6 +1570,9 @@ psymbol_compare (const void *addr1, const void *addr2, int length)
 	  && sym1->ginfo.language == sym2->ginfo.language
           && PSYMBOL_DOMAIN (sym1) == PSYMBOL_DOMAIN (sym2)
           && PSYMBOL_CLASS (sym1) == PSYMBOL_CLASS (sym2)
+	  /* Note that psymbol names are interned via
+	     symbol_set_names, so there's no need to compare the
+	     contents of the name here.  */
           && sym1->ginfo.name == sym2->ginfo.name);
 }