[PATCH 8/8] x86: split i386-gen's opcode hash entry struct

[Jan Beulich]

All glibc malloc() implementations I've checked have a smallest
allocation size worth of 3 pointers, with an increment worth of 2
pointers. Hence mnemonics with multiple templates can be stored more
efficiently when maintaining the shared "name" field only in the actual
hash entry. (To express the shared nature, also convert "name" to by
pointer-to-const.)

While doing the conversation also pull out common code from the involved
if/else construct in expand_templates().

--- a/opcodes/i386-gen.c
+++ b/opcodes/i386-gen.c
@@ -1293,10 +1293,13 @@ output_i386_opcode (FILE *table, const c
 
 struct opcode_hash_entry
 {
-  struct opcode_hash_entry *next;
-  char *name;
-  char *opcode;
-  int lineno;
+  const char *name;
+  struct opcode_entry
+  {
+    struct opcode_entry *next;
+    char *opcode;
+    int lineno;
+  } entry;
 };
 
 /* Calculate the hash value of an opcode hash entry P.  */
@@ -1432,7 +1435,8 @@ expand_templates (char *name, const char
 {
   static unsigned int idx, opcode_array_size;
   struct opcode_hash_entry **opcode_array = *opcode_array_p;
-  struct opcode_hash_entry **hash_slot, **entry;
+  struct opcode_hash_entry **hash_slot;
+  struct opcode_entry *entry;
   char *ptr1 = strchr(name, '<'), *ptr2;
 
   if (ptr1 == NULL)
@@ -1458,26 +1462,25 @@ expand_templates (char *name, const char
 
 	  opcode_array[idx] = (struct opcode_hash_entry *)
 	    xmalloc (sizeof (struct opcode_hash_entry));
-	  opcode_array[idx]->next = NULL;
 	  opcode_array[idx]->name = xstrdup (name);
-	  opcode_array[idx]->opcode = xstrdup (str);
-	  opcode_array[idx]->lineno = lineno;
 	  *hash_slot = opcode_array[idx];
+	  entry = &opcode_array[idx]->entry;
 	  idx++;
 	}
       else
 	{
 	  /* Append it to the existing one.  */
-	  entry = hash_slot;
-	  while ((*entry) != NULL)
-	    entry = &(*entry)->next;
-	  *entry = (struct opcode_hash_entry *)
-	    xmalloc (sizeof (struct opcode_hash_entry));
-	  (*entry)->next = NULL;
-	  (*entry)->name = (*hash_slot)->name;
-	  (*entry)->opcode = xstrdup (str);
-	  (*entry)->lineno = lineno;
+	  struct opcode_entry **entryp = &(*hash_slot)->entry.next;
+
+	  while (*entryp != NULL)
+	    entryp = &(*entryp)->next;
+	  entry = (struct opcode_entry *)xmalloc (sizeof (struct opcode_entry));
+	  *entryp = entry;
 	}
+
+      entry->next = NULL;
+      entry->opcode = xstrdup (str);
+      entry->lineno = lineno;
     }
   else if ((ptr2 = strchr(ptr1 + 1, '>')) == NULL)
     fail ("%s: %d: missing '>'\n", filename, lineno);
@@ -1599,7 +1602,7 @@ process_i386_opcodes (FILE *table)
   char buf[2048];
   unsigned int i, j, nr, offs;
   size_t l;
-  char *str, *p, *last, *name;
+  char *str, *p, *last;
   htab_t opcode_hash_table;
   struct opcode_hash_entry **opcode_array = NULL;
   int lineno = 0, marker = 0;
@@ -1619,6 +1622,8 @@ process_i386_opcodes (FILE *table)
   /* Put everything on opcode array.  */
   while (!feof (fp))
     {
+      char *name;
+
       if (fgets (buf, sizeof (buf), fp) == NULL)
 	break;
 
@@ -1700,11 +1705,11 @@ process_i386_opcodes (FILE *table)
   /* Process opcode array.  */
   for (j = 0; j < i; j++)
     {
-      struct opcode_hash_entry *next;
+      const char *name = opcode_array[j]->name;
+      struct opcode_entry *next;
 
-      for (next = opcode_array[j]; next; next = next->next)
+      for (next = &opcode_array[j]->entry; next; next = next->next)
 	{
-	  name = next->name;
 	  str = next->opcode;
 	  lineno = next->lineno;
 	  last = str + strlen (str);
@@ -1723,7 +1728,7 @@ process_i386_opcodes (FILE *table)
 
   for (nr = j = 0; j < i; j++)
     {
-      struct opcode_hash_entry *next = opcode_array[j];
+      struct opcode_entry *next = &opcode_array[j]->entry;
 
       do
 	{
@@ -1753,10 +1758,10 @@ process_i386_opcodes (FILE *table)
   str = NULL;
   for (l = strlen (opcode_array[offs = j = 0]->name); j < i; j++)
     {
+      const char *name = opcode_array[j]->name;
       const char *next = NULL;
       size_t l1 = j + 1 < i ? strlen(next = opcode_array[j + 1]->name) : 0;
 
-      name = opcode_array[j]->name;
       if (str == NULL)
 	str = mkident (name);
       if (l < l1 && !strcmp(name, next + l1 - l))