Instruction decode generator taken from the PowerPC simulator

and being made more generic.

sim/igen/ld-cache.h

@@ -0,0 +1,81 @@
+/*  This file is part of the program psim.
+
+    Copyright (C) 1994,1995,1996, Andrew Cagney <cagney@highland.com.au>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+ 
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ 
+    */
+
+/* Instruction unpacking:
+
+   Once the instruction has been decoded, the register (and other)
+   fields within the instruction need to be extracted.
+
+   The table that follows determines how each field should be treated.
+   Importantly it considers the case where the extracted field is to
+   be used immediatly or stored in an instruction cache.
+
+   <type>
+
+   Indicates what to do with the cache entry.  If a cache is to be
+   used.  SCRATCH and CACHE values are defined when a cache entry is
+   being filled while CACHE and COMPUTE values are defined in the
+   semantic code.
+
+   Zero marks the end of the table.  More importantly 1. indicates
+   that the entry is valid and can be cached. 2. indicates that that
+   the entry is valid but can not be cached.
+
+   <field_name>
+
+   The field name as given in the instruction spec.
+
+   <derived_name>
+
+   A new name for <field_name> once it has been extracted from the
+   instruction (and possibly stored in the instruction cache).
+
+   <type>
+
+   String specifying the storage type for <new_name> (the extracted
+   field>.
+
+   <expression>
+
+   Specifies how to get <new_name> from <old_name>.  If null, old and
+   new name had better be the same. */
+
+
+typedef enum {
+  scratch_value,
+  cache_value,
+  compute_value,
+} cache_rule_type;
+
+typedef struct _cache_table cache_table;
+struct _cache_table {
+  cache_rule_type type;
+  char *field_name;
+  char *derived_name;
+  char *type_def;
+  char *expression;
+  table_entry *file_entry;
+  cache_table *next;
+};
+
+
+extern cache_table *load_cache_table
+(char *file_name,
+ int hi_bit_nr);