[PATCH gnumach 3/3] ipc: use fast modulo operation in local hash table

[Justus Winter]

* ipc/ipc_table.h: Document that table sizes must be powers of two.
* ipc/ipc_hash.c (IH_LOCAL_HASH): Use fast modulo operation.
---
 ipc/ipc_hash.c  | 2 +-
 ipc/ipc_table.h | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/ipc/ipc_hash.c b/ipc/ipc_hash.c
index 8285717..c2c6d6e 100644
--- a/ipc/ipc_hash.c
+++ b/ipc/ipc_hash.c
@@ -326,7 +326,7 @@ ipc_hash_global_delete(
  */
 
 #define        IH_LOCAL_HASH(obj, size)                                \
-               ((((mach_port_index_t) (vm_offset_t) (obj)) >> 6) % (size))
+       ((((mach_port_index_t) (vm_offset_t) (obj)) >> 6) & (size - 1))
 
 /*
  *     Routine:        ipc_hash_local_lookup
diff --git a/ipc/ipc_table.h b/ipc/ipc_table.h
index 3cc5f56..311b9a7 100644
--- a/ipc/ipc_table.h
+++ b/ipc/ipc_table.h
@@ -45,6 +45,8 @@
  *     an ipc_table_size structure.  These structures must
  *     be elements of an array, ipc_table_entries.
  *
+ *     Every its_size value must must be a power of two.
+ *
  *     The array must end with two elements with the same its_size value.
  *     Except for the terminating element, the its_size values must
  *     be strictly increasing.  The largest (last) its_size value
-- 
2.1.0