comments (documentation about instruction formats)

1 files changed, 14 insertions, 15 deletions

diff --git a/lopcodes.h b/lopcodes.h
index 7f17de1c..3d69196c 100644
--- a/lopcodes.h
+++ b/lopcodes.h
@@ -1,5 +1,5 @@
 /*
-** $Id: lopcodes.h,v 1.157 2017/09/13 19:50:08 roberto Exp roberto $
+** $Id: lopcodes.h,v 1.158 2017/09/15 14:19:06 roberto Exp roberto $
 ** Opcodes for Lua virtual machine
 ** See Copyright Notice in lua.h
 */
@@ -11,21 +11,20 @@
 
 
 /*===========================================================================
-  We assume that instructions are unsigned numbers.
+  We assume that instructions are unsigned 32-bit integers.
   All instructions have an opcode in the first 6 bits.
-  Instructions can have the following fields:
-        'A' : 8 bits
-        'B' : 9 bits
-        'C' : 9 bits
-        'Ax' : 26 bits ('A', 'B', and 'C' together)
-        'Bx' : 18 bits ('B' and 'C' together)
-        'sBx' : signed Bx
-
-  A signed argument is represented in excess K; that is, the number
-  value is the unsigned value minus K. K is exactly the maximum value
-  for that argument (so that -max is represented by 0, and +max is
-  represented by 2*max), which is half the maximum for the corresponding
-  unsigned argument.
+  Instructions can have the following formats:
+
+        3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0
+        1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
+iABC    |       C(9)    | |       B(9)    | |     A(8)    | |   Op(6) |
+iABx    |              Bx(18)             | |     A(8)    | |   Op(6) |
+iAsBx   |             sBx (signed)(18)    | |     A(8)    | |   Op(6) |
+iAx     |                         Ax(26)                  | |   Op(6) |
+
+  A signed argument is represented in excess K: the represented value is
+  the written unsigned value minus K, where K is half the maximum for the
+  corresponding unsigned argument.
 ===========================================================================*/