diff --git a/vvp/opcodes.txt b/vvp/opcodes.txt
index b8d5dfe5d..981eae565 100644
--- a/vvp/opcodes.txt
+++ b/vvp/opcodes.txt
@@ -39,19 +39,11 @@ flags. These are used as destinations for operations that return
 boolean values, for example comparisons. They are also used as inputs
 for test and branch opcodes.
 
-* %abs/wr <bit-o>, <bit-i>
+* %abs/wr
 
 This instruction calculates the absolute value of a real value. It uses
-the fabs() function in the run-time to do the work.
-
-* %add <bit-l>, <bit-r>, <wid> (XXXX Old version)
-
-This instruction adds the right vector into the left vector, the
-vectors having the width <wid>. If any of the bits of either vector
-are x or z, the result is x. Otherwise, the result is the arithmetic
-sum.
-
-See also the %sub instruction.
+the fabs() function in the run-time to do the work, and manipulates
+the top of the real-value stack.
 
 * %add
 * %addi <vala>, <valb>, <wid>
@@ -65,7 +57,7 @@ immediate value (See %pushi/vec4).
 
 See also the %sub instruction.
 
-* %add/wr <bit-l>, <bit-r>
+* %add/wr
 
 This is the real valued version of the %add instruction. The arguments
 are popped from the stack, right operand then left, and the result
@@ -492,6 +484,10 @@ the format of the output is:
 <description> is a string, if string is 0 then the following default
 message is used: "Procedural tracing.".
 
+* %flag_inv <flag>
+
+This instruct inverts a flag bit.
+
 * %flag_mov <flag1>, <flag2>
 
 This instruction copies the flag bit from <flag2> to <flag1>.
diff --git a/vvp/vthread.cc b/vvp/vthread.cc
index e1ef90a70..6f80ea15c 100644
--- a/vvp/vthread.cc
+++ b/vvp/vthread.cc
@@ -726,6 +726,9 @@ vvp_context_item_t vthread_get_rd_context_item(unsigned context_idx)
       return vvp_get_context_item(running_thread->rd_context, context_idx);
 }
 
+/*
+ * %abs/wr
+ */
 bool of_ABS_WR(vthread_t thr, vvp_code_t)
 {
       thr->push_real( fabs(thr->pop_real()) );
@@ -849,6 +852,9 @@ bool of_ADDI(vthread_t thr, vvp_code_t cp)
       return true;
 }
 
+/*
+ * %add/wr
+ */
 bool of_ADD_WR(vthread_t thr, vvp_code_t)
 {
       double r = thr->pop_real();