> which is not much fewer than there are now.  Don't confuse encoding with
> semantics.  My Squeak compiler (heavily derivative of the current Squeak
> compiler) currently has 34 opcodes distributed over 253 bytecodes.  Of
> these, 7 are for optimizations other than inlining blocks, so reduce to
> 27.

GNU Smalltalk has 22 opcodes that are very close to Eliot's list (I
marked the changes with notes on the right):

  SEND (n, super, num_args);        << Eliot's "send" and "send super"
  PUSH_TEMPORARY_VARIABLE (n);
  PUSH_OUTER_TEMP (n, scopes);
  PUSH_LIT_VARIABLE (n);            << could be push constant + #value
  PUSH_RECEIVER_VARIABLE (n);
  STORE_TEMPORARY_VARIABLE (n);
  STORE_OUTER_TEMP (n, scopes);
  STORE_LIT_VARIABLE (n);           << could be #value:
  STORE_RECEIVER_VARIABLE (n);
  JUMP (ofs);                       << could be done with sends
  POP_JUMP_TRUE (ofs);              << likewise
  POP_JUMP_FALSE (ofs);             << likewise
  PUSH_INTEGER (n);                 << could be push constant
  PUSH_SELF;
  PUSH_SPECIAL (n);                 << could be push constant
  PUSH_LIT_CONSTANT (n);
  POP_INTO_NEW_STACKTOP (n);        << Eliot's make array
  POP_STACK_TOP;
  MAKE_DIRTY_BLOCK;
  RETURN_METHOD_STACK_TOP;
  RETURN_CONTEXT_STACK_TOP;
  DUP_STACK_TOP;

(24 counting the "line number" mark and a special "exit interpreter"
bytecode used by only one method in the entire system) distributed over
58 bytecodes.  There are 6 unused bytecodes, and 192 more bytecodes are
used for "composite" operations like

  PUSH_LIT_CONSTANT (arg);
  MAKE_DIRTY_BLOCK ();

or

  DUP_STACK_TOP ();
  PUSH_TEMPORARY_VARIABLE (arg);
  PUSH_INTEGER (1);
  PLUS_SPECIAL ();

My 2 cents,

Paolo