2 - Forth Interest Group

Pinhole optimization. I
These are samples of the pinhole optimizations in the system I'm using at the time
of writing. They are subject to change without notice.
A lowercase letter other than "b" represents a literal, constant, or variable. "b"
represents a literal or constant that is a power of 2.
n + x n + x + n + 0 + SWAP +
n - x n - x + n - 0 - SWAP -
x n * b * 1 * CHARS
x n / 1 /
X @ DUP @
x ! SWAP !
x + ! SWAP+!
n < SWAP < 0 <
n = n OVER = DUP n = 0 = FALSE =
n ALIGNED
n AND x n AND
n >BODY [I] x >BODY [ '1 >BODY n CELLS +
['I >BODY n CELLS + @ [ ' 1 >BODY n CELLS + !
n CELLS
n COUNT C" CCC" COUNT
DUP IF ?DUP IF DUP O= IF ?DUP O= IF
O< IF FALSE IF O< NOT IF O= NOT IF
1 +LOOP 1 CHARS +LOOP
x n LSHIFT x LSHIFT n LSHIFT n LSHIFT
b MOD
n OR x n OR
0 PICK OVER 1 PICK 1 PICK n PICK
ROT ROT ROT ROT ROT
n RSHIFT x n RSHIFT
n U< SWAP U<
n UNDER+
DUP UNTIL ?DUP UNTIL DUP O= UNTIL ?DUP O= UNTIL
O< UNTIL FALSE UNTIL O< NOT UNTIL O= NOT UNTIL
n XOR x n XOR
DUP WHILE ?DUP WHILE DUP O= WHILE ?DUP O= WHILE
O< WHILE FALSE WHILE O< NOT WHILE O= NOT WHILE
AGAIN ; QUIT ; ABORT ; BYE ;
Here is a typical implementation of the required control-flow words other than
LEAVE. Words that contain one or more lowercase letters, or are a single uppercase
letter other than I or J, are not in Standard Forth, and probably won't be available
to you.
Not all optimizations are given.
branch, compiles part of an unconditional branch;
?branch, compiles part of a conditional branch;
do,, loop,, and +loop, compile parts of the execution semantics of DO, LOOP, and
+LOOP.
>mark puts the origin of a forward branch on the control-flow stack;
resolve resolves the destination of a forward branch;