; Example of expression compilation with optimizations

; At one end of the spectrum, we use RAM for everything, 
; employ a strict, naive stack approach, do no optimizations
; for multiplication, perform no algebraic optimizations,
; no static computation, no right-biasing, etc.

  (z-z)+(z=(2+3*(7-5))+x*(x=READ))+63*(y=READ)-(2+3*(8-4))
  
  
  8 + READ^2 + 63*READ - 14
  
  [5,7]  =>  8 + 49 + 315 - 14  =>  358
  [7,5]  =>  8 + 25 + 441 - 14  => 
  
  
  Bop Diff
  (Bop Plus
  (Bop Plus (Bop Diff (Var 'z') (Var 'z'))
           (Bop Plus (Set 'z' (Bop Plus (Lit 2)
                                        (Bop Mult (Lit 3)
                                                  (Bop Diff (Lit 7) (Lit 5)))))
                     (Bop Mult (Var 'x') (Set 'x' READ))))
  (Bop Mult (Lit 63) (Set 'y' READ)))
  (Bop Plus (Lit 2)
            (Bop Mult (Lit 3)
                      (Bop Diff (Lit 8) (Lit 4))))
                      
	Push 4
	Push 8
	DoOp Diff
	Push 3
	DoOp Mult
	Push 2
	DoOp Plus
	Push 0
	Put 'y'
	Push 63
	DoOp Mult
	Push 0
	Put 'x'
	Get 'x'
	DoOp Mult
	Push 5
	Push 7
	DoOp Diff
	Push 3
	DoOp Mult
	Push 2
	DoOp Plus
	Put 'z'
	DoOp Plus
	Get 'z'
	Get 'z'
	DoOp Diff
	DoOp Plus
	DoOp Plus
	DoOp Diff

-- Try again with shorter expression!

  (z-z)+(z=(2+(7-5))+x*(x=READ))+63*(y=READ)-(2+3*(8-4))
  
  
  4 + READ^2 + 63*READ - 14
  
  [5,7]  =>  8 + 49 + 315 - 14  =>  358
  [7,5]  =>  8 + 25 + 441 - 14  => 
  
  
  Bop Diff
  (Bop Plus
  (Bop Plus (Bop Diff (Var 'z') (Var 'z'))
           (Bop Plus (Set 'z' (Bop Plus (Lit 2)
                                                  (Bop Diff (Lit 7) (Lit 5))))
                     (Bop Mult (Var 'x') (Set 'x' READ))))
  (Bop Mult (Lit 63) (Set 'y' READ)))
  (Bop Plus (Lit 2)
            (Bop Mult (Lit 3)
                      (Bop Diff (Lit 8) (Lit 4))))


Relative to current SP:

  Push k  ==>  DATA #LITk; LOAD R8,DR; STORE R8,R9; INC R9,-1;
  Get  x  ==>  DATA #VARx; LOAD R8,DR; STORE R8,R9; INC R9,-1;
  Put  x  ==>  DATA #VARx; LOAD R8,R9; STORE R8,DR;
  Pop     ==>  INC R9,1;
  DoOp +  ==>  INC R9,1; LOAD R8,R9; INC R9,1; LOAD R7,R9; ADD R8,R7; STORE R8,R9; INC R9,-1
  Input   ==>  READ R8,DD; STORE R8,R9; INC R9,-1;

  READ^2+63*READ-10
  
  
  ; 25 instructions vs. 224
  ;
  ; test: (5,7)    =>  362 (#39)	=>   354 (#245)
  ; test: (17,31)  => 2022 (#53)	=>  2022 (#271)
  ; test: (-8,-15) => -289 (#46)	=>  -289 (#260)
  
  READ  R0,DD	; 1st input in R0
  
  COPY  R0,R1
  ADD   R1,R1	; 2 * R1
  ADD   R1,R1	; 4 * R1
  ADD   R1,R1	; 8 * R1
  ADD   R1,R1	; 16 * R1
  ADD   R1,R1   ; 32 * R1
  ADD   R1,R1	; 64 * R1
  SUB   R0,R1	; 63 * R1
  INC   R1,-5   ; -5 twice
  INC   R1,-5
  READ  R0,DD   ; 2nd input in R0
  ; ---------	; squaring R0
  SHIFT R0,-1
  SHIFT R0,1	; abs R0
  COPY  R0,R2	; R2 = R0
  COPY  PC,J0	; loop back in J0
  SET   R3, 1	; mask in R3
  AND   R2,R3	; get low bit R2
  ADD   R0,R1	; SPECULATIVE ADD directly to R1
  ADD   R3,PC	; jump over SUB if we had 1 bit
  SUB   R0,R1	; when 0 bit, compensatory SUB
  SHIFT R2, 1
  SHIFT R0,-1
  JPIF  R2,NZ,J0
  WRITE R1,DD
  HALT
  
  
C00 901 611 611 611 611 611 611 701 419 C00 508 500 902 9FA 231 
823 601 63F 701 520 508 E2C D10 000 

  
  
  
  
  if x>0: (x<<6)-x
  if x<0:
  
  
  
  COPY  R0,R1
  COPY  R0,R2   ; get sign in R2
  SHIFT R2, 5
  SHIFT R2, 6
  SHIFT R1,-6	; R1 = R0 * 64
  SUB   R0,R1	; R1 = R0 * 63
  ADD   R2,PC
  SUB   R1,R3
  
  -------

DATA xFF
COPY DR,R9

DATA #LITB      ; Pushing 1
LOAD R8,DR
STORE R8,R9
INC R9,-1
DATA #LITC      ; Pushing 2
LOAD R8,DR
STORE R8,R9
INC R9,-1
DATA #VARX      ; Putting x
INC R9,1
LOAD R8,R9
STORE R8,DR
INC R9,-1
INC R9,1        ; Doing -
LOAD R8,R9
INC R9,1
LOAD R7,R9
SUB R7,R8
STORE R8,R9
INC R9,-1
DATA #LITD      ; Pushing 3
LOAD R8,DR
STORE R8,R9
INC R9,-1
DATA #VARX      ; Getting x
LOAD R8,DR
STORE R8,R9
INC R9,-1
INC R9,1        ; Doing +
LOAD R8,R9
INC R9,1
LOAD R7,R9
ADD R7,R8
STORE R8,R9
INC R9,-1
INC R9,1        ; Doing -
LOAD R8,R9
INC R9,1
LOAD R7,R9
SUB R7,R8
STORE R8,R9
INC R9,-1

*Main> dump samp
DATA #LITE      ; Pushing 4
LOAD R8,DR
STORE R8,R9
INC R9,-1
DATA #LITI      ; Pushing 8
LOAD R8,DR
STORE R8,R9
INC R9,-1
INC R9,1        ; Doing -
LOAD R8,R9
INC R9,1
LOAD R7,R9
SUB R7,R8
STORE R8,R9
INC R9,-1
DATA #LITD      ; Pushing 3
LOAD R8,DR
STORE R8,R9
INC R9,-1
ZERO R4 ; Doing *
INC R9,1
LOAD R0,R9
INC R9,1
LOAD R1,R9
COPY R0,R2
COPY R1,R3
SHIFT R2, 5
SHIFT R2, 6
SHIFT R3, 5
SHIFT R3, 6
SUB R3,R2
SHIFT R0,-1
SHIFT R0, 1
SHIFT R1,-1
SHIFT R1, 1
DATA #SKIPA
COPY DR,J3
DATA #LOOPA
COPY DR,J2
#LOOPA
SET R3, 1
AND R1,R3
JPIF R3,EZ,J3
ADD R0,R4
#SKIPA
SHIFT R0,-1
SHIFT R1, 1
JPIF R1,NZ,J2
DATA #DONEA
COPY DR,J3
JPIF R2,EZ,J3
ZERO R3
SUB R4,R3
COPY R3,R4
#DONEA
STORE R4,R9
INC R9,-1
DATA #LITC      ; Pushing 2
LOAD R8,DR
STORE R8,R9
INC R9,-1
INC R9,1        ; Doing +
LOAD R8,R9
INC R9,1
LOAD R7,R9
ADD R7,R8
STORE R8,R9
INC R9,-1
READ R8,DD      ; Reading input
STORE R8,R9
INC R9,-1
DATA #VARY      ; Putting y
INC R9,1
LOAD R8,R9
STORE R8,DR
INC R9,-1
DATA #LITL      ; Pushing 63
LOAD R8,DR
STORE R8,R9
INC R9,-1
ZERO R4 ; Doing *
INC R9,1
LOAD R0,R9
INC R9,1
LOAD R1,R9
COPY R0,R2
COPY R1,R3
SHIFT R2, 5
SHIFT R2, 6
SHIFT R3, 5
SHIFT R3, 6
SUB R3,R2
SHIFT R0,-1
SHIFT R0, 1
SHIFT R1,-1
SHIFT R1, 1
DATA #SKIPB
COPY DR,J3
DATA #LOOPB
COPY DR,J2
#LOOPB
SET R3, 1
AND R1,R3
JPIF R3,EZ,J3
ADD R0,R4
#SKIPB
SHIFT R0,-1
SHIFT R1, 1
JPIF R1,NZ,J2
DATA #DONEB
COPY DR,J3
JPIF R2,EZ,J3
ZERO R3
SUB R4,R3
COPY R3,R4
#DONEB
STORE R4,R9
INC R9,-1
READ R8,DD      ; Reading input
STORE R8,R9
INC R9,-1
DATA #VARX      ; Putting x
INC R9,1
LOAD R8,R9
STORE R8,DR
INC R9,-1
DATA #VARX      ; Getting x
LOAD R8,DR
STORE R8,R9
INC R9,-1
ZERO R4 ; Doing *
INC R9,1
LOAD R0,R9
INC R9,1
LOAD R1,R9
COPY R0,R2
COPY R1,R3
SHIFT R2, 5
SHIFT R2, 6
SHIFT R3, 5
SHIFT R3, 6
SUB R3,R2
SHIFT R0,-1
SHIFT R0, 1
SHIFT R1,-1
SHIFT R1, 1
DATA #SKIPC
COPY DR,J3
DATA #LOOPC
COPY DR,J2
#LOOPC
SET R3, 1
AND R1,R3
JPIF R3,EZ,J3
ADD R0,R4
#SKIPC
SHIFT R0,-1
SHIFT R1, 1
JPIF R1,NZ,J2
DATA #DONEC
COPY DR,J3
JPIF R2,EZ,J3
ZERO R3
SUB R4,R3
COPY R3,R4
#DONEC
STORE R4,R9
INC R9,-1
DATA #LITF      ; Pushing 5
LOAD R8,DR
STORE R8,R9
INC R9,-1
DATA #LITH      ; Pushing 7
LOAD R8,DR
STORE R8,R9
INC R9,-1
INC R9,1        ; Doing -
LOAD R8,R9
INC R9,1
LOAD R7,R9
SUB R7,R8
STORE R8,R9
INC R9,-1
DATA #LITC      ; Pushing 2
LOAD R8,DR
STORE R8,R9
INC R9,-1
INC R9,1        ; Doing +
LOAD R8,R9
INC R9,1
LOAD R7,R9
ADD R7,R8
STORE R8,R9
INC R9,-1
DATA #VARZ      ; Putting z
INC R9,1
LOAD R8,R9
STORE R8,DR
INC R9,-1
INC R9,1        ; Doing +
LOAD R8,R9
INC R9,1
LOAD R7,R9
ADD R7,R8
STORE R8,R9
INC R9,-1
DATA #VARZ      ; Getting z
LOAD R8,DR
STORE R8,R9
INC R9,-1
DATA #VARZ      ; Getting z
LOAD R8,DR
STORE R8,R9
INC R9,-1
INC R9,1        ; Doing -
LOAD R8,R9
INC R9,1
LOAD R7,R9
SUB R7,R8
STORE R8,R9
INC R9,-1
INC R9,1        ; Doing +
LOAD R8,R9
INC R9,1
LOAD R7,R9
ADD R7,R8
STORE R8,R9
INC R9,-1
INC R9,1        ; Doing +
LOAD R8,R9
INC R9,1
LOAD R7,R9
ADD R7,R8
STORE R8,R9
INC R9,-1
INC R9,1        ; Doing -
LOAD R8,R9
INC R9,1
LOAD R7,R9
SUB R7,R8
STORE R8,R9
INC R9,-1

INC R9,1
LOAD R0,R9
WRITE R0,DD
HALT

#LITC	CONST 2
#LITD   CONST 3
#LITE   CONST 4
#LITF	CONST 5
#LITH   CONST 7
#LITI   CONST 8
#LITL   CONST 63

#VARX   CONST 0
#VARY   CONST 0
#VARZ   CONST 0