From: ruvim.pinka@gmail.com   
      
   On 2024-03-04 21:24, Anton Ertl wrote:   
   > Many years ago I have read here about Forth systems where DO and ?DO   
   > push three items on the return stack: the two values from the data   
   > stack (initial index and limit) like many other Forth systems, but in   
   > addition they also push the address that LOOP/+LOOP later jumps to.   
   >   
   > I used to consider this to be inefficient, but it turns out that in an   
   > efficient interpreter-based Forth system like, say gforth-fast from   
   > 2022 it would actually be more efficient than compiling that address   
   > with the (LOOP)/(+LOOP) and loading it from there.   
   >   
   > My question is: Which Forth systems have a DO/?DO that pushes the   
   > address that LOOP/+LOOP then jumps to?   
      
      
   In SP-Forth v3 and v4 (they generate native code), "DO" pushes three   
   items on the return stack, and among them the address that "LEAVE" then   
   jumps to. The address (actually, an offset) for "LOOP" is inlined.   
      
      
   Code in SP-Forth/4   
      
   : foo 7 1 do i . loop ; see foo   
      
   579793 8945FC           MOV     FC [EBP] , EAX   
   579796 C745F807000000   MOV     F8 [EBP] , # 7   
   57979D B801000000       MOV     EAX , # 1   
   5797A2 8BD8             MOV     EBX , EAX   
   5797A4 81C000000080     ADD     EAX , # 80000000   
   5797AA 2B45F8           SUB     EAX , F8 [EBP]   
   5797AD 8BD0             MOV     EDX , EAX   
   5797AF 8B45FC           MOV     EAX , FC [EBP]   
   5797B2 68D7975700       PUSH    , # 5797D7   
   5797B7 52               PUSH    EDX   
   5797B8 53               PUSH    EBX   
   5797B9 90               XCHG     EAX, EAX   
   5797BA 90               XCHG     EAX, EAX   
   5797BB 90               XCHG     EAX, EAX   
   5797BC 8945FC           MOV     FC [EBP] , EAX   
   5797BF 8B0424           MOV     EAX , [ESP]   
   5797C2 8D6DFC           LEA     EBP , FC [EBP]   
   5797C5 E81ECDFDFF       CALL    5564E8  ( . )   
   5797CA FF0424           INC     [ESP]   
   5797CD FF442404         INC     4 [ESP]   
   5797D1 71E9             JNO     5797BC   
   5797D3 8D64240C         LEA     ESP , C [ESP]   
   5797D7 C3               RET     NEAR   
   END-CODE   
      
      
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