Description

Duplicates the top two-word item on the stack and inserts the duplicate before the previous (single-word) item on the stack. Alternatively, this instruction could also be used to duplicate two single-word items and insert them before the third single-word item on the stack.

Example

bipush 100
dconst_0

; stack now contains:
;     0.0 | double-word1
;     0.0 | double-word2
;     100   integer-word1

dup2_x1

; stack now contains:
;     0.0 | double-word1
;     0.0 | double-word2
;     100   integer-word1
;     0.0 | double-word1
;     0.0 | double-word2