==== 7.5.19 dup2 ====

Duplicate top two operand stack words 

Format 

dup2 

Forms 

dup2 = 62 (0x3e) 

Stack 

..., word2, word1 -> ..., word2, word1, word2, word1 

Description 

The top two words on the operand stack are duplicated and pushed onto the operand stack, in the original order. 

The dup2 instruction must not be used unless each of word1 and word2 is a word that contains a 16-bit data type or both together are the two words of a single 32-bit datum. 

Notes 

Except for restrictions preserving the integrity of 32-bit data types, the dup2 instruction operates on untyped words, ignoring the types of data they contain.