0x40 Assembly Riddles

Re:0x40 Assembly Riddles by jensnockert on Saturday January 10, 2015 @11:12AM (#8867015)

At first I thought the book was trolling me, but then I sat down and worked through a few of the pages on paper and realized that there were interesting tricks behind them.

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Re:0x40 Assembly Riddles by jgeralnik on Saturday January 10, 2015 @11:58AM (#8867126)

Agreed. The second snippet (http://www.xorpd.net/pages/xchg_rax/snip_01.html) is relatively simple to understand and is now my favorite two opcode program.

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Re:0x40 Assembly Riddles by kaoD on Saturday January 10, 2015 @02:14PM (#8867588)

Is this the Fibonacci sequence?

EDIT: For anyone curious, being rax and rdx the starting terms, the rcx-th term is found in rax at the end of the loop.

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Re:0x40 Assembly Riddles by jgeralnik on Saturday January 10, 2015 @02:17PM (#8867597)

Yup. The xadd opcode adds the two registers together and swaps them so that the previous element is always in the same register.

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