Monday, May 13, 2013

C magic

Your C compiler almost certainly recognizes this idiom and compiles it to a single processor instruction. 
unsigned int x, y;
y = (x << shift) | (x >> (sizeof(x)*8 - shift));
What instruction is that ?
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1 comment:

  1. $guidMay 13, 2013 at 5:27 PM

    C doesn`t have instruction to binary rotate variable, only to binary shift. But we can use this idiom to make binary rotate.

    In assembler code on Intel arch it is rol instruction, rotate dest register to the left

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