alt Hacker NewsI beg to differ.
A loop would also call for additional run-time analysis. And Knuth changed Step D3, if it were a loop he wouldn't have had to. Additionally, there is no loop in Program D, his implementation of Algorithm D in MIX.
If you read the whole chapter and not just the statement itself (though I'd argue the statement is enough), it's very clearly two if's.
In the edition here (I also have a legal hard copy but not with me)...
https://www.scribd.com/document/956350280/The-Art-of-Compute...
... on page 274 the MIX jumps in lines 058 and 060 to label 3H if the tests fail, where qhat is decremented again. I'm not at all a Mix expert, but where is the counter that the loop is only executed twice?