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The original post is about not using multipliers but using shift. One input is constant and so may be convertable to sum or difference of power of 2. As far as I Know the tool does not do this sort of conversion.
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Shift and add is the way how the synthesis tool does implement a multiplier without DSP blocks. In so far multstyle = "logic" does use it. But there's no point in design synthesis where you'll see explicite adders or shift registers, because everything is translated to logic elements.
The question is of course, if the synthesis tool implements the defined function effectively, but the problem isn't specific to constant multipliers. I'm under the impression that Quartus is quite good in implementing arithmetic. It has some obvious weaknesses in implementing non-arithmetic problems in arithmetic mode of logic elements.
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