Why does the Quartus II software version 12.0 software use more combinatorial ALUTs than earlier versions of the Quartus II software for the same function?

Description

The Quartus® II software version 12.0 uses a new optimization algorithm when the synthesis optimization technique is set to Speed. This algorithm does not infer any synchronous secondary signals on registers with an Fmax constraint of 300 MHz or more. When this algorithm is used, you may see higher combinatorial ALUT usage in your design. 

Resolution

To disable this algorithm, change the synthesis optimization technique to Balanced or Area.