[Oberon] ALU 2015 and 2018

Jörg joerg.straube at iaeth.ch
Wed May 11 22:10:49 CEST 2022


„Readable“ is a subjective term.

Purely from a compiler construction‘s point of view, the ternary operator ?:; and if-then-else CAN produce exactly the same outout during syntesis but they DON’T have to. It heavily depends on the Verilog compiler.

Generally, for assignments the ternary operator is cleaner as the output of both branches must have the same type.
The branches of the if-then-else are unrelated and it is not guaranteed that the same type is used.

br, Jörg

> Am 11.05.2022 um 20:26 schrieb Skulski, Wojciech <skulski at pas.rochester.edu>:
> Joerg:
>> I agree that this old Verilog code [I removed the code -- ws]
>> looks nicer than this new one
>> The new one has a shorter max latency! Eg in the old code decoding DIV 
>> passed thru 11 multiplexers. In the new one passing through 4 multiplexers 
>> is enough for all instructions.
>> Sequential vs binary search.
> Is there a way to write efficient code in Verilog that would also be readable? If not then why not? 
> According to ISE help, the ternary assignment is meant as a 2-to-1 multiplexer. Replacing <input> with another such instruction is a sort of abuse of the human reader. I wonder if the same effect can be achieved with the more readable if-then-else which is meant for the human eyes rather than compiler's. 
> assign <output_wire> = <1-bit_select> ? <input1> : <input0>;
> Any thoughts on this?
> Wojtek
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