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BUG: Verilog 1.0*(2.0**N) const expression evaluates to 0 if N is a localparam

algofoogle
Beginner
784 Views

Is it fine to report Quartus Prime Lite bugs here?

I'm using Quartus Prime Version 22.1std.0 Build 915 10/25/2022 SC Lite Edition with no patches. I will try a newer version later.

Given this Verilog code:

 

localparam N = 12.0;
initial begin
  $display("%f %d", 1.0*(2.0*N),     1.0*(2.0*N));      // Two products.
  $display("%f %d", 1.0*(2.0**12.0), 1.0*(2.0**12.0));  // Product & power.
  $display("%f %d", 1.0*(2.0**N),    1.0*(2.0**N)); //BUG! Product & power.
  $display("%f %d",     (2.0**N),        (2.0**N));     // Power only.
end

 

 ...at compile-time the log includes these unexpected results:

 

Info (10648): Verilog HDL Display System Task info at raybox.v(104): 24.000000 24
Info (10648): Verilog HDL Display System Task info at raybox.v(105): 4096.000000 4096
Info (10648): Verilog HDL Display System Task info at raybox.v(106): 0.000000 0
Info (10648): Verilog HDL Display System Task info at raybox.v(107): 4096.000000 4096

 

 Notice that specifically 1.0*(2.0**N) gives an incorrect result (0) while the others work as expected. This problem also happens if assigning this expression to another localparam, or trying to use it in logic.

I tried other definitions of the localparam, too, including:

 

localparam real N = 12.0;
localparam integer N = 12;
localparam [3:0] N = 12;

 

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SyafieqS
Moderator
732 Views

Hello,


Thanks for the update. I will feedback this to developer for fix.

Let me know if there is any other concern on this.

Really appreciate the feedback.


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SyafieqS
Moderator
708 Views

Have you tried this in Pro Edition or latest version as mentioned?

Does the value still reflect wrongly?


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SyafieqS
Moderator
674 Views

Let me know if there is any update from previous reply


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algofoogle
Beginner
631 Views

My apologies, I was unable to return to this for a while, but I've now tested in Quartus Prime Version 22.1.std.1 Build 917 02/14/2023 SC Lite Edition. The same issue exists, with exactly the same output.

 

This is the most recent version I can test, as I do not have a Pro license and version 23.1 hasn't been released as a Lite version yet.

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SyafieqS
Moderator
582 Views

Thanks for your feedback. I will feedback this and request for a fix.

This might be taking sometime as developer is prioritizing critical case.

Let me know if there is any other concern.


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