Is it better to first assign a value to a variable and then reassign in if block instead of using if-(else if)-else blocks where the assignment in if and else blocks are the same and the assignment in the else if block is a different assignment.
always @(*) begin
if condition1 begin
var = val1;
end
else if condition2 begin
var = val2;
end
else begin
var = val1;
end
end
vs
always @(*) begin
var = val1;
if condition2 begin
var = val2;
end
end
Given condition1 and condition2 are mutually exclusive, I am thinking that both of these blocks should synthesize the same logic and the choice of one over the other is purely aesthetic. Am I correct in thinking this or will one implementation synthesize differently from the other? If my thinking is correct, which method is preferred in the community?
Edit: Added mutually exclusive criteria after racraman's comment.
As for the general principle you're asking about: it doesn't matter which route you go. The synthesiser will be smart enough to work it out anyway. For simulation, it's possible that the option which carries out a default assignment first might execute more slowly (particularly if the assignment is a non-blocking one), but I wouldn't worry about it.
Personally, I prefer the second, because it's more obvious to the causual reader that you have covered your bases in terms of generating unwanted latches (in other words, you are always assigning to var).
Having said all that, your example is (in principle) very simple, and in this particular case it's obvious that a mux is required, and you probably don't need an always block at all, and should just use an assign with a ternary operator.
I say 'in principle' because you logic doesn't really make sense. You say your conditions are mutually exclusive, but what happens if neither condition is active? Do you actually need a latch to preserve the previous output? If not, why do you have two conditions at all?