Is it possible to implement constant propagation based on Slang AST?

[yanggeorge]

I just find some part of Spyglass lint rules depend this tech.

Such as DisabledAnd Lint Rule is part of Spyglass, which is used to find disabled AND logic.

Consider the following example:

module DisabledAnd(output x, output y);  
wire a,b,c,d,common;

assign x = a & b; //<-- 3. x is always disabled because of a
assign y = c & d;

assign a = common; // <-- 2. a is always 1'b0
assign c = common;

assign common = 1'b0; // <-- 1. common is always 1'b0
endmodule

For the above example, the following violation is reported:Input pin in1 on comb-and gate DisabledAnd.x (master RTL_AND) is tiedlow(connected to DisabledAnd.a)

So is it possible to implement such based on current Slang AST ? I just learns some about constant propagtion tech. I don't know if this appoach is correct.

[MikePopoloski]

Yes, it is possible. slang already does constant propagation in subexpressions, though it does not propagate constants through nets and variables, which is more challenging to do but still possible with some work.

[yanggeorge]

Thanks.