RE: [sv-ac] Hierarchical ref of local variable in action blocks

Hi Ben,
 
The reason you have to specify 'static' here is because variables initialization needs this keyword. Here is the text from LRM (section 6.21):

Variables declared in a static task, function, or procedural block default to a static lifetime and a local scope. However, an explicit static keyword shall be required when an initialization value is specified as part of a static variable's declaration to indicate the user's intent of executing that initialization only once at the beginning of simulation.

So, this behaviour is consistent with any other begin...end block.
 
Manisha
 
 

________________________________

From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On Behalf Of ben cohen
Sent: Tuesday, July 19, 2011 12:02 PM
To: sv-ac@eda-stds.org; Korchemny, Dmitry
Subject: [sv-ac] Hierarchical ref of local variable in action blocks

Ran the following 3 models:

From the current simulator that I have:
1) Action block local variable must be declared as "static" or "automatic"
2) If "static", then local var maintains its old value as expected.
3) assertion_label.var_name (e.g., a1.x) does not work
Ben
-----------------------------------------
module asn;
    static int result, count=0;
    logic a=1, b=1, clk=1;
    initial forever #10 clk=!clk;
    a1: assert property (@(posedge clk)a |-> ##3 b) begin
        static int x=0; x +=1; result = x;
    end
    always @(posedge clk) begin
        count+=1;
        if(count>=6) begin
        b<=0;
        $display("count=%d, result=%d", count, result);
        end
    end
endmodule

# count= 6, result= 2
# count= 7, result= 3
# ** Error: Assertion error.
# Time: 140 ns Started: 80 ns Scope: asn.a1 File: asn.sv Line: 18 Expr: b
# count= 8, result= 3
# ** Error: Assertion error.
# Time: 160 ns Started: 100 ns Scope: asn.a1 File: asn.sv Line: 18 Expr: b
# count= 9, result= 3
# ** Error: Assertion error.
# Time: 180 ns Started: 120 ns Scope: asn.a1 File: asn.sv Line: 18 Expr: b
# count= 10, result= 3
# ** Error: Assertion error.
# Time: 200 ns Started: 140 ns Scope: asn.a1 File: asn.sv Line: 18 Expr: b
============================================================
module asn_auto;
    static int result, count=0;
    logic a=1, b=1, clk=1;
    initial forever #10 clk=!clk;
    a1: assert property (@(posedge clk)a |-> ##3 b) begin
        automatic int x=0; x +=1; result = x;
    end
    always @(posedge clk) begin
        count+=1;
        if(count>=6) begin
        b<=0;
        $display("count=%d, result=%d", count, result);
        end
    end
endmodule : asn_auto
# count= 6, result= 1
# count= 7, result= 1
# ** Error: Assertion error.
# Time: 140 ns Started: 80 ns Scope: asn_auto.a1 File: asn_auto.sv Line: 18 Expr: b
# count= 8, result= 1
# ** Error: Assertion error.
# Time: 160 ns Started: 100 ns Scope: asn_auto.a1 File: asn_auto.sv Line: 18 Expr: b
# count= 9, result= 1
# ** Error: Assertion error.
# Time: 180 ns Started: 120 ns Scope: asn_auto.a1 File: asn_auto.sv Line: 18 Expr: b
# count= 10, result= 1
# ** Error: Assertion error.
# Time: 200 ns Started: 140 ns Scope: asn_auto.a1 File: asn_auto.sv Line: 18 Expr: b

 ==================================
module asn_2;
    static int result, count=0, path_result;
    logic a=1, b=1, clk=1;
    initial forever #10 clk=!clk;
    a1: assert property (@(posedge clk)a |-> ##3 b) begin
        static int x=0; x +=1; result = x;
    end
    always @(posedge clk) begin
        count+=1;
        path_result <= a1.x +1; // line 23
        if(count>=6) begin
            b<=0;
            $display("count=%d, result=%d", count, result);
            $display("path_result=%d", path_result);
        end
    end
endmodule
** Error: asn_2.sv(23): Unresolved reference to 'x'.
 

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