Normally in Associative Array, Rollover issue is taken care by the tool. But in QuestaSIM, I am facing the issue, like if key of the Associative Array is 64 bit variable, then after overflow, it does not store data properly.
Suppose index is 65'h1_0000_0000_0000_0002, then ideally it should store this data with index 64'h2, because of the size of the key (Even it does that, as I have printed whole Associative Array and Output of exists method also), but still I am getting Warning of Nonexistent Associative Array (as shown in the Output).
Here is the Code : ( I have tried bounded_address method, with 3 different logic, but in all case I am getting same results)
typedef struct packed {
bit [7:0] data;
bit valid;
} dword_memory_st;
program p;
dword_memory_st MEMORY[bit [63:0]];
bit [63:0] st = 64'hffff_ffff_ffff_fffa;
bit [63:0] temp;
bit [64:0] max_memory_address = (1 << 64);
initial
begin
for(bit[63:0] i = 0; i<=10; i++)
begin
$display("***** ***** ***** *****");
temp = bounded_address(st+i);
MEMORY[temp] = i;
$display("MEMORY['h%0h].exists - %0b MEMORY['h%0h] = %0d", temp, MEMORY.exists(temp), temp, MEMORY[temp]);
$display("MEMORY - %p", MEMORY);
$display("***** ***** ***** *****");
end
end
function bit[63:0] bounded_address(input bit [64:0] addr);
/* Option - 1
bounded_address = (addr % max_memory_address);
$display("KARAN bounded_address - %0h, addr - %0h, max_memory_address - %0h", bounded_address, addr, max_memory_address);
*/
/* Option - 2
$display("KARAN addr - %0h, max_memory_address - %0h", addr, max_memory_address);
if(addr > (max_memory_address - 1))
begin
$display("Greater than max_memory_address - 1");
return (addr - max_memory_address);
end
else
begin
$display("Less than max_memory_address - 1");
return addr;
end
*/
// Option - 3
addr[64] = 0;
$display("KARAN addr - %0h, max_memory_address - %0h", addr, max_memory_address);
return addr;
endfunction : bounded_address
endprogram
/* Output on QuestaSIM -
# ***** ***** ***** *****
# KARAN addr - fffffffffffffffa, max_memory_address - 10000000000000000
# MEMORY['hfffffffffffffffa].exists - 1 MEMORY['hfffffffffffffffa] = 0
# MEMORY - '{18446744073709551610:'{data:0, valid:0} }
# ***** ***** ***** *****
# ***** ***** ***** *****
# KARAN addr - fffffffffffffffb, max_memory_address - 10000000000000000
# MEMORY['hfffffffffffffffb].exists - 1 MEMORY['hfffffffffffffffb] = 1
# MEMORY - '{18446744073709551610:'{data:0, valid:0}, 18446744073709551611:'{data:0, valid:1} }
# ***** ***** ***** *****
# ***** ***** ***** *****
# KARAN addr - fffffffffffffffc, max_memory_address - 10000000000000000
# MEMORY['hfffffffffffffffc].exists - 1 MEMORY['hfffffffffffffffc] = 2
# MEMORY - '{18446744073709551610:'{data:0, valid:0}, 18446744073709551611:'{data:0, valid:1}, 18446744073709551612:'{data:1, valid:0} }
# ***** ***** ***** *****
# ***** ***** ***** *****
# KARAN addr - fffffffffffffffd, max_memory_address - 10000000000000000
# MEMORY['hfffffffffffffffd].exists - 1 MEMORY['hfffffffffffffffd] = 3
# MEMORY - '{18446744073709551610:'{data:0, valid:0}, 18446744073709551611:'{data:0, valid:1}, 18446744073709551612:'{data:1, valid:0}, 18446744073709551613:'{data:1, valid:1} }
# ***** ***** ***** *****
# ***** ***** ***** *****
# KARAN addr - fffffffffffffffe, max_memory_address - 10000000000000000
# MEMORY['hfffffffffffffffe].exists - 1 MEMORY['hfffffffffffffffe] = 4
# MEMORY - '{18446744073709551610:'{data:0, valid:0}, 18446744073709551611:'{data:0, valid:1}, 18446744073709551612:'{data:1, valid:0}, 18446744073709551613:'{data:1, valid:1}, 18446744073709551614:'{data:2, valid:0} }
# ***** ***** ***** *****
# ***** ***** ***** *****
# KARAN addr - ffffffffffffffff, max_memory_address - 10000000000000000
# MEMORY['hffffffffffffffff].exists - 1 MEMORY['hffffffffffffffff] = 5
# MEMORY - '{18446744073709551610:'{data:0, valid:0}, 18446744073709551611:'{data:0, valid:1}, 18446744073709551612:'{data:1, valid:0}, 18446744073709551613:'{data:1, valid:1}, 18446744073709551614:'{data:2, valid:0}, 18446744073709551615:'{data:2, valid:1} }
# ***** ***** ***** *****
# ***** ***** ***** *****
# KARAN addr - 0, max_memory_address - 10000000000000000
# MEMORY['h0].exists - 1 MEMORY['h0] = 6
# MEMORY - '{0:'{data:3, valid:0}, 18446744073709551610:'{data:0, valid:0}, 18446744073709551611:'{data:0, valid:1}, 18446744073709551612:'{data:1, valid:0}, 18446744073709551613:'{data:1, valid:1}, 18446744073709551614:'{data:2, valid:0}, 18446744073709551615:'{data:2, valid:1} }
# ***** ***** ***** *****
# ***** ***** ***** *****
# KARAN addr - 1, max_memory_address - 10000000000000000
# ** Warning: (vsim-3829) string_based_object_creation.sv(93): Non-existent associative array entry. Returning default value.
# MEMORY['h1].exists - 1 MEMORY['h1] = 0
# MEMORY - '{0:'{data:3, valid:0}, 1:'{data:3, valid:1}, 18446744073709551610:'{data:0, valid:0}, 18446744073709551611:'{data:0, valid:1}, 18446744073709551612:'{data:1, valid:0}, 18446744073709551613:'{data:1, valid:1}, 18446744073709551614:'{data:2, valid:0}, 18446744073709551615:'{data:2, valid:1} }
# ***** ***** ***** *****
# ***** ***** ***** *****
# KARAN addr - 2, max_memory_address - 10000000000000000
# ** Warning: (vsim-3829) string_based_object_creation.sv(93): Non-existent associative array entry. Returning default value.
# MEMORY['h2].exists - 1 MEMORY['h2] = 0
# MEMORY - '{0:'{data:3, valid:0}, 1:'{data:3, valid:1}, 2:'{data:4, valid:0}, 18446744073709551610:'{data:0, valid:0}, 18446744073709551611:'{data:0, valid:1}, 18446744073709551612:'{data:1, valid:0}, 18446744073709551613:'{data:1, valid:1}, 18446744073709551614:'{data:2, valid:0}, 18446744073709551615:'{data:2, valid:1} }
# ***** ***** ***** *****
# ***** ***** ***** *****
# KARAN addr - 3, max_memory_address - 10000000000000000
# ** Warning: (vsim-3829) string_based_object_creation.sv(93): Non-existent associative array entry. Returning default value.
# MEMORY['h3].exists - 1 MEMORY['h3] = 0
# MEMORY - '{0:'{data:3, valid:0}, 1:'{data:3, valid:1}, 2:'{data:4, valid:0}, 3:'{data:4, valid:1}, 18446744073709551610:'{data:0, valid:0}, 18446744073709551611:'{data:0, valid:1}, 18446744073709551612:'{data:1, valid:0}, 18446744073709551613:'{data:1, valid:1}, 18446744073709551614:'{data:2, valid:0}, 18446744073709551615:'{data:2, valid:1} }
# ***** ***** ***** *****
# ***** ***** ***** *****
# KARAN addr - 4, max_memory_address - 10000000000000000
# ** Warning: (vsim-3829) string_based_object_creation.sv(93): Non-existent associative array entry. Returning default value.
# MEMORY['h4].exists - 1 MEMORY['h4] = 0
# MEMORY - '{0:'{data:3, valid:0}, 1:'{data:3, valid:1}, 2:'{data:4, valid:0}, 3:'{data:4, valid:1}, 4:'{data:5, valid:0}, 18446744073709551610:'{data:0, valid:0}, 18446744073709551611:'{data:0, valid:1}, 18446744073709551612:'{data:1, valid:0}, 18446744073709551613:'{data:1, valid:1}, 18446744073709551614:'{data:2, valid:0}, 18446744073709551615:'{data:2, valid:1} }
# ***** ***** ***** *****
*/
I have found the answer. It is a QuestaSIM bug, but this solution can manipulate tool to store data properly without any warning.
Here is the Code, change in bounded_address method :
function bit[63:0] bounded_address(input bit [64:0] addr);
MEMORY.delete(addr); // Dont know why, but after overflow, if we delete that index, than it works.
bounded_address = (addr % max_memory_address);
$display("KARAN bounded_address - %0h, addr - %0h, max_memory_address - %0h", bounded_address, addr, max_memory_address);
endfunction : bounded_address