Assuming two (edit: unpacked) arrays of int are defind with different index ordering (downto vs. upto) but the same size, like

int  a [10:1];
int  b [1:10];

would an assignment between these,

assign b = a;

1. be illegal, or
2. result in a "same index" assignment (b[1]=a[1] ... b[10]=a[10]), or
3. result in a "mirrored index" assignment (b[1]=a[10] ... b[10]=a[1])?

I have not been able to find information in the language reference manual, and two commercial tools are behaving differently.

CodePudding user response：

This is legal code and you are showing an unpacked array, not a packed array. However either way, the range goes from left to right. So your option 3 is the correct behavior. See section 6.22.2 Equivalent types and 7.6 Array assignments in the IEEE 1800-2017 SystemVerilog LRM