vhdl-instance-name

vhdl-instance-name is a variable defined in `vhdl-mode.el'.
Its value is

(".*" . "\\&_%d")

Documentation:
Specifies how an instance name is obtained.
The instance name can be obtained by modifying the name of the component to be
instantiated (e.g. attaching or stripping off a substring). "%d" is replaced
by a unique number (starting with 1).
If TO STRING is empty, the instance name is queried.

FROM REGEXP is a regular expression matching the original name:
".*" matches the entire string
"\(...\)" matches a substring
TO STRING specifies the string to be inserted as new name:
"\&" means substitute entire matched text
"\N" means substitute what matched the Nth "\(...\)"
Examples:
".*" "\&" inserts original string
".*" "\&_i" attaches "_i" to original string
"\(.*\)_[io]$" "\1" strips off "_i" or "_o" from original string
".*" "foo" inserts constant string "foo"
".*" "" inserts empty string

You can customize this variable.