The actual signal code is trivial, but the emit expression code needed
to be enhanced to pass a flag that says if one of the arguments in a
binary (except the shifts) or ternary (excluding the condition) context
is unsigned. This information is used to prevent emitting an explicit
$unsigned() for a signal that is used in this context since it will be
implicitly cast to unsigned.
This patch adds support for finding and adding $signed() and $unsigned()
to procedural expressions for the binary, unary and concatenation
operators. Selects have partial support. The select implementation
uncovered limitations in the compiler that need to be fixed before they
will work 100%. Most of the limitations currently generate a message
about the issue.
We need to elaborate expressions so that function calls in
expressions (i.e. ranges) get bound to their proper scope.
This binding is in turn used to emit package scopes. This
is particularly interesting for ports of entities.
If constant functions are exited by a return/disable, fix
the leaked "disable" flag that causes blocks in the next
try at the function to not work.
There are also a lot of debug messages added to help find
this and similar problems.
The VHDL to_unsigned function with to arguments is best handled
in the ivl elaborator, so have it generate an $ivlh_to_unsigned
function call in the vhdlpp code, and implement it in the ivl
core.
Also, implement the 'length attribute as a $bits() call for
similar reasons.
The package emit of types and constants needs to know which names are
from the current type and which are imported from libraries. Rework
the scope handling of those names so that the information is preserved.
For constant bit/part selects, issue a warning if the select is out
of range or an undefined value. In any case, the RHS value should be
discarded, and the actual assignment should be skipped.
If a VPI call with real arguments has no calltf function, we still
need to pop the arguments off the vthread stack. Similarly, if it
has a real result, we need to push a value onto the vthread stack.
For constant word indices, issue a warning if the index is out of
range or an undefined value. In any case, the RHS value should be
discarded, and the actual assignment should be skipped.
Stephen Williams
Cary R
Martin Whitaker