If either the index or part offset expressions generate an undefined
value then the assignment is skipped. This patch reworks the code that
handles the flags used to detect this. For some simple cases a global
flag is not needed, but for other cases one is needed since there are
two expressions that can generate an error and even when there is only
a variable expression this error state needs to be preserved if there
is a variable delay. An undefined delay value defaults to zero and is
not an error.
When generating code for a condition expression, i.e. directly
before a %jmp/X statement, try to generate the result into the
flag bit without passing through the vec4 stack. For example, the
%cmpX/X instructions generate results into the flag bits, so it
makes no sense to push these bits into the vec4 stack then pop
them back into the flag bit. So try to handle this case.
A procedural continuous assignment is supposed to be updated any time
a variable on the RHS changes. Currently this only happens if the RHS
is a simple signal.
When you have an expression like this (extreme example):
a[idx[1]][idx[2]*4 +: 4] <= #(idx[3]) 4'ha;
where a is a reg array and idx is a reg or net array. The retrieval
of idx[2] was clobbering index register 3, which was set before
evaluating the part offset expression, then used in the %set/av of the
array value. (likewise for idx[1] and idx[3]])
To avoid this issue, this patch adds and uses a new instruction
%ix/mov which simply copies one indexed register to another. When
necessary, expressions are first evaluated into temporary registers to
avoid clobbering, then moved in to place before the %*/av instruction.
When a fork/join contains a task, the task completion may become
confused with the completion of another thread if any of the
threads are embedded in the main thread. So always create threads
for all the fork paths, and joins to match.
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.
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.
There was one section of code in the tgt-vvp back end that was using
deprecated functions. This patch fixes that. The functionality is still
missing (force/assign to part of a vector), but the code now compiles
cleanly (no warnings).
This will hopefully improve performance slightly, but also this
intended as a model for what to do when I get around to doing the
same thing to other data types.
Now we have a code generator that can handle compressed assignments
as they have been re-imagined in elaboration. There are some cases
that are not yet supported, we'll patch them up in due course.
This patch adds error messages that forcing a word to/from a variable
array is not currently supported. This is because variable arrays no
longer are fully populated and don't have an access functor for each
word. Forcing a word from/to a net array does work as expected since
each word in a net array is created.
Technically forcing a variable array word is not supported in 1364-2005.
Reading from an array word, which is supported, will be fixed in
development once the expression rework is finished.
The error message printed when forcing a bit/part select l-value was
also improved.
Cary R
Stephen Williams
Martin Whitaker
Jared Casper
Arun Persaud