The `%disable` instruction will stop the execution of all active
threads of a specific scope. This is what is required to implement
the semantics of the Verilog `disable` statement.
But it is not suited to implement the SystemVerilog flow control
statements such as `return`, `continue` and `break`. These only
affect the thread hierarchy from which it is called, but not other
concurrently running threads from the same scope.
Add a new `%disable/flow` instruction that will only disable the thread
closest to the current thread in the thread hierarchy. This can either be
the thread itself or one of its parents. This will leave other concurrent
threads of the same scope untouched and also allows function recursion
since only the closest parent thread is disabled.
Note that it is not possible to implement this using `%jmp` instructions
since a block in a function with variable declarations will be its own
sub-thread, but using flow control instructions it is possible to exit from
that thread to the parent scope, which is not possible with `%jmp`
instructions.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
IEEE Std 1800-2017 Section 7.6 Array assignments
Assignment of a dynamic array creates a duplicate of the source,
so that assignments to the copy don't impact the original. Handle
all sorts of dynamic array base types.
SystemVerilog allows a mixture of procedural and continuous assignments
to be applied to different parts of the same vector. The previous attempt
to make this work for non-blocking assignments was flawed (see preceding
fix for vvp_fun_part_pv::recv_vec4_pv). Instead, handle this case by
converting the non-blocking assignment into a delayed force statement,
which matches the way mixed continuous and blocking assignments are
handled.
Create The %callf/* opcodes to invoke user defined functions in a
more specialized way. This allows for some sanity checking on the
way, and also is a step towards keeping return values on stacks.
These bypass the vec4 stack in some common cases, saving instructions
and vec4 manipulations.
Also, minor improvement to the %flag/set/vec4 statement.
Kill a few warnings.
This goes all the way down to the vvp level, where we create support
for arrays of objects, generate the new code in the -tvvp code
generator, and elaborate the arrays in the first place.
%exec_ufunc assumed that because a function can never block, a call to
vthread_run() on the function code would only return when the final %end
instruction had been executed. This is not true if the function contains
a named block, which will be executed via a %fork instruction, allowing
the main function thread to suspend after a %join instruction. The fix
is to break %exec_ufunc into two instructions, the first setting the
function inputs and executing the function code, the second collecting
the function result. This provides the opportunity for the parent thread
to suspend after the %exec_ufunc instruction until all its children have
completed.
Lars-Peter Clausen
Cary R
Stephen Williams
Martin Whitaker