140 lines
4.9 KiB
C++
140 lines
4.9 KiB
C++
#ifndef __vvm_thread_H
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#define __vvm_thread_H
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/*
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* Copyright (c) 1998-2000 Stephen Williams (steve@icarus.com)
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*
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* This source code is free software; you can redistribute it
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* and/or modify it in source code form under the terms of the GNU
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* General Public License as published by the Free Software
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* Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#ifdef HAVE_CVS_IDENT
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#ident "$Id: vvm_thread.h,v 1.11 2002/08/12 01:35:07 steve Exp $"
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#endif
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# include "vvm.h"
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/*
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* A vvm_thread isn't really a thread in the POSIX sense, but a
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* representation of the verilog thread. It is implemented as a state
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* machine that performs an action, and possibly changes state, every
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* time the go method is called. The events and delays that cause a
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* thread to block arrange for the go method to be called in the
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* future.
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*
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* THREAD STEPS
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* The basic blocks of an executing thread are implemented as C/C++
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* functions that take a vvm_thread pointer and return a boolean. The
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* thread keeps a pointer to the function that is the current step. It
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* is the responsibility of each step to write into the step_ member
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* the pointer to the next step, and that is how things like branching
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* and looping work.
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*
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* A thread executes by calling the current step function. When the
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* step function returns, it uses the bolean return code to tell the
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* scheduler whether the next step should be executed. Thus, a thread
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* can give other threads a chance to execute by returning false.
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*
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* CALLING CONVENTION
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* There are a few members in the vvm_thread for supporting calling
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* other threads. This is like a function call in other languages, as
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* the calling thread blocks until the called thread(s) terminate. It
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* is also like functions in that thread calls nest.
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*
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* A thread is called by creating a new vvm_thread and saving a
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* pointer to the new thread in the callee_ member of the calling
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* thread. The called thread gets its back_ pointer set to that of the
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* calling thread. The new thread is then activated with a call to its
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* thread_yield() method, and the caller thread pauses by returning
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* from its step function with the value "false".
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*
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* When the called thread is ready to terminate, it uses its back_
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* pointer to find the calling thread, and activates it with the
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* thread_yield() method. Then, the called thread finishes by
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* returning false from its step method.
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*
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* When the caller resumes executing, it knows that the called thread
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* is done, so it uses the callee_ pointer to delete the now finished
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* thread, and the process is finished.
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*/
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class vvm_sync;
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class vvm_thread {
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public:
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explicit vvm_thread();
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~vvm_thread();
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void thread_yield(unsigned long delay =0);
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// This method executes a setp of the thread. The engine will
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// continue to call go as long as it returns true. The thread
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// will return false if it is ready to give up the CPU.
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bool (*step_)(vvm_thread*);
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// These members are used to handle task invocations.
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vvm_thread*callee_;
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unsigned ncallee_;
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vvm_thread*back_;
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// The sync class uses this to list all the threads blocked on it.
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vvm_sync*sync_back_;
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vvm_thread*sync_next_;
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struct __vpiScope*scope;
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};
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/*
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* $Log: vvm_thread.h,v $
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* Revision 1.11 2002/08/12 01:35:07 steve
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* conditional ident string using autoconfig.
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*
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* Revision 1.10 2000/10/28 00:51:42 steve
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* Add scope to threads in vvm, pass that scope
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* to vpi sysTaskFunc objects, and add vpi calls
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* to access that information.
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*
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* $display displays scope in %m (PR#1)
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*
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* Revision 1.9 2000/04/15 19:51:30 steve
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* fork-join support in vvm.
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*
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* Revision 1.8 2000/04/15 01:44:59 steve
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* Document the calling convention.
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*
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* Revision 1.7 2000/04/14 23:31:53 steve
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* No more class derivation from vvm_thread.
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*
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* Revision 1.6 2000/04/12 01:53:07 steve
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* Multiple thread can block on an event.
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*
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* Revision 1.5 2000/02/23 02:56:57 steve
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* Macintosh compilers do not support ident.
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*
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* Revision 1.4 2000/01/06 05:56:23 steve
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* Cleanup and some asserts.
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*
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* Revision 1.3 1999/12/12 19:47:54 steve
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* Remove the useless vvm_simulation class.
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*
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* Revision 1.2 1998/11/10 00:48:31 steve
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* Add support it vvm target for level-sensitive
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* triggers (i.e. the Verilog wait).
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* Fix display of $time is format strings.
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*
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* Revision 1.1 1998/11/09 23:44:11 steve
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* Add vvm library.
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*
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*/
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#endif
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