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diff --git a/src/mem/slicc/doc/SLICC_V03.txt b/src/mem/slicc/doc/SLICC_V03.txt deleted file mode 100644 index 1c2a95a39..000000000 --- a/src/mem/slicc/doc/SLICC_V03.txt +++ /dev/null @@ -1,307 +0,0 @@ -SLICC - Version 0.3 Design Document - January 17, 1999 -Milo Martin and Dan Sorin - -Question: Rethinking of support for profiling the transactions - -Question: How do we deal with functions/methods and resources - -Comment: We need to discuss the sequencer interface so it can work now - and for the speculative version buffer. - -Overview --------- - -We are in the process of designing and implementing SLICC v0.3, an -evolution of SLICC v0.2. The new design includes capabilities for -design of multilevel cache hierarchies including the specification of -multiple protocol state machines (PSMs) and the queues which connect -these PSMs and the network. We actually believe that most of the -network and network topology, including the ordered network, can be -expressed using the new hierarchical extensions to the language. - -In addition, many implicit aspects of the language will be eliminated -in favor of explicit declarations. For example functions, queues, and -objects declarations such as "cacheMemory" and "TBETable" will be -explicitly declared. This will allow for full static type checking -and easier extension for the language. Event triggering will be part -of "in_port" declarations and not "event" declarations. Finally, many -less fundamental, but important, features and internal code -improvements will be enhanced. - -SLICC History -------------- - -v0.1 - Initially the language only handled the generation of the PSM - transition table logic. All actions and event triggering were - still coded in C++. At this point it was still called, "the - language." - -v0.2 - Extended the language to include a simple C like syntax for - specifying actions, event triggering, and manipulating queues - and state elements. This version was the first version of the - language known as SLICC (suggested by Amir) and was used for - the Multifacet ISCA 2000 submission. - -v0.3 - Development effort started January 2000. Intended features and - enhancements are described by this document. - -Specifying Hierarchical Designs -------------------------------- - -Right now all of our protocols have two tables, a processor/cache PSM -and a directory PSM. In v0.2 this is a rigid requirement and -the names are implicit. SLICC v0.3 will allow for an arbitrary number -of different PSMs. - -The most significant improvement in v0.3 is the ability for the user -to define an arbitrary set of interconnected PSMs. PSMs may include -an L1 cache controller, L2 cache controller, directory controller, -speculative version buffer, network interface, etc. There are a -couple of "primitive PSMs" such as the sequencer. - -There will be a notion of a "node" of the system. In a node, each PSM -will be instantiated and connected together with queues. For example, -assume we define a PSMs and want to create a queue of RequestMessages -to communicate between it and the network. - - machine(CacheController) { - ... - out_port(to_network, RequestMessage, "To the network", desc="..."); - ... - } - - CacheController cache, desc="..."; - - connect(cache.to_network, network.from_cache, ordered="yes", desc="..."); - -Explicit State Manipulation ---------------------------- - -As before, PSMs have states, events, and transitions. New in v0.3 each -PSM must have user defined methods for get_state(address) and -set_state(address, state), and these methods are written explicitly, -instead of being implicit functions of memory states (e.g., our -current implementation which implicitly uses the TBE state if there is -a TBE or uses the cache state). Functions have a return value, -procedures do not. Function calls are expressions, procedure calls -are statements. All function and procedure parameters are considered -pass-by-value. - - procedure set_state(Address addr, State state) { - ... - } - - function State get_state(Address addr) { - ... - } - -Explicit Declaration --------------------- - -PSMs reference or declare structures, such as queues, ports, cache -memories, main memory, TBEs, write buffers, etc. These primitive -types and structures are written in C++, and their semantics are still -specified by the C++ coder. Examples of these primitive types include -"CacheMemory," "TBETable," as well as various types of queues. - -One major difference is that in v0.3 the interface for all of these -primitive objects will be declared (but not defined) in the SLICC -language. This also allows adding primitive structures by defining a -C++ implementation and a SLICC interface specification. This will -make the language much more extensible. Specifying the interface of -these primitive types, structures, and queues in SLICC will eliminate -much of the implicit semantics that is currently hiding in the -controllers. - -The interface declaration might be in one file and shared between all -protocols. The object instantiation would be internal to each PSM -that requires a cache memory. The syntax for messages will also be -enhanced by using this new syntax. Notice the support for default -values. - - structure(CacheMemory, "Cache memory", desc="...") { - void cache_change_state(Address addr, State state), desc="..."; - Data dataBlk, default="", desc=""; - bool cache_avail(Address addr), desc="..."; - Address cache_probe(Address addr), desc="..."; - void cache_allocate(Address addr), desc="..."; - } - - CacheMemory L1cacheMemory, desc="..."; - -Structure specification is going to require the introduction of an -object model in the language. The "." (dot) operator is going to be -extended beyond the use as structure element access, but also allow -for a object method call syntax similar to C++ and Java. - - L1cacheMemory.cache_allocate(addr); - -Polymorphism ------------- - -We are also going to want to allow for polymorphism for many of the -structures. We already have a limited degree of polymorphism between -different protocols by using the same cache memory structure with -different "CacheEntry" types in each protocol. Now that we are going -to have multiple levels of cache, each requiring slightly different -state bits, we are going to want to specify cache memory structures -which have different "CacheEntry" types in the same protocol. To do -this right, this is going to require adding full polymorphism support -to the language. Right now we imagine something like C++'s templates, -since they are a more natural fit to hardware synthesis in the future. - -Type Checker ------------- - -All of the above substantially complicates our type system by -requiring more types and scoping rules. As a step towards -understanding the implications of the type system, a type checking -system will be implemented. This is a hard requirement if we are ever -to distribute the system since receiving compile time errors in the -generated code is not acceptable. In order to ensure that we don't -accidentally design a language that is not statically type checkable, -it is important to add the type checker sooner rather than later. - -Event Triggering ----------------- - -In v0.2, PSM events were individually specified as sets of conditions. -The following SLICC v0.2 code is a simplified example from the origin -protocol. - - event(Dir_data_ack_0, "Data ack 0", desc="... ack count == 0") { - if (queue_ready(responseNetwork)) { - peek(responseNetwork, ResponseMsg) { - if(in_msg.NumPendingAcks == 0) { - trigger(in_msg.Address); - } - } - } - } - - event(Dir_data_ack_not_0, "Data ack not 0", desc="... ack count != 0") { - if (queue_ready(responseNetwork)) { - peek(responseNetwork, ResponseMsg) { - if(in_msg.NumPendingAcks != 0) { - trigger(in_msg.Address); - } - } - } - } - -The above code defines the exact conditions for the events to be -triggered. This type of event specification led to redundant code and -numerous bugs where conditions for different events were not -completely orthogonal. - -In v0.3, events will be declared with no accompanying code (similar to -how states are specified). Instead, the code that determines which -event is triggered will be part of each incoming port's declaration. -This approach should eliminate redundancy and bugs in trigger -conditions. The v0.3 code for the above would look like: - - event(Dir_data_ack_0, "Data ack 0", desc="... ack count = 0"); - event(Dir_data_ack_not_0, "Data ack not 0", desc="... ack count != 0"); - - in_port(responseNetwork, ResponseMsg, "Response Network", desc="...") { - if(in_msg.NumPendingAcks == 0) { - trigger(Dir_data_ack_0, in_msg.Address); - } else { - trigger(Dir_data_ack_not_0, in_msg.Address); - } - } - -Notice that one no longer needs to explicitly check if the queue is -ready or to perform the peek operation. - -Also notice that the type of messages that arrives on the port is -explicitly declared. All ports, incoming and outgoing, are now -explicitly type channels. You will still be required to include the -type of message when manipulating the queue. The type specified will -be statically type checked and also acts as self-documenting code. - -Other Improvements ------------------- - -There will be a number of other improvements in v0.3 such as general -performance tuning and clean up of the internals of the compiler. The -compiler will be modified to operate on multiple files. In addition, -the abstract syntax tree internal to the code will need to be extended -to encompass more information, including information parsed in from -multiple files. - -The affiliates talk and the document for the language should also be -updated to reflect the changes in the new version. - -Looking Forward ---------------- - -When designing v0.3 we are keeping future plans in mind. - -- When our designs of the multilevel cache hierarchy are complete, we - expect to have a large amount of replication between the protocols - and caches controllers within a protocol. For v0.4 we hope to look - at the patterns that have evolved and look for ways in which the - language can capture these patterns. Exploiting reuse will provide - quicker protocol development and maintainability. - -- By keeping the specification structural, we are looking towards - generating VHDL/Verilog from SLICC. The type system will help this, - as will more explicit instantiation and declaration of types and - structures. The structures now written in C++ (sequencer, network, - cache arrays) will be ported to the HDL we select. The rest of the - controllers will be generated by the compiler. At first the - generated controller will not be optimized. I believe that with - more effort we can automatically generate reasonably optimized, - pipelined implementation of the controllers. - -Implementation Plan -------------------- - -- HTML generator -- Extend internal parser AST nodes -- Add get_state function and set_state procedure declarations -- Move trigger logic from events to in_ports -- Types - - Change type declaration syntax - - Declare primitive types and corresponding C++ types - - Add default values to structures and types - - Add object method call syntax - - Write type checker -- Documentation - - Revise document - - Update presentation - -Document History ----------------- - -$Id: SLICC_V03.txt,v 3.0 2000/09/12 20:27:59 sorin Exp $ - -$Log: SLICC_V03.txt,v $ -Revision 3.0 2000/09/12 20:27:59 sorin -Version 3.0 signifies a checkpoint of the source tree right after the -final draft of the ASPLOS '00 paper. - -Revision 1.1.1.1 2000/03/09 10:18:38 milo -Initial import - -Revision 2.0 2000/01/19 07:21:13 milo -Version 2.0 - -Revision 1.5 2000/01/18 10:26:24 milo -Changed the SLICC parser so that it generates a full AST. This is the -first step in moving towards v0.3 - -Revision 1.4 2000/01/17 18:36:15 sorin -*** empty log message *** - -Revision 1.3 2000/01/15 10:30:16 milo -Added implementation list - -Revision 1.2 2000/01/15 08:11:44 milo -Minor revisions - -Revision 1.1 2000/01/15 07:14:17 milo -Converted Dan's first draft into a text file. Significant -modifications were made. - |