From 57971248f662e932a4593529cba83ce54961f4ed Mon Sep 17 00:00:00 2001 From: Nilay Vaish Date: Thu, 25 Jun 2015 11:58:30 -0500 Subject: ruby: slicc: remove README No longer maintained. Updates are only made to the wiki page. So being dropped. --- src/mem/slicc/README | 114 --------------------------------------------------- 1 file changed, 114 deletions(-) delete mode 100644 src/mem/slicc/README (limited to 'src/mem') diff --git a/src/mem/slicc/README b/src/mem/slicc/README deleted file mode 100644 index fb7f52dac..000000000 --- a/src/mem/slicc/README +++ /dev/null @@ -1,114 +0,0 @@ -Overview -======== -This is SLICC, a domain specific language to specify cache coherence protocol -we have developed in Multifacet group. - -It is developed by Milo Martin -This document is prepared by Min Xu while I am learning the -system. With minor correctness updates by Brad Beckmann - -It can be used to generate C++ code that works with RUBY cache simulator as -well as generate HTML and other document to describe the target protocol. - -Some user document is available in doc directory. - -Tech details -============ -SLICC take a text input with similar syntax to C++ language and use the lexer -and parser in parser directory to construct a Abstract Syntax Tree (AST) -internally. After having done this first pass, the AST is traversed to fill -several interval table, such as symbol table, type table, etc. Finally the code -is generated by traversing the tree once again. - -Note, by Milo's good coding habit, almost all C++ class define their private -copy/assignment constructor. This prevents accidentally copying/assigning an -object by its address. - -The AST basically looks like a hierarchical representation of the text input. -At the highest level, it has the "Machine", each Machine has several "states" -and "events" and "actions" and "transistions". - -Since the language is domain specific, many assumptions of the target system is -hardcoded in SLICC. For example, ruby would expect the generated code for each -system node, has the following components: - processor(sequencer, not generated?) - cache - directory (with memory block value, only when compiled with tester) - network interface (NI) - -Directory generator/ contains routines to generate HTML/MIF format output. -fileio.[Ch] has a routine to conditionally write a file only when the original -content of the file is different from what is going to be written, this avoid -re-make those file after regenerate the protocol. html_gen.[Ch] contains the -symbol name munge and index page generation. mif_gen.[Ch] contains the entire -MIF output generation routine, mainly a table buildup. - -Directory symbol/ contains classes to represent symbols in the slicc input -file. Base class is "Symbol". Derived subclasses are "Action Event Func State -StateMachine Transition Type Var". "Symbol" has knowledge about its locations -in the source file and short name, long name. "SymbolTable" is a list of -symbols and g_sym_table is the global SymbolTable of the slicc system. -One can query a SymbolTable by symbol's id. Also SymbolTable is responsible for -keeping track of Symbol's declaration in correct scope. The current -implementation uses a stack which dynamically determine the scope of symbol -lookups. Global scope is at bottom of the stack (vector[0]). SymbolTable is -also the main place to write out the generated C++/HTML/MIF files. -SymbolTable::writeNodeFiles() is one of the place to look for hardcoded C++ -code for node.[Ch]. And Type.[Ch] is the place where generating enumeration and -Message/NetworkMessage declaration and implementation. Func.[Ch] is used to -generate function of the class Chip. StateMachine.[Ch] wrap the whole thing -up by putting States, Actions, Events together. It actually has a two dimension -table like the one represented in the HTML output. Actions are indexed with -the initial state and observed event. After the tabel being built, the -StateMachine class can write out Transitions/Controller/wakeup_logic into C++ -outputs. Finally, in symbol directory, Var.[Ch] seem to incomplete? - -Demystify all those "predefined" external types, like "Address". Where are -they defined? They are in ../protocol/RubySlicc-*.sm and -../protocol/RubySlicc_interfaces.slicc is include in the slicc invocation -command in ../ruby/Makefile. - -Another myth: "trigger" method is hardcoded in ast/InPortDeclAST.C and -ast/FuncCallExprAST.C. The function is similar to inlined function in the -output generated code, so you cannot find any occurance of string "trigger" in -the generated code. "trigger" also increment a counter that is checked every -time a transition is done. In one ruby cycle, only TRANSITIONS_PER_RUBY_CYCLE -number of transitions can be done. ast/FuncCallExprAST.C also contains some -code for function "error" and "assert" and "DEBUG_EXPR", all in the same -manner. Ruby always issues transitions from the first port while there is any. -Stalled transition in Ruby does not consume a sub-cycle. This models the -hardware that probe all port in parallel, pick one transition from the highest -priority queue if the transistion was not stalled by any resources constraint. - -Another note: scheduleEvent() call of ruby make sure a consumer is woken up at -specified cycle, and only once per cycle. - -Action z_stall, where is it? It is hardcoded in symbols/StateMachine.C. In -function StateMachine::printCSwitch(), z_stall cause the generated code return -TransitionResult_ProtocolStall. Also the HTML output for z_stall has to be -consequently hardcoded. I am not sure that's really a good idea or not. :-) - -Question: How comes there is no "for" loop statement in slicc? -Answer: Been there, done that. That is easy to add, first of all. But unbound -loop make slicc eventually un-synthesizable. We want to avoid that. If you want -to loop through a bounded array do something, make the action done in a -external interface in RubySlicc_Util.h. Inside, you just pass the vector as -parameter to the external interface to achieve the same effects. - -Another bad thing of using loop statement like for is that we can not determine -how many buffer space to allocate before the transition. With a vector, if it -easy to understand we can always allocate the worst case number of hardware -resources. - -Question: Wait! It seems statement check_allocate does nothing! -Answer: No, it does call areNSoltsAvailable() function of the object before any -statement is executed in one action. It does *NOT* generate code in its -original place in the code, instead, it scan the body of the action code and -determine how many slots are needed to allocated before hand. So the -transaction is all done or nothing done. I had tried to make all actions return -boolean values and the false return cause a transition to abort with -ResourceStall. But it is later on deemed to be too flexible in its semantics. -We should never introduce control flow inside the transitions, so that each -transition is either "all" or "nothing". Just that simple. BTW, if you call -check_allocate twice, areNSoltsAvailable(2) is generated, three times generates -areNSoltsAvailable(3), etc. -- cgit v1.2.3