From: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Make this file easier to read by removing the name at the beginning of each line. Put its source and attribution at the beginning of the file. Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> --- Documentation/data-structures.txt | 107 ++++++++++++++-------------- 1 file changed, 54 insertions(+), 53 deletions(-) --- sprs-2018-0119.orig/Documentation/data-structures.txt +++ sprs-2018-0119/Documentation/data-structures.txt @@ -1,54 +1,55 @@ +- A slightly edited irc discussion with Josh Triplett. +- Describes most data structures used in sparse. -<JoshTriplett> As far as the parsing structures go... -<JoshTriplett> The C parser exists in two main files: parse.c, which parses statements, and expression.c, which parses expressions. -<JoshTriplett> parse.h contains the definition of struct statement, which represents a C statement. -<JoshTriplett> That includes only those things which can't appear as an expression, which primarily includes control flow statements such as if, loops, switch/case, and goto. -<JoshTriplett> expression.h contains the definition of struct expression, which represents a C expression. That has a lot more content, since most C constructs can appear in expressions. -<JoshTriplett> A series of statements forms a compound statement (STMT_COMPOUND). -<JoshTriplett> That appears as another struct statement which has a statement_list member. -<JoshTriplett> A function body consists of a compound statement. -<JoshTriplett> When you look at a loop body, if or else body, or case body, you'll notice that they just have a struct statement, not a statement_list; they can have multiple statements by using a compound statement. -<JoshTriplett> Also note that all loops get turned into a single "iterator" statement. -<JoshTriplett> for, while, and do-while. -<JoshTriplett> A symbol, then, represents a name in a C file. A symbol might represent a variable, a function, a label, or various other things. -<JoshTriplett> See symbol.h. -<JoshTriplett> "struct symbol" represents one symbol. -<JoshTriplett> As with the various other structures, it has some common data and a union of sub-structures for the parts that differ between different types. -<JoshTriplett> Most of the interesting bits come in the NS_SYMBOL case. -<JoshTriplett> Among other things, it has a struct statement for the body of a function (if any), a list of symbols for the arguments, an expression for a variable initializer, and so on. -<JoshTriplett> Together, struct symbol, struct statement, and struct expression represent most of the abstract syntax tree for C. -<JoshTriplett> So, that represents most of the "front-end" of Sparse: parsing C and generating that abstract syntax tree. -<JoshTriplett> That much occurs in pretty much any program using the Sparse frontend. -<JoshTriplett> The backend varies among programs. -<JoshTriplett> For instance, the c2xml backend goes that far, then outputs XML. -<JoshTriplett> The sparse static analysis backend has a few steps: it generates linearized bytecode, does some evaluation on that, and outputs some warnings. -<JoshTriplett> Several other backends run that linearized bytecode stage. -<JoshTriplett> The linearized bytecode itself has a set of nested structures. -<JoshTriplett> linearize.h defines all of them. -<JoshTriplett> At the top level, it has struct entrypoint. -<JoshTriplett> That represents an entrypoint to the code, which would normally mean a function. -<JoshTriplett> An entrypoint has a list of basic blocks. -<JoshTriplett> struct basic_block. -<JoshTriplett> A basic block represents a series of instructions with no branches. -<JoshTriplett> Straight-line code. -<JoshTriplett> A branch only occurs at the end of a basic block, and branches can only target the beginning of a basic block. -<JoshTriplett> Typically, a conditional will consist of a basic block leading up to the branch, a basic block for the true case, a basic block for the false case, and a basic block where the two paths merge back together. -<JoshTriplett> Either the true or the false case may not exist. -<JoshTriplett> A loop will normally have a basic block for the loop body, which can branch to the top at the end or continue to the next basic block. -<JoshTriplett> So basic blocks represent a node in the control flow graph. -<JoshTriplett> The edges in that graph lead from one basic block to a basic block which can follow it in the execution of the program. -<JoshTriplett> Each basic block has a series of instructions, "struct instruction". -<JoshTriplett> "enum opcode" lists all the instructions. -<JoshTriplett> Fairly high-level instruction set, corresponding directly to bits of C. -<JoshTriplett> So you have an entrypoint, which has a graph of basic blocks, each of which has a list of instructions. -<JoshTriplett> An entrypoint also has a pointer to the first instruction. -<JoshTriplett> One last bit of trickiness: struct pseudo. -<JoshTriplett> Have you ever heard of "static single assignment" or SSA form? -<JoshTriplett> struct pseudo represents one of those single-assignment variables. -<JoshTriplett> Each one has a pointer to the symbol it represents (which may have many pseudos referencing it). -<JoshTriplett> Each one also has a pointer to the instruction that defines it. -<JoshTriplett> That covers most of the major data structures in Sparse. -<JoshTriplett> Now, given all that, some of the top-level stuff in sparse.c may make more sense. -<JoshTriplett> For instance, the context checking works in terms of basic blocks. -<JoshTriplett> Hopefully some of that helped you understand Sparse better. - +As far as the parsing structures go... +The C parser exists in two main files: parse.c, which parses statements, and expression.c, which parses expressions. +parse.h contains the definition of struct statement, which represents a C statement. +That includes only those things which can't appear as an expression, which primarily includes control flow statements such as if, loops, switch/case, and goto. +expression.h contains the definition of struct expression, which represents a C expression. That has a lot more content, since most C constructs can appear in expressions. +A series of statements forms a compound statement (STMT_COMPOUND). +That appears as another struct statement which has a statement_list member. +A function body consists of a compound statement. +When you look at a loop body, if or else body, or case body, you'll notice that they just have a struct statement, not a statement_list; they can have multiple statements by using a compound statement. +Also note that all loops get turned into a single "iterator" statement. +for, while, and do-while. +A symbol, then, represents a name in a C file. A symbol might represent a variable, a function, a label, or various other things. +See symbol.h. +"struct symbol" represents one symbol. +As with the various other structures, it has some common data and a union of sub-structures for the parts that differ between different types. +Most of the interesting bits come in the NS_SYMBOL case. +Among other things, it has a struct statement for the body of a function (if any), a list of symbols for the arguments, an expression for a variable initializer, and so on. +Together, struct symbol, struct statement, and struct expression represent most of the abstract syntax tree for C. +So, that represents most of the "front-end" of Sparse: parsing C and generating that abstract syntax tree. +That much occurs in pretty much any program using the Sparse frontend. +The backend varies among programs. +For instance, the c2xml backend goes that far, then outputs XML. +The sparse static analysis backend has a few steps: it generates linearized bytecode, does some evaluation on that, and outputs some warnings. +Several other backends run that linearized bytecode stage. +The linearized bytecode itself has a set of nested structures. +linearize.h defines all of them. +At the top level, it has struct entrypoint. +That represents an entrypoint to the code, which would normally mean a function. +An entrypoint has a list of basic blocks. +struct basic_block. +A basic block represents a series of instructions with no branches. +Straight-line code. +A branch only occurs at the end of a basic block, and branches can only target the beginning of a basic block. +Typically, a conditional will consist of a basic block leading up to the branch, a basic block for the true case, a basic block for the false case, and a basic block where the two paths merge back together. +Either the true or the false case may not exist. +A loop will normally have a basic block for the loop body, which can branch to the top at the end or continue to the next basic block. +So basic blocks represent a node in the control flow graph. +The edges in that graph lead from one basic block to a basic block which can follow it in the execution of the program. +Each basic block has a series of instructions, "struct instruction". +"enum opcode" lists all the instructions. +Fairly high-level instruction set, corresponding directly to bits of C. +So you have an entrypoint, which has a graph of basic blocks, each of which has a list of instructions. +An entrypoint also has a pointer to the first instruction. +One last bit of trickiness: struct pseudo. +Have you ever heard of "static single assignment" or SSA form? +struct pseudo represents one of those single-assignment variables. +Each one has a pointer to the symbol it represents (which may have many pseudos referencing it). +Each one also has a pointer to the instruction that defines it. +That covers most of the major data structures in Sparse. +Now, given all that, some of the top-level stuff in sparse.c may make more sense. +For instance, the context checking works in terms of basic blocks. +Hopefully some of that helped you understand Sparse better. -- To unsubscribe from this list: send the line "unsubscribe linux-sparse" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
