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diff --git a/gnu/llvm/docs/tutorial/OCamlLangImpl3.rst b/gnu/llvm/docs/tutorial/OCamlLangImpl3.rst deleted file mode 100644 index a76b46d1bf6..00000000000 --- a/gnu/llvm/docs/tutorial/OCamlLangImpl3.rst +++ /dev/null @@ -1,961 +0,0 @@ -======================================== -Kaleidoscope: Code generation to LLVM IR -======================================== - -.. contents:: - :local: - -Chapter 3 Introduction -====================== - -Welcome to Chapter 3 of the "`Implementing a language with -LLVM <index.html>`_" tutorial. This chapter shows you how to transform -the `Abstract Syntax Tree <OCamlLangImpl2.html>`_, built in Chapter 2, -into LLVM IR. This will teach you a little bit about how LLVM does -things, as well as demonstrate how easy it is to use. It's much more -work to build a lexer and parser than it is to generate LLVM IR code. :) - -**Please note**: the code in this chapter and later require LLVM 2.3 or -LLVM SVN to work. LLVM 2.2 and before will not work with it. - -Code Generation Setup -===================== - -In order to generate LLVM IR, we want some simple setup to get started. -First we define virtual code generation (codegen) methods in each AST -class: - -.. code-block:: ocaml - - let rec codegen_expr = function - | Ast.Number n -> ... - | Ast.Variable name -> ... - -The ``Codegen.codegen_expr`` function says to emit IR for that AST node -along with all the things it depends on, and they all return an LLVM -Value object. "Value" is the class used to represent a "`Static Single -Assignment -(SSA) <http://en.wikipedia.org/wiki/Static_single_assignment_form>`_ -register" or "SSA value" in LLVM. The most distinct aspect of SSA values -is that their value is computed as the related instruction executes, and -it does not get a new value until (and if) the instruction re-executes. -In other words, there is no way to "change" an SSA value. For more -information, please read up on `Static Single -Assignment <http://en.wikipedia.org/wiki/Static_single_assignment_form>`_ -- the concepts are really quite natural once you grok them. - -The second thing we want is an "Error" exception like we used for the -parser, which will be used to report errors found during code generation -(for example, use of an undeclared parameter): - -.. code-block:: ocaml - - exception Error of string - - let context = global_context () - let the_module = create_module context "my cool jit" - let builder = builder context - let named_values:(string, llvalue) Hashtbl.t = Hashtbl.create 10 - let double_type = double_type context - -The static variables will be used during code generation. -``Codgen.the_module`` is the LLVM construct that contains all of the -functions and global variables in a chunk of code. In many ways, it is -the top-level structure that the LLVM IR uses to contain code. - -The ``Codegen.builder`` object is a helper object that makes it easy to -generate LLVM instructions. Instances of the -`IRBuilder <http://llvm.org/doxygen/IRBuilder_8h-source.html>`_ -class keep track of the current place to insert instructions and has -methods to create new instructions. - -The ``Codegen.named_values`` map keeps track of which values are defined -in the current scope and what their LLVM representation is. (In other -words, it is a symbol table for the code). In this form of Kaleidoscope, -the only things that can be referenced are function parameters. As such, -function parameters will be in this map when generating code for their -function body. - -With these basics in place, we can start talking about how to generate -code for each expression. Note that this assumes that the -``Codgen.builder`` has been set up to generate code *into* something. -For now, we'll assume that this has already been done, and we'll just -use it to emit code. - -Expression Code Generation -========================== - -Generating LLVM code for expression nodes is very straightforward: less -than 30 lines of commented code for all four of our expression nodes. -First we'll do numeric literals: - -.. code-block:: ocaml - - | Ast.Number n -> const_float double_type n - -In the LLVM IR, numeric constants are represented with the -``ConstantFP`` class, which holds the numeric value in an ``APFloat`` -internally (``APFloat`` has the capability of holding floating point -constants of Arbitrary Precision). This code basically just creates -and returns a ``ConstantFP``. Note that in the LLVM IR that constants -are all uniqued together and shared. For this reason, the API uses "the -foo::get(..)" idiom instead of "new foo(..)" or "foo::Create(..)". - -.. code-block:: ocaml - - | Ast.Variable name -> - (try Hashtbl.find named_values name with - | Not_found -> raise (Error "unknown variable name")) - -References to variables are also quite simple using LLVM. In the simple -version of Kaleidoscope, we assume that the variable has already been -emitted somewhere and its value is available. In practice, the only -values that can be in the ``Codegen.named_values`` map are function -arguments. This code simply checks to see that the specified name is in -the map (if not, an unknown variable is being referenced) and returns -the value for it. In future chapters, we'll add support for `loop -induction variables <LangImpl5.html#for-loop-expression>`_ in the symbol table, and for -`local variables <LangImpl7.html#user-defined-local-variables>`_. - -.. code-block:: ocaml - - | Ast.Binary (op, lhs, rhs) -> - let lhs_val = codegen_expr lhs in - let rhs_val = codegen_expr rhs in - begin - match op with - | '+' -> build_fadd lhs_val rhs_val "addtmp" builder - | '-' -> build_fsub lhs_val rhs_val "subtmp" builder - | '*' -> build_fmul lhs_val rhs_val "multmp" builder - | '<' -> - (* Convert bool 0/1 to double 0.0 or 1.0 *) - let i = build_fcmp Fcmp.Ult lhs_val rhs_val "cmptmp" builder in - build_uitofp i double_type "booltmp" builder - | _ -> raise (Error "invalid binary operator") - end - -Binary operators start to get more interesting. The basic idea here is -that we recursively emit code for the left-hand side of the expression, -then the right-hand side, then we compute the result of the binary -expression. In this code, we do a simple switch on the opcode to create -the right LLVM instruction. - -In the example above, the LLVM builder class is starting to show its -value. IRBuilder knows where to insert the newly created instruction, -all you have to do is specify what instruction to create (e.g. with -``Llvm.create_add``), which operands to use (``lhs`` and ``rhs`` here) -and optionally provide a name for the generated instruction. - -One nice thing about LLVM is that the name is just a hint. For instance, -if the code above emits multiple "addtmp" variables, LLVM will -automatically provide each one with an increasing, unique numeric -suffix. Local value names for instructions are purely optional, but it -makes it much easier to read the IR dumps. - -`LLVM instructions <../LangRef.html#instruction-reference>`_ are constrained by strict -rules: for example, the Left and Right operators of an `add -instruction <../LangRef.html#add-instruction>`_ must have the same type, and the -result type of the add must match the operand types. Because all values -in Kaleidoscope are doubles, this makes for very simple code for add, -sub and mul. - -On the other hand, LLVM specifies that the `fcmp -instruction <../LangRef.html#fcmp-instruction>`_ always returns an 'i1' value (a -one bit integer). The problem with this is that Kaleidoscope wants the -value to be a 0.0 or 1.0 value. In order to get these semantics, we -combine the fcmp instruction with a `uitofp -instruction <../LangRef.html#uitofp-to-instruction>`_. This instruction converts its -input integer into a floating point value by treating the input as an -unsigned value. In contrast, if we used the `sitofp -instruction <../LangRef.html#sitofp-to-instruction>`_, the Kaleidoscope '<' operator -would return 0.0 and -1.0, depending on the input value. - -.. code-block:: ocaml - - | Ast.Call (callee, args) -> - (* Look up the name in the module table. *) - let callee = - match lookup_function callee the_module with - | Some callee -> callee - | None -> raise (Error "unknown function referenced") - in - let params = params callee in - - (* If argument mismatch error. *) - if Array.length params == Array.length args then () else - raise (Error "incorrect # arguments passed"); - let args = Array.map codegen_expr args in - build_call callee args "calltmp" builder - -Code generation for function calls is quite straightforward with LLVM. -The code above initially does a function name lookup in the LLVM -Module's symbol table. Recall that the LLVM Module is the container that -holds all of the functions we are JIT'ing. By giving each function the -same name as what the user specifies, we can use the LLVM symbol table -to resolve function names for us. - -Once we have the function to call, we recursively codegen each argument -that is to be passed in, and create an LLVM `call -instruction <../LangRef.html#call-instruction>`_. Note that LLVM uses the native C -calling conventions by default, allowing these calls to also call into -standard library functions like "sin" and "cos", with no additional -effort. - -This wraps up our handling of the four basic expressions that we have so -far in Kaleidoscope. Feel free to go in and add some more. For example, -by browsing the `LLVM language reference <../LangRef.html>`_ you'll find -several other interesting instructions that are really easy to plug into -our basic framework. - -Function Code Generation -======================== - -Code generation for prototypes and functions must handle a number of -details, which make their code less beautiful than expression code -generation, but allows us to illustrate some important points. First, -lets talk about code generation for prototypes: they are used both for -function bodies and external function declarations. The code starts -with: - -.. code-block:: ocaml - - let codegen_proto = function - | Ast.Prototype (name, args) -> - (* Make the function type: double(double,double) etc. *) - let doubles = Array.make (Array.length args) double_type in - let ft = function_type double_type doubles in - let f = - match lookup_function name the_module with - -This code packs a lot of power into a few lines. Note first that this -function returns a "Function\*" instead of a "Value\*" (although at the -moment they both are modeled by ``llvalue`` in ocaml). Because a -"prototype" really talks about the external interface for a function -(not the value computed by an expression), it makes sense for it to -return the LLVM Function it corresponds to when codegen'd. - -The call to ``Llvm.function_type`` creates the ``Llvm.llvalue`` that -should be used for a given Prototype. Since all function arguments in -Kaleidoscope are of type double, the first line creates a vector of "N" -LLVM double types. It then uses the ``Llvm.function_type`` method to -create a function type that takes "N" doubles as arguments, returns one -double as a result, and that is not vararg (that uses the function -``Llvm.var_arg_function_type``). Note that Types in LLVM are uniqued -just like ``Constant``'s are, so you don't "new" a type, you "get" it. - -The final line above checks if the function has already been defined in -``Codegen.the_module``. If not, we will create it. - -.. code-block:: ocaml - - | None -> declare_function name ft the_module - -This indicates the type and name to use, as well as which module to -insert into. By default we assume a function has -``Llvm.Linkage.ExternalLinkage``. "`external -linkage <../LangRef.html#linkage>`_" means that the function may be defined -outside the current module and/or that it is callable by functions -outside the module. The "``name``" passed in is the name the user -specified: this name is registered in "``Codegen.the_module``"s symbol -table, which is used by the function call code above. - -In Kaleidoscope, I choose to allow redefinitions of functions in two -cases: first, we want to allow 'extern'ing a function more than once, as -long as the prototypes for the externs match (since all arguments have -the same type, we just have to check that the number of arguments -match). Second, we want to allow 'extern'ing a function and then -defining a body for it. This is useful when defining mutually recursive -functions. - -.. code-block:: ocaml - - (* If 'f' conflicted, there was already something named 'name'. If it - * has a body, don't allow redefinition or reextern. *) - | Some f -> - (* If 'f' already has a body, reject this. *) - if Array.length (basic_blocks f) == 0 then () else - raise (Error "redefinition of function"); - - (* If 'f' took a different number of arguments, reject. *) - if Array.length (params f) == Array.length args then () else - raise (Error "redefinition of function with different # args"); - f - in - -In order to verify the logic above, we first check to see if the -pre-existing function is "empty". In this case, empty means that it has -no basic blocks in it, which means it has no body. If it has no body, it -is a forward declaration. Since we don't allow anything after a full -definition of the function, the code rejects this case. If the previous -reference to a function was an 'extern', we simply verify that the -number of arguments for that definition and this one match up. If not, -we emit an error. - -.. code-block:: ocaml - - (* Set names for all arguments. *) - Array.iteri (fun i a -> - let n = args.(i) in - set_value_name n a; - Hashtbl.add named_values n a; - ) (params f); - f - -The last bit of code for prototypes loops over all of the arguments in -the function, setting the name of the LLVM Argument objects to match, -and registering the arguments in the ``Codegen.named_values`` map for -future use by the ``Ast.Variable`` variant. Once this is set up, it -returns the Function object to the caller. Note that we don't check for -conflicting argument names here (e.g. "extern foo(a b a)"). Doing so -would be very straight-forward with the mechanics we have already used -above. - -.. code-block:: ocaml - - let codegen_func = function - | Ast.Function (proto, body) -> - Hashtbl.clear named_values; - let the_function = codegen_proto proto in - -Code generation for function definitions starts out simply enough: we -just codegen the prototype (Proto) and verify that it is ok. We then -clear out the ``Codegen.named_values`` map to make sure that there isn't -anything in it from the last function we compiled. Code generation of -the prototype ensures that there is an LLVM Function object that is -ready to go for us. - -.. code-block:: ocaml - - (* Create a new basic block to start insertion into. *) - let bb = append_block context "entry" the_function in - position_at_end bb builder; - - try - let ret_val = codegen_expr body in - -Now we get to the point where the ``Codegen.builder`` is set up. The -first line creates a new `basic -block <http://en.wikipedia.org/wiki/Basic_block>`_ (named "entry"), -which is inserted into ``the_function``. The second line then tells the -builder that new instructions should be inserted into the end of the new -basic block. Basic blocks in LLVM are an important part of functions -that define the `Control Flow -Graph <http://en.wikipedia.org/wiki/Control_flow_graph>`_. Since we -don't have any control flow, our functions will only contain one block -at this point. We'll fix this in `Chapter 5 <OCamlLangImpl5.html>`_ :). - -.. code-block:: ocaml - - let ret_val = codegen_expr body in - - (* Finish off the function. *) - let _ = build_ret ret_val builder in - - (* Validate the generated code, checking for consistency. *) - Llvm_analysis.assert_valid_function the_function; - - the_function - -Once the insertion point is set up, we call the ``Codegen.codegen_func`` -method for the root expression of the function. If no error happens, -this emits code to compute the expression into the entry block and -returns the value that was computed. Assuming no error, we then create -an LLVM `ret instruction <../LangRef.html#ret-instruction>`_, which completes the -function. Once the function is built, we call -``Llvm_analysis.assert_valid_function``, which is provided by LLVM. This -function does a variety of consistency checks on the generated code, to -determine if our compiler is doing everything right. Using this is -important: it can catch a lot of bugs. Once the function is finished and -validated, we return it. - -.. code-block:: ocaml - - with e -> - delete_function the_function; - raise e - -The only piece left here is handling of the error case. For simplicity, -we handle this by merely deleting the function we produced with the -``Llvm.delete_function`` method. This allows the user to redefine a -function that they incorrectly typed in before: if we didn't delete it, -it would live in the symbol table, with a body, preventing future -redefinition. - -This code does have a bug, though. Since the ``Codegen.codegen_proto`` -can return a previously defined forward declaration, our code can -actually delete a forward declaration. There are a number of ways to fix -this bug, see what you can come up with! Here is a testcase: - -:: - - extern foo(a b); # ok, defines foo. - def foo(a b) c; # error, 'c' is invalid. - def bar() foo(1, 2); # error, unknown function "foo" - -Driver Changes and Closing Thoughts -=================================== - -For now, code generation to LLVM doesn't really get us much, except that -we can look at the pretty IR calls. The sample code inserts calls to -Codegen into the "``Toplevel.main_loop``", and then dumps out the LLVM -IR. This gives a nice way to look at the LLVM IR for simple functions. -For example: - -:: - - ready> 4+5; - Read top-level expression: - define double @""() { - entry: - %addtmp = fadd double 4.000000e+00, 5.000000e+00 - ret double %addtmp - } - -Note how the parser turns the top-level expression into anonymous -functions for us. This will be handy when we add `JIT -support <OCamlLangImpl4.html#adding-a-jit-compiler>`_ in the next chapter. Also note that -the code is very literally transcribed, no optimizations are being -performed. We will `add -optimizations <OCamlLangImpl4.html#trivial-constant-folding>`_ explicitly in the -next chapter. - -:: - - ready> def foo(a b) a*a + 2*a*b + b*b; - Read function definition: - define double @foo(double %a, double %b) { - entry: - %multmp = fmul double %a, %a - %multmp1 = fmul double 2.000000e+00, %a - %multmp2 = fmul double %multmp1, %b - %addtmp = fadd double %multmp, %multmp2 - %multmp3 = fmul double %b, %b - %addtmp4 = fadd double %addtmp, %multmp3 - ret double %addtmp4 - } - -This shows some simple arithmetic. Notice the striking similarity to the -LLVM builder calls that we use to create the instructions. - -:: - - ready> def bar(a) foo(a, 4.0) + bar(31337); - Read function definition: - define double @bar(double %a) { - entry: - %calltmp = call double @foo(double %a, double 4.000000e+00) - %calltmp1 = call double @bar(double 3.133700e+04) - %addtmp = fadd double %calltmp, %calltmp1 - ret double %addtmp - } - -This shows some function calls. Note that this function will take a long -time to execute if you call it. In the future we'll add conditional -control flow to actually make recursion useful :). - -:: - - ready> extern cos(x); - Read extern: - declare double @cos(double) - - ready> cos(1.234); - Read top-level expression: - define double @""() { - entry: - %calltmp = call double @cos(double 1.234000e+00) - ret double %calltmp - } - -This shows an extern for the libm "cos" function, and a call to it. - -:: - - ready> ^D - ; ModuleID = 'my cool jit' - - define double @""() { - entry: - %addtmp = fadd double 4.000000e+00, 5.000000e+00 - ret double %addtmp - } - - define double @foo(double %a, double %b) { - entry: - %multmp = fmul double %a, %a - %multmp1 = fmul double 2.000000e+00, %a - %multmp2 = fmul double %multmp1, %b - %addtmp = fadd double %multmp, %multmp2 - %multmp3 = fmul double %b, %b - %addtmp4 = fadd double %addtmp, %multmp3 - ret double %addtmp4 - } - - define double @bar(double %a) { - entry: - %calltmp = call double @foo(double %a, double 4.000000e+00) - %calltmp1 = call double @bar(double 3.133700e+04) - %addtmp = fadd double %calltmp, %calltmp1 - ret double %addtmp - } - - declare double @cos(double) - - define double @""() { - entry: - %calltmp = call double @cos(double 1.234000e+00) - ret double %calltmp - } - -When you quit the current demo, it dumps out the IR for the entire -module generated. Here you can see the big picture with all the -functions referencing each other. - -This wraps up the third chapter of the Kaleidoscope tutorial. Up next, -we'll describe how to `add JIT codegen and optimizer -support <OCamlLangImpl4.html>`_ to this so we can actually start running -code! - -Full Code Listing -================= - -Here is the complete code listing for our running example, enhanced with -the LLVM code generator. Because this uses the LLVM libraries, we need -to link them in. To do this, we use the -`llvm-config <http://llvm.org/cmds/llvm-config.html>`_ tool to inform -our makefile/command line about which options to use: - -.. code-block:: bash - - # Compile - ocamlbuild toy.byte - # Run - ./toy.byte - -Here is the code: - -\_tags: - :: - - <{lexer,parser}.ml>: use_camlp4, pp(camlp4of) - <*.{byte,native}>: g++, use_llvm, use_llvm_analysis - -myocamlbuild.ml: - .. code-block:: ocaml - - open Ocamlbuild_plugin;; - - ocaml_lib ~extern:true "llvm";; - ocaml_lib ~extern:true "llvm_analysis";; - - flag ["link"; "ocaml"; "g++"] (S[A"-cc"; A"g++"]);; - -token.ml: - .. code-block:: ocaml - - (*===----------------------------------------------------------------------=== - * Lexer Tokens - *===----------------------------------------------------------------------===*) - - (* The lexer returns these 'Kwd' if it is an unknown character, otherwise one of - * these others for known things. *) - type token = - (* commands *) - | Def | Extern - - (* primary *) - | Ident of string | Number of float - - (* unknown *) - | Kwd of char - -lexer.ml: - .. code-block:: ocaml - - (*===----------------------------------------------------------------------=== - * Lexer - *===----------------------------------------------------------------------===*) - - let rec lex = parser - (* Skip any whitespace. *) - | [< ' (' ' | '\n' | '\r' | '\t'); stream >] -> lex stream - - (* identifier: [a-zA-Z][a-zA-Z0-9] *) - | [< ' ('A' .. 'Z' | 'a' .. 'z' as c); stream >] -> - let buffer = Buffer.create 1 in - Buffer.add_char buffer c; - lex_ident buffer stream - - (* number: [0-9.]+ *) - | [< ' ('0' .. '9' as c); stream >] -> - let buffer = Buffer.create 1 in - Buffer.add_char buffer c; - lex_number buffer stream - - (* Comment until end of line. *) - | [< ' ('#'); stream >] -> - lex_comment stream - - (* Otherwise, just return the character as its ascii value. *) - | [< 'c; stream >] -> - [< 'Token.Kwd c; lex stream >] - - (* end of stream. *) - | [< >] -> [< >] - - and lex_number buffer = parser - | [< ' ('0' .. '9' | '.' as c); stream >] -> - Buffer.add_char buffer c; - lex_number buffer stream - | [< stream=lex >] -> - [< 'Token.Number (float_of_string (Buffer.contents buffer)); stream >] - - and lex_ident buffer = parser - | [< ' ('A' .. 'Z' | 'a' .. 'z' | '0' .. '9' as c); stream >] -> - Buffer.add_char buffer c; - lex_ident buffer stream - | [< stream=lex >] -> - match Buffer.contents buffer with - | "def" -> [< 'Token.Def; stream >] - | "extern" -> [< 'Token.Extern; stream >] - | id -> [< 'Token.Ident id; stream >] - - and lex_comment = parser - | [< ' ('\n'); stream=lex >] -> stream - | [< 'c; e=lex_comment >] -> e - | [< >] -> [< >] - -ast.ml: - .. code-block:: ocaml - - (*===----------------------------------------------------------------------=== - * Abstract Syntax Tree (aka Parse Tree) - *===----------------------------------------------------------------------===*) - - (* expr - Base type for all expression nodes. *) - type expr = - (* variant for numeric literals like "1.0". *) - | Number of float - - (* variant for referencing a variable, like "a". *) - | Variable of string - - (* variant for a binary operator. *) - | Binary of char * expr * expr - - (* variant for function calls. *) - | Call of string * expr array - - (* proto - This type represents the "prototype" for a function, which captures - * its name, and its argument names (thus implicitly the number of arguments the - * function takes). *) - type proto = Prototype of string * string array - - (* func - This type represents a function definition itself. *) - type func = Function of proto * expr - -parser.ml: - .. code-block:: ocaml - - (*===---------------------------------------------------------------------=== - * Parser - *===---------------------------------------------------------------------===*) - - (* binop_precedence - This holds the precedence for each binary operator that is - * defined *) - let binop_precedence:(char, int) Hashtbl.t = Hashtbl.create 10 - - (* precedence - Get the precedence of the pending binary operator token. *) - let precedence c = try Hashtbl.find binop_precedence c with Not_found -> -1 - - (* primary - * ::= identifier - * ::= numberexpr - * ::= parenexpr *) - let rec parse_primary = parser - (* numberexpr ::= number *) - | [< 'Token.Number n >] -> Ast.Number n - - (* parenexpr ::= '(' expression ')' *) - | [< 'Token.Kwd '('; e=parse_expr; 'Token.Kwd ')' ?? "expected ')'" >] -> e - - (* identifierexpr - * ::= identifier - * ::= identifier '(' argumentexpr ')' *) - | [< 'Token.Ident id; stream >] -> - let rec parse_args accumulator = parser - | [< e=parse_expr; stream >] -> - begin parser - | [< 'Token.Kwd ','; e=parse_args (e :: accumulator) >] -> e - | [< >] -> e :: accumulator - end stream - | [< >] -> accumulator - in - let rec parse_ident id = parser - (* Call. *) - | [< 'Token.Kwd '('; - args=parse_args []; - 'Token.Kwd ')' ?? "expected ')'">] -> - Ast.Call (id, Array.of_list (List.rev args)) - - (* Simple variable ref. *) - | [< >] -> Ast.Variable id - in - parse_ident id stream - - | [< >] -> raise (Stream.Error "unknown token when expecting an expression.") - - (* binoprhs - * ::= ('+' primary)* *) - and parse_bin_rhs expr_prec lhs stream = - match Stream.peek stream with - (* If this is a binop, find its precedence. *) - | Some (Token.Kwd c) when Hashtbl.mem binop_precedence c -> - let token_prec = precedence c in - - (* If this is a binop that binds at least as tightly as the current binop, - * consume it, otherwise we are done. *) - if token_prec < expr_prec then lhs else begin - (* Eat the binop. *) - Stream.junk stream; - - (* Parse the primary expression after the binary operator. *) - let rhs = parse_primary stream in - - (* Okay, we know this is a binop. *) - let rhs = - match Stream.peek stream with - | Some (Token.Kwd c2) -> - (* If BinOp binds less tightly with rhs than the operator after - * rhs, let the pending operator take rhs as its lhs. *) - let next_prec = precedence c2 in - if token_prec < next_prec - then parse_bin_rhs (token_prec + 1) rhs stream - else rhs - | _ -> rhs - in - - (* Merge lhs/rhs. *) - let lhs = Ast.Binary (c, lhs, rhs) in - parse_bin_rhs expr_prec lhs stream - end - | _ -> lhs - - (* expression - * ::= primary binoprhs *) - and parse_expr = parser - | [< lhs=parse_primary; stream >] -> parse_bin_rhs 0 lhs stream - - (* prototype - * ::= id '(' id* ')' *) - let parse_prototype = - let rec parse_args accumulator = parser - | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e - | [< >] -> accumulator - in - - parser - | [< 'Token.Ident id; - 'Token.Kwd '(' ?? "expected '(' in prototype"; - args=parse_args []; - 'Token.Kwd ')' ?? "expected ')' in prototype" >] -> - (* success. *) - Ast.Prototype (id, Array.of_list (List.rev args)) - - | [< >] -> - raise (Stream.Error "expected function name in prototype") - - (* definition ::= 'def' prototype expression *) - let parse_definition = parser - | [< 'Token.Def; p=parse_prototype; e=parse_expr >] -> - Ast.Function (p, e) - - (* toplevelexpr ::= expression *) - let parse_toplevel = parser - | [< e=parse_expr >] -> - (* Make an anonymous proto. *) - Ast.Function (Ast.Prototype ("", [||]), e) - - (* external ::= 'extern' prototype *) - let parse_extern = parser - | [< 'Token.Extern; e=parse_prototype >] -> e - -codegen.ml: - .. code-block:: ocaml - - (*===----------------------------------------------------------------------=== - * Code Generation - *===----------------------------------------------------------------------===*) - - open Llvm - - exception Error of string - - let context = global_context () - let the_module = create_module context "my cool jit" - let builder = builder context - let named_values:(string, llvalue) Hashtbl.t = Hashtbl.create 10 - let double_type = double_type context - - let rec codegen_expr = function - | Ast.Number n -> const_float double_type n - | Ast.Variable name -> - (try Hashtbl.find named_values name with - | Not_found -> raise (Error "unknown variable name")) - | Ast.Binary (op, lhs, rhs) -> - let lhs_val = codegen_expr lhs in - let rhs_val = codegen_expr rhs in - begin - match op with - | '+' -> build_add lhs_val rhs_val "addtmp" builder - | '-' -> build_sub lhs_val rhs_val "subtmp" builder - | '*' -> build_mul lhs_val rhs_val "multmp" builder - | '<' -> - (* Convert bool 0/1 to double 0.0 or 1.0 *) - let i = build_fcmp Fcmp.Ult lhs_val rhs_val "cmptmp" builder in - build_uitofp i double_type "booltmp" builder - | _ -> raise (Error "invalid binary operator") - end - | Ast.Call (callee, args) -> - (* Look up the name in the module table. *) - let callee = - match lookup_function callee the_module with - | Some callee -> callee - | None -> raise (Error "unknown function referenced") - in - let params = params callee in - - (* If argument mismatch error. *) - if Array.length params == Array.length args then () else - raise (Error "incorrect # arguments passed"); - let args = Array.map codegen_expr args in - build_call callee args "calltmp" builder - - let codegen_proto = function - | Ast.Prototype (name, args) -> - (* Make the function type: double(double,double) etc. *) - let doubles = Array.make (Array.length args) double_type in - let ft = function_type double_type doubles in - let f = - match lookup_function name the_module with - | None -> declare_function name ft the_module - - (* If 'f' conflicted, there was already something named 'name'. If it - * has a body, don't allow redefinition or reextern. *) - | Some f -> - (* If 'f' already has a body, reject this. *) - if block_begin f <> At_end f then - raise (Error "redefinition of function"); - - (* If 'f' took a different number of arguments, reject. *) - if element_type (type_of f) <> ft then - raise (Error "redefinition of function with different # args"); - f - in - - (* Set names for all arguments. *) - Array.iteri (fun i a -> - let n = args.(i) in - set_value_name n a; - Hashtbl.add named_values n a; - ) (params f); - f - - let codegen_func = function - | Ast.Function (proto, body) -> - Hashtbl.clear named_values; - let the_function = codegen_proto proto in - - (* Create a new basic block to start insertion into. *) - let bb = append_block context "entry" the_function in - position_at_end bb builder; - - try - let ret_val = codegen_expr body in - - (* Finish off the function. *) - let _ = build_ret ret_val builder in - - (* Validate the generated code, checking for consistency. *) - Llvm_analysis.assert_valid_function the_function; - - the_function - with e -> - delete_function the_function; - raise e - -toplevel.ml: - .. code-block:: ocaml - - (*===----------------------------------------------------------------------=== - * Top-Level parsing and JIT Driver - *===----------------------------------------------------------------------===*) - - open Llvm - - (* top ::= definition | external | expression | ';' *) - let rec main_loop stream = - match Stream.peek stream with - | None -> () - - (* ignore top-level semicolons. *) - | Some (Token.Kwd ';') -> - Stream.junk stream; - main_loop stream - - | Some token -> - begin - try match token with - | Token.Def -> - let e = Parser.parse_definition stream in - print_endline "parsed a function definition."; - dump_value (Codegen.codegen_func e); - | Token.Extern -> - let e = Parser.parse_extern stream in - print_endline "parsed an extern."; - dump_value (Codegen.codegen_proto e); - | _ -> - (* Evaluate a top-level expression into an anonymous function. *) - let e = Parser.parse_toplevel stream in - print_endline "parsed a top-level expr"; - dump_value (Codegen.codegen_func e); - with Stream.Error s | Codegen.Error s -> - (* Skip token for error recovery. *) - Stream.junk stream; - print_endline s; - end; - print_string "ready> "; flush stdout; - main_loop stream - -toy.ml: - .. code-block:: ocaml - - (*===----------------------------------------------------------------------=== - * Main driver code. - *===----------------------------------------------------------------------===*) - - open Llvm - - let main () = - (* Install standard binary operators. - * 1 is the lowest precedence. *) - Hashtbl.add Parser.binop_precedence '<' 10; - Hashtbl.add Parser.binop_precedence '+' 20; - Hashtbl.add Parser.binop_precedence '-' 20; - Hashtbl.add Parser.binop_precedence '*' 40; (* highest. *) - - (* Prime the first token. *) - print_string "ready> "; flush stdout; - let stream = Lexer.lex (Stream.of_channel stdin) in - - (* Run the main "interpreter loop" now. *) - Toplevel.main_loop stream; - - (* Print out all the generated code. *) - dump_module Codegen.the_module - ;; - - main () - -`Next: Adding JIT and Optimizer Support <OCamlLangImpl4.html>`_ - |