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diff --git a/gnu/llvm/docs/tutorial/OCamlLangImpl4.rst b/gnu/llvm/docs/tutorial/OCamlLangImpl4.rst deleted file mode 100644 index feeba01be24..00000000000 --- a/gnu/llvm/docs/tutorial/OCamlLangImpl4.rst +++ /dev/null @@ -1,915 +0,0 @@ -============================================== -Kaleidoscope: Adding JIT and Optimizer Support -============================================== - -.. contents:: - :local: - -Chapter 4 Introduction -====================== - -Welcome to Chapter 4 of the "`Implementing a language with -LLVM <index.html>`_" tutorial. Chapters 1-3 described the implementation -of a simple language and added support for generating LLVM IR. This -chapter describes two new techniques: adding optimizer support to your -language, and adding JIT compiler support. These additions will -demonstrate how to get nice, efficient code for the Kaleidoscope -language. - -Trivial Constant Folding -======================== - -**Note:** the default ``IRBuilder`` now always includes the constant -folding optimisations below. - -Our demonstration for Chapter 3 is elegant and easy to extend. -Unfortunately, it does not produce wonderful code. For example, when -compiling simple code, we don't get obvious optimizations: - -:: - - ready> def test(x) 1+2+x; - Read function definition: - define double @test(double %x) { - entry: - %addtmp = fadd double 1.000000e+00, 2.000000e+00 - %addtmp1 = fadd double %addtmp, %x - ret double %addtmp1 - } - -This code is a very, very literal transcription of the AST built by -parsing the input. As such, this transcription lacks optimizations like -constant folding (we'd like to get "``add x, 3.0``" in the example -above) as well as other more important optimizations. Constant folding, -in particular, is a very common and very important optimization: so much -so that many language implementors implement constant folding support in -their AST representation. - -With LLVM, you don't need this support in the AST. Since all calls to -build LLVM IR go through the LLVM builder, it would be nice if the -builder itself checked to see if there was a constant folding -opportunity when you call it. If so, it could just do the constant fold -and return the constant instead of creating an instruction. This is -exactly what the ``LLVMFoldingBuilder`` class does. - -All we did was switch from ``LLVMBuilder`` to ``LLVMFoldingBuilder``. -Though we change no other code, we now have all of our instructions -implicitly constant folded without us having to do anything about it. -For example, the input above now compiles to: - -:: - - ready> def test(x) 1+2+x; - Read function definition: - define double @test(double %x) { - entry: - %addtmp = fadd double 3.000000e+00, %x - ret double %addtmp - } - -Well, that was easy :). In practice, we recommend always using -``LLVMFoldingBuilder`` when generating code like this. It has no -"syntactic overhead" for its use (you don't have to uglify your compiler -with constant checks everywhere) and it can dramatically reduce the -amount of LLVM IR that is generated in some cases (particular for -languages with a macro preprocessor or that use a lot of constants). - -On the other hand, the ``LLVMFoldingBuilder`` is limited by the fact -that it does all of its analysis inline with the code as it is built. If -you take a slightly more complex example: - -:: - - ready> def test(x) (1+2+x)*(x+(1+2)); - ready> Read function definition: - define double @test(double %x) { - entry: - %addtmp = fadd double 3.000000e+00, %x - %addtmp1 = fadd double %x, 3.000000e+00 - %multmp = fmul double %addtmp, %addtmp1 - ret double %multmp - } - -In this case, the LHS and RHS of the multiplication are the same value. -We'd really like to see this generate "``tmp = x+3; result = tmp*tmp;``" -instead of computing "``x*3``" twice. - -Unfortunately, no amount of local analysis will be able to detect and -correct this. This requires two transformations: reassociation of -expressions (to make the add's lexically identical) and Common -Subexpression Elimination (CSE) to delete the redundant add instruction. -Fortunately, LLVM provides a broad range of optimizations that you can -use, in the form of "passes". - -LLVM Optimization Passes -======================== - -LLVM provides many optimization passes, which do many different sorts of -things and have different tradeoffs. Unlike other systems, LLVM doesn't -hold to the mistaken notion that one set of optimizations is right for -all languages and for all situations. LLVM allows a compiler implementor -to make complete decisions about what optimizations to use, in which -order, and in what situation. - -As a concrete example, LLVM supports both "whole module" passes, which -look across as large of body of code as they can (often a whole file, -but if run at link time, this can be a substantial portion of the whole -program). It also supports and includes "per-function" passes which just -operate on a single function at a time, without looking at other -functions. For more information on passes and how they are run, see the -`How to Write a Pass <../WritingAnLLVMPass.html>`_ document and the -`List of LLVM Passes <../Passes.html>`_. - -For Kaleidoscope, we are currently generating functions on the fly, one -at a time, as the user types them in. We aren't shooting for the -ultimate optimization experience in this setting, but we also want to -catch the easy and quick stuff where possible. As such, we will choose -to run a few per-function optimizations as the user types the function -in. If we wanted to make a "static Kaleidoscope compiler", we would use -exactly the code we have now, except that we would defer running the -optimizer until the entire file has been parsed. - -In order to get per-function optimizations going, we need to set up a -`Llvm.PassManager <../WritingAnLLVMPass.html#what-passmanager-does>`_ to hold and -organize the LLVM optimizations that we want to run. Once we have that, -we can add a set of optimizations to run. The code looks like this: - -.. code-block:: ocaml - - (* Create the JIT. *) - let the_execution_engine = ExecutionEngine.create Codegen.the_module in - let the_fpm = PassManager.create_function Codegen.the_module in - - (* Set up the optimizer pipeline. Start with registering info about how the - * target lays out data structures. *) - DataLayout.add (ExecutionEngine.target_data the_execution_engine) the_fpm; - - (* Do simple "peephole" optimizations and bit-twiddling optzn. *) - add_instruction_combining the_fpm; - - (* reassociate expressions. *) - add_reassociation the_fpm; - - (* Eliminate Common SubExpressions. *) - add_gvn the_fpm; - - (* Simplify the control flow graph (deleting unreachable blocks, etc). *) - add_cfg_simplification the_fpm; - - ignore (PassManager.initialize the_fpm); - - (* Run the main "interpreter loop" now. *) - Toplevel.main_loop the_fpm the_execution_engine stream; - -The meat of the matter here, is the definition of "``the_fpm``". It -requires a pointer to the ``the_module`` to construct itself. Once it is -set up, we use a series of "add" calls to add a bunch of LLVM passes. -The first pass is basically boilerplate, it adds a pass so that later -optimizations know how the data structures in the program are laid out. -The "``the_execution_engine``" variable is related to the JIT, which we -will get to in the next section. - -In this case, we choose to add 4 optimization passes. The passes we -chose here are a pretty standard set of "cleanup" optimizations that are -useful for a wide variety of code. I won't delve into what they do but, -believe me, they are a good starting place :). - -Once the ``Llvm.PassManager.`` is set up, we need to make use of it. We -do this by running it after our newly created function is constructed -(in ``Codegen.codegen_func``), but before it is returned to the client: - -.. code-block:: ocaml - - let codegen_func the_fpm = function - ... - 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; - - (* Optimize the function. *) - let _ = PassManager.run_function the_function the_fpm in - - the_function - -As you can see, this is pretty straightforward. The ``the_fpm`` -optimizes and updates the LLVM Function\* in place, improving -(hopefully) its body. With this in place, we can try our test above -again: - -:: - - ready> def test(x) (1+2+x)*(x+(1+2)); - ready> Read function definition: - define double @test(double %x) { - entry: - %addtmp = fadd double %x, 3.000000e+00 - %multmp = fmul double %addtmp, %addtmp - ret double %multmp - } - -As expected, we now get our nicely optimized code, saving a floating -point add instruction from every execution of this function. - -LLVM provides a wide variety of optimizations that can be used in -certain circumstances. Some `documentation about the various -passes <../Passes.html>`_ is available, but it isn't very complete. -Another good source of ideas can come from looking at the passes that -``Clang`` runs to get started. The "``opt``" tool allows you to -experiment with passes from the command line, so you can see if they do -anything. - -Now that we have reasonable code coming out of our front-end, lets talk -about executing it! - -Adding a JIT Compiler -===================== - -Code that is available in LLVM IR can have a wide variety of tools -applied to it. For example, you can run optimizations on it (as we did -above), you can dump it out in textual or binary forms, you can compile -the code to an assembly file (.s) for some target, or you can JIT -compile it. The nice thing about the LLVM IR representation is that it -is the "common currency" between many different parts of the compiler. - -In this section, we'll add JIT compiler support to our interpreter. The -basic idea that we want for Kaleidoscope is to have the user enter -function bodies as they do now, but immediately evaluate the top-level -expressions they type in. For example, if they type in "1 + 2;", we -should evaluate and print out 3. If they define a function, they should -be able to call it from the command line. - -In order to do this, we first declare and initialize the JIT. This is -done by adding a global variable and a call in ``main``: - -.. code-block:: ocaml - - ... - let main () = - ... - (* Create the JIT. *) - let the_execution_engine = ExecutionEngine.create Codegen.the_module in - ... - -This creates an abstract "Execution Engine" which can be either a JIT -compiler or the LLVM interpreter. LLVM will automatically pick a JIT -compiler for you if one is available for your platform, otherwise it -will fall back to the interpreter. - -Once the ``Llvm_executionengine.ExecutionEngine.t`` is created, the JIT -is ready to be used. There are a variety of APIs that are useful, but -the simplest one is the -"``Llvm_executionengine.ExecutionEngine.run_function``" function. This -method JIT compiles the specified LLVM Function and returns a function -pointer to the generated machine code. In our case, this means that we -can change the code that parses a top-level expression to look like -this: - -.. code-block:: ocaml - - (* Evaluate a top-level expression into an anonymous function. *) - let e = Parser.parse_toplevel stream in - print_endline "parsed a top-level expr"; - let the_function = Codegen.codegen_func the_fpm e in - dump_value the_function; - - (* JIT the function, returning a function pointer. *) - let result = ExecutionEngine.run_function the_function [||] - the_execution_engine in - - print_string "Evaluated to "; - print_float (GenericValue.as_float Codegen.double_type result); - print_newline (); - -Recall that we compile top-level expressions into a self-contained LLVM -function that takes no arguments and returns the computed double. -Because the LLVM JIT compiler matches the native platform ABI, this -means that you can just cast the result pointer to a function pointer of -that type and call it directly. This means, there is no difference -between JIT compiled code and native machine code that is statically -linked into your application. - -With just these two changes, lets see how Kaleidoscope works now! - -:: - - ready> 4+5; - define double @""() { - entry: - ret double 9.000000e+00 - } - - Evaluated to 9.000000 - -Well this looks like it is basically working. The dump of the function -shows the "no argument function that always returns double" that we -synthesize for each top level expression that is typed in. This -demonstrates very basic functionality, but can we do more? - -:: - - ready> def testfunc(x y) x + y*2; - Read function definition: - define double @testfunc(double %x, double %y) { - entry: - %multmp = fmul double %y, 2.000000e+00 - %addtmp = fadd double %multmp, %x - ret double %addtmp - } - - ready> testfunc(4, 10); - define double @""() { - entry: - %calltmp = call double @testfunc(double 4.000000e+00, double 1.000000e+01) - ret double %calltmp - } - - Evaluated to 24.000000 - -This illustrates that we can now call user code, but there is something -a bit subtle going on here. Note that we only invoke the JIT on the -anonymous functions that *call testfunc*, but we never invoked it on -*testfunc* itself. What actually happened here is that the JIT scanned -for all non-JIT'd functions transitively called from the anonymous -function and compiled all of them before returning from -``run_function``. - -The JIT provides a number of other more advanced interfaces for things -like freeing allocated machine code, rejit'ing functions to update them, -etc. However, even with this simple code, we get some surprisingly -powerful capabilities - check this out (I removed the dump of the -anonymous functions, you should get the idea by now :) : - -:: - - ready> extern sin(x); - Read extern: - declare double @sin(double) - - ready> extern cos(x); - Read extern: - declare double @cos(double) - - ready> sin(1.0); - Evaluated to 0.841471 - - ready> def foo(x) sin(x)*sin(x) + cos(x)*cos(x); - Read function definition: - define double @foo(double %x) { - entry: - %calltmp = call double @sin(double %x) - %multmp = fmul double %calltmp, %calltmp - %calltmp2 = call double @cos(double %x) - %multmp4 = fmul double %calltmp2, %calltmp2 - %addtmp = fadd double %multmp, %multmp4 - ret double %addtmp - } - - ready> foo(4.0); - Evaluated to 1.000000 - -Whoa, how does the JIT know about sin and cos? The answer is -surprisingly simple: in this example, the JIT started execution of a -function and got to a function call. It realized that the function was -not yet JIT compiled and invoked the standard set of routines to resolve -the function. In this case, there is no body defined for the function, -so the JIT ended up calling "``dlsym("sin")``" on the Kaleidoscope -process itself. Since "``sin``" is defined within the JIT's address -space, it simply patches up calls in the module to call the libm version -of ``sin`` directly. - -The LLVM JIT provides a number of interfaces (look in the -``llvm_executionengine.mli`` file) for controlling how unknown functions -get resolved. It allows you to establish explicit mappings between IR -objects and addresses (useful for LLVM global variables that you want to -map to static tables, for example), allows you to dynamically decide on -the fly based on the function name, and even allows you to have the JIT -compile functions lazily the first time they're called. - -One interesting application of this is that we can now extend the -language by writing arbitrary C code to implement operations. For -example, if we add: - -.. code-block:: c++ - - /* putchard - putchar that takes a double and returns 0. */ - extern "C" - double putchard(double X) { - putchar((char)X); - return 0; - } - -Now we can produce simple output to the console by using things like: -"``extern putchard(x); putchard(120);``", which prints a lowercase 'x' -on the console (120 is the ASCII code for 'x'). Similar code could be -used to implement file I/O, console input, and many other capabilities -in Kaleidoscope. - -This completes the JIT and optimizer chapter of the Kaleidoscope -tutorial. At this point, we can compile a non-Turing-complete -programming language, optimize and JIT compile it in a user-driven way. -Next up we'll look into `extending the language with control flow -constructs <OCamlLangImpl5.html>`_, tackling some interesting LLVM IR -issues along the way. - -Full Code Listing -================= - -Here is the complete code listing for our running example, enhanced with -the LLVM JIT and optimizer. To build this example, 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 - <*.{byte,native}>: use_llvm_executionengine, use_llvm_target - <*.{byte,native}>: use_llvm_scalar_opts, use_bindings - -myocamlbuild.ml: - .. code-block:: ocaml - - open Ocamlbuild_plugin;; - - ocaml_lib ~extern:true "llvm";; - ocaml_lib ~extern:true "llvm_analysis";; - ocaml_lib ~extern:true "llvm_executionengine";; - ocaml_lib ~extern:true "llvm_target";; - ocaml_lib ~extern:true "llvm_scalar_opts";; - - flag ["link"; "ocaml"; "g++"] (S[A"-cc"; A"g++"]);; - dep ["link"; "ocaml"; "use_bindings"] ["bindings.o"];; - -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 the_fpm = 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; - - (* Optimize the function. *) - let _ = PassManager.run_function the_function the_fpm in - - the_function - with e -> - delete_function the_function; - raise e - -toplevel.ml: - .. code-block:: ocaml - - (*===----------------------------------------------------------------------=== - * Top-Level parsing and JIT Driver - *===----------------------------------------------------------------------===*) - - open Llvm - open Llvm_executionengine - - (* top ::= definition | external | expression | ';' *) - let rec main_loop the_fpm the_execution_engine stream = - match Stream.peek stream with - | None -> () - - (* ignore top-level semicolons. *) - | Some (Token.Kwd ';') -> - Stream.junk stream; - main_loop the_fpm the_execution_engine 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 the_fpm 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"; - let the_function = Codegen.codegen_func the_fpm e in - dump_value the_function; - - (* JIT the function, returning a function pointer. *) - let result = ExecutionEngine.run_function the_function [||] - the_execution_engine in - - print_string "Evaluated to "; - print_float (GenericValue.as_float Codegen.double_type result); - print_newline (); - 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 the_fpm the_execution_engine stream - -toy.ml: - .. code-block:: ocaml - - (*===----------------------------------------------------------------------=== - * Main driver code. - *===----------------------------------------------------------------------===*) - - open Llvm - open Llvm_executionengine - open Llvm_target - open Llvm_scalar_opts - - let main () = - ignore (initialize_native_target ()); - - (* 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 - - (* Create the JIT. *) - let the_execution_engine = ExecutionEngine.create Codegen.the_module in - let the_fpm = PassManager.create_function Codegen.the_module in - - (* Set up the optimizer pipeline. Start with registering info about how the - * target lays out data structures. *) - DataLayout.add (ExecutionEngine.target_data the_execution_engine) the_fpm; - - (* Do simple "peephole" optimizations and bit-twiddling optzn. *) - add_instruction_combination the_fpm; - - (* reassociate expressions. *) - add_reassociation the_fpm; - - (* Eliminate Common SubExpressions. *) - add_gvn the_fpm; - - (* Simplify the control flow graph (deleting unreachable blocks, etc). *) - add_cfg_simplification the_fpm; - - ignore (PassManager.initialize the_fpm); - - (* Run the main "interpreter loop" now. *) - Toplevel.main_loop the_fpm the_execution_engine stream; - - (* Print out all the generated code. *) - dump_module Codegen.the_module - ;; - - main () - -bindings.c - .. code-block:: c - - #include <stdio.h> - - /* putchard - putchar that takes a double and returns 0. */ - extern double putchard(double X) { - putchar((char)X); - return 0; - } - -`Next: Extending the language: control flow <OCamlLangImpl5.html>`_ - |