| ============================================================ |
| Kaleidoscope: Extending the Language: User-defined Operators |
| ============================================================ |
| |
| .. contents:: |
| :local: |
| |
| Chapter 6 Introduction |
| ====================== |
| |
| Welcome to Chapter 6 of the "`Implementing a language with |
| LLVM <index.html>`_" tutorial. At this point in our tutorial, we now |
| have a fully functional language that is fairly minimal, but also |
| useful. There is still one big problem with it, however. Our language |
| doesn't have many useful operators (like division, logical negation, or |
| even any comparisons besides less-than). |
| |
| This chapter of the tutorial takes a wild digression into adding |
| user-defined operators to the simple and beautiful Kaleidoscope |
| language. This digression now gives us a simple and ugly language in |
| some ways, but also a powerful one at the same time. One of the great |
| things about creating your own language is that you get to decide what |
| is good or bad. In this tutorial we'll assume that it is okay to use |
| this as a way to show some interesting parsing techniques. |
| |
| At the end of this tutorial, we'll run through an example Kaleidoscope |
| application that `renders the Mandelbrot set <#kicking-the-tires>`_. This gives an |
| example of what you can build with Kaleidoscope and its feature set. |
| |
| User-defined Operators: the Idea |
| ================================ |
| |
| The "operator overloading" that we will add to Kaleidoscope is more |
| general than languages like C++. In C++, you are only allowed to |
| redefine existing operators: you can't programmatically change the |
| grammar, introduce new operators, change precedence levels, etc. In this |
| chapter, we will add this capability to Kaleidoscope, which will let the |
| user round out the set of operators that are supported. |
| |
| The point of going into user-defined operators in a tutorial like this |
| is to show the power and flexibility of using a hand-written parser. |
| Thus far, the parser we have been implementing uses recursive descent |
| for most parts of the grammar and operator precedence parsing for the |
| expressions. See `Chapter 2 <OCamlLangImpl2.html>`_ for details. Without |
| using operator precedence parsing, it would be very difficult to allow |
| the programmer to introduce new operators into the grammar: the grammar |
| is dynamically extensible as the JIT runs. |
| |
| The two specific features we'll add are programmable unary operators |
| (right now, Kaleidoscope has no unary operators at all) as well as |
| binary operators. An example of this is: |
| |
| :: |
| |
| # Logical unary not. |
| def unary!(v) |
| if v then |
| 0 |
| else |
| 1; |
| |
| # Define > with the same precedence as <. |
| def binary> 10 (LHS RHS) |
| RHS < LHS; |
| |
| # Binary "logical or", (note that it does not "short circuit") |
| def binary| 5 (LHS RHS) |
| if LHS then |
| 1 |
| else if RHS then |
| 1 |
| else |
| 0; |
| |
| # Define = with slightly lower precedence than relationals. |
| def binary= 9 (LHS RHS) |
| !(LHS < RHS | LHS > RHS); |
| |
| Many languages aspire to being able to implement their standard runtime |
| library in the language itself. In Kaleidoscope, we can implement |
| significant parts of the language in the library! |
| |
| We will break down implementation of these features into two parts: |
| implementing support for user-defined binary operators and adding unary |
| operators. |
| |
| User-defined Binary Operators |
| ============================= |
| |
| Adding support for user-defined binary operators is pretty simple with |
| our current framework. We'll first add support for the unary/binary |
| keywords: |
| |
| .. code-block:: ocaml |
| |
| type token = |
| ... |
| (* operators *) |
| | Binary | Unary |
| |
| ... |
| |
| and lex_ident buffer = parser |
| ... |
| | "for" -> [< 'Token.For; stream >] |
| | "in" -> [< 'Token.In; stream >] |
| | "binary" -> [< 'Token.Binary; stream >] |
| | "unary" -> [< 'Token.Unary; stream >] |
| |
| This just adds lexer support for the unary and binary keywords, like we |
| did in `previous chapters <OCamlLangImpl5.html#lexer-extensions-for-if-then-else>`_. One nice |
| thing about our current AST, is that we represent binary operators with |
| full generalisation by using their ASCII code as the opcode. For our |
| extended operators, we'll use this same representation, so we don't need |
| any new AST or parser support. |
| |
| On the other hand, we have to be able to represent the definitions of |
| these new operators, in the "def binary\| 5" part of the function |
| definition. In our grammar so far, the "name" for the function |
| definition is parsed as the "prototype" production and into the |
| ``Ast.Prototype`` AST node. To represent our new user-defined operators |
| as prototypes, we have to extend the ``Ast.Prototype`` AST node like |
| this: |
| |
| .. code-block:: ocaml |
| |
| (* 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 |
| | BinOpPrototype of string * string array * int |
| |
| Basically, in addition to knowing a name for the prototype, we now keep |
| track of whether it was an operator, and if it was, what precedence |
| level the operator is at. The precedence is only used for binary |
| operators (as you'll see below, it just doesn't apply for unary |
| operators). Now that we have a way to represent the prototype for a |
| user-defined operator, we need to parse it: |
| |
| .. code-block:: ocaml |
| |
| (* prototype |
| * ::= id '(' id* ')' |
| * ::= binary LETTER number? (id, id) |
| * ::= unary LETTER number? (id) *) |
| let parse_prototype = |
| let rec parse_args accumulator = parser |
| | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e |
| | [< >] -> accumulator |
| in |
| let parse_operator = parser |
| | [< 'Token.Unary >] -> "unary", 1 |
| | [< 'Token.Binary >] -> "binary", 2 |
| in |
| let parse_binary_precedence = parser |
| | [< 'Token.Number n >] -> int_of_float n |
| | [< >] -> 30 |
| 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)) |
| | [< (prefix, kind)=parse_operator; |
| 'Token.Kwd op ?? "expected an operator"; |
| (* Read the precedence if present. *) |
| binary_precedence=parse_binary_precedence; |
| 'Token.Kwd '(' ?? "expected '(' in prototype"; |
| args=parse_args []; |
| 'Token.Kwd ')' ?? "expected ')' in prototype" >] -> |
| let name = prefix ^ (String.make 1 op) in |
| let args = Array.of_list (List.rev args) in |
| |
| (* Verify right number of arguments for operator. *) |
| if Array.length args != kind |
| then raise (Stream.Error "invalid number of operands for operator") |
| else |
| if kind == 1 then |
| Ast.Prototype (name, args) |
| else |
| Ast.BinOpPrototype (name, args, binary_precedence) |
| | [< >] -> |
| raise (Stream.Error "expected function name in prototype") |
| |
| This is all fairly straightforward parsing code, and we have already |
| seen a lot of similar code in the past. One interesting part about the |
| code above is the couple lines that set up ``name`` for binary |
| operators. This builds names like "binary@" for a newly defined "@" |
| operator. This then takes advantage of the fact that symbol names in the |
| LLVM symbol table are allowed to have any character in them, including |
| embedded nul characters. |
| |
| The next interesting thing to add, is codegen support for these binary |
| operators. Given our current structure, this is a simple addition of a |
| default case for our existing binary operator node: |
| |
| .. code-block:: ocaml |
| |
| let codegen_expr = function |
| ... |
| | 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 |
| | _ -> |
| (* If it wasn't a builtin binary operator, it must be a user defined |
| * one. Emit a call to it. *) |
| let callee = "binary" ^ (String.make 1 op) in |
| let callee = |
| match lookup_function callee the_module with |
| | Some callee -> callee |
| | None -> raise (Error "binary operator not found!") |
| in |
| build_call callee [|lhs_val; rhs_val|] "binop" builder |
| end |
| |
| As you can see above, the new code is actually really simple. It just |
| does a lookup for the appropriate operator in the symbol table and |
| generates a function call to it. Since user-defined operators are just |
| built as normal functions (because the "prototype" boils down to a |
| function with the right name) everything falls into place. |
| |
| The final piece of code we are missing, is a bit of top level magic: |
| |
| .. code-block:: ocaml |
| |
| let codegen_func the_fpm = function |
| | Ast.Function (proto, body) -> |
| Hashtbl.clear named_values; |
| let the_function = codegen_proto proto in |
| |
| (* If this is an operator, install it. *) |
| begin match proto with |
| | Ast.BinOpPrototype (name, args, prec) -> |
| let op = name.[String.length name - 1] in |
| Hashtbl.add Parser.binop_precedence op prec; |
| | _ -> () |
| end; |
| |
| (* Create a new basic block to start insertion into. *) |
| let bb = append_block context "entry" the_function in |
| position_at_end bb builder; |
| ... |
| |
| Basically, before codegening a function, if it is a user-defined |
| operator, we register it in the precedence table. This allows the binary |
| operator parsing logic we already have in place to handle it. Since we |
| are working on a fully-general operator precedence parser, this is all |
| we need to do to "extend the grammar". |
| |
| Now we have useful user-defined binary operators. This builds a lot on |
| the previous framework we built for other operators. Adding unary |
| operators is a bit more challenging, because we don't have any framework |
| for it yet - lets see what it takes. |
| |
| User-defined Unary Operators |
| ============================ |
| |
| Since we don't currently support unary operators in the Kaleidoscope |
| language, we'll need to add everything to support them. Above, we added |
| simple support for the 'unary' keyword to the lexer. In addition to |
| that, we need an AST node: |
| |
| .. code-block:: ocaml |
| |
| type expr = |
| ... |
| (* variant for a unary operator. *) |
| | Unary of char * expr |
| ... |
| |
| This AST node is very simple and obvious by now. It directly mirrors the |
| binary operator AST node, except that it only has one child. With this, |
| we need to add the parsing logic. Parsing a unary operator is pretty |
| simple: we'll add a new function to do it: |
| |
| .. code-block:: ocaml |
| |
| (* unary |
| * ::= primary |
| * ::= '!' unary *) |
| and parse_unary = parser |
| (* If this is a unary operator, read it. *) |
| | [< 'Token.Kwd op when op != '(' && op != ')'; operand=parse_expr >] -> |
| Ast.Unary (op, operand) |
| |
| (* If the current token is not an operator, it must be a primary expr. *) |
| | [< stream >] -> parse_primary stream |
| |
| The grammar we add is pretty straightforward here. If we see a unary |
| operator when parsing a primary operator, we eat the operator as a |
| prefix and parse the remaining piece as another unary operator. This |
| allows us to handle multiple unary operators (e.g. "!!x"). Note that |
| unary operators can't have ambiguous parses like binary operators can, |
| so there is no need for precedence information. |
| |
| The problem with this function, is that we need to call ParseUnary from |
| somewhere. To do this, we change previous callers of ParsePrimary to |
| call ``parse_unary`` instead: |
| |
| .. code-block:: ocaml |
| |
| (* binoprhs |
| * ::= ('+' primary)* *) |
| and parse_bin_rhs expr_prec lhs stream = |
| ... |
| (* Parse the unary expression after the binary operator. *) |
| let rhs = parse_unary stream in |
| ... |
| |
| ... |
| |
| (* expression |
| * ::= primary binoprhs *) |
| and parse_expr = parser |
| | [< lhs=parse_unary; stream >] -> parse_bin_rhs 0 lhs stream |
| |
| With these two simple changes, we are now able to parse unary operators |
| and build the AST for them. Next up, we need to add parser support for |
| prototypes, to parse the unary operator prototype. We extend the binary |
| operator code above with: |
| |
| .. code-block:: ocaml |
| |
| (* prototype |
| * ::= id '(' id* ')' |
| * ::= binary LETTER number? (id, id) |
| * ::= unary LETTER number? (id) *) |
| let parse_prototype = |
| let rec parse_args accumulator = parser |
| | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e |
| | [< >] -> accumulator |
| in |
| let parse_operator = parser |
| | [< 'Token.Unary >] -> "unary", 1 |
| | [< 'Token.Binary >] -> "binary", 2 |
| in |
| let parse_binary_precedence = parser |
| | [< 'Token.Number n >] -> int_of_float n |
| | [< >] -> 30 |
| 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)) |
| | [< (prefix, kind)=parse_operator; |
| 'Token.Kwd op ?? "expected an operator"; |
| (* Read the precedence if present. *) |
| binary_precedence=parse_binary_precedence; |
| 'Token.Kwd '(' ?? "expected '(' in prototype"; |
| args=parse_args []; |
| 'Token.Kwd ')' ?? "expected ')' in prototype" >] -> |
| let name = prefix ^ (String.make 1 op) in |
| let args = Array.of_list (List.rev args) in |
| |
| (* Verify right number of arguments for operator. *) |
| if Array.length args != kind |
| then raise (Stream.Error "invalid number of operands for operator") |
| else |
| if kind == 1 then |
| Ast.Prototype (name, args) |
| else |
| Ast.BinOpPrototype (name, args, binary_precedence) |
| | [< >] -> |
| raise (Stream.Error "expected function name in prototype") |
| |
| As with binary operators, we name unary operators with a name that |
| includes the operator character. This assists us at code generation |
| time. Speaking of, the final piece we need to add is codegen support for |
| unary operators. It looks like this: |
| |
| .. code-block:: ocaml |
| |
| let rec codegen_expr = function |
| ... |
| | Ast.Unary (op, operand) -> |
| let operand = codegen_expr operand in |
| let callee = "unary" ^ (String.make 1 op) in |
| let callee = |
| match lookup_function callee the_module with |
| | Some callee -> callee |
| | None -> raise (Error "unknown unary operator") |
| in |
| build_call callee [|operand|] "unop" builder |
| |
| This code is similar to, but simpler than, the code for binary |
| operators. It is simpler primarily because it doesn't need to handle any |
| predefined operators. |
| |
| Kicking the Tires |
| ================= |
| |
| It is somewhat hard to believe, but with a few simple extensions we've |
| covered in the last chapters, we have grown a real-ish language. With |
| this, we can do a lot of interesting things, including I/O, math, and a |
| bunch of other things. For example, we can now add a nice sequencing |
| operator (printd is defined to print out the specified value and a |
| newline): |
| |
| :: |
| |
| ready> extern printd(x); |
| Read extern: declare double @printd(double) |
| ready> def binary : 1 (x y) 0; # Low-precedence operator that ignores operands. |
| .. |
| ready> printd(123) : printd(456) : printd(789); |
| 123.000000 |
| 456.000000 |
| 789.000000 |
| Evaluated to 0.000000 |
| |
| We can also define a bunch of other "primitive" operations, such as: |
| |
| :: |
| |
| # Logical unary not. |
| def unary!(v) |
| if v then |
| 0 |
| else |
| 1; |
| |
| # Unary negate. |
| def unary-(v) |
| 0-v; |
| |
| # Define > with the same precedence as <. |
| def binary> 10 (LHS RHS) |
| RHS < LHS; |
| |
| # Binary logical or, which does not short circuit. |
| def binary| 5 (LHS RHS) |
| if LHS then |
| 1 |
| else if RHS then |
| 1 |
| else |
| 0; |
| |
| # Binary logical and, which does not short circuit. |
| def binary& 6 (LHS RHS) |
| if !LHS then |
| 0 |
| else |
| !!RHS; |
| |
| # Define = with slightly lower precedence than relationals. |
| def binary = 9 (LHS RHS) |
| !(LHS < RHS | LHS > RHS); |
| |
| Given the previous if/then/else support, we can also define interesting |
| functions for I/O. For example, the following prints out a character |
| whose "density" reflects the value passed in: the lower the value, the |
| denser the character: |
| |
| :: |
| |
| ready> |
| |
| extern putchard(char) |
| def printdensity(d) |
| if d > 8 then |
| putchard(32) # ' ' |
| else if d > 4 then |
| putchard(46) # '.' |
| else if d > 2 then |
| putchard(43) # '+' |
| else |
| putchard(42); # '*' |
| ... |
| ready> printdensity(1): printdensity(2): printdensity(3) : |
| printdensity(4): printdensity(5): printdensity(9): putchard(10); |
| *++.. |
| Evaluated to 0.000000 |
| |
| Based on these simple primitive operations, we can start to define more |
| interesting things. For example, here's a little function that solves |
| for the number of iterations it takes a function in the complex plane to |
| converge: |
| |
| :: |
| |
| # determine whether the specific location diverges. |
| # Solve for z = z^2 + c in the complex plane. |
| def mandelconverger(real imag iters creal cimag) |
| if iters > 255 | (real*real + imag*imag > 4) then |
| iters |
| else |
| mandelconverger(real*real - imag*imag + creal, |
| 2*real*imag + cimag, |
| iters+1, creal, cimag); |
| |
| # return the number of iterations required for the iteration to escape |
| def mandelconverge(real imag) |
| mandelconverger(real, imag, 0, real, imag); |
| |
| This "z = z\ :sup:`2`\ + c" function is a beautiful little creature |
| that is the basis for computation of the `Mandelbrot |
| Set <http://en.wikipedia.org/wiki/Mandelbrot_set>`_. Our |
| ``mandelconverge`` function returns the number of iterations that it |
| takes for a complex orbit to escape, saturating to 255. This is not a |
| very useful function by itself, but if you plot its value over a |
| two-dimensional plane, you can see the Mandelbrot set. Given that we are |
| limited to using putchard here, our amazing graphical output is limited, |
| but we can whip together something using the density plotter above: |
| |
| :: |
| |
| # compute and plot the mandelbrot set with the specified 2 dimensional range |
| # info. |
| def mandelhelp(xmin xmax xstep ymin ymax ystep) |
| for y = ymin, y < ymax, ystep in ( |
| (for x = xmin, x < xmax, xstep in |
| printdensity(mandelconverge(x,y))) |
| : putchard(10) |
| ) |
| |
| # mandel - This is a convenient helper function for plotting the mandelbrot set |
| # from the specified position with the specified Magnification. |
| def mandel(realstart imagstart realmag imagmag) |
| mandelhelp(realstart, realstart+realmag*78, realmag, |
| imagstart, imagstart+imagmag*40, imagmag); |
| |
| Given this, we can try plotting out the mandelbrot set! Lets try it out: |
| |
| :: |
| |
| ready> mandel(-2.3, -1.3, 0.05, 0.07); |
| *******************************+++++++++++************************************* |
| *************************+++++++++++++++++++++++******************************* |
| **********************+++++++++++++++++++++++++++++**************************** |
| *******************+++++++++++++++++++++.. ...++++++++************************* |
| *****************++++++++++++++++++++++.... ...+++++++++*********************** |
| ***************+++++++++++++++++++++++..... ...+++++++++********************* |
| **************+++++++++++++++++++++++.... ....+++++++++******************** |
| *************++++++++++++++++++++++...... .....++++++++******************* |
| ************+++++++++++++++++++++....... .......+++++++****************** |
| ***********+++++++++++++++++++.... ... .+++++++***************** |
| **********+++++++++++++++++....... .+++++++**************** |
| *********++++++++++++++........... ...+++++++*************** |
| ********++++++++++++............ ...++++++++************** |
| ********++++++++++... .......... .++++++++************** |
| *******+++++++++..... .+++++++++************* |
| *******++++++++...... ..+++++++++************* |
| *******++++++....... ..+++++++++************* |
| *******+++++...... ..+++++++++************* |
| *******.... .... ...+++++++++************* |
| *******.... . ...+++++++++************* |
| *******+++++...... ...+++++++++************* |
| *******++++++....... ..+++++++++************* |
| *******++++++++...... .+++++++++************* |
| *******+++++++++..... ..+++++++++************* |
| ********++++++++++... .......... .++++++++************** |
| ********++++++++++++............ ...++++++++************** |
| *********++++++++++++++.......... ...+++++++*************** |
| **********++++++++++++++++........ .+++++++**************** |
| **********++++++++++++++++++++.... ... ..+++++++**************** |
| ***********++++++++++++++++++++++....... .......++++++++***************** |
| ************+++++++++++++++++++++++...... ......++++++++****************** |
| **************+++++++++++++++++++++++.... ....++++++++******************** |
| ***************+++++++++++++++++++++++..... ...+++++++++********************* |
| *****************++++++++++++++++++++++.... ...++++++++*********************** |
| *******************+++++++++++++++++++++......++++++++************************* |
| *********************++++++++++++++++++++++.++++++++*************************** |
| *************************+++++++++++++++++++++++******************************* |
| ******************************+++++++++++++************************************ |
| ******************************************************************************* |
| ******************************************************************************* |
| ******************************************************************************* |
| Evaluated to 0.000000 |
| ready> mandel(-2, -1, 0.02, 0.04); |
| **************************+++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| ***********************++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| *********************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++. |
| *******************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++... |
| *****************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++..... |
| ***************++++++++++++++++++++++++++++++++++++++++++++++++++++++++........ |
| **************++++++++++++++++++++++++++++++++++++++++++++++++++++++........... |
| ************+++++++++++++++++++++++++++++++++++++++++++++++++++++.............. |
| ***********++++++++++++++++++++++++++++++++++++++++++++++++++........ . |
| **********++++++++++++++++++++++++++++++++++++++++++++++............. |
| ********+++++++++++++++++++++++++++++++++++++++++++.................. |
| *******+++++++++++++++++++++++++++++++++++++++....................... |
| ******+++++++++++++++++++++++++++++++++++........................... |
| *****++++++++++++++++++++++++++++++++............................ |
| *****++++++++++++++++++++++++++++............................... |
| ****++++++++++++++++++++++++++...... ......................... |
| ***++++++++++++++++++++++++......... ...... ........... |
| ***++++++++++++++++++++++............ |
| **+++++++++++++++++++++.............. |
| **+++++++++++++++++++................ |
| *++++++++++++++++++................. |
| *++++++++++++++++............ ... |
| *++++++++++++++.............. |
| *+++....++++................ |
| *.......... ........... |
| * |
| *.......... ........... |
| *+++....++++................ |
| *++++++++++++++.............. |
| *++++++++++++++++............ ... |
| *++++++++++++++++++................. |
| **+++++++++++++++++++................ |
| **+++++++++++++++++++++.............. |
| ***++++++++++++++++++++++............ |
| ***++++++++++++++++++++++++......... ...... ........... |
| ****++++++++++++++++++++++++++...... ......................... |
| *****++++++++++++++++++++++++++++............................... |
| *****++++++++++++++++++++++++++++++++............................ |
| ******+++++++++++++++++++++++++++++++++++........................... |
| *******+++++++++++++++++++++++++++++++++++++++....................... |
| ********+++++++++++++++++++++++++++++++++++++++++++.................. |
| Evaluated to 0.000000 |
| ready> mandel(-0.9, -1.4, 0.02, 0.03); |
| ******************************************************************************* |
| ******************************************************************************* |
| ******************************************************************************* |
| **********+++++++++++++++++++++************************************************ |
| *+++++++++++++++++++++++++++++++++++++++*************************************** |
| +++++++++++++++++++++++++++++++++++++++++++++********************************** |
| ++++++++++++++++++++++++++++++++++++++++++++++++++***************************** |
| ++++++++++++++++++++++++++++++++++++++++++++++++++++++************************* |
| +++++++++++++++++++++++++++++++++++++++++++++++++++++++++********************** |
| +++++++++++++++++++++++++++++++++.........++++++++++++++++++******************* |
| +++++++++++++++++++++++++++++++.... ......+++++++++++++++++++**************** |
| +++++++++++++++++++++++++++++....... ........+++++++++++++++++++************** |
| ++++++++++++++++++++++++++++........ ........++++++++++++++++++++************ |
| +++++++++++++++++++++++++++......... .. ...+++++++++++++++++++++********** |
| ++++++++++++++++++++++++++........... ....++++++++++++++++++++++******** |
| ++++++++++++++++++++++++............. .......++++++++++++++++++++++****** |
| +++++++++++++++++++++++............. ........+++++++++++++++++++++++**** |
| ++++++++++++++++++++++........... ..........++++++++++++++++++++++*** |
| ++++++++++++++++++++........... .........++++++++++++++++++++++* |
| ++++++++++++++++++............ ...........++++++++++++++++++++ |
| ++++++++++++++++............... .............++++++++++++++++++ |
| ++++++++++++++................. ...............++++++++++++++++ |
| ++++++++++++.................. .................++++++++++++++ |
| +++++++++.................. .................+++++++++++++ |
| ++++++........ . ......... ..++++++++++++ |
| ++............ ...... ....++++++++++ |
| .............. ...++++++++++ |
| .............. ....+++++++++ |
| .............. .....++++++++ |
| ............. ......++++++++ |
| ........... .......++++++++ |
| ......... ........+++++++ |
| ......... ........+++++++ |
| ......... ....+++++++ |
| ........ ...+++++++ |
| ....... ...+++++++ |
| ....+++++++ |
| .....+++++++ |
| ....+++++++ |
| ....+++++++ |
| ....+++++++ |
| Evaluated to 0.000000 |
| ready> ^D |
| |
| At this point, you may be starting to realize that Kaleidoscope is a |
| real and powerful language. It may not be self-similar :), but it can be |
| used to plot things that are! |
| |
| With this, we conclude the "adding user-defined operators" chapter of |
| the tutorial. We have successfully augmented our language, adding the |
| ability to extend the language in the library, and we have shown how |
| this can be used to build a simple but interesting end-user application |
| in Kaleidoscope. At this point, Kaleidoscope can build a variety of |
| applications that are functional and can call functions with |
| side-effects, but it can't actually define and mutate a variable itself. |
| |
| Strikingly, variable mutation is an important feature of some languages, |
| and it is not at all obvious how to `add support for mutable |
| variables <OCamlLangImpl7.html>`_ without having to add an "SSA |
| construction" phase to your front-end. In the next chapter, we will |
| describe how you can add variable mutation without building SSA in your |
| front-end. |
| |
| Full Code Listing |
| ================= |
| |
| Here is the complete code listing for our running example, enhanced with |
| the if/then/else and for expressions.. 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++"; A"-cclib"; A"-rdynamic"]);; |
| 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 |
| |
| (* control *) |
| | If | Then | Else |
| | For | In |
| |
| (* operators *) |
| | Binary | Unary |
| |
| 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 >] |
| | "if" -> [< 'Token.If; stream >] |
| | "then" -> [< 'Token.Then; stream >] |
| | "else" -> [< 'Token.Else; stream >] |
| | "for" -> [< 'Token.For; stream >] |
| | "in" -> [< 'Token.In; stream >] |
| | "binary" -> [< 'Token.Binary; stream >] |
| | "unary" -> [< 'Token.Unary; 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 unary operator. *) |
| | Unary of char * expr |
| |
| (* variant for a binary operator. *) |
| | Binary of char * expr * expr |
| |
| (* variant for function calls. *) |
| | Call of string * expr array |
| |
| (* variant for if/then/else. *) |
| | If of expr * expr * expr |
| |
| (* variant for for/in. *) |
| | For of string * expr * expr * expr option * expr |
| |
| (* 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 |
| | BinOpPrototype of string * string array * int |
| |
| (* 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 |
| * ::= ifexpr |
| * ::= forexpr *) |
| 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 |
| |
| (* ifexpr ::= 'if' expr 'then' expr 'else' expr *) |
| | [< 'Token.If; c=parse_expr; |
| 'Token.Then ?? "expected 'then'"; t=parse_expr; |
| 'Token.Else ?? "expected 'else'"; e=parse_expr >] -> |
| Ast.If (c, t, e) |
| |
| (* forexpr |
| ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression *) |
| | [< 'Token.For; |
| 'Token.Ident id ?? "expected identifier after for"; |
| 'Token.Kwd '=' ?? "expected '=' after for"; |
| stream >] -> |
| begin parser |
| | [< |
| start=parse_expr; |
| 'Token.Kwd ',' ?? "expected ',' after for"; |
| end_=parse_expr; |
| stream >] -> |
| let step = |
| begin parser |
| | [< 'Token.Kwd ','; step=parse_expr >] -> Some step |
| | [< >] -> None |
| end stream |
| in |
| begin parser |
| | [< 'Token.In; body=parse_expr >] -> |
| Ast.For (id, start, end_, step, body) |
| | [< >] -> |
| raise (Stream.Error "expected 'in' after for") |
| end stream |
| | [< >] -> |
| raise (Stream.Error "expected '=' after for") |
| end stream |
| |
| | [< >] -> raise (Stream.Error "unknown token when expecting an expression.") |
| |
| (* unary |
| * ::= primary |
| * ::= '!' unary *) |
| and parse_unary = parser |
| (* If this is a unary operator, read it. *) |
| | [< 'Token.Kwd op when op != '(' && op != ')'; operand=parse_expr >] -> |
| Ast.Unary (op, operand) |
| |
| (* If the current token is not an operator, it must be a primary expr. *) |
| | [< stream >] -> parse_primary stream |
| |
| (* 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 unary expression after the binary operator. *) |
| let rhs = parse_unary 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_unary; stream >] -> parse_bin_rhs 0 lhs stream |
| |
| (* prototype |
| * ::= id '(' id* ')' |
| * ::= binary LETTER number? (id, id) |
| * ::= unary LETTER number? (id) *) |
| let parse_prototype = |
| let rec parse_args accumulator = parser |
| | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e |
| | [< >] -> accumulator |
| in |
| let parse_operator = parser |
| | [< 'Token.Unary >] -> "unary", 1 |
| | [< 'Token.Binary >] -> "binary", 2 |
| in |
| let parse_binary_precedence = parser |
| | [< 'Token.Number n >] -> int_of_float n |
| | [< >] -> 30 |
| 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)) |
| | [< (prefix, kind)=parse_operator; |
| 'Token.Kwd op ?? "expected an operator"; |
| (* Read the precedence if present. *) |
| binary_precedence=parse_binary_precedence; |
| 'Token.Kwd '(' ?? "expected '(' in prototype"; |
| args=parse_args []; |
| 'Token.Kwd ')' ?? "expected ')' in prototype" >] -> |
| let name = prefix ^ (String.make 1 op) in |
| let args = Array.of_list (List.rev args) in |
| |
| (* Verify right number of arguments for operator. *) |
| if Array.length args != kind |
| then raise (Stream.Error "invalid number of operands for operator") |
| else |
| if kind == 1 then |
| Ast.Prototype (name, args) |
| else |
| Ast.BinOpPrototype (name, args, binary_precedence) |
| | [< >] -> |
| 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.Unary (op, operand) -> |
| let operand = codegen_expr operand in |
| let callee = "unary" ^ (String.make 1 op) in |
| let callee = |
| match lookup_function callee the_module with |
| | Some callee -> callee |
| | None -> raise (Error "unknown unary operator") |
| in |
| build_call callee [|operand|] "unop" builder |
| | 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 |
| | _ -> |
| (* If it wasn't a builtin binary operator, it must be a user defined |
| * one. Emit a call to it. *) |
| let callee = "binary" ^ (String.make 1 op) in |
| let callee = |
| match lookup_function callee the_module with |
| | Some callee -> callee |
| | None -> raise (Error "binary operator not found!") |
| in |
| build_call callee [|lhs_val; rhs_val|] "binop" builder |
| 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 |
| | Ast.If (cond, then_, else_) -> |
| let cond = codegen_expr cond in |
| |
| (* Convert condition to a bool by comparing equal to 0.0 *) |
| let zero = const_float double_type 0.0 in |
| let cond_val = build_fcmp Fcmp.One cond zero "ifcond" builder in |
| |
| (* Grab the first block so that we might later add the conditional branch |
| * to it at the end of the function. *) |
| let start_bb = insertion_block builder in |
| let the_function = block_parent start_bb in |
| |
| let then_bb = append_block context "then" the_function in |
| |
| (* Emit 'then' value. *) |
| position_at_end then_bb builder; |
| let then_val = codegen_expr then_ in |
| |
| (* Codegen of 'then' can change the current block, update then_bb for the |
| * phi. We create a new name because one is used for the phi node, and the |
| * other is used for the conditional branch. *) |
| let new_then_bb = insertion_block builder in |
| |
| (* Emit 'else' value. *) |
| let else_bb = append_block context "else" the_function in |
| position_at_end else_bb builder; |
| let else_val = codegen_expr else_ in |
| |
| (* Codegen of 'else' can change the current block, update else_bb for the |
| * phi. *) |
| let new_else_bb = insertion_block builder in |
| |
| (* Emit merge block. *) |
| let merge_bb = append_block context "ifcont" the_function in |
| position_at_end merge_bb builder; |
| let incoming = [(then_val, new_then_bb); (else_val, new_else_bb)] in |
| let phi = build_phi incoming "iftmp" builder in |
| |
| (* Return to the start block to add the conditional branch. *) |
| position_at_end start_bb builder; |
| ignore (build_cond_br cond_val then_bb else_bb builder); |
| |
| (* Set a unconditional branch at the end of the 'then' block and the |
| * 'else' block to the 'merge' block. *) |
| position_at_end new_then_bb builder; ignore (build_br merge_bb builder); |
| position_at_end new_else_bb builder; ignore (build_br merge_bb builder); |
| |
| (* Finally, set the builder to the end of the merge block. *) |
| position_at_end merge_bb builder; |
| |
| phi |
| | Ast.For (var_name, start, end_, step, body) -> |
| (* Emit the start code first, without 'variable' in scope. *) |
| let start_val = codegen_expr start in |
| |
| (* Make the new basic block for the loop header, inserting after current |
| * block. *) |
| let preheader_bb = insertion_block builder in |
| let the_function = block_parent preheader_bb in |
| let loop_bb = append_block context "loop" the_function in |
| |
| (* Insert an explicit fall through from the current block to the |
| * loop_bb. *) |
| ignore (build_br loop_bb builder); |
| |
| (* Start insertion in loop_bb. *) |
| position_at_end loop_bb builder; |
| |
| (* Start the PHI node with an entry for start. *) |
| let variable = build_phi [(start_val, preheader_bb)] var_name builder in |
| |
| (* Within the loop, the variable is defined equal to the PHI node. If it |
| * shadows an existing variable, we have to restore it, so save it |
| * now. *) |
| let old_val = |
| try Some (Hashtbl.find named_values var_name) with Not_found -> None |
| in |
| Hashtbl.add named_values var_name variable; |
| |
| (* Emit the body of the loop. This, like any other expr, can change the |
| * current BB. Note that we ignore the value computed by the body, but |
| * don't allow an error *) |
| ignore (codegen_expr body); |
| |
| (* Emit the step value. *) |
| let step_val = |
| match step with |
| | Some step -> codegen_expr step |
| (* If not specified, use 1.0. *) |
| | None -> const_float double_type 1.0 |
| in |
| |
| let next_var = build_add variable step_val "nextvar" builder in |
| |
| (* Compute the end condition. *) |
| let end_cond = codegen_expr end_ in |
| |
| (* Convert condition to a bool by comparing equal to 0.0. *) |
| let zero = const_float double_type 0.0 in |
| let end_cond = build_fcmp Fcmp.One end_cond zero "loopcond" builder in |
| |
| (* Create the "after loop" block and insert it. *) |
| let loop_end_bb = insertion_block builder in |
| let after_bb = append_block context "afterloop" the_function in |
| |
| (* Insert the conditional branch into the end of loop_end_bb. *) |
| ignore (build_cond_br end_cond loop_bb after_bb builder); |
| |
| (* Any new code will be inserted in after_bb. *) |
| position_at_end after_bb builder; |
| |
| (* Add a new entry to the PHI node for the backedge. *) |
| add_incoming (next_var, loop_end_bb) variable; |
| |
| (* Restore the unshadowed variable. *) |
| begin match old_val with |
| | Some old_val -> Hashtbl.add named_values var_name old_val |
| | None -> () |
| end; |
| |
| (* for expr always returns 0.0. *) |
| const_null double_type |
| |
| let codegen_proto = function |
| | Ast.Prototype (name, args) | Ast.BinOpPrototype (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 |
| |
| (* If this is an operator, install it. *) |
| begin match proto with |
| | Ast.BinOpPrototype (name, args, prec) -> |
| let op = name.[String.length name - 1] in |
| Hashtbl.add Parser.binop_precedence op prec; |
| | _ -> () |
| end; |
| |
| (* 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; |
| } |
| |
| /* printd - printf that takes a double prints it as "%f\n", returning 0. */ |
| extern double printd(double X) { |
| printf("%f\n", X); |
| return 0; |
| } |
| |
| `Next: Extending the language: mutable variables / SSA |
| construction <OCamlLangImpl7.html>`_ |
| |
