forked from OSchip/llvm-project
1442 lines
58 KiB
ReStructuredText
1442 lines
58 KiB
ReStructuredText
============================================================
|
|
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 <#example>`_. 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 programatically 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#iflexer>`_. 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 mandleconverger(real imag iters creal cimag)
|
|
if iters > 255 | (real*real + imag*imag > 4) then
|
|
iters
|
|
else
|
|
mandleconverger(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 mandleconverge(real imag)
|
|
mandleconverger(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 mandlebrot 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(mandleconverge(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 mandlebrot 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>`_
|
|
|