.. contents::
:local:
-Written by `Chris Lattner <mailto:sabre@nondot.org>`_
-
Chapter 3 Introduction
======================
well as demonstrate how easy it is to use. It's much more work to build
a lexer and parser than it is to generate LLVM IR code. :)
-**Please note**: the code in this chapter and later require LLVM 2.2 or
-later. LLVM 2.1 and before will not work with it. Also note that you
+**Please note**: the code in this chapter and later require LLVM 3.7 or
+later. LLVM 3.6 and before will not work with it. Also note that you
need to use a version of this tutorial that matches your LLVM release:
If you are using an official LLVM release, use the version of the
documentation included with your release or on the `llvm.org releases
class ExprAST {
public:
virtual ~ExprAST() {}
- virtual Value *Codegen() = 0;
+ virtual Value *codegen() = 0;
};
/// NumberExprAST - Expression class for numeric literals like "1.0".
class NumberExprAST : public ExprAST {
double Val;
+
public:
- NumberExprAST(double val) : Val(val) {}
- virtual Value *Codegen();
+ NumberExprAST(double Val) : Val(Val) {}
+ virtual Value *codegen();
};
...
-The Codegen() method says to emit IR for that AST node along with all
+The codegen() method says to emit IR for that AST node along with all
the things it depends on, and they all return an LLVM Value object.
"Value" is the class used to represent a "`Static Single Assignment
(SSA) <http://en.wikipedia.org/wiki/Static_single_assignment_form>`_
.. code-block:: c++
- Value *ErrorV(const char *Str) { Error(Str); return 0; }
-
- static Module *TheModule;
+ static std::unique_ptr<Module> *TheModule;
static IRBuilder<> Builder(getGlobalContext());
static std::map<std::string, Value*> NamedValues;
+ Value *ErrorV(const char *Str) {
+ Error(Str);
+ return nullptr;
+ }
+
The static variables will be used during code generation. ``TheModule``
-is the LLVM construct that contains all of the functions and global
-variables in a chunk of code. In many ways, it is the top-level
-structure that the LLVM IR uses to contain code.
+is an LLVM construct that contains functions and global variables. In many
+ways, it is the top-level structure that the LLVM IR uses to contain code.
+It will own the memory for all of the IR that we generate, which is why
+the codegen() method returns a raw Value\*, rather than a unique_ptr<Value>.
The ``Builder`` object is a helper object that makes it easy to generate
LLVM instructions. Instances of the
-```IRBuilder`` <http://llvm.org/doxygen/IRBuilder_8h-source.html>`_
+`IRBuilder <http://llvm.org/doxygen/IRBuilder_8h-source.html>`_
class template keep track of the current place to insert instructions
and has methods to create new instructions.
.. code-block:: c++
- Value *NumberExprAST::Codegen() {
+ Value *NumberExprAST::codegen() {
return ConstantFP::get(getGlobalContext(), APFloat(Val));
}
.. code-block:: c++
- Value *VariableExprAST::Codegen() {
+ Value *VariableExprAST::codegen() {
// Look this variable up in the function.
Value *V = NamedValues[Name];
- return V ? V : ErrorV("Unknown variable name");
+ if (!V)
+ ErrorV("Unknown variable name");
+ return V;
}
References to variables are also quite simple using LLVM. In the simple
This code simply checks to see that the specified name is in the map (if
not, an unknown variable is being referenced) and returns the value for
it. In future chapters, we'll add support for `loop induction
-variables <LangImpl5.html#for>`_ in the symbol table, and for `local
-variables <LangImpl7.html#localvars>`_.
+variables <LangImpl5.html#for-loop-expression>`_ in the symbol table, and for `local
+variables <LangImpl7.html#user-defined-local-variables>`_.
.. code-block:: c++
- Value *BinaryExprAST::Codegen() {
- Value *L = LHS->Codegen();
- Value *R = RHS->Codegen();
- if (L == 0 || R == 0) return 0;
+ Value *BinaryExprAST::codegen() {
+ Value *L = LHS->codegen();
+ Value *R = RHS->codegen();
+ if (!L || !R)
+ return nullptr;
switch (Op) {
- case '+': return Builder.CreateFAdd(L, R, "addtmp");
- case '-': return Builder.CreateFSub(L, R, "subtmp");
- case '*': return Builder.CreateFMul(L, R, "multmp");
+ case '+':
+ return Builder.CreateFAdd(L, R, "addtmp");
+ case '-':
+ return Builder.CreateFSub(L, R, "subtmp");
+ case '*':
+ return Builder.CreateFMul(L, R, "multmp");
case '<':
L = Builder.CreateFCmpULT(L, R, "cmptmp");
// Convert bool 0/1 to double 0.0 or 1.0
return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
"booltmp");
- default: return ErrorV("invalid binary operator");
+ default:
+ return ErrorV("invalid binary operator");
}
}
suffix. Local value names for instructions are purely optional, but it
makes it much easier to read the IR dumps.
-`LLVM instructions <../LangRef.html#instref>`_ are constrained by strict
+`LLVM instructions <../LangRef.html#instruction-reference>`_ are constrained by strict
rules: for example, the Left and Right operators of an `add
-instruction <../LangRef.html#i_add>`_ must have the same type, and the
+instruction <../LangRef.html#add-instruction>`_ must have the same type, and the
result type of the add must match the operand types. Because all values
in Kaleidoscope are doubles, this makes for very simple code for add,
sub and mul.
On the other hand, LLVM specifies that the `fcmp
-instruction <../LangRef.html#i_fcmp>`_ always returns an 'i1' value (a
+instruction <../LangRef.html#fcmp-instruction>`_ always returns an 'i1' value (a
one bit integer). The problem with this is that Kaleidoscope wants the
value to be a 0.0 or 1.0 value. In order to get these semantics, we
combine the fcmp instruction with a `uitofp
-instruction <../LangRef.html#i_uitofp>`_. This instruction converts its
+instruction <../LangRef.html#uitofp-to-instruction>`_. This instruction converts its
input integer into a floating point value by treating the input as an
unsigned value. In contrast, if we used the `sitofp
-instruction <../LangRef.html#i_sitofp>`_, the Kaleidoscope '<' operator
+instruction <../LangRef.html#sitofp-to-instruction>`_, the Kaleidoscope '<' operator
would return 0.0 and -1.0, depending on the input value.
.. code-block:: c++
- Value *CallExprAST::Codegen() {
+ Value *CallExprAST::codegen() {
// Look up the name in the global module table.
Function *CalleeF = TheModule->getFunction(Callee);
- if (CalleeF == 0)
+ if (!CalleeF)
return ErrorV("Unknown function referenced");
// If argument mismatch error.
if (CalleeF->arg_size() != Args.size())
return ErrorV("Incorrect # arguments passed");
- std::vector<Value*> ArgsV;
+ std::vector<Value *> ArgsV;
for (unsigned i = 0, e = Args.size(); i != e; ++i) {
- ArgsV.push_back(Args[i]->Codegen());
- if (ArgsV.back() == 0) return 0;
+ ArgsV.push_back(Args[i]->codegen());
+ if (!ArgsV.back())
+ return nullptr;
}
return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
}
-Code generation for function calls is quite straightforward with LLVM.
-The code above initially does a function name lookup in the LLVM
-Module's symbol table. Recall that the LLVM Module is the container that
-holds all of the functions we are JIT'ing. By giving each function the
-same name as what the user specifies, we can use the LLVM symbol table
-to resolve function names for us.
+Code generation for function calls is quite straightforward with LLVM. The code
+above initially does a function name lookup in the LLVM Module's symbol table.
+Recall that the LLVM Module is the container that holds the functions we are
+JIT'ing. By giving each function the same name as what the user specifies, we
+can use the LLVM symbol table to resolve function names for us.
Once we have the function to call, we recursively codegen each argument
that is to be passed in, and create an LLVM `call
-instruction <../LangRef.html#i_call>`_. Note that LLVM uses the native C
+instruction <../LangRef.html#call-instruction>`_. Note that LLVM uses the native C
calling conventions by default, allowing these calls to also call into
standard library functions like "sin" and "cos", with no additional
effort.
.. code-block:: c++
- Function *PrototypeAST::Codegen() {
+ Function *PrototypeAST::codegen() {
// Make the function type: double(double,double) etc.
std::vector<Type*> Doubles(Args.size(),
Type::getDoubleTy(getGlobalContext()));
- FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
- Doubles, false);
+ FunctionType *FT =
+ FunctionType::get(Type::getDoubleTy(getGlobalContext()), Doubles, false);
- Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
+ Function *F =
+ Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
This code packs a lot of power into a few lines. Note first that this
function returns a "Function\*" instead of a "Value\*". Because a
indicates this). Note that Types in LLVM are uniqued just like Constants
are, so you don't "new" a type, you "get" it.
-The final line above actually creates the function that the prototype
-will correspond to. This indicates the type, linkage and name to use, as
+The final line above actually creates the IR Function corresponding to
+the Prototype. This indicates the type, linkage and name to use, as
well as which module to insert into. "`external
linkage <../LangRef.html#linkage>`_" means that the function may be
defined outside the current module and/or that it is callable by
functions outside the module. The Name passed in is the name the user
specified: since "``TheModule``" is specified, this name is registered
-in "``TheModule``"s symbol table, which is used by the function call
-code above.
+in "``TheModule``"s symbol table.
.. code-block:: c++
- // If F conflicted, there was already something named 'Name'. If it has a
- // body, don't allow redefinition or reextern.
- if (F->getName() != Name) {
- // Delete the one we just made and get the existing one.
- F->eraseFromParent();
- F = TheModule->getFunction(Name);
-
-The Module symbol table works just like the Function symbol table when
-it comes to name conflicts: if a new function is created with a name
-that was previously added to the symbol table, the new function will get
-implicitly renamed when added to the Module. The code above exploits
-this fact to determine if there was a previous definition of this
-function.
-
-In Kaleidoscope, I choose to allow redefinitions of functions in two
-cases: first, we want to allow 'extern'ing a function more than once, as
-long as the prototypes for the externs match (since all arguments have
-the same type, we just have to check that the number of arguments
-match). Second, we want to allow 'extern'ing a function and then
-defining a body for it. This is useful when defining mutually recursive
-functions.
-
-In order to implement this, the code above first checks to see if there
-is a collision on the name of the function. If so, it deletes the
-function we just created (by calling ``eraseFromParent``) and then
-calling ``getFunction`` to get the existing function with the specified
-name. Note that many APIs in LLVM have "erase" forms and "remove" forms.
-The "remove" form unlinks the object from its parent (e.g. a Function
-from a Module) and returns it. The "erase" form unlinks the object and
-then deletes it.
+ // Set names for all arguments.
+ unsigned Idx = 0;
+ for (auto &Arg : F->args())
+ Arg.setName(Args[Idx++]);
-.. code-block:: c++
+ return F;
- // If F already has a body, reject this.
- if (!F->empty()) {
- ErrorF("redefinition of function");
- return 0;
- }
-
- // If F took a different number of args, reject.
- if (F->arg_size() != Args.size()) {
- ErrorF("redefinition of function with different # args");
- return 0;
- }
- }
+Finally, we set the name of each of the function's arguments according to the
+names given in the Prototype. This step isn't strictly necessary, but keeping
+the names consistent makes the IR more readable, and allows subsequent code to
+refer directly to the arguments for their names, rather than having to look up
+them up in the Prototype AST.
-In order to verify the logic above, we first check to see if the
-pre-existing function is "empty". In this case, empty means that it has
-no basic blocks in it, which means it has no body. If it has no body, it
-is a forward declaration. Since we don't allow anything after a full
-definition of the function, the code rejects this case. If the previous
-reference to a function was an 'extern', we simply verify that the
-number of arguments for that definition and this one match up. If not,
-we emit an error.
+At this point we have a function prototype with no body. This is how LLVM IR
+represents function declarations. For extern statements in Kaleidoscope, this
+is as far as we need to go. For function definitions however, we need to
+codegen and attach a function body.
.. code-block:: c++
- // Set names for all arguments.
- unsigned Idx = 0;
- for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
- ++AI, ++Idx) {
- AI->setName(Args[Idx]);
-
- // Add arguments to variable symbol table.
- NamedValues[Args[Idx]] = AI;
- }
- return F;
- }
+ Function *FunctionAST::codegen() {
+ // First, check for an existing function from a previous 'extern' declaration.
+ Function *TheFunction = TheModule->getFunction(Proto->getName());
-The last bit of code for prototypes loops over all of the arguments in
-the function, setting the name of the LLVM Argument objects to match,
-and registering the arguments in the ``NamedValues`` map for future use
-by the ``VariableExprAST`` AST node. Once this is set up, it returns the
-Function object to the caller. Note that we don't check for conflicting
-argument names here (e.g. "extern foo(a b a)"). Doing so would be very
-straight-forward with the mechanics we have already used above.
+ if (!TheFunction)
+ TheFunction = Proto->codegen();
-.. code-block:: c++
+ if (!TheFunction)
+ return nullptr;
- Function *FunctionAST::Codegen() {
- NamedValues.clear();
+ if (!TheFunction->empty())
+ return (Function*)ErrorV("Function cannot be redefined.");
- Function *TheFunction = Proto->Codegen();
- if (TheFunction == 0)
- return 0;
-Code generation for function definitions starts out simply enough: we
-just codegen the prototype (Proto) and verify that it is ok. We then
-clear out the ``NamedValues`` map to make sure that there isn't anything
-in it from the last function we compiled. Code generation of the
-prototype ensures that there is an LLVM Function object that is ready to
-go for us.
+For function definitions, we start by searching TheModule's symbol table for an
+existing version of this function, in case one has already been created using an
+'extern' statement. If Module::getFunction returns null then no previous version
+exists, so we'll codegen one from the Prototype. In either case, we want to
+assert that the function is empty (i.e. has no body yet) before we start.
.. code-block:: c++
- // Create a new basic block to start insertion into.
- BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
- Builder.SetInsertPoint(BB);
+ // Create a new basic block to start insertion into.
+ BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
+ Builder.SetInsertPoint(BB);
- if (Value *RetVal = Body->Codegen()) {
+ // Record the function arguments in the NamedValues map.
+ NamedValues.clear();
+ for (auto &Arg : TheFunction->args())
+ NamedValues[Arg.getName()] = &Arg;
Now we get to the point where the ``Builder`` is set up. The first line
creates a new `basic block <http://en.wikipedia.org/wiki/Basic_block>`_
don't have any control flow, our functions will only contain one block
at this point. We'll fix this in `Chapter 5 <LangImpl5.html>`_ :).
+Next we add the function arguments to the NamedValues map (after first clearing
+it out) so that they're accessible to ``VariableExprAST`` nodes.
+
.. code-block:: c++
- if (Value *RetVal = Body->Codegen()) {
+ if (Value *RetVal = Body->codegen()) {
// Finish off the function.
Builder.CreateRet(RetVal);
return TheFunction;
}
-Once the insertion point is set up, we call the ``CodeGen()`` method for
-the root expression of the function. If no error happens, this emits
-code to compute the expression into the entry block and returns the
-value that was computed. Assuming no error, we then create an LLVM `ret
-instruction <../LangRef.html#i_ret>`_, which completes the function.
+Once the insertion point has been set up and the NamedValues map populated,
+we call the ``codegen()`` method for the root expression of the function. If no
+error happens, this emits code to compute the expression into the entry block
+and returns the value that was computed. Assuming no error, we then create an
+LLVM `ret instruction <../LangRef.html#ret-instruction>`_, which completes the function.
Once the function is built, we call ``verifyFunction``, which is
provided by LLVM. This function does a variety of consistency checks on
the generated code, to determine if our compiler is doing everything
// Error reading body, remove function.
TheFunction->eraseFromParent();
- return 0;
+ return nullptr;
}
The only piece left here is handling of the error case. For simplicity,
that they incorrectly typed in before: if we didn't delete it, it would
live in the symbol table, with a body, preventing future redefinition.
-This code does have a bug, though. Since the ``PrototypeAST::Codegen``
-can return a previously defined forward declaration, our code can
-actually delete a forward declaration. There are a number of ways to fix
-this bug, see what you can come up with! Here is a testcase:
+This code does have a bug, though: If the ``FunctionAST::codegen()`` method
+finds an existing IR Function, it does not validate its signature against the
+definition's own prototype. This means that an earlier 'extern' declaration will
+take precedence over the function definition's signature, which can cause
+codegen to fail, for instance if the function arguments are named differently.
+There are a number of ways to fix this bug, see what you can come up with! Here
+is a testcase:
::
- extern foo(a b); # ok, defines foo.
- def foo(a b) c; # error, 'c' is invalid.
- def bar() foo(1, 2); # error, unknown function "foo"
+ extern foo(a); # ok, defines foo.
+ def foo(b) b; # Error: Unknown variable name. (decl using 'a' takes precedence).
Driver Changes and Closing Thoughts
===================================
For now, code generation to LLVM doesn't really get us much, except that
we can look at the pretty IR calls. The sample code inserts calls to
-Codegen into the "``HandleDefinition``", "``HandleExtern``" etc
+codegen into the "``HandleDefinition``", "``HandleExtern``" etc
functions, and then dumps out the LLVM IR. This gives a nice way to look
at the LLVM IR for simple functions. For example:
Note how the parser turns the top-level expression into anonymous
functions for us. This will be handy when we add `JIT
-support <LangImpl4.html#jit>`_ in the next chapter. Also note that the
+support <LangImpl4.html#adding-a-jit-compiler>`_ in the next chapter. Also note that the
code is very literally transcribed, no optimizations are being performed
except simple constant folding done by IRBuilder. We will `add
-optimizations <LangImpl4.html#trivialconstfold>`_ explicitly in the next
+optimizations <LangImpl4.html#trivial-constant-folding>`_ explicitly in the next
chapter.
::
.. code-block:: bash
# Compile
- clang++ -g -O3 toy.cpp `llvm-config --cppflags --ldflags --libs core` -o toy
+ clang++ -g -O3 toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs core` -o toy
# Run
./toy
Here is the code:
-.. code-block:: c++
-
- // To build this:
- // See example below.
-
- #include "llvm/DerivedTypes.h"
- #include "llvm/IRBuilder.h"
- #include "llvm/LLVMContext.h"
- #include "llvm/Module.h"
- #include "llvm/Analysis/Verifier.h"
- #include <cstdio>
- #include <string>
- #include <map>
- #include <vector>
- using namespace llvm;
-
- //===----------------------------------------------------------------------===//
- // Lexer
- //===----------------------------------------------------------------------===//
-
- // The lexer returns tokens [0-255] if it is an unknown character, otherwise one
- // of these for known things.
- enum Token {
- tok_eof = -1,
-
- // commands
- tok_def = -2, tok_extern = -3,
-
- // primary
- tok_identifier = -4, tok_number = -5
- };
-
- static std::string IdentifierStr; // Filled in if tok_identifier
- static double NumVal; // Filled in if tok_number
-
- /// gettok - Return the next token from standard input.
- static int gettok() {
- static int LastChar = ' ';
-
- // Skip any whitespace.
- while (isspace(LastChar))
- LastChar = getchar();
-
- if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
- IdentifierStr = LastChar;
- while (isalnum((LastChar = getchar())))
- IdentifierStr += LastChar;
-
- if (IdentifierStr == "def") return tok_def;
- if (IdentifierStr == "extern") return tok_extern;
- return tok_identifier;
- }
-
- if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+
- std::string NumStr;
- do {
- NumStr += LastChar;
- LastChar = getchar();
- } while (isdigit(LastChar) || LastChar == '.');
-
- NumVal = strtod(NumStr.c_str(), 0);
- return tok_number;
- }
-
- if (LastChar == '#') {
- // Comment until end of line.
- do LastChar = getchar();
- while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
-
- if (LastChar != EOF)
- return gettok();
- }
-
- // Check for end of file. Don't eat the EOF.
- if (LastChar == EOF)
- return tok_eof;
-
- // Otherwise, just return the character as its ascii value.
- int ThisChar = LastChar;
- LastChar = getchar();
- return ThisChar;
- }
-
- //===----------------------------------------------------------------------===//
- // Abstract Syntax Tree (aka Parse Tree)
- //===----------------------------------------------------------------------===//
-
- /// ExprAST - Base class for all expression nodes.
- class ExprAST {
- public:
- virtual ~ExprAST() {}
- virtual Value *Codegen() = 0;
- };
-
- /// NumberExprAST - Expression class for numeric literals like "1.0".
- class NumberExprAST : public ExprAST {
- double Val;
- public:
- NumberExprAST(double val) : Val(val) {}
- virtual Value *Codegen();
- };
-
- /// VariableExprAST - Expression class for referencing a variable, like "a".
- class VariableExprAST : public ExprAST {
- std::string Name;
- public:
- VariableExprAST(const std::string &name) : Name(name) {}
- virtual Value *Codegen();
- };
-
- /// BinaryExprAST - Expression class for a binary operator.
- class BinaryExprAST : public ExprAST {
- char Op;
- ExprAST *LHS, *RHS;
- public:
- BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
- : Op(op), LHS(lhs), RHS(rhs) {}
- virtual Value *Codegen();
- };
-
- /// CallExprAST - Expression class for function calls.
- class CallExprAST : public ExprAST {
- std::string Callee;
- std::vector<ExprAST*> Args;
- public:
- CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
- : Callee(callee), Args(args) {}
- virtual Value *Codegen();
- };
-
- /// PrototypeAST - This class represents the "prototype" for a function,
- /// which captures its name, and its argument names (thus implicitly the number
- /// of arguments the function takes).
- class PrototypeAST {
- std::string Name;
- std::vector<std::string> Args;
- public:
- PrototypeAST(const std::string &name, const std::vector<std::string> &args)
- : Name(name), Args(args) {}
-
- Function *Codegen();
- };
-
- /// FunctionAST - This class represents a function definition itself.
- class FunctionAST {
- PrototypeAST *Proto;
- ExprAST *Body;
- public:
- FunctionAST(PrototypeAST *proto, ExprAST *body)
- : Proto(proto), Body(body) {}
-
- Function *Codegen();
- };
-
- //===----------------------------------------------------------------------===//
- // Parser
- //===----------------------------------------------------------------------===//
-
- /// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
- /// token the parser is looking at. getNextToken reads another token from the
- /// lexer and updates CurTok with its results.
- static int CurTok;
- static int getNextToken() {
- return CurTok = gettok();
- }
-
- /// BinopPrecedence - This holds the precedence for each binary operator that is
- /// defined.
- static std::map<char, int> BinopPrecedence;
-
- /// GetTokPrecedence - Get the precedence of the pending binary operator token.
- static int GetTokPrecedence() {
- if (!isascii(CurTok))
- return -1;
-
- // Make sure it's a declared binop.
- int TokPrec = BinopPrecedence[CurTok];
- if (TokPrec <= 0) return -1;
- return TokPrec;
- }
-
- /// Error* - These are little helper functions for error handling.
- ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
- PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
- FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
-
- static ExprAST *ParseExpression();
-
- /// identifierexpr
- /// ::= identifier
- /// ::= identifier '(' expression* ')'
- static ExprAST *ParseIdentifierExpr() {
- std::string IdName = IdentifierStr;
-
- getNextToken(); // eat identifier.
-
- if (CurTok != '(') // Simple variable ref.
- return new VariableExprAST(IdName);
-
- // Call.
- getNextToken(); // eat (
- std::vector<ExprAST*> Args;
- if (CurTok != ')') {
- while (1) {
- ExprAST *Arg = ParseExpression();
- if (!Arg) return 0;
- Args.push_back(Arg);
-
- if (CurTok == ')') break;
-
- if (CurTok != ',')
- return Error("Expected ')' or ',' in argument list");
- getNextToken();
- }
- }
-
- // Eat the ')'.
- getNextToken();
-
- return new CallExprAST(IdName, Args);
- }
-
- /// numberexpr ::= number
- static ExprAST *ParseNumberExpr() {
- ExprAST *Result = new NumberExprAST(NumVal);
- getNextToken(); // consume the number
- return Result;
- }
-
- /// parenexpr ::= '(' expression ')'
- static ExprAST *ParseParenExpr() {
- getNextToken(); // eat (.
- ExprAST *V = ParseExpression();
- if (!V) return 0;
-
- if (CurTok != ')')
- return Error("expected ')'");
- getNextToken(); // eat ).
- return V;
- }
-
- /// primary
- /// ::= identifierexpr
- /// ::= numberexpr
- /// ::= parenexpr
- static ExprAST *ParsePrimary() {
- switch (CurTok) {
- default: return Error("unknown token when expecting an expression");
- case tok_identifier: return ParseIdentifierExpr();
- case tok_number: return ParseNumberExpr();
- case '(': return ParseParenExpr();
- }
- }
-
- /// binoprhs
- /// ::= ('+' primary)*
- static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
- // If this is a binop, find its precedence.
- while (1) {
- int TokPrec = GetTokPrecedence();
-
- // If this is a binop that binds at least as tightly as the current binop,
- // consume it, otherwise we are done.
- if (TokPrec < ExprPrec)
- return LHS;
-
- // Okay, we know this is a binop.
- int BinOp = CurTok;
- getNextToken(); // eat binop
-
- // Parse the primary expression after the binary operator.
- ExprAST *RHS = ParsePrimary();
- if (!RHS) return 0;
-
- // If BinOp binds less tightly with RHS than the operator after RHS, let
- // the pending operator take RHS as its LHS.
- int NextPrec = GetTokPrecedence();
- if (TokPrec < NextPrec) {
- RHS = ParseBinOpRHS(TokPrec+1, RHS);
- if (RHS == 0) return 0;
- }
-
- // Merge LHS/RHS.
- LHS = new BinaryExprAST(BinOp, LHS, RHS);
- }
- }
-
- /// expression
- /// ::= primary binoprhs
- ///
- static ExprAST *ParseExpression() {
- ExprAST *LHS = ParsePrimary();
- if (!LHS) return 0;
-
- return ParseBinOpRHS(0, LHS);
- }
-
- /// prototype
- /// ::= id '(' id* ')'
- static PrototypeAST *ParsePrototype() {
- if (CurTok != tok_identifier)
- return ErrorP("Expected function name in prototype");
-
- std::string FnName = IdentifierStr;
- getNextToken();
-
- if (CurTok != '(')
- return ErrorP("Expected '(' in prototype");
-
- std::vector<std::string> ArgNames;
- while (getNextToken() == tok_identifier)
- ArgNames.push_back(IdentifierStr);
- if (CurTok != ')')
- return ErrorP("Expected ')' in prototype");
-
- // success.
- getNextToken(); // eat ')'.
-
- return new PrototypeAST(FnName, ArgNames);
- }
-
- /// definition ::= 'def' prototype expression
- static FunctionAST *ParseDefinition() {
- getNextToken(); // eat def.
- PrototypeAST *Proto = ParsePrototype();
- if (Proto == 0) return 0;
-
- if (ExprAST *E = ParseExpression())
- return new FunctionAST(Proto, E);
- return 0;
- }
-
- /// toplevelexpr ::= expression
- static FunctionAST *ParseTopLevelExpr() {
- if (ExprAST *E = ParseExpression()) {
- // Make an anonymous proto.
- PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
- return new FunctionAST(Proto, E);
- }
- return 0;
- }
-
- /// external ::= 'extern' prototype
- static PrototypeAST *ParseExtern() {
- getNextToken(); // eat extern.
- return ParsePrototype();
- }
-
- //===----------------------------------------------------------------------===//
- // Code Generation
- //===----------------------------------------------------------------------===//
-
- static Module *TheModule;
- static IRBuilder<> Builder(getGlobalContext());
- static std::map<std::string, Value*> NamedValues;
-
- Value *ErrorV(const char *Str) { Error(Str); return 0; }
-
- Value *NumberExprAST::Codegen() {
- return ConstantFP::get(getGlobalContext(), APFloat(Val));
- }
-
- Value *VariableExprAST::Codegen() {
- // Look this variable up in the function.
- Value *V = NamedValues[Name];
- return V ? V : ErrorV("Unknown variable name");
- }
-
- Value *BinaryExprAST::Codegen() {
- Value *L = LHS->Codegen();
- Value *R = RHS->Codegen();
- if (L == 0 || R == 0) return 0;
-
- switch (Op) {
- case '+': return Builder.CreateFAdd(L, R, "addtmp");
- case '-': return Builder.CreateFSub(L, R, "subtmp");
- case '*': return Builder.CreateFMul(L, R, "multmp");
- case '<':
- L = Builder.CreateFCmpULT(L, R, "cmptmp");
- // Convert bool 0/1 to double 0.0 or 1.0
- return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
- "booltmp");
- default: return ErrorV("invalid binary operator");
- }
- }
-
- Value *CallExprAST::Codegen() {
- // Look up the name in the global module table.
- Function *CalleeF = TheModule->getFunction(Callee);
- if (CalleeF == 0)
- return ErrorV("Unknown function referenced");
-
- // If argument mismatch error.
- if (CalleeF->arg_size() != Args.size())
- return ErrorV("Incorrect # arguments passed");
-
- std::vector<Value*> ArgsV;
- for (unsigned i = 0, e = Args.size(); i != e; ++i) {
- ArgsV.push_back(Args[i]->Codegen());
- if (ArgsV.back() == 0) return 0;
- }
-
- return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
- }
-
- Function *PrototypeAST::Codegen() {
- // Make the function type: double(double,double) etc.
- std::vector<Type*> Doubles(Args.size(),
- Type::getDoubleTy(getGlobalContext()));
- FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
- Doubles, false);
-
- Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
-
- // If F conflicted, there was already something named 'Name'. If it has a
- // body, don't allow redefinition or reextern.
- if (F->getName() != Name) {
- // Delete the one we just made and get the existing one.
- F->eraseFromParent();
- F = TheModule->getFunction(Name);
-
- // If F already has a body, reject this.
- if (!F->empty()) {
- ErrorF("redefinition of function");
- return 0;
- }
-
- // If F took a different number of args, reject.
- if (F->arg_size() != Args.size()) {
- ErrorF("redefinition of function with different # args");
- return 0;
- }
- }
-
- // Set names for all arguments.
- unsigned Idx = 0;
- for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
- ++AI, ++Idx) {
- AI->setName(Args[Idx]);
-
- // Add arguments to variable symbol table.
- NamedValues[Args[Idx]] = AI;
- }
-
- return F;
- }
-
- Function *FunctionAST::Codegen() {
- NamedValues.clear();
-
- Function *TheFunction = Proto->Codegen();
- if (TheFunction == 0)
- return 0;
-
- // Create a new basic block to start insertion into.
- BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
- Builder.SetInsertPoint(BB);
-
- if (Value *RetVal = Body->Codegen()) {
- // Finish off the function.
- Builder.CreateRet(RetVal);
-
- // Validate the generated code, checking for consistency.
- verifyFunction(*TheFunction);
-
- return TheFunction;
- }
-
- // Error reading body, remove function.
- TheFunction->eraseFromParent();
- return 0;
- }
-
- //===----------------------------------------------------------------------===//
- // Top-Level parsing and JIT Driver
- //===----------------------------------------------------------------------===//
-
- static void HandleDefinition() {
- if (FunctionAST *F = ParseDefinition()) {
- if (Function *LF = F->Codegen()) {
- fprintf(stderr, "Read function definition:");
- LF->dump();
- }
- } else {
- // Skip token for error recovery.
- getNextToken();
- }
- }
-
- static void HandleExtern() {
- if (PrototypeAST *P = ParseExtern()) {
- if (Function *F = P->Codegen()) {
- fprintf(stderr, "Read extern: ");
- F->dump();
- }
- } else {
- // Skip token for error recovery.
- getNextToken();
- }
- }
-
- static void HandleTopLevelExpression() {
- // Evaluate a top-level expression into an anonymous function.
- if (FunctionAST *F = ParseTopLevelExpr()) {
- if (Function *LF = F->Codegen()) {
- fprintf(stderr, "Read top-level expression:");
- LF->dump();
- }
- } else {
- // Skip token for error recovery.
- getNextToken();
- }
- }
-
- /// top ::= definition | external | expression | ';'
- static void MainLoop() {
- while (1) {
- fprintf(stderr, "ready> ");
- switch (CurTok) {
- case tok_eof: return;
- case ';': getNextToken(); break; // ignore top-level semicolons.
- case tok_def: HandleDefinition(); break;
- case tok_extern: HandleExtern(); break;
- default: HandleTopLevelExpression(); break;
- }
- }
- }
-
- //===----------------------------------------------------------------------===//
- // "Library" functions that can be "extern'd" from user code.
- //===----------------------------------------------------------------------===//
-
- /// putchard - putchar that takes a double and returns 0.
- extern "C"
- double putchard(double X) {
- putchar((char)X);
- return 0;
- }
-
- //===----------------------------------------------------------------------===//
- // Main driver code.
- //===----------------------------------------------------------------------===//
-
- int main() {
- LLVMContext &Context = getGlobalContext();
-
- // Install standard binary operators.
- // 1 is lowest precedence.
- BinopPrecedence['<'] = 10;
- BinopPrecedence['+'] = 20;
- BinopPrecedence['-'] = 20;
- BinopPrecedence['*'] = 40; // highest.
-
- // Prime the first token.
- fprintf(stderr, "ready> ");
- getNextToken();
-
- // Make the module, which holds all the code.
- TheModule = new Module("my cool jit", Context);
-
- // Run the main "interpreter loop" now.
- MainLoop();
-
- // Print out all of the generated code.
- TheModule->dump();
-
- return 0;
- }
+.. literalinclude:: ../../examples/Kaleidoscope/Chapter3/toy.cpp
+ :language: c++
`Next: Adding JIT and Optimizer Support <LangImpl4.html>`_
projects / oota-llvm.git / blobdiff