parser than it is to generate LLVM IR code. :)
</p>
+<p><b>Please note</b>: 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 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 <a href="http://llvm.org/releases/">llvm.org
+releases page</a>.</p>
+
</div>
<!-- *********************************************************************** -->
<div class="doc_text">
<p>
-In order to generate LLVM IR, we want some simple setup to get started. First,
-we define virtual codegen methods in each AST class:</p>
+In order to generate LLVM IR, we want some simple setup to get started. First
+we define virtual code generation (codegen) methods in each AST class:</p>
<div class="doc_code">
<pre>
class NumberExprAST : public ExprAST {
double Val;
public:
- explicit NumberExprAST(double val) : Val(val) {}
+ NumberExprAST(double val) : Val(val) {}
<b>virtual Value *Codegen();</b>
};
...
Assignment</a> - the concepts are really quite natural once you grok them.</p>
<p>Note that instead of adding virtual methods to the ExprAST class hierarchy,
-it could also make sense to use a visitor pattern or some other way to model
-this. Again, this tutorial won't dwell on good software engineering practices:
-for our purposes, adding a virtual method is simplest.</p>
+it could also make sense to use a <a
+href="http://en.wikipedia.org/wiki/Visitor_pattern">visitor pattern</a> or some
+other way to model this. Again, this tutorial won't dwell on good software
+engineering practices: for our purposes, adding a virtual method is
+simplest.</p>
<p>The
second thing we want is an "Error" method like we used for the parser, which will
Value *ErrorV(const char *Str) { Error(Str); return 0; }
static Module *TheModule;
-static LLVMBuilder Builder;
+static IRBuilder<> Builder(getGlobalContext());
static std::map<std::string, Value*> NamedValues;
</pre>
</div>
<p>The <tt>Builder</tt> object is a helper object that makes it easy to generate
LLVM instructions. Instances of the <a
-href="http://llvm.org/doxygen/LLVMBuilder_8h-source.html"><tt>LLVMBuilder</tt>
-class</a> keep track of the current place to
-insert instructions and has methods to create new instructions.</p>
+href="http://llvm.org/doxygen/IRBuilder_8h-source.html"><tt>IRBuilder</tt></a>
+class template keep track of the current place to insert instructions and has
+methods to create new instructions.</p>
<p>The <tt>NamedValues</tt> map keeps track of which values are defined in the
-current scope and what their LLVM representation is (in other words, it is a
-symbol table for the code). In this form of
-Kaleidoscope, the only things that can be referenced are function parameters.
-As such, function parameters will be in this map when generating code for their
-function body.</p>
+current scope and what their LLVM representation is. (In other words, it is a
+symbol table for the code). In this form of Kaleidoscope, the only things that
+can be referenced are function parameters. As such, function parameters will
+be in this map when generating code for their function body.</p>
<p>
With these basics in place, we can start talking about how to generate code for
<div class="doc_text">
<p>Generating LLVM code for expression nodes is very straightforward: less
-than 45 lines of commented code for all four of our expression nodes. First,
+than 45 lines of commented code for all four of our expression nodes. First
we'll do numeric literals:</p>
<div class="doc_code">
<pre>
Value *NumberExprAST::Codegen() {
- return ConstantFP::get(Type::DoubleTy, APFloat(Val));
+ return ConstantFP::get(getGlobalContext(), APFloat(Val));
}
</pre>
</div>
constants of <em>A</em>rbitrary <em>P</em>recision). This code basically just
creates and returns a <tt>ConstantFP</tt>. Note that in the LLVM IR
that constants are all uniqued together and shared. For this reason, the API
-uses "the foo::get(..)" idiom instead of "new foo(..)" or "foo::create(..)".</p>
+uses the "foo::get(...)" idiom instead of "new foo(..)" or "foo::Create(..)".</p>
<div class="doc_code">
<pre>
</div>
<p>References to variables are also quite simple using LLVM. In the simple version
-of Kaleidoscope, we assume that the variable has already been emited somewhere
+of Kaleidoscope, we assume that the variable has already been emitted somewhere
and its value is available. In practice, the only values that can be in the
<tt>NamedValues</tt> map are function arguments. This
code simply checks to see that the specified name is in the map (if not, an
case '<':
L = Builder.CreateFCmpULT(L, R, "cmptmp");
// Convert bool 0/1 to double 0.0 or 1.0
- return Builder.CreateUIToFP(L, Type::DoubleTy, "booltmp");
+ return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
+ "booltmp");
default: return ErrorV("invalid binary operator");
}
}
</p>
<p>In the example above, the LLVM builder class is starting to show its value.
-LLVMBuilder knows where to insert the newly created instruction, all you have to
+IRBuilder knows where to insert the newly created instruction, all you have to
do is specify what instruction to create (e.g. with <tt>CreateAdd</tt>), which
operands to use (<tt>L</tt> and <tt>R</tt> here) and optionally provide a name
-for the generated instruction. One nice thing about LLVM is that the name is
-just a hint: if there are multiple additions in a single function, the first
-will be named "addtmp" and the second will be "autorenamed" by adding a suffix,
-giving it a name like "addtmp42". Local value names for instructions are purely
-optional, but it makes it much easier to read the IR dumps.</p>
+for the generated instruction.</p>
+
+<p>One nice thing about LLVM is that the name is just a hint. For instance, if
+the code above emits multiple "addtmp" variables, LLVM will automatically
+provide each one with an increasing, unique numeric suffix. Local value names
+for instructions are purely optional, but it makes it much easier to read the
+IR dumps.</p>
<p><a href="../LangRef.html#instref">LLVM instructions</a> are constrained by
strict rules: for example, the Left and Right operators of
<pre>
Function *PrototypeAST::Codegen() {
// Make the function type: double(double,double) etc.
- std::vector<const Type*> Doubles(Args.size(), Type::DoubleTy);
- FunctionType *FT = FunctionType::get(Type::DoubleTy, Doubles, false);
+ std::vector<const Type*> Doubles(Args.size(),
+ Type::getDoubleTy(getGlobalContext()));
+ FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
+ Doubles, false);
- Function *F = new Function(FT, Function::ExternalLinkage, Name, TheModule);
+ Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
</pre>
</div>
<p>The call to <tt>FunctionType::get</tt> creates
the <tt>FunctionType</tt> that should be used for a given Prototype. Since all
function arguments in Kaleidoscope are of type double, the first line creates
-a vector of "N" LLVM double types. It then uses the <tt>FunctionType::get</tt>
+a vector of "N" LLVM double types. It then uses the <tt>Functiontype::get</tt>
method to create a function type that takes "N" doubles as arguments, returns
one double as a result, and that is not vararg (the false parameter indicates
this). Note that Types in LLVM are uniqued just like Constants are, so you
<p>The final line above actually creates the function that the prototype will
correspond to. This indicates the type, linkage and name to use, as well as which
-module to insert into. "<a href="LangRef.html#linkage">external linkage</a>"
+module to insert into. "<a href="../LangRef.html#linkage">external linkage</a>"
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 "<tt>TheModule</tt>" is specified, this name is registered
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 definining a body for it. This is useful
+allow 'extern'ing a function and then defining a body for it. This is useful
when defining mutually recursive functions.</p>
<p>In order to implement this, the code above first checks to see if there is
<div class="doc_code">
<pre>
// Create a new basic block to start insertion into.
- BasicBlock *BB = new BasicBlock("entry", TheFunction);
+ BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
Builder.SetInsertPoint(BB);
if (Value *RetVal = Body->Codegen()) {
if (Value *RetVal = Body->Codegen()) {
// Finish off the function.
Builder.CreateRet(RetVal);
-
+
// Validate the generated code, checking for consistency.
verifyFunction(*TheFunction);
+
return TheFunction;
}
</pre>
Read top-level expression:
define double @""() {
entry:
- %addtmp = add double 4.000000e+00, 5.000000e+00
- ret double %addtmp
+ ret double 9.000000e+00
}
</pre>
</div>
<p>Note how the parser turns the top-level expression into anonymous functions
for us. This will be handy when we add <a href="LangImpl4.html#jit">JIT
support</a> in the next chapter. Also note that the code is very literally
-transcribed, no optimizations are being performed. We will
+transcribed, no optimizations are being performed except simple constant
+folding done by IRBuilder. We will
<a href="LangImpl4.html#trivialconstfold">add optimizations</a> explicitly in
the next chapter.</p>
Read function definition:
define double @foo(double %a, double %b) {
entry:
- %multmp = mul double %a, %a
- %multmp1 = mul double 2.000000e+00, %a
- %multmp2 = mul double %multmp1, %b
- %addtmp = add double %multmp, %multmp2
- %multmp3 = mul double %b, %b
- %addtmp4 = add double %addtmp, %multmp3
+ %multmp = fmul double %a, %a
+ %multmp1 = fmul double 2.000000e+00, %a
+ %multmp2 = fmul double %multmp1, %b
+ %addtmp = fadd double %multmp, %multmp2
+ %multmp3 = fmul double %b, %b
+ %addtmp4 = fadd double %addtmp, %multmp3
ret double %addtmp4
}
</pre>
entry:
%calltmp = call double @foo( double %a, double 4.000000e+00 )
%calltmp1 = call double @bar( double 3.133700e+04 )
- %addtmp = add double %calltmp, %calltmp1
+ %addtmp = fadd double %calltmp, %calltmp1
ret double %addtmp
}
</pre>
define double @""() {
entry:
- %addtmp = add double 4.000000e+00, 5.000000e+00
+ %addtmp = fadd double 4.000000e+00, 5.000000e+00
ret double %addtmp
}
define double @foo(double %a, double %b) {
entry:
- %multmp = mul double %a, %a
- %multmp1 = mul double 2.000000e+00, %a
- %multmp2 = mul double %multmp1, %b
- %addtmp = add double %multmp, %multmp2
- %multmp3 = mul double %b, %b
- %addtmp4 = add double %addtmp, %multmp3
+ %multmp = fmul double %a, %a
+ %multmp1 = fmul double 2.000000e+00, %a
+ %multmp2 = fmul double %multmp1, %b
+ %addtmp = fadd double %multmp, %multmp2
+ %multmp3 = fmul double %b, %b
+ %addtmp4 = fadd double %addtmp, %multmp3
ret double %addtmp4
}
entry:
%calltmp = call double @foo( double %a, double 4.000000e+00 )
%calltmp1 = call double @bar( double 3.133700e+04 )
- %addtmp = add double %calltmp, %calltmp1
+ %addtmp = fadd double %calltmp, %calltmp1
ret double %addtmp
}
// See example below.
#include "llvm/DerivedTypes.h"
+#include "llvm/LLVMContext.h"
#include "llvm/Module.h"
#include "llvm/Analysis/Verifier.h"
-#include "llvm/Support/LLVMBuilder.h"
+#include "llvm/Support/IRBuilder.h"
#include <cstdio>
#include <string>
#include <map>
tok_def = -2, tok_extern = -3,
// primary
- tok_identifier = -4, tok_number = -5,
+ tok_identifier = -4, tok_number = -5
};
static std::string IdentifierStr; // Filled in if tok_identifier
if (LastChar == '#') {
// Comment until end of line.
do LastChar = getchar();
- while (LastChar != EOF && LastChar != '\n' & LastChar != '\r');
+ while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
if (LastChar != EOF)
return gettok();
class NumberExprAST : public ExprAST {
double Val;
public:
- explicit NumberExprAST(double val) : Val(val) {}
+ NumberExprAST(double val) : Val(val) {}
virtual Value *Codegen();
};
class VariableExprAST : public ExprAST {
std::string Name;
public:
- explicit VariableExprAST(const std::string &name) : Name(name) {}
+ VariableExprAST(const std::string &name) : Name(name) {}
virtual Value *Codegen();
};
};
/// PrototypeAST - This class represents the "prototype" for a function,
-/// which captures its argument names as well as if it is an operator.
+/// 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;
//===----------------------------------------------------------------------===//
/// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
-/// token the parser it looking at. getNextToken reads another token from the
+/// 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() {
ExprAST *Arg = ParseExpression();
if (!Arg) return 0;
Args.push_back(Arg);
-
+
if (CurTok == ')') break;
-
+
if (CurTok != ',')
- return Error("Expected ')'");
+ return Error("Expected ')' or ',' in argument list");
getNextToken();
}
}
//===----------------------------------------------------------------------===//
static Module *TheModule;
-static LLVMBuilder Builder;
+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(Type::DoubleTy, APFloat(Val));
+ return ConstantFP::get(getGlobalContext(), APFloat(Val));
}
Value *VariableExprAST::Codegen() {
case '<':
L = Builder.CreateFCmpULT(L, R, "cmptmp");
// Convert bool 0/1 to double 0.0 or 1.0
- return Builder.CreateUIToFP(L, Type::DoubleTy, "booltmp");
+ return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
+ "booltmp");
default: return ErrorV("invalid binary operator");
}
}
Function *PrototypeAST::Codegen() {
// Make the function type: double(double,double) etc.
- std::vector<const Type*> Doubles(Args.size(), Type::DoubleTy);
- FunctionType *FT = FunctionType::get(Type::DoubleTy, Doubles, false);
+ std::vector<const Type*> Doubles(Args.size(),
+ Type::getDoubleTy(getGlobalContext()));
+ FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
+ Doubles, false);
- Function *F = new Function(FT, Function::ExternalLinkage, Name, TheModule);
+ 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.
return 0;
// Create a new basic block to start insertion into.
- BasicBlock *BB = new BasicBlock("entry", TheFunction);
+ 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;
}
}
static void HandleTopLevelExpression() {
- // Evaluate a top level expression into an anonymous function.
+ // Evaluate a top-level expression into an anonymous function.
if (FunctionAST *F = ParseTopLevelExpr()) {
if (Function *LF = F->Codegen()) {
fprintf(stderr, "Read top-level expression:");
fprintf(stderr, "ready> ");
switch (CurTok) {
case tok_eof: return;
- case ';': getNextToken(); break; // ignore top level semicolons.
+ 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.
//===----------------------------------------------------------------------===//
//===----------------------------------------------------------------------===//
int main() {
- TheModule = new Module("my cool jit");
+ LLVMContext &Context = getGlobalContext();
// Install standard binary operators.
// 1 is lowest precedence.
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;
}
</pre>
</div>
+<a href="LangImpl4.html">Next: Adding JIT and Optimizer Support</a>
</div>
<!-- *********************************************************************** -->
<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
<a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
- Last modified: $Date: 2007-10-17 11:05:13 -0700 (Wed, 17 Oct 2007) $
+ Last modified: $Date$
</address>
</body>
</html>
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