i'm pretty new to llvm and only did the online tutorial here: http://llvm.org/docs/tutorial/LangImpl1.html Now I wanted to do my own little language and got a little problem. I want to parse this:
(def i 1)
It should do two things:
The function gets created correctly, but I have a problem with using it as an expression. the AST looks like this:
FunctionAST // the whole statement
- Prototype // is an nameless statement
- Body // contains the definition expression
- DefExprAST
- Body // contains the Function definition
- FunctionAST
- Prototype // named i
- Body // the value 1
The Code for the Code Creation for the function looks like this:
Function *FunctionAST::Codegen() {
NamedValues.clear();
Function *TheFunction = Proto->Codegen();
if ( TheFunction == 0 ) return 0;
BasicBlock *BB = BasicBlock::Create( getGlobalContext(), "entry", TheFunction );
Builder.SetInsertPoint( BB );
if ( Value *RetVal = Body->Codegen() ) {
Builder.CreateRet( RetVal );
verifyFunction( *TheFunction );
return TheFunction;
}
return 0;
}
And the DefExprAST like this:
Value *DefExprAST::Codegen() {
if ( Body->Codegen() == 0 ) return 0;
return ConstantFP::get( getGlobalContext(), APFloat( 0.0 ) );
}
The verifyFunction
gives the following error:
Basic Block in function '' does not have terminator!
label %entry
LLVM ERROR: Broken module, no Basic Block terminator!
And indeed, the generated function does not have a ret entry. Its empty:
define double @0() {
entry:
}
But RetVal
is correctly filled with an double and Builder.CreateRet( RetVal )
gives back the ret statement but it doesn't get inserted into the entry.
Sometimes formulating an question and taking a little break helps to solve problems very well. I changed the DefExprAST::Codegen
to remember the Parent block and set it as the insertion point for the return value.
Value *DefExprAST::Codegen() {
BasicBlock *Parent = Builder.GetInsertBlock();
if ( Body->Codegen() == 0 ) return 0;
Builder.SetInsertPoint( Parent );
return ConstantFP::get( getGlobalContext(), APFloat( 0.0 ) );
}