.. code-block:: c++
// control
- tok_if = -6, tok_then = -7, tok_else = -8,
+ tok_if = -6,
+ tok_then = -7,
+ tok_else = -8,
Once we have that, we recognize the new keywords in the lexer. This is
pretty simple stuff:
.. code-block:: c++
...
- if (IdentifierStr == "def") return tok_def;
- if (IdentifierStr == "extern") return tok_extern;
- if (IdentifierStr == "if") return tok_if;
- if (IdentifierStr == "then") return tok_then;
- if (IdentifierStr == "else") return tok_else;
+ if (IdentifierStr == "def")
+ return tok_def;
+ if (IdentifierStr == "extern")
+ return tok_extern;
+ if (IdentifierStr == "if")
+ return tok_if;
+ if (IdentifierStr == "then")
+ return tok_then;
+ if (IdentifierStr == "else")
+ return tok_else;
return tok_identifier;
AST Extensions for If/Then/Else
/// IfExprAST - Expression class for if/then/else.
class IfExprAST : public ExprAST {
- ExprAST *Cond, *Then, *Else;
+ std::unique<ExprAST> Cond, Then, Else;
+
public:
- IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
- : Cond(cond), Then(then), Else(_else) {}
+ IfExprAST(std::unique_ptr<ExprAST> Cond, std::unique_ptr<ExprAST> Then,
+ std::unique_ptr<ExprAST> Else)
+ : Cond(std::move(Cond)), Then(std::move(Then)), Else(std::move(Else)) {}
virtual Value *Codegen();
};
.. code-block:: c++
/// ifexpr ::= 'if' expression 'then' expression 'else' expression
- static ExprAST *ParseIfExpr() {
+ static std::unique_ptr<ExprAST> ParseIfExpr() {
getNextToken(); // eat the if.
// condition.
- ExprAST *Cond = ParseExpression();
- if (!Cond) return 0;
+ auto Cond = ParseExpression();
+ if (!Cond)
+ return nullptr;
if (CurTok != tok_then)
return Error("expected then");
getNextToken(); // eat the then
- ExprAST *Then = ParseExpression();
- if (Then == 0) return 0;
+ auto Then = ParseExpression();
+ if (!Then)
+ return nullptr;
if (CurTok != tok_else)
return Error("expected else");
getNextToken();
- ExprAST *Else = ParseExpression();
- if (!Else) return 0;
+ auto Else = ParseExpression();
+ if (!Else)
+ return nullptr;
- return new IfExprAST(Cond, Then, Else);
+ return llvm::make_unique<IfExprAST>(std::move(Cond), std::move(Then),
+ std::move(Else));
}
Next we hook it up as a primary expression:
.. code-block:: c++
- static ExprAST *ParsePrimary() {
+ static std::unique_ptr<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();
- case tok_if: return ParseIfExpr();
+ default:
+ return Error("unknown token when expecting an expression");
+ case tok_identifier:
+ return ParseIdentifierExpr();
+ case tok_number:
+ return ParseNumberExpr();
+ case '(':
+ return ParseParenExpr();
+ case tok_if:
+ return ParseIfExpr();
}
}
we'll talk about #1 in depth. For now, just believe me that you don't
need SSA construction to handle this case. For #2, you have the choice
of using the techniques that we will describe for #1, or you can insert
-Phi nodes directly, if convenient. In this case, it is really really
+Phi nodes directly, if convenient. In this case, it is really
easy to generate the Phi node, so we choose to do it directly.
Okay, enough of the motivation and overview, lets generate code!
Value *IfExprAST::Codegen() {
Value *CondV = Cond->Codegen();
- if (CondV == 0) return 0;
+ if (!CondV)
+ return nullptr;
// Convert condition to a bool by comparing equal to 0.0.
- CondV = Builder.CreateFCmpONE(CondV,
- ConstantFP::get(getGlobalContext(), APFloat(0.0)),
- "ifcond");
+ CondV = Builder.CreateFCmpONE(
+ CondV, ConstantFP::get(getGlobalContext(), APFloat(0.0)), "ifcond");
This code is straightforward and similar to what we saw before. We emit
the expression for the condition, then compare that value to zero to get
// Create blocks for the then and else cases. Insert the 'then' block at the
// end of the function.
- BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
+ BasicBlock *ThenBB =
+ BasicBlock::Create(getGlobalContext(), "then", TheFunction);
BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
Builder.SetInsertPoint(ThenBB);
Value *ThenV = Then->Codegen();
- if (ThenV == 0) return 0;
+ if (!ThenV)
+ return nullptr;
Builder.CreateBr(MergeBB);
// Codegen of 'Then' can change the current block, update ThenBB for the PHI.
Builder.SetInsertPoint(ElseBB);
Value *ElseV = Else->Codegen();
- if (ElseV == 0) return 0;
+ if (!ElseV)
+ return nullptr;
Builder.CreateBr(MergeBB);
// Codegen of 'Else' can change the current block, update ElseBB for the PHI.
// Emit merge block.
TheFunction->getBasicBlockList().push_back(MergeBB);
Builder.SetInsertPoint(MergeBB);
- PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
- "iftmp");
+ PHINode *PN =
+ Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2, "iftmp");
PN->addIncoming(ThenV, ThenBB);
PN->addIncoming(ElseV, ElseBB);
The first two lines here are now familiar: the first adds the "merge"
block to the Function object (it was previously floating, like the else
-block above). The second block changes the insertion point so that newly
+block above). The second changes the insertion point so that newly
created code will go into the "merge" block. Once that is done, we need
to create the PHI node and set up the block/value pairs for the PHI.
tok_for = -9, tok_in = -10
... in gettok ...
- if (IdentifierStr == "def") return tok_def;
- if (IdentifierStr == "extern") return tok_extern;
- if (IdentifierStr == "if") return tok_if;
- if (IdentifierStr == "then") return tok_then;
- if (IdentifierStr == "else") return tok_else;
- if (IdentifierStr == "for") return tok_for;
- if (IdentifierStr == "in") return tok_in;
+ if (IdentifierStr == "def")
+ return tok_def;
+ if (IdentifierStr == "extern")
+ return tok_extern;
+ if (IdentifierStr == "if")
+ return tok_if;
+ if (IdentifierStr == "then")
+ return tok_then;
+ if (IdentifierStr == "else")
+ return tok_else;
+ if (IdentifierStr == "for")
+ return tok_for;
+ if (IdentifierStr == "in")
+ return tok_in;
return tok_identifier;
AST Extensions for the 'for' Loop
/// ForExprAST - Expression class for for/in.
class ForExprAST : public ExprAST {
std::string VarName;
- ExprAST *Start, *End, *Step, *Body;
+ std::unique_ptr<ExprAST> Start, End, Step, Body;
+
public:
- ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
- ExprAST *step, ExprAST *body)
- : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
+ ForExprAST(const std::string &VarName, std::unique_ptr<ExprAST> Start,
+ std::unique_ptr<ExprAST> End, std::unique_ptr<ExprAST> Step,
+ std::unique_ptr<ExprAST> Body)
+ : VarName(VarName), Start(std::move(Start)), End(std::move(End)),
+ Step(std::move(Step)), Body(std::move(Body)) {}
virtual Value *Codegen();
};
.. code-block:: c++
/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
- static ExprAST *ParseForExpr() {
+ static std::unique_ptr<ExprAST> ParseForExpr() {
getNextToken(); // eat the for.
if (CurTok != tok_identifier)
getNextToken(); // eat '='.
- ExprAST *Start = ParseExpression();
- if (Start == 0) return 0;
+ auto Start = ParseExpression();
+ if (!Start)
+ return nullptr;
if (CurTok != ',')
return Error("expected ',' after for start value");
getNextToken();
- ExprAST *End = ParseExpression();
- if (End == 0) return 0;
+ auto End = ParseExpression();
+ if (!End)
+ return nullptr;
// The step value is optional.
- ExprAST *Step = 0;
+ std::unique_ptr<ExprAST> Step;
if (CurTok == ',') {
getNextToken();
Step = ParseExpression();
- if (Step == 0) return 0;
+ if (!Step)
+ return nullptr;
}
if (CurTok != tok_in)
return Error("expected 'in' after for");
getNextToken(); // eat 'in'.
- ExprAST *Body = ParseExpression();
- if (Body == 0) return 0;
+ auto Body = ParseExpression();
+ if (!Body)
+ return nullptr;
- return new ForExprAST(IdName, Start, End, Step, Body);
+ return llvm::make_unique<ForExprAST>(IdName, std::move(Start),
+ std::move(End), std::move(Step),
+ std::move(Body));
}
LLVM IR for the 'for' Loop
// block.
Function *TheFunction = Builder.GetInsertBlock()->getParent();
BasicBlock *PreheaderBB = Builder.GetInsertBlock();
- BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
+ BasicBlock *LoopBB =
+ BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
// Insert an explicit fall through from the current block to the LoopBB.
Builder.CreateBr(LoopBB);
Builder.SetInsertPoint(LoopBB);
// Start the PHI node with an entry for Start.
- PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2, VarName.c_str());
+ PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()),
+ 2, VarName.c_str());
Variable->addIncoming(StartVal, PreheaderBB);
Now that the "preheader" for the loop is set up, we switch to emitting
// 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.
- if (Body->Codegen() == 0)
- return 0;
+ if (!Body->Codegen())
+ return nullptr;
Now the code starts to get more interesting. Our 'for' loop introduces a
new variable to the symbol table. This means that our symbol table can
.. code-block:: c++
// Emit the step value.
- Value *StepVal;
+ Value *StepVal = nullptr;
if (Step) {
StepVal = Step->Codegen();
- if (StepVal == 0) return 0;
+ if (!StepVal)
+ return nullptr;
} else {
// If not specified, use 1.0.
StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
// Compute the end condition.
Value *EndCond = End->Codegen();
- if (EndCond == 0) return EndCond;
+ if (!EndCond)
+ return nullptr;
// Convert condition to a bool by comparing equal to 0.0.
- EndCond = Builder.CreateFCmpONE(EndCond,
- ConstantFP::get(getGlobalContext(), APFloat(0.0)),
- "loopcond");
+ EndCond = Builder.CreateFCmpONE(
+ EndCond, ConstantFP::get(getGlobalContext(), APFloat(0.0)), "loopcond");
Finally, we evaluate the exit value of the loop, to determine whether
the loop should exit. This mirrors the condition evaluation for the
// Create the "after loop" block and insert it.
BasicBlock *LoopEndBB = Builder.GetInsertBlock();
- BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
+ BasicBlock *AfterBB =
+ BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
// Insert the conditional branch into the end of LoopEndBB.
Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
.. code-block:: bash
# Compile
- clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs core jit native` -O3 -o toy
+ clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs core mcjit native` -O3 -o toy
# Run
./toy
projects / oota-llvm.git / blobdiff