Update Kaleidoscope tutorial and improve Windows support
Many quoted code blocks were not in sync with the actual toy.cpp
files. Improve tutorial text slightly in several places.
Added some step descriptions crucial to avoid crashes (like
InitializeNativeTarget* calls).
Solve/workaround problems with Windows (JIT'ed method not found, using
custom and standard library functions from host process).
Patch by: Moritz Kroll <moritz.kroll@gmx.de>
Differential Revision: https://reviews.llvm.org/D29864
llvm-svn: 294870
diff --git a/llvm/docs/tutorial/LangImpl05.rst b/llvm/docs/tutorial/LangImpl05.rst
index ae0935d..dcf45bc 100644
--- a/llvm/docs/tutorial/LangImpl05.rst
+++ b/llvm/docs/tutorial/LangImpl05.rst
@@ -103,7 +103,8 @@
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();
+
+ Value *codegen() override;
};
The AST node just has pointers to the various subexpressions.
@@ -290,9 +291,9 @@
if (!CondV)
return nullptr;
- // Convert condition to a bool by comparing equal to 0.0.
+ // Convert condition to a bool by comparing non-equal to 0.0.
CondV = Builder.CreateFCmpONE(
- CondV, ConstantFP::get(LLVMContext, APFloat(0.0)), "ifcond");
+ CondV, ConstantFP::get(TheContext, 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
@@ -305,9 +306,9 @@
// Create blocks for the then and else cases. Insert the 'then' block at the
// end of the function.
BasicBlock *ThenBB =
- BasicBlock::Create(LLVMContext, "then", TheFunction);
- BasicBlock *ElseBB = BasicBlock::Create(LLVMContext, "else");
- BasicBlock *MergeBB = BasicBlock::Create(LLVMContext, "ifcont");
+ BasicBlock::Create(TheContext, "then", TheFunction);
+ BasicBlock *ElseBB = BasicBlock::Create(TheContext, "else");
+ BasicBlock *MergeBB = BasicBlock::Create(TheContext, "ifcont");
Builder.CreateCondBr(CondV, ThenBB, ElseBB);
@@ -400,7 +401,7 @@
TheFunction->getBasicBlockList().push_back(MergeBB);
Builder.SetInsertPoint(MergeBB);
PHINode *PN =
- Builder.CreatePHI(Type::getDoubleTy(LLVMContext), 2, "iftmp");
+ Builder.CreatePHI(Type::getDoubleTy(TheContext), 2, "iftmp");
PN->addIncoming(ThenV, ThenBB);
PN->addIncoming(ElseV, ElseBB);
@@ -433,7 +434,7 @@
::
- extern putchard(char)
+ extern putchard(char);
def printstar(n)
for i = 1, i < n, 1.0 in
putchard(42); # ascii 42 = '*'
@@ -500,7 +501,8 @@
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();
+
+ Value *codegen() override;
};
Parser Extensions for the 'for' Loop
@@ -561,6 +563,27 @@
std::move(Body));
}
+And again we hook it up as a primary expression:
+
+.. code-block:: c++
+
+ static std::unique_ptr<ExprAST> ParsePrimary() {
+ switch (CurTok) {
+ default:
+ return LogError("unknown token when expecting an expression");
+ case tok_identifier:
+ return ParseIdentifierExpr();
+ case tok_number:
+ return ParseNumberExpr();
+ case '(':
+ return ParseParenExpr();
+ case tok_if:
+ return ParseIfExpr();
+ case tok_for:
+ return ParseForExpr();
+ }
+ }
+
LLVM IR for the 'for' Loop
--------------------------
@@ -610,7 +633,8 @@
Value *ForExprAST::codegen() {
// Emit the start code first, without 'variable' in scope.
Value *StartVal = Start->codegen();
- if (StartVal == 0) return 0;
+ if (!StartVal)
+ return nullptr;
With this out of the way, the next step is to set up the LLVM basic
block for the start of the loop body. In the case above, the whole loop
@@ -625,7 +649,7 @@
Function *TheFunction = Builder.GetInsertBlock()->getParent();
BasicBlock *PreheaderBB = Builder.GetInsertBlock();
BasicBlock *LoopBB =
- BasicBlock::Create(LLVMContext, "loop", TheFunction);
+ BasicBlock::Create(TheContext, "loop", TheFunction);
// Insert an explicit fall through from the current block to the LoopBB.
Builder.CreateBr(LoopBB);
@@ -642,7 +666,7 @@
Builder.SetInsertPoint(LoopBB);
// Start the PHI node with an entry for Start.
- PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(LLVMContext),
+ PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(TheContext),
2, VarName.c_str());
Variable->addIncoming(StartVal, PreheaderBB);
@@ -693,7 +717,7 @@
return nullptr;
} else {
// If not specified, use 1.0.
- StepVal = ConstantFP::get(LLVMContext, APFloat(1.0));
+ StepVal = ConstantFP::get(TheContext, APFloat(1.0));
}
Value *NextVar = Builder.CreateFAdd(Variable, StepVal, "nextvar");
@@ -710,9 +734,9 @@
if (!EndCond)
return nullptr;
- // Convert condition to a bool by comparing equal to 0.0.
+ // Convert condition to a bool by comparing non-equal to 0.0.
EndCond = Builder.CreateFCmpONE(
- EndCond, ConstantFP::get(LLVMContext, APFloat(0.0)), "loopcond");
+ EndCond, ConstantFP::get(TheContext, 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
@@ -723,7 +747,7 @@
// Create the "after loop" block and insert it.
BasicBlock *LoopEndBB = Builder.GetInsertBlock();
BasicBlock *AfterBB =
- BasicBlock::Create(LLVMContext, "afterloop", TheFunction);
+ BasicBlock::Create(TheContext, "afterloop", TheFunction);
// Insert the conditional branch into the end of LoopEndBB.
Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
@@ -751,7 +775,7 @@
NamedValues.erase(VarName);
// for expr always returns 0.0.
- return Constant::getNullValue(Type::getDoubleTy(LLVMContext));
+ return Constant::getNullValue(Type::getDoubleTy(TheContext));
}
The final code handles various cleanups: now that we have the "NextVar"
@@ -772,7 +796,7 @@
=================
Here is the complete code listing for our running example, enhanced with
-the if/then/else and for expressions.. To build this example, use:
+the if/then/else and for expressions. To build this example, use:
.. code-block:: bash