-=======================================================
-Kaleidoscope: Extending the Language: Debug Information
-=======================================================
+======================================
+Kaleidoscope: Adding Debug Information
+======================================
.. contents::
:local:
static DIBuilder *DBuilder;
struct DebugInfo {
- DICompileUnit TheCU;
- DIType DblTy;
+ DICompileUnit *TheCU;
+ DIType *DblTy;
- DIType getDoubleTy();
+ DIType *getDoubleTy();
} KSDbgInfo;
- DIType DebugInfo::getDoubleTy() {
+ DIType *DebugInfo::getDoubleTy() {
if (DblTy.isValid())
return DblTy;
.. code-block:: c++
- DIFile Unit = DBuilder->createFile(KSDbgInfo.TheCU.getFilename(),
- KSDbgInfo.TheCU.getDirectory());
+ DIFile *Unit = DBuilder->createFile(KSDbgInfo.TheCU.getFilename(),
+ KSDbgInfo.TheCU.getDirectory());
-giving us a DIFile and asking the ``Compile Unit`` we created above for the
+giving us an DIFile and asking the ``Compile Unit`` we created above for the
directory and filename where we are currently. Then, for now, we use some
source locations of 0 (since our AST doesn't currently have source location
information) and construct our function definition:
.. code-block:: c++
- DIDescriptor FContext(Unit);
+ DIScope *FContext = Unit;
unsigned LineNo = 0;
unsigned ScopeLine = 0;
- DISubprogram SP = DBuilder->createFunction(
+ DISubprogram *SP = DBuilder->createFunction(
FContext, Name, StringRef(), Unit, LineNo,
CreateFunctionType(Args.size(), Unit), false /* internal linkage */,
- true /* definition */, ScopeLine, DIDescriptor::FlagPrototyped, false, F);
+ true /* definition */, ScopeLine, DINode::FlagPrototyped, false, F);
-and we now have a DISubprogram that contains a reference to all of our metadata
-for the function.
+and we now have an DISubprogram that contains a reference to all of our
+metadata for the function.
Source Locations
================
void DebugInfo::emitLocation(ExprAST *AST) {
DIScope *Scope;
if (LexicalBlocks.empty())
- Scope = &TheCU;
+ Scope = TheCU;
else
Scope = LexicalBlocks.back();
Builder.SetCurrentDebugLocation(
- DebugLoc::get(AST->getLine(), AST->getCol(), DIScope(*Scope)));
+ DebugLoc::get(AST->getLine(), AST->getCol(), Scope));
}
that both tells the main ``IRBuilder`` where we are, but also what scope
.. code-block:: c++
std::vector<DIScope *> LexicalBlocks;
- std::map<const PrototypeAST *, DIScope> FnScopeMap;
+ std::map<const PrototypeAST *, DIScope *> FnScopeMap;
-and keep a map of each function to the scope that it represents (a DISubprogram
-is also a DIScope).
+and keep a map of each function to the scope that it represents (an
+DISubprogram is also an DIScope).
Then we make sure to:
when we start generating the code for each function.
+also, don't forget to pop the scope back off of your scope stack at the
+end of the code generation for the function:
+
+.. code-block:: c++
+
+ // Pop off the lexical block for the function since we added it
+ // unconditionally.
+ KSDbgInfo.LexicalBlocks.pop_back();
+
+Variables
+=========
+
+Now that we have functions, we need to be able to print out the variables
+we have in scope. Let's get our function arguments set up so we can get
+decent backtraces and see how our functions are being called. It isn't
+a lot of code, and we generally handle it when we're creating the
+argument allocas in ``PrototypeAST::CreateArgumentAllocas``.
+
+.. code-block:: c++
+
+ DIScope *Scope = KSDbgInfo.LexicalBlocks.back();
+ DIFile *Unit = DBuilder->createFile(KSDbgInfo.TheCU.getFilename(),
+ KSDbgInfo.TheCU.getDirectory());
+ DILocalVariable D = DBuilder->createLocalVariable(
+ dwarf::DW_TAG_arg_variable, Scope, Args[Idx], Unit, Line,
+ KSDbgInfo.getDoubleTy(), true, 0, Idx + 1);
+
+ Instruction *Call = DBuilder->insertDeclare(
+ Alloca, D, DBuilder->createExpression(), Builder.GetInsertBlock());
+ Call->setDebugLoc(DebugLoc::get(Line, 0, Scope));
+
+Here we're doing a few things. First, we're grabbing our current scope
+for the variable so we can say what range of code our variable is valid
+through. Second, we're creating the variable, giving it the scope,
+the name, source location, type, and since it's an argument, the argument
+index. Third, we create an ``lvm.dbg.declare`` call to indicate at the IR
+level that we've got a variable in an alloca (and it gives a starting
+location for the variable). Lastly, we set a source location for the
+beginning of the scope on the declare.
+
One interesting thing to note at this point is that various debuggers have
assumptions based on how code and debug information was generated for them
in the past. In this case we need to do a little bit of a hack to avoid
KSDbgInfo.emitLocation(Body);
-also, don't forget to pop the scope back off of your scope stack at the
-end of the code generation for the function:
-
-.. code-block:: c++
-
- // Pop off the lexical block for the function since we added it
- // unconditionally.
- KSDbgInfo.LexicalBlocks.pop_back();
-
+With this we have enough debug information to set breakpoints in functions,
+print out argument variables, and call functions. Not too bad for just a
+few simple lines of code!
Full Code Listing
=================
.. 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