[DebugInfo] Prepare DIBuilder for labels

[HsiangKai]

Summary

Implement createLabel() to allocate DILabel objects.

[probinson]

I suggest combining this with a patch that actually uses the API. We don't generally have commits that add APIs without uses or tests.

[HsiangKai]

In D45088#1053387, @probinson wrote:

I suggest combining this with a patch that actually uses the API. We don't generally have commits that add APIs without uses or tests.

Merged into D45024, this patch should be abandoned.

include/llvm/IR/DIBuilder.h

public:
     /// If \c AlwaysPreserve, this variable will be referenced from its
     /// containing subprogram, and will survive some optimizations.
     DILocalVariable *
     createAutoVariable(DIScope *Scope, StringRef Name, DIFile *File,
                        unsigned LineNo, DIType *Ty, bool AlwaysPreserve = false,
                        DINode::DIFlags Flags = DINode::FlagZero,
                        uint32_t AlignInBits = 0);
 
+    /// Create a new descriptor for an label.
+    ///
+    /// \c Scope must be a \a DILocalScope, and thus its scope chain eventually
+    /// leads to a \a DISubprogram.
+    DILabel *
+    createLabel(DIScope *Scope, StringRef Name, DIFile *File, unsigned LineNo);
+
     /// Create a new descriptor for a parameter variable.
     ///
     /// \c Scope must be a \a DILocalScope, and thus its scope chain eventually
     /// leads to a \a DISubprogram.
     ///
     /// \c ArgNo is the index (starting from \c 1) of this variable in the
     /// subprogram parameters.  \c ArgNo should not conflict with other
     /// parameters of the same subprogram.

lib/IR/DIBuilder.cpp

DILocalVariable *DIBuilder::createParameterVariable(
     DIScope *Scope, StringRef Name, unsigned ArgNo, DIFile *File,
     unsigned LineNo, DIType *Ty, bool AlwaysPreserve, DINode::DIFlags Flags) {
   assert(ArgNo && "Expected non-zero argument number for parameter");
   return createLocalVariable(VMContext, PreservedVariables, Scope, Name, ArgNo,
                              File, LineNo, Ty, AlwaysPreserve, Flags,
                              /* AlignInBits */0);
 }
 
+DILabel *DIBuilder::createLabel(DIScope *Scope, StringRef Name, DIFile *File,
+                                unsigned LineNo) {
+  DIScope *Context = getNonCompileUnitScope(Scope);
+
+  auto *Node =
+      DILabel::get(VMContext, cast_or_null<DILocalScope>(Context), Name,
+                   File, LineNo);
+  return Node;
+}
+
 DIExpression *DIBuilder::createExpression(ArrayRef<uint64_t> Addr) {
   return DIExpression::get(VMContext, Addr);
 }
 
 DIExpression *DIBuilder::createExpression(ArrayRef<int64_t> Signed) {
   // TODO: Remove the callers of this signed version and delete.
   SmallVector<uint64_t, 8> Addr(Signed.begin(), Signed.end());
   return createExpression(Addr);