IR: Allow GenericDebugNode construction from MDString

Allow `GenericDebugNode` construction directly from `MDString`, rather
than requiring `StringRef`s.  I've refactored the `StringRef`
constructors to use these.  There's no real functionality change here,
except for exposing the lower-level API.

The purpose of this is to simplify construction of string operands when
reading bitcode.  It's unnecessarily indirect to parse an `MDString` ID,
lookup the `MDString` in the bitcode reader list, get the `StringRef`
out of that, and then have `GenericDebugNode::getImpl()` use
`MDString::get()` to acquire the original `MDString`.  Instead, this
allows the bitcode reader to directly pass in the `MDString`.

llvm-svn: 227848

2 files changed, 30 insertions, 8 deletions

diff --git a/llvm/include/llvm/IR/DebugInfoMetadata.h b/llvm/include/llvm/IR/DebugInfoMetadata.h
index 96d35cc0323..0439e7f7b23 100644
--- a/llvm/include/llvm/IR/DebugInfoMetadata.h
+++ b/llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -111,6 +111,12 @@ protected:
     return StringRef();
   }
 
+  static MDString *getCanonicalMDString(LLVMContext &Context, StringRef S) {
+    if (S.empty())
+      return nullptr;
+    return MDString::get(Context, S);
+  }
+
 public:
   unsigned getTag() const { return SubclassData16; }
 
@@ -144,6 +150,15 @@ class GenericDebugNode : public DebugNode {
                                    StringRef Header,
                                    ArrayRef<Metadata *> DwarfOps,
                                    StorageType Storage,
+                                   bool ShouldCreate = true) {
+    return getImpl(Context, Tag, getCanonicalMDString(Context, Header),
+                   DwarfOps, Storage, ShouldCreate);
+  }
+
+  static GenericDebugNode *getImpl(LLVMContext &Context, unsigned Tag,
+                                   MDString *Header,
+                                   ArrayRef<Metadata *> DwarfOps,
+                                   StorageType Storage,
                                    bool ShouldCreate = true);
 
   TempGenericDebugNode cloneImpl() const {
@@ -158,6 +173,9 @@ public:
   DEFINE_MDNODE_GET(GenericDebugNode, (unsigned Tag, StringRef Header,
                                        ArrayRef<Metadata *> DwarfOps),
                     (Tag, Header, DwarfOps))
+  DEFINE_MDNODE_GET(GenericDebugNode, (unsigned Tag, MDString *Header,
+                                       ArrayRef<Metadata *> DwarfOps),
+                    (Tag, Header, DwarfOps))
 
   /// \brief Return a (temporary) clone of this.
   TempGenericDebugNode clone() const { return cloneImpl(); }
diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 66dcc8e8055..21a95f9f9fc 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -71,21 +71,24 @@ MDLocation *MDLocation::getImpl(LLVMContext &Context, unsigned Line,
                    Storage, Context.pImpl->MDLocations);
 }
 
-/// \brief Get the MDString, or nullptr if the string is empty.
-static MDString *getCanonicalMDString(LLVMContext &Context, StringRef S) {
-  if (S.empty())
-    return nullptr;
-  return MDString::get(Context, S);
+static StringRef getString(const MDString *S) {
+  if (S)
+    return S->getString();
+  return StringRef();
+}
+
+static bool isCanonical(const MDString *S) {
+  return !S || !S->getString().empty();
 }
 
 GenericDebugNode *GenericDebugNode::getImpl(LLVMContext &Context, unsigned Tag,
-                                            StringRef Header,
+                                            MDString *Header,
                                             ArrayRef<Metadata *> DwarfOps,
                                             StorageType Storage,
                                             bool ShouldCreate) {
   unsigned Hash = 0;
   if (Storage == Uniqued) {
-    GenericDebugNodeInfo::KeyTy Key(Tag, Header, DwarfOps);
+    GenericDebugNodeInfo::KeyTy Key(Tag, getString(Header), DwarfOps);
     if (auto *N = getUniqued(Context.pImpl->GenericDebugNodes, Key))
       return N;
     if (!ShouldCreate)
@@ -96,7 +99,8 @@ GenericDebugNode *GenericDebugNode::getImpl(LLVMContext &Context, unsigned Tag,
   }
 
   // Use a nullptr for empty headers.
-  Metadata *PreOps[] = {getCanonicalMDString(Context, Header)};
+  assert(isCanonical(Header) && "Expected canonical MDString");
+  Metadata *PreOps[] = {Header};
   return storeImpl(new (DwarfOps.size() + 1) GenericDebugNode(
                        Context, Storage, Hash, Tag, PreOps, DwarfOps),
                    Storage, Context.pImpl->GenericDebugNodes);