IR: Enable debug info type ODR uniquing for forward decls

Add a new method, DICompositeType::buildODRType, that will create or
mutate the DICompositeType for a given ODR identifier, and use it in
LLParser and BitcodeReader instead of DICompositeType::getODRType.

The logic is as follows:

  - If there's no node, create one with the given arguments.
  - Else, if the current node is a forward declaration and the new
    arguments would create a definition, mutate the node to match the
    new arguments.
  - Else, return the old node.

This adds a missing feature supported by the current DITypeIdentifierMap
(which I'm slowly making redudant).  The only remaining difference is
that the DITypeIdentifierMap has a "the-last-one-wins" rule, whereas
DICompositeType::buildODRType has a "the-first-one-wins" rule.

For now I'm leaving behind DICompositeType::getODRType since it has
obvious, low-level semantics that are convenient for unit testing.

llvm-svn: 266786

1 files changed, 35 insertions, 0 deletions

diff --git a/llvm/lib/IR/DebugInfoMetadata.cpp b/llvm/lib/IR/DebugInfoMetadata.cpp
index 37986f73ab1..c2ecd4e5fc8 100644
--- a/llvm/lib/IR/DebugInfoMetadata.cpp
+++ b/llvm/lib/IR/DebugInfoMetadata.cpp
@@ -255,6 +255,7 @@ DICompositeType *DICompositeType::getImpl(
     bool ShouldCreate) {
   assert(isCanonical(Name) && "Expected canonical MDString");
 
+  // Keep this in sync with buildODRType.
   DEFINE_GETIMPL_LOOKUP(
       DICompositeType, (Tag, Name, File, Line, Scope, BaseType, SizeInBits,
                         AlignInBits, OffsetInBits, Flags, Elements, RuntimeLang,
@@ -266,6 +267,40 @@ DICompositeType *DICompositeType::getImpl(
                        Ops);
 }
 
+DICompositeType *DICompositeType::buildODRType(
+    LLVMContext &Context, MDString &Identifier, unsigned Tag, MDString *Name,
+    Metadata *File, unsigned Line, Metadata *Scope, Metadata *BaseType,
+    uint64_t SizeInBits, uint64_t AlignInBits, uint64_t OffsetInBits,
+    unsigned Flags, Metadata *Elements, unsigned RuntimeLang,
+    Metadata *VTableHolder, Metadata *TemplateParams) {
+  assert(!Identifier.getString().empty() && "Expected valid identifier");
+  if (!Context.isODRUniquingDebugTypes())
+    return nullptr;
+  auto *&CT = (*Context.pImpl->DITypeMap)[&Identifier];
+  if (!CT)
+    return CT = DICompositeType::getDistinct(
+               Context, Tag, Name, File, Line, Scope, BaseType, SizeInBits,
+               AlignInBits, OffsetInBits, Flags, Elements, RuntimeLang,
+               VTableHolder, TemplateParams, &Identifier);
+
+  // Only mutate CT if it's a forward declaration and the new operands aren't.
+  assert(CT->getRawIdentifier() == &Identifier && "Wrong ODR identifier?");
+  if (!CT->isForwardDecl() || (Flags & DINode::FlagFwdDecl))
+    return CT;
+
+  // Mutate CT in place.  Keep this in sync with getImpl.
+  CT->mutate(Tag, Line, RuntimeLang, SizeInBits, AlignInBits, OffsetInBits,
+             Flags);
+  Metadata *Ops[] = {File,     Scope,        Name,           BaseType,
+                     Elements, VTableHolder, TemplateParams, &Identifier};
+  assert(std::end(Ops) - std::begin(Ops) == CT->getNumOperands() &&
+         "Mismatched number of operands");
+  for (unsigned I = 0, E = CT->getNumOperands(); I != E; ++I)
+    if (Ops[I] != CT->getOperand(I))
+      CT->setOperand(I, Ops[I]);
+  return CT;
+}
+
 DICompositeType *DICompositeType::getODRType(
     LLVMContext &Context, MDString &Identifier, unsigned Tag, MDString *Name,
     Metadata *File, unsigned Line, Metadata *Scope, Metadata *BaseType,