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, 3 insertions, 4 deletions

diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index fb27ab5..d9b7f3e 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -3839,10 +3839,9 @@ bool LLParser::ParseDICompositeType(MDNode *&Result, bool IsDistinct) {
   PARSE_MD_FIELDS();
 #undef VISIT_MD_FIELDS
 
-  // If this isn't a forward declaration and it has a UUID, check for it in the
-  // type map in the context.
-  if (!(flags.Val & DINode::FlagFwdDecl) && identifier.Val)
-    if (auto *CT = DICompositeType::getODRType(
+  // If this has an identifier try to build an ODR type.
+  if (identifier.Val)
+    if (auto *CT = DICompositeType::buildODRType(
             Context, *identifier.Val, tag.Val, name.Val, file.Val, line.Val,
             scope.Val, baseType.Val, size.Val, align.Val, offset.Val, flags.Val,
             elements.Val, runtimeLang.Val, vtableHolder.Val,