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, 1 deletions

diff --git a/llvm/test/Linker/Inputs/dicompositetype-unique.ll b/llvm/test/Linker/Inputs/dicompositetype-unique.ll
index c2389e9a63c..e1537b93dfe 100644
--- a/llvm/test/Linker/Inputs/dicompositetype-unique.ll
+++ b/llvm/test/Linker/Inputs/dicompositetype-unique.ll
@@ -1,4 +1,6 @@
-!named = !{!0, !1}
+!named = !{!0, !1, !2, !3}
 
 !0 = !DIFile(filename: "abc", directory: "/path/to")
 !1 = !DICompositeType(tag: DW_TAG_class_type, name: "T2", identifier: "T", file: !0)
+!2 = !DICompositeType(tag: DW_TAG_class_type, name: "FwdTDef", identifier: "FwdT", file: !0)
+!3 = !DICompositeType(tag: DW_TAG_class_type, flags: DIFlagFwdDecl, name: "BothFwdT2", identifier: "BothFwdT", file: !0)