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

2 files changed, 31 insertions, 4 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)
diff --git a/llvm/test/Linker/dicompositetype-unique.ll b/llvm/test/Linker/dicompositetype-unique.ll
index 6e4e34bdc2a..ab1fdaa3616 100644
--- a/llvm/test/Linker/dicompositetype-unique.ll
+++ b/llvm/test/Linker/dicompositetype-unique.ll
@@ -17,9 +17,9 @@
 
 ; Check that the type map will unique two DICompositeTypes.
 
-; CHECK:   !named = !{!0, !1, !0, !1}
-; NOMAP:   !named = !{!0, !1, !0, !2}
-!named = !{!0, !1}
+; CHECK:   !named = !{!0, !1, !2, !3, !0, !1, !2, !3}
+; NOMAP:   !named = !{!0, !1, !2, !3, !0, !4, !5, !6}
+!named = !{!0, !1, !2, !3}
 
 ; Check both directions.
 ; CHECK:        !1 = distinct !DICompositeType(
@@ -27,14 +27,39 @@
 ; REVERSE-SAME:                                name: "T2"
 ; CHECK-SAME:                                  identifier: "T"
 ; CHECK-NOT:       identifier: "T"
+; CHECK:        !2 = distinct !DICompositeType(
+; CHECK-SAME:                                  name: "FwdTDef"
+; CHECK-SAME:                                  identifier: "FwdT"
+; CHECK-NOT:       identifier: "FwdT"
+; CHECK:        !3 = distinct !DICompositeType(
+; FORWARD-SAME:                                name: "BothFwdT1"
+; REVERSE-SAME:                                name: "BothFwdT2"
+; CHECK-SAME:                                  identifier: "BothFwdT"
+; CHECK-NOT:       identifier: "BothFwdT"
 
 ; These types are different, so we should get both copies when there is no map.
 ; NOMAP:        !1 = !DICompositeType(
 ; NOMAP-SAME:                         name: "T1"
 ; NOMAP-SAME:                         identifier: "T"
 ; NOMAP:        !2 = !DICompositeType(
+; NOMAP-SAME:                         name: "FwdTFwd"
+; NOMAP-SAME:                         identifier: "FwdT"
+; NOMAP:        !3 = !DICompositeType(
+; NOMAP-SAME:                         name: "BothFwdT1"
+; NOMAP-SAME:                         identifier: "BothFwdT"
+; NOMAP:        !4 = !DICompositeType(
 ; NOMAP-SAME:                         name: "T2"
 ; NOMAP-SAME:                         identifier: "T"
 ; NOMAP-NOT:       identifier: "T"
+; NOMAP:        !5 = !DICompositeType(
+; NOMAP-SAME:                         name: "FwdTDef"
+; NOMAP-SAME:                         identifier: "FwdT"
+; NOMAP-NOT:       identifier: "FwdT"
+; NOMAP:        !6 = !DICompositeType(
+; NOMAP-SAME:                         name: "BothFwdT2"
+; NOMAP-SAME:                         identifier: "BothFwdT"
+; NOMAP-NOT:       identifier: "BothFwdT"
 !0 = !DIFile(filename: "abc", directory: "/path/to")
 !1 = !DICompositeType(tag: DW_TAG_class_type, name: "T1", identifier: "T", file: !0)
+!2 = !DICompositeType(tag: DW_TAG_class_type, flags: DIFlagFwdDecl, name: "FwdTFwd", identifier: "FwdT", file: !0)
+!3 = !DICompositeType(tag: DW_TAG_class_type, flags: DIFlagFwdDecl, name: "BothFwdT1", identifier: "BothFwdT", file: !0)