[DebugInfo][RemoveDIs] Find types hidden in DbgRecords (#106547)

When serialising to textual IR, there can be constant Values referred to
by DbgRecords that don't appear anywhere else, and have types hidden
even deeper in side them. Enumerate these when enumerating all types.

Test by Mikael Holmén.

(cherry picked from commit 25f87f2)

llvm/lib/IR/DebugProgramInstruction.cpp

@@ -473,11 +473,12 @@ DbgLabelRecord::createDebugIntrinsic(Module *M,
 
 Value *DbgVariableRecord::getAddress() const {
   auto *MD = getRawAddress();
-  if (auto *V = dyn_cast<ValueAsMetadata>(MD))
+  if (auto *V = dyn_cast_or_null<ValueAsMetadata>(MD))
     return V->getValue();
 
   // When the value goes to null, it gets replaced by an empty MDNode.
-  assert(!cast<MDNode>(MD)->getNumOperands() && "Expected an empty MDNode");
+  assert(!MD ||
+         !cast<MDNode>(MD)->getNumOperands() && "Expected an empty MDNode");
   return nullptr;
 }
 

llvm/lib/IR/TypeFinder.cpp

@@ -88,6 +88,20 @@ void TypeFinder::run(const Module &M, bool onlyNamed) {
         for (const auto &MD : MDForInst)
           incorporateMDNode(MD.second);
         MDForInst.clear();
+
+        // Incorporate types hiding in variable-location information.
+        for (const auto &Dbg : I.getDbgRecordRange()) {
+          // Pick out records that have Values.
+          if (const DbgVariableRecord *DVI =
+                  dyn_cast<DbgVariableRecord>(&Dbg)) {
+            for (Value *V : DVI->location_ops())
+              incorporateValue(V);
+            if (DVI->isDbgAssign()) {
+              if (Value *Addr = DVI->getAddress())
+                incorporateValue(Addr);
+            }
+          }
+        }
       }
   }
 

llvm/test/DebugInfo/type-finder-w-dbg-records.ll

@@ -0,0 +1,51 @@
+; RUN: opt --passes=verify %s -o - -S | FileCheck %s
+
+;; Test that the type definitions are discovered when serialising to LLVM-IR,
+;; even if they're only present inside a DbgRecord, and thus not normally
+;; visible.
+
+; CHECK: %union.anon = type { %struct.a }
+; CHECK: %struct.a = type { i32 }
+; CHECK: %union.anon2 = type { %struct.a2 }
+; CHECK: %struct.a2 = type { i32 }
+
+; ModuleID = 'bbi-98372.ll'
+source_filename = "bbi-98372.ll"
+
+%union.anon = type { %struct.a }
+%struct.a = type { i32 }
+%union.anon2 = type { %struct.a2 }
+%struct.a2 = type { i32 }
+
+@d = global [1 x { i16, i16 }] [{ i16, i16 } { i16 0, i16 undef }], align 1
+@e = global [1 x { i16, i16 }] [{ i16, i16 } { i16 0, i16 undef }], align 1
+
+define void @f() {
+entry:
+    #dbg_value(ptr getelementptr inbounds ([1 x %union.anon], ptr @d, i32 0, i32 3), !7, !DIExpression(), !14)
+    #dbg_assign(ptr null, !7, !DIExpression(), !16, ptr getelementptr inbounds ([1 x %union.anon2], ptr @e, i32 0, i32 3), !17, !14)
+  ret void, !dbg !15
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5}
+!llvm.ident = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "foo.c", directory: "/bar")
+!2 = !{i32 7, !"Dwarf Version", i32 4}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 1}
+!5 = !{i32 7, !"frame-pointer", i32 2}
+!6 = !{!"clang"}
+!7 = !DILocalVariable(name: "f", scope: !8, file: !1, line: 8, type: !12)
+!8 = distinct !DISubprogram(name: "e", scope: !1, file: !1, line: 8, type: !9, scopeLine: 8, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !11)
+!9 = !DISubroutineType(types: !10)
+!10 = !{null}
+!11 = !{!7}
+!12 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !13, size: 16)
+!13 = !DIBasicType(name: "int", size: 16, encoding: DW_ATE_signed)
+!14 = !DILocation(line: 0, scope: !8)
+!15 = !DILocation(line: 8, column: 28, scope: !8)
+!16 = distinct !DIAssignID()
+!17 = !DIExpression()