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

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-ir

Author: Jeremy Morse (jmorse)

<details>
<summary>Changes</summary>

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.

---
Full diff: https://github.com/llvm/llvm-project/pull/106547.diff


2 Files Affected:

- (modified) llvm/lib/IR/TypeFinder.cpp (+11) 
- (added) llvm/test/DebugInfo/type-finder-w-dbg-records.ll (+43) 


``````````diff
diff --git a/llvm/lib/IR/TypeFinder.cpp b/llvm/lib/IR/TypeFinder.cpp
index 003155a4af4877..d2ffe1ba77b4e3 100644
--- a/llvm/lib/IR/TypeFinder.cpp
+++ b/llvm/lib/IR/TypeFinder.cpp
@@ -88,6 +88,17 @@ 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 (Dbg.getRecordKind() != DbgRecord::Kind::ValueKind)
+            continue;
+          const DbgVariableRecord &DVI = static_cast<const DbgVariableRecord &>(Dbg);
+          for (Value *V : DVI.location_ops()) {
+            incorporateValue(V);
+          }
+        }
       }
   }
 
diff --git a/llvm/test/DebugInfo/type-finder-w-dbg-records.ll b/llvm/test/DebugInfo/type-finder-w-dbg-records.ll
new file mode 100644
index 00000000000000..d2daabc40a3ac3
--- /dev/null
+++ b/llvm/test/DebugInfo/type-finder-w-dbg-records.ll
@@ -0,0 +1,43 @@
+; 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 }
+
+; ModuleID = 'bbi-98372.ll'
+source_filename = "bbi-98372.ll"
+
+%union.anon = type { %struct.a }
+%struct.a = type { i32 }
+
+ at d = global [1 x { i16, i16 }] [{ i16, i16 } { i16 0, i16 undef }], align 1
+
+define void @e() {
+entry:
+    #dbg_value(ptr getelementptr inbounds ([1 x %union.anon], ptr @d, i32 0, i32 3), !7, !DIExpression(), !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)

``````````

</details>


https://github.com/llvm/llvm-project/pull/106547