release/19.x: [DebugInfo][RemoveDIs] Find types hidden in DbgRecords (#106547)

[llvmbot]

Backport 25f87f2

Requested by: @jmorse

[llvmbot]

@OCHyams What do you think about merging this PR to the release branch?

[llvmbot]

@llvm/pr-subscribers-debuginfo

@llvm/pr-subscribers-llvm-ir

Author: None (llvmbot)

Changes

Backport 25f87f2

Requested by: @jmorse

---

Full diff: https://github.com/llvm/llvm-project/pull/107060.diff

3 Files Affected:

• (modified) llvm/lib/IR/DebugProgramInstruction.cpp (+3-2)
• (modified) llvm/lib/IR/TypeFinder.cpp (+14)
• (added) llvm/test/DebugInfo/type-finder-w-dbg-records.ll (+51)

diff --git a/llvm/lib/IR/DebugProgramInstruction.cpp b/llvm/lib/IR/DebugProgramInstruction.cpp
index 362d467beeb11b..5d2189b54204fb 100644
--- a/llvm/lib/IR/DebugProgramInstruction.cpp
+++ b/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;
 }
 
diff --git a/llvm/lib/IR/TypeFinder.cpp b/llvm/lib/IR/TypeFinder.cpp
index 003155a4af4877..963f4b4806e1f9 100644
--- a/llvm/lib/IR/TypeFinder.cpp
+++ b/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);
+            }
+          }
+        }
       }
   }
 
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..8259b4a9f1c3a5
--- /dev/null
+++ b/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()

[OCHyams]

@OCHyams What do you think about merging this PR to the release branch?

LGTM, this fixes a bug where invalid IR gets produced, so getting it backported sounds good.

For peace of mind: we don't need a null check in the DVI->location_ops() loop because location_ops() returns an empty range rather than a single-nullptr-location, and multiple locations (through DIArgList) should never be nullptr.

[github-actions]

@jmorse (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR.