[llvm] [DebugInfo][RemoveDIs] Fix error from not tracking seen debug labels (PR #88718)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-debuginfo

Author: Stephen Tozer (SLTozer)

<details>
<summary>Changes</summary>

Fixes the reported errors on: https://github.com/llvm/llvm-project/pull/87379

A previous patch updated the bitcode reading for debug intrinsics/records to not perform the expensive debug info format conversion from records to intrinsics in cases where no records were present, but the patch did not actually track when debug labels had been seen, resulting in errors when parsing bitcode where functions contained debug label records but no other debug records. This patch fixes that case and adds a test for it.

---
Full diff: https://github.com/llvm/llvm-project/pull/88718.diff


2 Files Affected:

- (modified) llvm/lib/Bitcode/Reader/BitcodeReader.cpp (+1) 
- (added) llvm/test/Bitcode/dbg-label-record-bc.ll (+50) 


``````````diff
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index fe4f0d6dca6c0c..0b7fcd88418894 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -6454,6 +6454,7 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
     case bitc::FUNC_CODE_DEBUG_RECORD_LABEL: {
       // DbgLabelRecords are placed after the Instructions that they are
       // attached to.
+      SeenDebugRecord = true;
       Instruction *Inst = getLastInstruction();
       if (!Inst)
         return error("Invalid dbg record: missing instruction");
diff --git a/llvm/test/Bitcode/dbg-label-record-bc.ll b/llvm/test/Bitcode/dbg-label-record-bc.ll
new file mode 100644
index 00000000000000..e151f7f6cc157d
--- /dev/null
+++ b/llvm/test/Bitcode/dbg-label-record-bc.ll
@@ -0,0 +1,50 @@
+;; Tests that we can parse and print a function containing a debug label record
+;; and no other debug record kinds.
+
+; RUN: llvm-as --write-experimental-debuginfo-iterators-to-bitcode=true %s -o - \
+; RUN: | opt -S | FileCheck %s --check-prefixes=CHECK,INTRINSIC
+
+; RUN: llvm-as --write-experimental-debuginfo-iterators-to-bitcode=true %s -o - \
+; RUN: | opt -S --preserve-input-debuginfo-format=true \
+; RUN: | FileCheck %s --check-prefixes=CHECK,RECORD
+
+source_filename = "bbi-94196.c"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+; CHECK-LABEL: void @foo()
+; CHECK: bar:
+; INTRINSIC-NEXT: call void @llvm.dbg.label(metadata ![[LABEL:[0-9]+]]), !dbg ![[LOC:[0-9]+]]
+; RECORD-NEXT: #dbg_label(![[LABEL:[0-9]+]], ![[LOC:[0-9]+]])
+
+; CHECK-DAG: ![[LABEL]] = !DILabel({{.*}}name: "bar"
+; CHECK-DAG: ![[LOC]] = !DILocation(line: 5, column: 1
+
+define dso_local void @foo() !dbg !5 {
+entry:
+  br label %bar, !dbg !9
+
+bar:                                              ; preds = %entry
+  tail call void @llvm.dbg.label(metadata !10), !dbg !11
+  ret void, !dbg !12
+}
+
+declare void @llvm.dbg.label(metadata)
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3}
+!llvm.ident = !{!4}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C11, file: !1, producer: "clang version 19.0.0git", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "<stdin>", directory: "/home/gbtozers/dev/llvm-project-ddd-textual-ir")
+!2 = !{i32 2, !"Debug Info Version", i32 3}
+!3 = !{i32 1, !"wchar_size", i32 4}
+!4 = !{!"clang version 19.0.0git"}
+!5 = distinct !DISubprogram(name: "foo", scope: !6, file: !6, line: 1, type: !7, scopeLine: 2, spFlags: DISPFlagDefinition, unit: !0)
+!6 = !DIFile(filename: "bbi-94196.c", directory: "/home/gbtozers/dev/llvm-project-ddd-textual-ir")
+!7 = !DISubroutineType(types: !8)
+!8 = !{null}
+!9 = !DILocation(line: 3, column: 3, scope: !5)
+!10 = !DILabel(scope: !5, name: "bar", file: !6, line: 5)
+!11 = !DILocation(line: 5, column: 1, scope: !5)
+!12 = !DILocation(line: 6, column: 3, scope: !5)

``````````

</details>


https://github.com/llvm/llvm-project/pull/88718