[llvm] [DebugInfo] Preserve linkage names for profiling (PR #217536)

[Haohai Wen via llvm-commits]

https://github.com/HaohaiWen created https://github.com/llvm/llvm-project/pull/217536

Keep DISubprogram linkage names when stripping non-line-table debug
info if the compile unit has debugInfoForProfiling set. This mirrors
-gline-tables-only, which keeps linkage names when
-fdebug-info-for-profiling is enabled.

>From 0a6ed4dcd215c134c4cfefbcc54638daa8e46f78 Mon Sep 17 00:00:00 2001
From: Haohai Wen <haohai.wen at intel.com>
Date: Wed, 19 Aug 2026 17:51:40 +0800
Subject: [PATCH] [DebugInfo] Preserve linkage names for profiling

Keep DISubprogram linkage names when stripping non-line-table debug
info if the compile unit has debugInfoForProfiling set. This mirrors
-gline-tables-only, which keeps linkage names when
-fdebug-info-for-profiling is enabled.
---
 llvm/lib/IR/DebugInfo.cpp                     |  5 ++-
 ...trip-nonlinetable-debuginfo-linkagename.ll | 39 +++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/Transforms/Util/strip-nonlinetable-debuginfo-linkagename.ll

diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
index e164ec54ead60..25852faada2b8 100644
--- a/llvm/lib/IR/DebugInfo.cpp
+++ b/llvm/lib/IR/DebugInfo.cpp
@@ -781,7 +781,6 @@ class DebugTypeInfoRemoval {
   // Create a new DISubprogram, to replace the one given.
   DISubprogram *getReplacementSubprogram(DISubprogram *MDS) {
     auto *FileAndScope = cast_or_null<DIFile>(map(MDS->getFile()));
-    StringRef LinkageName = MDS->getName().empty() ? MDS->getLinkageName() : "";
     DISubprogram *Declaration = nullptr;
     auto *Type = cast_or_null<DISubroutineType>(map(MDS->getType()));
     DIType *ContainingType =
@@ -789,6 +788,10 @@ class DebugTypeInfoRemoval {
     auto *Unit = cast_or_null<DICompileUnit>(map(MDS->getUnit()));
     auto Variables = nullptr;
     auto TemplateParams = nullptr;
+    // Keep linkage names for profiling CUs, as -gline-tables-only does.
+    StringRef LinkageName;
+    if (MDS->getName().empty() || (Unit && Unit->getDebugInfoForProfiling()))
+      LinkageName = MDS->getLinkageName();
 
     // Make a distinct DISubprogram, for situations that warrant it.
     auto distinctMDSubprogram = [&]() {
diff --git a/llvm/test/Transforms/Util/strip-nonlinetable-debuginfo-linkagename.ll b/llvm/test/Transforms/Util/strip-nonlinetable-debuginfo-linkagename.ll
new file mode 100644
index 0000000000000..0fd204b1205c8
--- /dev/null
+++ b/llvm/test/Transforms/Util/strip-nonlinetable-debuginfo-linkagename.ll
@@ -0,0 +1,39 @@
+; RUN: opt -S -passes=strip-nonlinetable-debuginfo %s -o - | FileCheck %s
+
+define void @_Z3foov() !dbg !4 {
+  ret void, !dbg !6
+}
+
+define void @_Z3barv() !dbg !7 {
+  ret void, !dbg !8
+}
+
+define void @_Z3bazv() !dbg !9 {
+  ret void, !dbg !10
+}
+
+; CHECK: define void @_Z3foov() !dbg ![[FOO:[0-9]+]]
+; CHECK: define void @_Z3barv() !dbg ![[BAR:[0-9]+]]
+; CHECK: define void @_Z3bazv() !dbg ![[BAZ:[0-9]+]]
+; CHECK: ![[PROFILING_CU:[0-9]+]] = distinct !DICompileUnit({{.*}}emissionKind: LineTablesOnly, debugInfoForProfiling: true)
+; CHECK: ![[REGULAR_CU:[0-9]+]] = distinct !DICompileUnit({{.*}}emissionKind: LineTablesOnly)
+; CHECK: ![[FOO]] = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", {{.*}}unit: ![[PROFILING_CU]])
+; CHECK: ![[BAR]] = distinct !DISubprogram(name: "bar", scope:
+; CHECK-NOT: linkageName:
+; CHECK-SAME: unit: ![[REGULAR_CU]])
+; CHECK: ![[BAZ]] = distinct !DISubprogram(linkageName: "_Z3bazv", {{.*}}unit: ![[REGULAR_CU]])
+
+!llvm.dbg.cu = !{!0, !1}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !2, emissionKind: FullDebug, debugInfoForProfiling: true)
+!1 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !2, emissionKind: FullDebug)
+!2 = !DIFile(filename: "foo.cpp", directory: "/")
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", scope: !2, file: !2, line: 1, type: !5, scopeLine: 1, spFlags: DISPFlagDefinition, unit: !0)
+!5 = !DISubroutineType(types: !{})
+!6 = !DILocation(line: 1, column: 1, scope: !4)
+!7 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !2, file: !2, line: 2, type: !5, scopeLine: 2, spFlags: DISPFlagDefinition, unit: !1)
+!8 = !DILocation(line: 2, column: 1, scope: !7)
+!9 = distinct !DISubprogram(linkageName: "_Z3bazv", scope: !2, file: !2, line: 3, type: !5, scopeLine: 3, spFlags: DISPFlagDefinition, unit: !1)
+!10 = !DILocation(line: 3, column: 1, scope: !9)