commit 1b112c80a68697687189ddf5bb01b2edacb618af
Author: David Blaikie <dblaikie@gmail.com>
Date:   Sun Jun 27 14:34:18 2021 -0700

    PR37255: DebugInfo: LTO with -g inlined into -gmlt combined with Split DWARF without CU cross-references
    
    A combination of features ^ that lead to a mismatch of expectations
    about how a subprogram definition DIE would be produced with/without a
    declaration when taking full -g debug info and inlining it into a -gmlt
    CU - specifically when using Split DWARF that doesn't support cross-CU
    references, so we have to put the -g debug info into the -gmlt CU, which
    gets confusing about which mode is respected.
    
    This patch comes down on respecting the CU the debug info is emitted
    into, rather than preserving the full debug info when it's emitted into
    the gmlt CU.
---
 llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp          | 50 +++++++-------
 llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h            |  2 +-
 .../DebugInfo/X86/split-dwarf-cross-cu-gmlt-g.ll   | 80 ++++++++++++++++++++++
 3 files changed, 107 insertions(+), 25 deletions(-)

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 82dbb8a74375..5c6dd43b8163 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1130,32 +1130,34 @@ DIE *DwarfUnit::getOrCreateSubprogramDIE(const DISubprogram *SP, bool Minimal) {
 }
 
 bool DwarfUnit::applySubprogramDefinitionAttributes(const DISubprogram *SP,
-                                                    DIE &SPDie) {
+                                                    DIE &SPDie, bool Minimal) {
   DIE *DeclDie = nullptr;
   StringRef DeclLinkageName;
   if (auto *SPDecl = SP->getDeclaration()) {
-    DITypeRefArray DeclArgs, DefinitionArgs;
-    DeclArgs = SPDecl->getType()->getTypeArray();
-    DefinitionArgs = SP->getType()->getTypeArray();
-
-    if (DeclArgs.size() && DefinitionArgs.size())
-      if (DefinitionArgs[0] != NULL && DeclArgs[0] != DefinitionArgs[0])
-        addType(SPDie, DefinitionArgs[0]);
-
-    DeclDie = getDIE(SPDecl);
-    assert(DeclDie && "This DIE should've already been constructed when the "
-                      "definition DIE was created in "
-                      "getOrCreateSubprogramDIE");
-    // Look at the Decl's linkage name only if we emitted it.
-    if (DD->useAllLinkageNames())
-      DeclLinkageName = SPDecl->getLinkageName();
-    unsigned DeclID = getOrCreateSourceID(SPDecl->getFile());
-    unsigned DefID = getOrCreateSourceID(SP->getFile());
-    if (DeclID != DefID)
-      addUInt(SPDie, dwarf::DW_AT_decl_file, None, DefID);
-
-    if (SP->getLine() != SPDecl->getLine())
-      addUInt(SPDie, dwarf::DW_AT_decl_line, None, SP->getLine());
+    if (!Minimal) {
+      DITypeRefArray DeclArgs, DefinitionArgs;
+      DeclArgs = SPDecl->getType()->getTypeArray();
+      DefinitionArgs = SP->getType()->getTypeArray();
+
+      if (DeclArgs.size() && DefinitionArgs.size())
+        if (DefinitionArgs[0] != NULL && DeclArgs[0] != DefinitionArgs[0])
+          addType(SPDie, DefinitionArgs[0]);
+
+      DeclDie = getDIE(SPDecl);
+      assert(DeclDie && "This DIE should've already been constructed when the "
+                        "definition DIE was created in "
+                        "getOrCreateSubprogramDIE");
+      // Look at the Decl's linkage name only if we emitted it.
+      if (DD->useAllLinkageNames())
+        DeclLinkageName = SPDecl->getLinkageName();
+      unsigned DeclID = getOrCreateSourceID(SPDecl->getFile());
+      unsigned DefID = getOrCreateSourceID(SP->getFile());
+      if (DeclID != DefID)
+        addUInt(SPDie, dwarf::DW_AT_decl_file, None, DefID);
+
+      if (SP->getLine() != SPDecl->getLine())
+        addUInt(SPDie, dwarf::DW_AT_decl_line, None, SP->getLine());
+    }
   }
 
   // Add function template parameters.
@@ -1187,7 +1189,7 @@ void DwarfUnit::applySubprogramAttributes(const DISubprogram *SP, DIE &SPDie,
   bool SkipSPSourceLocation = SkipSPAttributes &&
                               !CUNode->getDebugInfoForProfiling();
   if (!SkipSPSourceLocation)
-    if (applySubprogramDefinitionAttributes(SP, SPDie))
+    if (applySubprogramDefinitionAttributes(SP, SPDie, SkipSPAttributes))
       return;
 
   // Constructors and operators for anonymous aggregates do not have names.
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
index df1ead03dc05..4d31dd0daf59 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.h
@@ -73,7 +73,7 @@ protected:
   DwarfUnit(dwarf::Tag, const DICompileUnit *Node, AsmPrinter *A, DwarfDebug *DW,
             DwarfFile *DWU);
 
-  bool applySubprogramDefinitionAttributes(const DISubprogram *SP, DIE &SPDie);
+  bool applySubprogramDefinitionAttributes(const DISubprogram *SP, DIE &SPDie, bool Minimal);
 
   bool isShareableAcrossCUs(const DINode *D) const;
 
diff --git a/llvm/test/DebugInfo/X86/split-dwarf-cross-cu-gmlt-g.ll b/llvm/test/DebugInfo/X86/split-dwarf-cross-cu-gmlt-g.ll
new file mode 100644
index 000000000000..ac5a10652ba9
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/split-dwarf-cross-cu-gmlt-g.ll
@@ -0,0 +1,80 @@
+; RUN: llc -mtriple=x86_64-linux -split-dwarf-file=foo.dwo -filetype=obj -o %t < %s
+; RUN: llvm-dwarfdump -debug-info %t | FileCheck %s
+
+; CHECK: DW_AT_name ("b.cpp")
+; CHECK: DW_TAG_subprogram
+; CHECK-NEXT:   DW_AT_linkage_name      ("_ZN5outer2f2Ev")
+; CHECK-NEXT:   DW_AT_name      ("f2")
+; CHECK-NEXT:   DW_AT_decl_file (0x02)
+; CHECK-NEXT:   DW_AT_decl_line (4)
+
+; Function Attrs: noinline nounwind optnone uwtable mustprogress
+define dso_local void @_Z2f1v() local_unnamed_addr #0 !dbg !12 {
+entry:
+  ret void, !dbg !15
+}
+
+; Function Attrs: nounwind uwtable mustprogress
+define dso_local void @_ZN5outer2f2Ev() local_unnamed_addr #1 align 2 !dbg !16 {
+entry:
+  tail call void @_Z2f1v(), !dbg !21
+  ret void, !dbg !22
+}
+
+; Function Attrs: nounwind uwtable mustprogress
+define dso_local void @_Z2f2v() local_unnamed_addr #1 !dbg !23 {
+entry:
+  tail call void @_Z2f1v(), !dbg !24
+  ret void, !dbg !25
+}
+
+; Function Attrs: norecurse nounwind uwtable mustprogress
+define dso_local i32 @main() local_unnamed_addr #2 !dbg !26 {
+entry:
+  tail call void @_Z2f1v() #3, !dbg !28
+  tail call void @_Z2f1v() #3, !dbg !30
+  ret i32 0, !dbg !32
+}
+
+attributes #0 = { noinline nounwind optnone uwtable mustprogress "frame-pointer"="none" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+attributes #1 = { nounwind uwtable mustprogress "frame-pointer"="none" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+attributes #2 = { norecurse nounwind uwtable mustprogress "frame-pointer"="none" "min-legal-vector-width"="0" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "tune-cpu"="generic" }
+attributes #3 = { nounwind }
+
+!llvm.dbg.cu = !{!0, !3}
+!llvm.ident = !{!5, !5}
+!llvm.module.flags = !{!6, !7, !8, !9, !10, !11}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang version 13.0.0 (git@github.com:llvm/llvm-project.git 9aa951e80e72decd95c7d972e1e0dde24260d336)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, splitDebugInlining: false, debugInfoForProfiling: true, nameTableKind: None)
+!1 = !DIFile(filename: "a.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch")
+!2 = !{}
+!3 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !4, producer: "clang version 13.0.0 (git@github.com:llvm/llvm-project.git 9aa951e80e72decd95c7d972e1e0dde24260d336)", isOptimized: true, runtimeVersion: 0, emissionKind: LineTablesOnly, enums: !2, splitDebugInlining: false, debugInfoForProfiling: true, nameTableKind: None)
+!4 = !DIFile(filename: "b.cpp", directory: "/usr/local/google/home/blaikie/dev/scratch")
+!5 = !{!"clang version 13.0.0 (git@github.com:llvm/llvm-project.git 9aa951e80e72decd95c7d972e1e0dde24260d336)"}
+!6 = !{i32 7, !"Dwarf Version", i32 4}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{i32 1, !"wchar_size", i32 4}
+!9 = !{i32 7, !"uwtable", i32 1}
+!10 = !{i32 1, !"ThinLTO", i32 0}
+!11 = !{i32 1, !"EnableSplitLTOUnit", i32 1}
+!12 = distinct !DISubprogram(name: "f1", linkageName: "_Z2f1v", scope: !1, file: !1, line: 2, type: !13, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
+!13 = !DISubroutineType(types: !14)
+!14 = !{null}
+!15 = !DILocation(line: 3, column: 1, scope: !12)
+!16 = distinct !DISubprogram(name: "f2", linkageName: "_ZN5outer2f2Ev", scope: !17, file: !1, line: 4, type: !13, scopeLine: 4, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, declaration: !20, retainedNodes: !2)
+!17 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "outer", file: !18, line: 1, size: 8, flags: DIFlagTypePassByValue, elements: !19, identifier: "_ZTS5outer")
+!18 = !DIFile(filename: "./a.h", directory: "/usr/local/google/home/blaikie/dev/scratch")
+!19 = !{!20}
+!20 = !DISubprogram(name: "f2", linkageName: "_ZN5outer2f2Ev", scope: !17, file: !18, line: 2, type: !13, scopeLine: 2, flags: DIFlagPrototyped | DIFlagStaticMember, spFlags: DISPFlagOptimized)
+!21 = !DILocation(line: 5, column: 3, scope: !16)
+!22 = !DILocation(line: 6, column: 1, scope: !16)
+!23 = distinct !DISubprogram(name: "f2", linkageName: "_Z2f2v", scope: !1, file: !1, line: 7, type: !13, scopeLine: 7, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !2)
+!24 = !DILocation(line: 8, column: 3, scope: !23)
+!25 = !DILocation(line: 9, column: 1, scope: !23)
+!26 = distinct !DISubprogram(name: "main", scope: !4, file: !4, line: 2, type: !27, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !3, retainedNodes: !2)
+!27 = !DISubroutineType(types: !2)
+!28 = !DILocation(line: 5, column: 3, scope: !16, inlinedAt: !29)
+!29 = distinct !DILocation(line: 3, column: 3, scope: !26)
+!30 = !DILocation(line: 8, column: 3, scope: !23, inlinedAt: !31)
+!31 = distinct !DILocation(line: 4, column: 3, scope: !26)
+!32 = !DILocation(line: 5, column: 1, scope: !26)