Index: llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -197,9 +197,7 @@
   // together.
   if (isDwoUnit() && !DD->shareAcrossDWOCUs())
     return false;
-  return (isa<DIType>(D) ||
-          (isa<DISubprogram>(D) && !cast<DISubprogram>(D)->isDefinition())) &&
-         !DD->generateTypeUnits();
+  return (isa<DIType>(D) || isa<DISubprogram>(D)) && !DD->generateTypeUnits();
 }
 
 DIE *DwarfUnit::getDIE(const DINode *D) const {
Index: llvm/test/DebugInfo/X86/lto-cross-cu-call-origin-ref.ll
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/X86/lto-cross-cu-call-origin-ref.ll
@@ -0,0 +1,108 @@
+; RUN: llc -mtriple=x86_64-apple-darwin -filetype=obj < %s | llvm-dwarfdump - \
+; RUN:   | FileCheck %s
+
+; Source:
+
+;; // a.c
+;; volatile int sink;
+;; 
+;; __attribute__((noinline)) void bar() { ++sink; }
+;; 
+;; void foo() { 
+;;   bar();
+;; }
+
+;; // b.c
+;; extern void foo();
+;; 
+;; int main() {
+;;   foo();
+;;   return 0;
+;; }
+
+; Command:
+;; clang -O2 -Xclang -femit-debug-entry-values -g -flto -o a.o -c a.c
+;; clang -O2 -Xclang -femit-debug-entry-values -g -flto -o b.o -c b.c
+;; clang -O2 -Xclang -femit-debug-entry-values -g -flto -o main a.o b.o -Wl,-object_path_lto,lto.o,-save-temps
+
+; CHECK: DW_TAG_compile_unit
+; CHECK: DW_AT_name ("a.c")
+
+; Check for a definition subprogram for "bar". Note that AT_call_all_calls
+; implies that this is not a declaration.
+; CHECK: 0x[[BAR_DIE:.*]]: DW_TAG_subprogram
+; CHECK: DW_AT_call_all_calls    (true)
+; CHECK: DW_AT_name      ("bar")
+
+; CHECK: DW_TAG_compile_unit
+; CHECK: DW_AT_name ("b.c")
+
+; Check that "main" can reference the definition of "bar" in "a.c". (Previously
+; we would not share definition subprograms across CUs, so the call site info
+; logic would create an empty 'definition' subprogram for "bar" which never got
+; filled in. This breaks both entry value evaluation & artificial tail call
+; frame synthesis in the LTO setting.)
+; CHECK: DW_TAG_subprogram
+; CHECK: DW_AT_name      ("main")
+; CHECK:     DW_TAG_call_site
+; CHECK-NEXT: DW_AT_call_origin (0x{{.*}}[[BAR_DIE]])
+
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.14.0"
+
+@sink = internal global i32 0, align 4, !dbg !0
+
+define internal fastcc void @bar() unnamed_addr !dbg !20 {
+entry:
+  %0 = load volatile i32, i32* @sink, align 4, !dbg !23, !tbaa !24
+  %inc = add nsw i32 %0, 1, !dbg !23
+  store volatile i32 %inc, i32* @sink, align 4, !dbg !23, !tbaa !24
+  ret void, !dbg !28
+}
+
+define i32 @main() local_unnamed_addr !dbg !29 {
+entry:
+  tail call fastcc void @bar(), !dbg !32
+  ret i32 0, !dbg !35
+}
+
+!llvm.dbg.cu = !{!2, !8}
+!llvm.ident = !{!14, !14}
+!llvm.module.flags = !{!15, !16, !17, !18, !19}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "sink", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 10.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
+!3 = !DIFile(filename: "a.c", directory: "/Users/vsk/tmp/lto-entry-vals")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !7)
+!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!8 = distinct !DICompileUnit(language: DW_LANG_C99, file: !9, producer: "clang version 10.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, retainedTypes: !10, nameTableKind: None)
+!9 = !DIFile(filename: "b.c", directory: "/Users/vsk/tmp/lto-entry-vals")
+!10 = !{!11}
+!11 = !DISubprogram(name: "foo", scope: !9, file: !9, line: 1, type: !12, spFlags: DISPFlagOptimized, retainedNodes: !4)
+!12 = !DISubroutineType(types: !13)
+!13 = !{null, null}
+!14 = !{!"clang version 10.0.0"}
+!15 = !{i32 2, !"Dwarf Version", i32 4}
+!16 = !{i32 2, !"Debug Info Version", i32 3}
+!17 = !{i32 1, !"wchar_size", i32 4}
+!18 = !{i32 7, !"PIC Level", i32 2}
+!19 = !{i32 1, !"LTOPostLink", i32 1}
+!20 = distinct !DISubprogram(name: "bar", scope: !3, file: !3, line: 3, type: !21, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !4)
+!21 = !DISubroutineType(types: !22)
+!22 = !{null}
+!23 = !DILocation(line: 3, column: 40, scope: !20)
+!24 = !{!25, !25, i64 0}
+!25 = !{!"int", !26, i64 0}
+!26 = !{!"omnipotent char", !27, i64 0}
+!27 = !{!"Simple C/C++ TBAA"}
+!28 = !DILocation(line: 3, column: 48, scope: !20)
+!29 = distinct !DISubprogram(name: "main", scope: !9, file: !9, line: 3, type: !30, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !8, retainedNodes: !4)
+!30 = !DISubroutineType(types: !31)
+!31 = !{!7}
+!32 = !DILocation(line: 6, column: 3, scope: !33, inlinedAt: !34)
+!33 = distinct !DISubprogram(name: "foo", scope: !3, file: !3, line: 5, type: !21, scopeLine: 5, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !4)
+!34 = distinct !DILocation(line: 4, column: 3, scope: !29)
+!35 = !DILocation(line: 5, column: 3, scope: !29)