Index: include/llvm/IR/DIBuilder.h
===================================================================
--- include/llvm/IR/DIBuilder.h
+++ include/llvm/IR/DIBuilder.h
@@ -665,7 +665,8 @@
                    DISubprogram::DISPFlags SPFlags = DISubprogram::SPFlagZero,
                    DITemplateParameterArray TParams = nullptr,
                    DISubprogram *Decl = nullptr,
-                   DITypeArray ThrownTypes = nullptr);
+                   DITypeArray ThrownTypes = nullptr,
+                   bool isDeclForCallSite = false);
 
     /// Identical to createFunction,
     /// except that the resulting DbgNode is meant to be RAUWed.
Index: include/llvm/IR/DebugInfoFlags.def
===================================================================
--- include/llvm/IR/DebugInfoFlags.def
+++ include/llvm/IR/DebugInfoFlags.def
@@ -88,11 +88,12 @@
 HANDLE_DISP_FLAG((1u << 6), Elemental)
 HANDLE_DISP_FLAG((1u << 7), Recursive)
 HANDLE_DISP_FLAG((1u << 8), MainSubprogram)
+HANDLE_DISP_FLAG((1u << 9), DeclForCallSite)
 
 #ifdef DISP_FLAG_LARGEST_NEEDED
 // Intended to be used with ADT/BitmaskEnum.h.
 // NOTE: Always must be equal to largest flag, check this when adding new flags.
-HANDLE_DISP_FLAG((1 << 8), Largest)
+HANDLE_DISP_FLAG((1 << 9), Largest)
 #undef DISP_FLAG_LARGEST_NEEDED
 #endif
 
Index: include/llvm/IR/DebugInfoMetadata.h
===================================================================
--- include/llvm/IR/DebugInfoMetadata.h
+++ include/llvm/IR/DebugInfoMetadata.h
@@ -1789,6 +1789,7 @@
   bool isDefinition() const { return getSPFlags() & SPFlagDefinition; }
   bool isOptimized() const { return getSPFlags() & SPFlagOptimized; }
   bool isMainSubprogram() const { return getSPFlags() & SPFlagMainSubprogram; }
+  bool isDeclForCallSite() const { return getSPFlags() & SPFlagDeclForCallSite; }
 
   bool isArtificial() const { return getFlags() & FlagArtificial; }
   bool isPrivate() const {
Index: lib/CodeGen/AsmPrinter/DwarfDebug.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -665,6 +665,11 @@
     NewCU.setSection(Asm->getObjFileLowering().getDwarfInfoSection());
   }
 
+  // Create DIEs for function declaraions used for dbg call sites.
+  for (auto Scope : DIUnit->getRetainedTypes())
+    if (auto *SP = dyn_cast_or_null<DISubprogram>(Scope))
+      NewCU.getOrCreateSubprogramDIE(SP);
+
   CUMap.insert({DIUnit, &NewCU});
   CUDieMap.insert({&NewCU.getUnitDie(), &NewCU});
   return NewCU;
Index: lib/CodeGen/AsmPrinter/DwarfUnit.cpp
===================================================================
--- lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1114,7 +1114,7 @@
 
   // Stop here and fill this in later, depending on whether or not this
   // subprogram turns out to have inlined instances or not.
-  if (SP->isDefinition())
+  if (SP->isDefinition() && !SP->isDeclForCallSite())
     return &SPDie;
 
   static_cast<DwarfUnit *>(SPDie.getUnit())
Index: lib/IR/DIBuilder.cpp
===================================================================
--- lib/IR/DIBuilder.cpp
+++ lib/IR/DIBuilder.cpp
@@ -753,7 +753,7 @@
     unsigned LineNo, DISubroutineType *Ty, unsigned ScopeLine,
     DINode::DIFlags Flags, DISubprogram::DISPFlags SPFlags,
     DITemplateParameterArray TParams, DISubprogram *Decl,
-    DITypeArray ThrownTypes) {
+    DITypeArray ThrownTypes, bool isDeclForCallSite) {
   bool IsDefinition = SPFlags & DISubprogram::SPFlagDefinition;
   auto *Node = getSubprogram(
       /*IsDistinct=*/IsDefinition, VMContext, getNonCompileUnitScope(Context),
@@ -761,7 +761,7 @@
       SPFlags, IsDefinition ? CUNode : nullptr, TParams, Decl,
       MDTuple::getTemporary(VMContext, None).release(), ThrownTypes);
 
-  if (IsDefinition)
+  if (IsDefinition || isDeclForCallSite)
     AllSubprograms.push_back(Node);
   trackIfUnresolved(Node);
   return Node;
Index: lib/IR/Verifier.cpp
===================================================================
--- lib/IR/Verifier.cpp
+++ lib/IR/Verifier.cpp
@@ -2222,8 +2222,6 @@
            MDs.empty() ? nullptr : MDs.front().second);
   } else if (F.isDeclaration()) {
     for (const auto &I : MDs) {
-      AssertDI(I.first != LLVMContext::MD_dbg,
-               "function declaration may not have a !dbg attachment", &F);
       Assert(I.first != LLVMContext::MD_prof,
              "function declaration may not have a !prof attachment", &F);
 
@@ -2959,7 +2957,8 @@
   // debug-info-bearing function has a debug location attached to it. Failure to
   // do so causes assertion failures when the inliner sets up inline scope info.
   if (Call.getFunction()->getSubprogram() && Call.getCalledFunction() &&
-      Call.getCalledFunction()->getSubprogram())
+      Call.getCalledFunction()->getSubprogram() &&
+      !Call.getCalledFunction()->getSubprogram()->isDeclForCallSite())
     AssertDI(Call.getDebugLoc(),
              "inlinable function call in a function with "
              "debug info must have a !dbg location",
Index: test/Verifier/metadata-function-dbg.ll
===================================================================
--- test/Verifier/metadata-function-dbg.ll
+++ test/Verifier/metadata-function-dbg.ll
@@ -1,8 +1,5 @@
 ; RUN: llvm-as %s -disable-output 2>&1 | FileCheck %s
 
-; CHECK:      function declaration may not have a !dbg attachment
-declare !dbg !4 void @f1()
-
 ; CHECK:      function must have a single !dbg attachment
 define void @f2() !dbg !4 !dbg !4 {
   unreachable