diff --git a/llvm/include/llvm/CodeGen/AsmPrinter.h b/llvm/include/llvm/CodeGen/AsmPrinter.h
--- a/llvm/include/llvm/CodeGen/AsmPrinter.h
+++ b/llvm/include/llvm/CodeGen/AsmPrinter.h
@@ -778,6 +778,9 @@
   GCMetadataPrinter *GetOrCreateGCPrinter(GCStrategy &S);
   /// Emit GlobalAlias or GlobalIFunc.
   void emitGlobalIndirectSymbol(Module &M, const GlobalIndirectSymbol &GIS);
+
+  /// This method decides whether the specified basic block requires a label.
+  bool shouldEmitLabelForBasicBlock(const MachineBasicBlock &MBB) const;
 };
 
 } // end namespace llvm
diff --git a/llvm/include/llvm/CodeGen/MachineBasicBlock.h b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
--- a/llvm/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/llvm/include/llvm/CodeGen/MachineBasicBlock.h
@@ -434,6 +434,9 @@
 
   bool hasEHPadSuccessor() const;
 
+  /// Returns true if this is the entry block of the function.
+  bool isEntryBlock() const;
+
   /// Returns true if this is the entry block of an EH scope, i.e., the block
   /// that used to have a catchpad or cleanuppad instruction in the LLVM IR.
   bool isEHScopeEntry() const { return IsEHScopeEntry; }
diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1053,7 +1053,7 @@
   // Emit BB Information for each basic block in the funciton.
   for (const MachineBasicBlock &MBB : MF) {
     const MCSymbol *MBBSymbol =
-        MBB.pred_empty() ? FunctionSymbol : MBB.getSymbol();
+        MBB.isEntryBlock() ? FunctionSymbol : MBB.getSymbol();
     // Emit the basic block offset.
     emitLabelDifferenceAsULEB128(MBBSymbol, FunctionSymbol);
     // Emit the basic block size. When BBs have alignments, their size cannot
@@ -3052,7 +3052,7 @@
   // Switch to a new section if this basic block must begin a section. The
   // entry block is always placed in the function section and is handled
   // separately.
-  if (MBB.isBeginSection() && !MBB.pred_empty()) {
+  if (MBB.isBeginSection() && !MBB.isEntryBlock()) {
     OutStreamer->SwitchSection(
         getObjFileLowering().getSectionForMachineBasicBlock(MF->getFunction(),
                                                             MBB, TM));
@@ -3090,24 +3090,22 @@
   }
 
   // Print the main label for the block.
-  if (MBB.pred_empty() ||
-      (!MF->hasBBLabels() && isBlockOnlyReachableByFallthrough(&MBB) &&
-       !MBB.isEHFuncletEntry() && !MBB.hasLabelMustBeEmitted())) {
+  if (shouldEmitLabelForBasicBlock(MBB)) {
+    if (isVerbose() && MBB.hasLabelMustBeEmitted())
+      OutStreamer->AddComment("Label of block must be emitted");
+    OutStreamer->emitLabel(MBB.getSymbol());
+  } else {
     if (isVerbose()) {
       // NOTE: Want this comment at start of line, don't emit with AddComment.
       OutStreamer->emitRawComment(" %bb." + Twine(MBB.getNumber()) + ":",
                                   false);
     }
-  } else {
-    if (isVerbose() && MBB.hasLabelMustBeEmitted())
-      OutStreamer->AddComment("Label of block must be emitted");
-    OutStreamer->emitLabel(MBB.getSymbol());
   }
 
   // With BB sections, each basic block must handle CFI information on its own
   // if it begins a section (Entry block is handled separately by
   // AsmPrinterHandler::beginFunction).
-  if (MBB.isBeginSection() && !MBB.pred_empty())
+  if (MBB.isBeginSection() && !MBB.isEntryBlock())
     for (const HandlerInfo &HI : Handlers)
       HI.Handler->beginBasicBlock(MBB);
 }
@@ -3141,15 +3139,29 @@
     OutStreamer->emitSymbolAttribute(Sym, Attr);
 }
 
+/// shouldEmitLabelForBasicBlock - Return true if the given basic block requires
+/// a basic block label. The symbol is constructed later by a call to
+/// MachineBasicBlock::getSymbol.
+bool AsmPrinter::shouldEmitLabelForBasicBlock(
+    const MachineBasicBlock &MBB) const {
+  // With `-fbasic-block-sections=`, a label is needed for every non-entry block
+  // in the labels mode (option `=labels`) and every section beginning in the
+  // sections mode (`=all` and `=list=`).
+  if ((MF->hasBBLabels() || MBB.isBeginSection()) && !MBB.isEntryBlock())
+    return true;
+  // A label is needed for any block with at least one predecessor (when that
+  // predecessor is not the fallthrough predecessor, or if it is an EH funclet
+  // entry, or if a label is forced).
+  return !MBB.pred_empty() &&
+         (!isBlockOnlyReachableByFallthrough(&MBB) || MBB.isEHFuncletEntry() ||
+          MBB.hasLabelMustBeEmitted());
+}
+
 /// isBlockOnlyReachableByFallthough - Return true if the basic block has
 /// exactly one predecessor and the control transfer mechanism between
 /// the predecessor and this block is a fall-through.
 bool AsmPrinter::
 isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const {
-  // With BasicBlock Sections, beginning of the section is not a fallthrough.
-  if (MBB->isBeginSection())
-    return false;
-
   // If this is a landing pad, it isn't a fall through.  If it has no preds,
   // then nothing falls through to it.
   if (MBB->isEHPad() || MBB->pred_empty())
diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -266,6 +266,10 @@
   return false;
 }
 
+bool MachineBasicBlock::isEntryBlock() const {
+  return getParent()->begin() == getIterator();
+}
+
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 LLVM_DUMP_METHOD void MachineBasicBlock::dump() const {
   print(dbgs());
diff --git a/llvm/test/CodeGen/X86/basic-block-sections-unreachable.ll b/llvm/test/CodeGen/X86/basic-block-sections-unreachable.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/X86/basic-block-sections-unreachable.ll
@@ -0,0 +1,18 @@
+; Check that basic block section is emitted when a non-entry block has no predecessors.
+; RUN: llc < %s -mtriple=x86_64 -O0 -basic-block-sections=all | FileCheck %s --check-prefix=CHECK-SECTIONS
+; RUN: llc < %s -mtriple=x86_64 -O0 | FileCheck %s --check-prefix=CHECK-NOSECTIONS
+define void @foo(i32* %bar) {
+  %v = load i32, i32* %bar
+  switch i32 %v, label %default [
+    i32 0, label %target
+  ]
+target:
+  ret void
+;; This is the block which will not have any predecessors. If the block is not garbage collected, it must
+;; be placed in a basic block section with a corresponding symbol.
+default:
+  unreachable
+; CHECK-NOSECTIONS:     # %bb.2:     # %default
+; CHECK-SECTIONS:       .section .text,"ax",@progbits,unique,2
+; CHECK-SECTIONS-NEXT:  foo.2:       # %default
+}