[MC] Add interface to finish pending labels.

When manually finishing the object writer in dsymutil, it's possible
that there are pending labels that haven't been resolved. This results
in an assertion when the assembler tries to fixup a label that doesn't
have an address yet.

Differential revision: https://reviews.llvm.org/D49131

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@336688 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 7 insertions, 2 deletions

diff --git a/include/llvm/MC/MCObjectStreamer.h b/include/llvm/MC/MCObjectStreamer.h
index ac204de31a3..e21eb680f1c 100644
--- a/include/llvm/MC/MCObjectStreamer.h
+++ b/include/llvm/MC/MCObjectStreamer.h
@@ -90,6 +90,9 @@ protected:
 public:
   void visitUsedSymbol(const MCSymbol &Sym) override;
 
+  /// Create a dummy fragment to assign any pending labels.
+  void flushPendingLabels() { flushPendingLabels(nullptr); }
+
   MCAssembler &getAssembler() { return *Assembler; }
   MCAssembler *getAssemblerPtr() override;
   /// \name MCStreamer Interface
diff --git a/lib/MC/MCObjectStreamer.cpp b/lib/MC/MCObjectStreamer.cpp
index 8122af459b7..9fab8d835f8 100644
--- a/lib/MC/MCObjectStreamer.cpp
+++ b/lib/MC/MCObjectStreamer.cpp
@@ -671,6 +671,6 @@ void MCObjectStreamer::FinishImpl() {
   // Dump out the dwarf file & directory tables and line tables.
   MCDwarfLineTable::Emit(this, getAssembler().getDWARFLinetableParams());
 
-  flushPendingLabels(nullptr);
+  flushPendingLabels();
   getAssembler().Finish();
 }
diff --git a/tools/dsymutil/MachOUtils.cpp b/tools/dsymutil/MachOUtils.cpp
index 5d70afdc9f7..eda530b810c 100644
--- a/tools/dsymutil/MachOUtils.cpp
+++ b/tools/dsymutil/MachOUtils.cpp
@@ -322,8 +322,10 @@ bool generateDsymCompanion(const DebugMap &DM, MCStreamer &MS,
   auto &ObjectStreamer = static_cast<MCObjectStreamer &>(MS);
   MCAssembler &MCAsm = ObjectStreamer.getAssembler();
   auto &Writer = static_cast<MachObjectWriter &>(MCAsm.getWriter());
-  MCAsmLayout Layout(MCAsm);
 
+  // Layout but don't emit.
+  ObjectStreamer.flushPendingLabels();
+  MCAsmLayout Layout(MCAsm);
   MCAsm.layout(Layout);
 
   BinaryHolder InputBinaryHolder(false);