[MC] Factor out non-COFF handling of COFF-specific directives.

Instead of requiring every non-COFF MCObjectStreamer to implement the
COFF hooks just to do an llvm_unreachable to say that they're not
supported, do the llvm_unreachable in the default implementation, as
suggested by rnk in https://reviews.llvm.org/D26722.

llvm-svn: 296403
diff --git a/llvm/lib/MC/MCELFStreamer.cpp b/llvm/lib/MC/MCELFStreamer.cpp
index 789cf3f..1724400 100644
--- a/llvm/lib/MC/MCELFStreamer.cpp
+++ b/llvm/lib/MC/MCELFStreamer.cpp
@@ -625,22 +625,6 @@
   llvm_unreachable("ELF doesn't support this directive");
 }
 
-void MCELFStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
-  llvm_unreachable("ELF doesn't support this directive");
-}
-
-void MCELFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
-  llvm_unreachable("ELF doesn't support this directive");
-}
-
-void MCELFStreamer::EmitCOFFSymbolType(int Type) {
-  llvm_unreachable("ELF doesn't support this directive");
-}
-
-void MCELFStreamer::EndCOFFSymbolDef() {
-  llvm_unreachable("ELF doesn't support this directive");
-}
-
 void MCELFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
                                  uint64_t Size, unsigned ByteAlignment) {
   llvm_unreachable("ELF doesn't support this directive");
diff --git a/llvm/lib/MC/MCMachOStreamer.cpp b/llvm/lib/MC/MCMachOStreamer.cpp
index 5820d97..3ed89c4 100644
--- a/llvm/lib/MC/MCMachOStreamer.cpp
+++ b/llvm/lib/MC/MCMachOStreamer.cpp
@@ -92,22 +92,6 @@
   void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                         unsigned ByteAlignment) override;
 
-  void BeginCOFFSymbolDef(const MCSymbol *Symbol) override {
-    llvm_unreachable("macho doesn't support this directive");
-  }
-
-  void EmitCOFFSymbolStorageClass(int StorageClass) override {
-    llvm_unreachable("macho doesn't support this directive");
-  }
-
-  void EmitCOFFSymbolType(int Type) override {
-    llvm_unreachable("macho doesn't support this directive");
-  }
-
-  void EndCOFFSymbolDef() override {
-    llvm_unreachable("macho doesn't support this directive");
-  }
-
   void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                              unsigned ByteAlignment) override;
   void EmitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index cdecd48..860c1bd 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -807,11 +807,19 @@
 void MCStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {}
 void MCStreamer::EmitThumbFunc(MCSymbol *Func) {}
 void MCStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {}
-void MCStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {}
-void MCStreamer::EndCOFFSymbolDef() {}
+void MCStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
+  llvm_unreachable("this directive only supported on COFF targets");
+}
+void MCStreamer::EndCOFFSymbolDef() {
+  llvm_unreachable("this directive only supported on COFF targets");
+}
 void MCStreamer::EmitFileDirective(StringRef Filename) {}
-void MCStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {}
-void MCStreamer::EmitCOFFSymbolType(int Type) {}
+void MCStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
+  llvm_unreachable("this directive only supported on COFF targets");
+}
+void MCStreamer::EmitCOFFSymbolType(int Type) {
+  llvm_unreachable("this directive only supported on COFF targets");
+}
 void MCStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {}
 void MCStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                        unsigned ByteAlignment) {}
diff --git a/llvm/lib/MC/MCWasmStreamer.cpp b/llvm/lib/MC/MCWasmStreamer.cpp
index 11a00ad..708050b 100644
--- a/llvm/lib/MC/MCWasmStreamer.cpp
+++ b/llvm/lib/MC/MCWasmStreamer.cpp
@@ -212,22 +212,6 @@
   llvm_unreachable("Wasm doesn't support this directive");
 }
 
-void MCWasmStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
-  llvm_unreachable("Wasm doesn't support this directive");
-}
-
-void MCWasmStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
-  llvm_unreachable("Wasm doesn't support this directive");
-}
-
-void MCWasmStreamer::EmitCOFFSymbolType(int Type) {
-  llvm_unreachable("Wasm doesn't support this directive");
-}
-
-void MCWasmStreamer::EndCOFFSymbolDef() {
-  llvm_unreachable("Wasm doesn't support this directive");
-}
-
 void MCWasmStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
                                   uint64_t Size, unsigned ByteAlignment) {
   llvm_unreachable("Wasm doesn't support this directive");