add llvm-mc support for parsing the .subsections_via_symbols directive.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75500 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/MC/MCStreamer.h

@@ -89,6 +89,11 @@ namespace llvm {
     // symbol section in the constructor and initialize it here?
     virtual void EmitLabel(MCSymbol *Symbol) = 0;
 
+    /// SubsectionsViaSymbols - Note in the output that the conventions used in
+    /// in the assembly file allows the bytes of a section to be divided up at
+    /// the boundaries of the symbols by a link editor for processing as atoms.
+    virtual void SubsectionsViaSymbols(void) = 0;
+
     /// EmitAssignment - Emit an assignment of @param Value to @param Symbol.
     ///
     /// This corresponds to an assembler statement such as:

lib/MC/MCAsmStreamer.cpp

@@ -38,6 +38,8 @@ namespace {
 
     virtual void EmitLabel(MCSymbol *Symbol);
 
+    virtual void SubsectionsViaSymbols(void);
+
     virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
                                 bool MakeAbsolute = false);
 
@@ -117,6 +119,10 @@ void MCAsmStreamer::EmitLabel(MCSymbol *Symbol) {
   Symbol->setExternal(false);
 }
 
+void MCAsmStreamer::SubsectionsViaSymbols(void) {
+  OS << ".subsections_via_symbols\n";
+}
+
 void MCAsmStreamer::EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
                                    bool MakeAbsolute) {
   assert(!Symbol->getSection() && "Cannot assign to a label!");

test/MC/AsmParser/directive_subsections_via_symbols.s

@@ -0,0 +1,6 @@
+# RUN: llvm-mc %s | FileCheck %s
+
+# CHECK: TEST0:
+# CHECK: .subsections_via_symbols
+TEST0:  
+	.subsections_via_symbols

tools/llvm-mc/AsmParser.cpp

@@ -527,6 +527,9 @@ bool AsmParser::ParseStatement() {
     if (!strcmp(IDVal, ".zerofill"))
       return ParseDirectiveDarwinZerofill();
 
+    if (!strcmp(IDVal, ".subsections_via_symbols"))
+      return ParseDirectiveDarwinSubsectionsViaSymbols();
+
     Warning(IDLoc, "ignoring directive for now");
     EatToEndOfStatement();
     return false;
@@ -1052,3 +1055,16 @@ bool AsmParser::ParseDirectiveDarwinZerofill() {
 
   return false;
 }
+
+/// ParseDirectiveDarwinSubsectionsViaSymbols
+///  ::= .subsections_via_symbols
+bool AsmParser::ParseDirectiveDarwinSubsectionsViaSymbols() {
+  if (Lexer.isNot(asmtok::EndOfStatement))
+    return TokError("unexpected token in '.subsections_via_symbols' directive");
+  
+  Lexer.Lex();
+
+  Out.SubsectionsViaSymbols();
+
+  return false;
+}

tools/llvm-mc/AsmParser.h

@@ -112,6 +112,9 @@ private:
 
   bool ParseDirectiveComm(bool IsLocal); // ".comm" and ".lcomm"
   bool ParseDirectiveDarwinZerofill(); // Darwin specific ".zerofill"
+
+  // Darwin specific ".subsections_via_symbols"
+  bool ParseDirectiveDarwinSubsectionsViaSymbols();
 };
 
 } // end namespace llvm