[AArch64] Emit StackMaps for all binary formats

[rlyerly]

Summary

Changed AArch64AsmPrinter to emit LLVM stackmap [1] section for all binary formats in AArch64 backend. Currently, this section is only emitted for Mach binary files.

[1] http://llvm.org/docs/StackMaps.html

Patch by Rob Lyerly.

[reames]

Sorry this slipped through without notice for so long. This looks entirely reasonable, but could you include a test case to ensure it doesn't break in the future?

lib/Target/AArch64/AArch64AsmPrinter.cpp

void AArch64AsmPrinter::EmitEndOfAsmFile(Module &M) {
   const Triple &TT = TM.getTargetTriple();
   if (TT.isOSBinFormatMachO()) {
     // Funny Darwin hack: This flag tells the linker that no global symbols
     // contain code that falls through to other global symbols (e.g. the obvious
     // implementation of multiple entry points).  If this doesn't occur, the
     // linker can safely perform dead code stripping.  Since LLVM never
     // generates code that does this, it is always safe to set.
     OutStreamer->EmitAssemblerFlag(MCAF_SubsectionsViaSymbols);
-    SM.serializeToStackMapSection();
   }
+  SM.serializeToStackMapSection();
 }
 
 void AArch64AsmPrinter::EmitLOHs() {
   SmallVector<MCSymbol *, 3> MCArgs;
 
   for (const auto &D : AArch64FI->getLOHContainer()) {
     for (const MachineInstr *MI : D.getArgs()) {
       MInstToMCSymbol::iterator LabelIt = LOHInstToLabel.find(MI);