add PCRelative values emmiting into MCObjectStreamer

[seandree]

Summary

Add additional function to emit PCRelative values through MCObjectStreamer,
it allows to use MCObjectStreamer to emit PCRelative fixups.
By default it always emits nonPCRelative.

[seandree]

Hello Sanjoy. Could you review this please?

[sanjoy]

I don't think I'm the right person to review this? How about @rafael?

Btw, please upload with full context: http://llvm.org/docs/Phabricator.html

[seandree]

In D29483#668500, @sanjoy wrote:

I don't think I'm the right person to review this? How about @rafael?

Btw, please upload with full context: http://llvm.org/docs/Phabricator.html

Yes, thank you.
@rafael can you take a look?

[kyulee1]

LGTM

include/llvm/MC/MCObjectStreamer.h

   void ChangeSection(MCSection *Section, const MCExpr *Subsection) override;
   void EmitInstruction(const MCInst &Inst, const MCSubtargetInfo& STI) override;
 
+  /// \brief EmitValueImpl with additional param, that allows to emit PCRelative
+  /// MCFixup.
+  void EmitValueImpl(const MCExpr *Value, unsigned Size,
+                     SMLoc Loc, bool isPCRelative);
+
   /// \brief Emit an instruction to a special fragment, because this instruction
   /// can change its size during relaxation.
   virtual void EmitInstToFragment(const MCInst &Inst, const MCSubtargetInfo &);

lib/MC/MCObjectStreamer.cpp

 }
 
 void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
-                                     SMLoc Loc) {
+    SMLoc Loc, bool isPCRelative) {
   MCStreamer::EmitValueImpl(Value, Size, Loc);
   MCDataFragment *DF = getOrCreateDataFragment();
   flushPendingLabels(DF, DF->getContents().size());

   }
   DF->getFixups().push_back(
       MCFixup::create(DF->getContents().size(), Value,
-                      MCFixup::getKindForSize(Size, false), Loc));
+                      MCFixup::getKindForSize(Size, isPCRelative), Loc));
   DF->getContents().resize(DF->getContents().size() + Size, 0);
 }
 
+
+void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
+                                     SMLoc Loc) {
+  EmitValueImpl(Value, Size, Loc, false);
+}
+
 void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
   // We need to create a local symbol to avoid relocations.
   Frame.Begin = getContext().createTempSymbol();