[PowerPC] 32-bit ELF PIC support

This adds initial support for PPC32 ELF PIC (Position Independent Code; the
-fPIC variety), thus rectifying a long-standing deficiency in the PowerPC
backend.

Patch by Justin Hibbits!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213427 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/PPCMachineFunctionInfo.cpp

@@ -8,8 +8,16 @@
 //===----------------------------------------------------------------------===//
 
 #include "PPCMachineFunctionInfo.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/Target/TargetMachine.h"
 
 using namespace llvm;
 
 void PPCFunctionInfo::anchor() { }
 
+MCSymbol *PPCFunctionInfo::getPICOffsetSymbol() const {
+  const DataLayout *DL = MF.getTarget().getDataLayout();
+  return MF.getContext().GetOrCreateSymbol(Twine(DL->getPrivateGlobalPrefix())+
+    Twine(MF.getFunctionNumber())+"$poff");
+}