X86AsmPrinter MCJIT MSVC bug fix.

[jklontz]

Summary

This bug was introduced in r213006 which makes an assumption that MCSection is COFF for Windows MSVC. This assumption is broken for MCJIT users where ELF is used instead [1]. The fix is to change the MCSection cast to a dyn_cast.

[1] http://lists.cs.uiuc.edu/pipermail/llvmdev/2013-December/068407.html.

[majnemer]

LGTM

[jklontz]

Closed by commit rL216173 (authored by @jklontz).

llvm/trunk/lib/Target/X86/X86AsmPrinter.cpp

 MCSymbol *X86AsmPrinter::GetCPISymbol(unsigned CPID) const {
   if (Subtarget->isTargetKnownWindowsMSVC()) {
     const MachineConstantPoolEntry &CPE =
         MF->getConstantPool()->getConstants()[CPID];
     if (!CPE.isMachineConstantPoolEntry()) {
       SectionKind Kind =
           CPE.getSectionKind(TM.getSubtargetImpl()->getDataLayout());
       const Constant *C = CPE.Val.ConstVal;
-      const MCSectionCOFF *S = cast<MCSectionCOFF>(
-          getObjFileLowering().getSectionForConstant(Kind, C));
+      if (const MCSectionCOFF *S = dyn_cast<MCSectionCOFF>(
+            getObjFileLowering().getSectionForConstant(Kind, C))) {
         if (MCSymbol *Sym = S->getCOMDATSymbol()) {
           if (Sym->isUndefined())
             OutStreamer.EmitSymbolAttribute(Sym, MCSA_Global);
           return Sym;
         }
       }
     }
+  }
 
   return AsmPrinter::GetCPISymbol(CPID);
 }
 
 void X86AsmPrinter::GenerateExportDirective(const MCSymbol *Sym, bool IsData) {
   SmallString<128> Directive;
   raw_svector_ostream OS(Directive);
   StringRef Name = Sym->getName();