Expression: correct relocation model for Windows

[compnerd]

Summary

The Windows CG model cannot generate code with the PIC relocation model as all code is implicitly PIC. Invert the condition and inline the single use. This improves expression handling on Windows.

[JDevlieghere]

I don't know much about this, but the change seems reasonable.

[compnerd]

SVN r361443

source/Expression/IRExecutionUnit.cpp

     log->Printf("Module being sent to JIT: \n%s", s.c_str());
   }
 
-  llvm::Triple triple(m_module->getTargetTriple());
-  llvm::Reloc::Model relocModel;
-
-  if (triple.isOSBinFormatELF()) {
-    relocModel = llvm::Reloc::Static;
-  } else {
-    relocModel = llvm::Reloc::PIC_;
-  }
-
   m_module_up->getContext().setInlineAsmDiagnosticHandler(ReportInlineAsmError,
                                                           &error);
 
   llvm::EngineBuilder builder(std::move(m_module_up));
+  llvm::Triple triple(m_module->getTargetTriple());
 
   builder.setEngineKind(llvm::EngineKind::JIT)
       .setErrorStr(&error_string)
-      .setRelocationModel(relocModel)
+      .setRelocationModel(triple.isOSBinFormatMacho()
+                              ? llvm::Reloc::PIC_
+                              : llvm::Reloc::Static)
       .setMCJITMemoryManager(
           std::unique_ptr<MemoryManager>(new MemoryManager(*this)))
       .setOptLevel(llvm::CodeGenOpt::Less);