Add option -polly-code-generator=none

This allows us to test Polly and the Polly optimizer without actually doing
code generation at the end. By enabling this option, we can also measure the
compile time overhead due to code generation and the cost of LLVM optimizing the
newly generated code.t

llvm-svn: 177516

polly/lib/RegisterPasses.cpp

@@ -68,7 +68,8 @@ enum CodeGenChoice {
 #ifdef CLOOG_FOUND
   CODEGEN_CLOOG,
 #endif
-  CODEGEN_ISL
+  CODEGEN_ISL,
+  CODEGEN_NONE
 };
 
 #ifdef CLOOG_FOUND
@@ -86,6 +87,7 @@ CodeGenerator("polly-code-generator",
                          clEnumValN(CODEGEN_CLOOG, "cloog", "CLooG"),
 #endif
                          clEnumValN(CODEGEN_ISL, "isl", "isl code generator"),
+                         clEnumValN(CODEGEN_NONE, "none", "no code generation"),
                          clEnumValEnd),
           cl::Hidden, cl::init(DefaultCodeGen), cl::ZeroOrMore);
 
@@ -279,6 +281,8 @@ static void registerPollyPasses(llvm::PassManagerBase &PM) {
   case CODEGEN_ISL:
     PM.add(polly::createIslCodeGenerationPass());
     break;
+  case CODEGEN_NONE:
+    break;
   }
 
   if (CFGPrinter)