Disable Subzero IR generation for performance testing.

src/IceCfg.cpp

 //===- subzero/src/IceCfg.cpp - Control flow graph implementation ---------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the Cfg class, including constant pool
@@ skipping 13 matching lines @@
 namespace Ice {
 
 Cfg::Cfg(GlobalContext *Ctx)
     : Ctx(Ctx), FunctionName(""), ReturnType(IceType_void),
       IsInternalLinkage(false), HasError(false), FocusedTiming(false),
       ErrorMessage(""), Entry(NULL), NextInstNumber(1), Live(nullptr),
       Target(TargetLowering::createLowering(Ctx->getTargetArch(), this)),
       VMetadata(new VariablesMetadata(this)),
       TargetAssembler(
           TargetLowering::createAssembler(Ctx->getTargetArch(), this)),
-      CurrentNode(NULL) {}
+      CurrentNode(NULL) {
+  assert(!Ctx->isIRGenerationDisabled() &&
+         "Attempt to build cfg when IR generation disabled");
+}
 
 Cfg::~Cfg() {}
 
 void Cfg::setError(const IceString &Message) {
   HasError = true;
   ErrorMessage = Message;
   Ctx->getStrDump() << "ICE translation error: " << ErrorMessage << "\n";
 }
 
 CfgNode *Cfg::makeNode(const IceString &Name) {
@@ skipping 434 matching lines @@
     }
   }
   // Print each basic block
   for (CfgNode *Node : Nodes)
     Node->dump(this);
   if (getContext()->isVerbose(IceV_Instructions))
     Str << "}\n";
 }
 
 } // end of namespace Ice