Subzero: Randomly insert nops.

src/IceTargetLoweringX8632.h

Index: src/IceTargetLoweringX8632.h
diff --git a/src/IceTargetLoweringX8632.h b/src/IceTargetLoweringX8632.h
index 6d209dc8f4c72d179953ef8d9a0c83adea4b9cce..0395a75fc10f97d7388f63407ed82a38f2196f34 100644
--- a/src/IceTargetLoweringX8632.h
+++ b/src/IceTargetLoweringX8632.h
@@ -104,6 +104,7 @@ protected:
   virtual void lowerUnreachable(const InstUnreachable *Inst);
   virtual void doAddressOptLoad();
   virtual void doAddressOptStore();
+  virtual void randomlyInsertNop(float Probability);
 
   // Naive lowering of cmpxchg.
   void lowerAtomicCmpxchg(Variable *DestPrev, Operand *Ptr, Operand *Expected,
@@ -325,6 +326,9 @@ protected:
   void _neg(Variable *SrcDest) {
     Context.insert(InstX8632Neg::create(Func, SrcDest));
   }
+  void _nop(SizeT Length = 1) {
+    Context.insert(InstX8632Nop::create(Func, Length));
+  }
   void _or(Variable *Dest, Operand *Src0) {
     Context.insert(InstX8632Or::create(Func, Dest, Src0));
   }