Introduce the ability to insert IACA (Intel Architecture Code Analyzer) marks to

src/IceTargetLoweringX86Base.h

Index: src/IceTargetLoweringX86Base.h
diff --git a/src/IceTargetLoweringX86Base.h b/src/IceTargetLoweringX86Base.h
index d89d74753dfab9f136338a4895051c6b9b256b6b..c0a2d4239c8cf8250eab973bfd0f3e951e9ae11e 100644
--- a/src/IceTargetLoweringX86Base.h
+++ b/src/IceTargetLoweringX86Base.h
@@ -582,6 +582,37 @@ protected:
     Context.insert(Traits::Insts::XorRMW::create(Func, DestSrc0, Src1));
   }
 
+  void _iaca_start() {
+    if (!BuildDefs::minimal())
+      Context.insert(Traits::Insts::IacaStart::create(Func));
+  }
+  void _iaca_end() {
+    if (!BuildDefs::minimal())
+      Context.insert(Traits::Insts::IacaEnd::create(Func));
+  }
+
+  /// This class helps wrap IACA markers around the code generated by the
+  /// current scope. It means you don't need to put an end before each return.
+  class ScopedIacaMark {
+    ScopedIacaMark(const ScopedIacaMark &) = delete;
+    ScopedIacaMark &operator=(const ScopedIacaMark &) = delete;
+
+  public:
+    ScopedIacaMark(TargetX86Base *Lowering) : Lowering(Lowering) {
+      Lowering->_iaca_start();
+    }
+    ~ScopedIacaMark() { end(); }
+    void end() {
+      if (!Lowering)
+        return;
+      Lowering->_iaca_end();
+      Lowering = nullptr;
+    }
+
+  private:
+    TargetX86Base *Lowering;
+  };
+
   bool optimizeScalarMul(Variable *Dest, Operand *Src0, int32_t Src1);
   void findRMW();