diff --git a/bolt/include/bolt/Core/MCPlusBuilder.h b/bolt/include/bolt/Core/MCPlusBuilder.h
--- a/bolt/include/bolt/Core/MCPlusBuilder.h
+++ b/bolt/include/bolt/Core/MCPlusBuilder.h
@@ -526,11 +526,6 @@
     return false;
   }
 
-  virtual bool isMOVSX64rm32(const MCInst &Inst) const {
-    llvm_unreachable("not implemented");
-    return false;
-  }
-
   virtual bool isLeave(const MCInst &Inst) const {
     llvm_unreachable("not implemented");
     return false;
diff --git a/bolt/lib/Target/X86/X86MCPlusBuilder.cpp b/bolt/lib/Target/X86/X86MCPlusBuilder.cpp
--- a/bolt/lib/Target/X86/X86MCPlusBuilder.cpp
+++ b/bolt/lib/Target/X86/X86MCPlusBuilder.cpp
@@ -265,6 +265,10 @@
   }
 }
 
+bool isMOVSX64rm32(const MCInst &Inst) {
+  return Inst.getOpcode() == X86::MOVSX64rm32;
+}
+
 class X86MCPlusBuilder : public MCPlusBuilder {
 public:
   X86MCPlusBuilder(const MCInstrAnalysis *Analysis, const MCInstrInfo *Info,
@@ -542,10 +546,6 @@
     return Inst.getOpcode() == X86::LEA64r;
   }
 
-  bool isMOVSX64rm32(const MCInst &Inst) const override {
-    return Inst.getOpcode() == X86::MOVSX64rm32;
-  }
-
   bool isLeave(const MCInst &Inst) const override {
     return Inst.getOpcode() == X86::LEAVE || Inst.getOpcode() == X86::LEAVE64;
   }