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
@@ -497,12 +497,10 @@
   }
 
   virtual bool isPrefix(const MCInst &Inst) const {
-    llvm_unreachable("not implemented");
     return false;
   }
 
   virtual bool isRep(const MCInst &Inst) const {
-    llvm_unreachable("not implemented");
     return false;
   }
 
@@ -516,7 +514,6 @@
   }
 
   virtual bool isPop(const MCInst &Inst) const {
-    llvm_unreachable("not implemented");
     return false;
   }
 
@@ -556,7 +553,6 @@
   }
 
   virtual bool isLeave(const MCInst &Inst) const {
-    llvm_unreachable("not implemented");
     return false;
   }
 
@@ -575,7 +571,6 @@
   }
 
   virtual bool isMoveMem2Reg(const MCInst &Inst) const {
-    llvm_unreachable("not implemented");
     return false;
   }
 
@@ -862,7 +857,6 @@
 
   /// Return true if the instruction is encoded using EVEX (AVX-512).
   virtual bool hasEVEXEncoding(const MCInst &Inst) const {
-    llvm_unreachable("not implemented");
     return false;
   }
 
diff --git a/bolt/lib/Target/AArch64/AArch64MCPlusBuilder.cpp b/bolt/lib/Target/AArch64/AArch64MCPlusBuilder.cpp
--- a/bolt/lib/Target/AArch64/AArch64MCPlusBuilder.cpp
+++ b/bolt/lib/Target/AArch64/AArch64MCPlusBuilder.cpp
@@ -45,8 +45,6 @@
                                  *AArch64ExprB.getSubExpr(), Comp);
   }
 
-  bool hasEVEXEncoding(const MCInst &) const override { return false; }
-
   bool isMacroOpFusionPair(ArrayRef<MCInst> Insts) const override {
     return false;
   }
@@ -1091,14 +1089,6 @@
     return true;
   }
 
-  bool isMoveMem2Reg(const MCInst &Inst) const override { return false; }
-
-  bool isLeave(const MCInst &Inst) const override { return false; }
-
-  bool isPop(const MCInst &Inst) const override { return false; }
-
-  bool isPrefix(const MCInst &Inst) const override { return false; }
-
   bool createReturn(MCInst &Inst) const override {
     Inst.setOpcode(AArch64::RET);
     Inst.clear();