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
@@ -1747,10 +1747,35 @@
       }
     }
 
+    Inst.setOpcode(NewOpcode);
+
+    // Replace `movl $0x0, %eax` with `xorl %eax, %eax`
+    switch (NewOpcode) {
+    default:
+      break;
+
+    case X86::MOV64ri:
+    case X86::MOV64ri32:
+    case X86::MOV32ri:
+      auto OpNum = MCPlus::getNumPrimeOperands(Inst) - 1;
+      if (Inst.getOperand(OpNum).isImm() && !Inst.getOperand(OpNum).getImm()) {
+        if (NewOpcode == X86::MOV32ri)
+          NewOpcode = X86::XOR32rr;
+        else
+          NewOpcode = X86::XOR64rr;
+        MCOperand Op = Inst.getOperand(0);
+        Inst.setOpcode(NewOpcode);
+        Inst.clear();
+        Inst.addOperand(Op);
+        Inst.addOperand(Op);
+        Inst.addOperand(Op);
+      }
+      break;
+    }
+
     if (NewOpcode == OldOpcode)
       return false;
 
-    Inst.setOpcode(NewOpcode);
     return true;
   }