Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -235,6 +235,7 @@
 option(LLVM_ENABLE_LIBCXX "Use libc++ if available." OFF)
 option(LLVM_ENABLE_PEDANTIC "Compile with pedantic enabled." ON)
 option(LLVM_ENABLE_WERROR "Fail and stop if a warning is triggered." OFF)
+option(LLVM_ENABLE_MACHINE_VERIFIER "Enable the LLVM machine verifier by default" OFF)
 
 if( NOT uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG" )
   option(LLVM_ENABLE_ASSERTIONS "Enable assertions" OFF)
Index: lib/CodeGen/CMakeLists.txt
===================================================================
--- lib/CodeGen/CMakeLists.txt
+++ lib/CodeGen/CMakeLists.txt
@@ -125,3 +125,9 @@
 
 add_subdirectory(SelectionDAG)
 add_subdirectory(AsmPrinter)
+
+if (LLVM_ENABLE_MACHINE_VERIFIER)
+  set_property(SOURCE Passes.cpp APPEND_STRING
+    PROPERTY COMPILE_DEFINITIONS "LLVM_ENABLE_MACHINE_VERIFIER")
+endif()
+
Index: lib/CodeGen/MachineVerifier.cpp
===================================================================
--- lib/CodeGen/MachineVerifier.cpp
+++ lib/CodeGen/MachineVerifier.cpp
@@ -55,15 +55,13 @@
 
     MachineVerifier(Pass *pass, const char *b) :
       PASS(pass),
-      Banner(b),
-      OutFileName(getenv("LLVM_VERIFY_MACHINEINSTRS"))
+      Banner(b)
       {}
 
     bool runOnMachineFunction(MachineFunction &MF);
 
     Pass *const PASS;
     const char *Banner;
-    const char *const OutFileName;
     raw_ostream *OS;
     const MachineFunction *MF;
     const TargetMachine *TM;
@@ -277,21 +275,7 @@
 }
 
 bool MachineVerifier::runOnMachineFunction(MachineFunction &MF) {
-  raw_ostream *OutFile = nullptr;
-  if (OutFileName) {
-    std::error_code EC;
-    OutFile = new raw_fd_ostream(OutFileName, EC,
-                                 sys::fs::F_Append | sys::fs::F_Text);
-    if (EC) {
-      errs() << "Error opening '" << OutFileName << "': " << EC.message()
-             << '\n';
-      exit(1);
-    }
-
-    OS = OutFile;
-  } else {
-    OS = &errs();
-  }
+  OS = &errs();
 
   foundErrors = 0;
 
@@ -363,9 +347,7 @@
   }
   visitMachineFunctionAfter();
 
-  if (OutFile)
-    delete OutFile;
-  else if (foundErrors)
+  if (foundErrors)
     report_fatal_error("Found "+Twine(foundErrors)+" machine code errors.");
 
   // Clean up.
Index: lib/CodeGen/Passes.cpp
===================================================================
--- lib/CodeGen/Passes.cpp
+++ lib/CodeGen/Passes.cpp
@@ -81,7 +81,12 @@
     cl::desc("Dump garbage collector data"));
 static cl::opt<bool> VerifyMachineCode("verify-machineinstrs", cl::Hidden,
     cl::desc("Verify generated machine code"),
-    cl::init(getenv("LLVM_VERIFY_MACHINEINSTRS")!=nullptr));
+#ifdef LLVM_ENABLE_MACHINE_VERIFIER
+    cl::init(true));
+#else
+    cl::init(false));
+#endif
+
 static cl::opt<std::string>
 PrintMachineInstrs("print-machineinstrs", cl::ValueOptional,
                    cl::desc("Print machine instrs"),