Disable machine copy propagation for now. It's known to be buggy (PR11940) and introduces subtle miscompiles in many places.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@150703 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/Passes.cpp b/lib/CodeGen/Passes.cpp
index ec1f2b4..401ca65 100644
--- a/lib/CodeGen/Passes.cpp
+++ b/lib/CodeGen/Passes.cpp
@@ -69,7 +69,7 @@
 static cl::opt<bool> DisableCGP("disable-cgp", cl::Hidden,
     cl::desc("Disable Codegen Prepare"));
 static cl::opt<bool> DisableCopyProp("disable-copyprop", cl::Hidden,
-    cl::desc("Disable Copy Propagation pass"));
+    cl::desc("Disable Copy Propagation pass"), cl::init(true)); // PR11940
 static cl::opt<bool> PrintLSR("print-lsr-output", cl::Hidden,
     cl::desc("Print LLVM IR produced by the loop-reduce pass"));
 static cl::opt<bool> PrintISelInput("print-isel-input", cl::Hidden,