2 files changed, 12 insertions, 1 deletions
diff --git a/lib/CodeGen/LLVMTargetMachine.cpp b/lib/CodeGen/LLVMTargetMachine.cpp
index f07a85f39c..d14fbb2c33 100644
--- a/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/lib/CodeGen/LLVMTargetMachine.cpp
@@ -147,6 +147,8 @@ static MCContext *addPassesToGenerateCode(LLVMTargetMachine *TM,
 
   PassConfig->addMachinePasses();
 
+  PassConfig->setInitialized();
+
   return Context;
 }
 
diff --git a/lib/CodeGen/Passes.cpp b/lib/CodeGen/Passes.cpp
index 2877cf165b..6d12dd839c 100644
--- a/lib/CodeGen/Passes.cpp
+++ b/lib/CodeGen/Passes.cpp
@@ -84,7 +84,10 @@ char TargetPassConfig::ID = 0;
 TargetPassConfig::~TargetPassConfig() {}
 
 TargetPassConfig::TargetPassConfig(TargetMachine *tm, PassManagerBase &pm)
-  : ImmutablePass(ID), TM(tm), PM(pm), DisableVerify(false) {
+  : ImmutablePass(ID), TM(tm), PM(pm), Initialized(false),
+    DisableVerify(false),
+    EnableTailMerge(true) {
+
   // Register all target independent codegen passes to activate their PassIDs,
   // including this pass itself.
   initializeCodeGen(*PassRegistry::getPassRegistry());
@@ -103,6 +106,12 @@ TargetPassConfig::TargetPassConfig()
   llvm_unreachable("TargetPassConfig should not be constructed on-the-fly");
 }
 
+// Helper to verify the analysis is really immutable.
+void TargetPassConfig::setOpt(bool &Opt, bool Val) {
+  assert(!Initialized && "PassConfig is immutable");
+  Opt = Val;
+}
+
 void TargetPassConfig::addPass(char &ID) {
   // FIXME: check user overrides
   Pass *P = Pass::createPass(ID);