Move the memory fences out of the path for single-threaded mode.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73775 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 5 deletions

diff --git a/lib/VMCore/Pass.cpp b/lib/VMCore/Pass.cpp
index 3fce83d..e943e31 100644
--- a/lib/VMCore/Pass.cpp
+++ b/lib/VMCore/Pass.cpp
@@ -198,9 +198,9 @@ static PassRegistrar *getPassRegistrar() {
   // Use double-checked locking to safely initialize the registrar when
   // we're running in multithreaded mode.
   PassRegistrar* tmp = PassRegistrarObj;
-  sys::MemoryFence();
-  if (!tmp) {
-    if (llvm_is_multithreaded()) {
+  if (llvm_is_multithreaded()) {
+    sys::MemoryFence();
+    if (!tmp) {
       llvm_acquire_global_lock();
       tmp = PassRegistrarObj;
       if (!tmp) {
@@ -209,10 +209,11 @@ static PassRegistrar *getPassRegistrar() {
         PassRegistrarObj = tmp;
       }
       llvm_release_global_lock();
-    } else {
-      PassRegistrarObj = new PassRegistrar();
     }
+  } else if (!tmp) {
+    PassRegistrarObj = new PassRegistrar();
   }
+  
   return PassRegistrarObj;
 }