move assertion into mutex guard, a partial fix for PR1606.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41050 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/ExecutionEngine/JIT/JIT.cpp b/lib/ExecutionEngine/JIT/JIT.cpp
index 57ae15e..766d62c 100644
--- a/lib/ExecutionEngine/JIT/JIT.cpp
+++ b/lib/ExecutionEngine/JIT/JIT.cpp
@@ -238,9 +238,9 @@
 ///
 void JIT::runJITOnFunction(Function *F) {
   static bool isAlreadyCodeGenerating = false;
-  assert(!isAlreadyCodeGenerating && "Error: Recursive compilation detected!");
 
   MutexGuard locked(lock);
+  assert(!isAlreadyCodeGenerating && "Error: Recursive compilation detected!");
 
   // JIT the function
   isAlreadyCodeGenerating = true;