New approach to r136737: insert the necessary fences for atomic ops in platform-independent code, since a bunch of platforms (ARM, Mips, PPC, Alpha are the relevant targets here) need to do essentially the same thing.

I think this completes the basic CodeGen for atomicrmw and cmpxchg.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@136813 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/Alpha/AlphaISelLowering.cpp

@@ -160,6 +160,8 @@ AlphaTargetLowering::AlphaTargetLowering(TargetMachine &TM)
 
   setMinFunctionAlignment(4);
 
+  setInsertFencesForAtomic(true);
+
   computeRegisterProperties();
 }