[mips] Define patterns for the atomic_{load,store}_{8,16,32,64} nodes.

Summary:
Without these patterns we would generate a complete LL/SC sequence.
This would be problematic for memory regions marked as WRITE-only or
READ-only, as the instructions LL/SC would read/write to the protected
memory regions correspondingly.

Reviewers: dsanders

Subscribers: llvm-commits, dsanders

Differential Revision: http://reviews.llvm.org/D14397

llvm-svn: 252293
diff --git a/llvm/lib/Target/Mips/MipsISelLowering.cpp b/llvm/lib/Target/Mips/MipsISelLowering.cpp
index b88af5a..75dc2f1 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.cpp
+++ b/llvm/lib/Target/Mips/MipsISelLowering.cpp
@@ -391,10 +391,10 @@
   setOperationAction(ISD::STACKSAVE,         MVT::Other, Expand);
   setOperationAction(ISD::STACKRESTORE,      MVT::Other, Expand);
 
-  setOperationAction(ISD::ATOMIC_LOAD,       MVT::i32,    Expand);
-  setOperationAction(ISD::ATOMIC_LOAD,       MVT::i64,    Expand);
-  setOperationAction(ISD::ATOMIC_STORE,      MVT::i32,    Expand);
-  setOperationAction(ISD::ATOMIC_STORE,      MVT::i64,    Expand);
+  if (!Subtarget.isGP64bit()) {
+    setOperationAction(ISD::ATOMIC_LOAD,     MVT::i64,   Expand);
+    setOperationAction(ISD::ATOMIC_STORE,    MVT::i64,   Expand);
+  }
 
   setInsertFencesForAtomic(true);