Implement x86 support for @llvm.prefetch. It corresponds to prefetcht{0|1|2} and prefetchnta instructions.

llvm-svn: 48042
diff --git a/llvm/lib/Target/Mips/MipsISelLowering.cpp b/llvm/lib/Target/Mips/MipsISelLowering.cpp
index ed76621..5a0daf8 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.cpp
+++ b/llvm/lib/Target/Mips/MipsISelLowering.cpp
@@ -85,6 +85,7 @@
   setOperationAction(ISD::MEMSET, MVT::Other, Expand);
   setOperationAction(ISD::MEMCPY, MVT::Other, Expand);
   setOperationAction(ISD::MEMBARRIER, MVT::Other, Expand);
+  setOperationAction(ISD::PREFETCH, MVT::Other, Expand);
 
   setOperationAction(ISD::CTPOP, MVT::i32, Expand);
   setOperationAction(ISD::CTTZ , MVT::i32, Expand);