R600: Add a pass that merge Vector Register

Previously commited @183279 but tests were failing, reverted @183286
It was broken because @183336 was missing, now it's there.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@183343 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/R600/AMDGPUTargetMachine.cpp b/lib/Target/R600/AMDGPUTargetMachine.cpp
index 88dc583..c52af56 100644
--- a/lib/Target/R600/AMDGPUTargetMachine.cpp
+++ b/lib/Target/R600/AMDGPUTargetMachine.cpp
@@ -130,6 +130,11 @@
 
 bool AMDGPUPassConfig::addPreRegAlloc() {
   addPass(createAMDGPUConvertToISAPass(*TM));
+  const AMDGPUSubtarget &ST = TM->getSubtarget<AMDGPUSubtarget>();
+  
+  if (ST.device()->getGeneration() <= AMDGPUDeviceInfo::HD6XXX) {
+    addPass(createR600VectorRegMerger(*TM));
+  }
   return false;
 }