Ignore special ARM allocation hints for unexpected register classes.

Add an assertion to linear scan to prevent it from allocating registers outside
the register class.

<rdar://problem/9183021>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@128254 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index e99d910..8ee1064 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -1110,6 +1110,7 @@
   // list.
   if (physReg) {
     DEBUG(dbgs() <<  tri_->getName(physReg) << '\n');
+    assert(RC->contains(physReg) && "Invalid candidate");
     vrm_->assignVirt2Phys(cur->reg, physReg);
     addRegUse(physReg);
     active_.push_back(std::make_pair(cur, cur->begin()));