SelectionDAG: Pass along the original argument/element type in ISD::InputArg

For some targets, it is useful to be able to look at the original
type of an argument without having to dig through the original IR.

This also fixes a bug in SelectionDAGBuilder where InputArg.PartOffset
was not taking into account the offset of structure elements.

Patch by: Justin Holewinski

Tom Stellard:
  - Changed the type of ArgVT to EVT, so it can store non-simple types
    like v3i32.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193214 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TargetLoweringBase.cpp b/lib/CodeGen/TargetLoweringBase.cpp
index e770942..bfed53e 100644
--- a/lib/CodeGen/TargetLoweringBase.cpp
+++ b/lib/CodeGen/TargetLoweringBase.cpp
@@ -1202,7 +1202,7 @@
       Flags.setZExt();
 
     for (unsigned i = 0; i < NumParts; ++i)
-      Outs.push_back(ISD::OutputArg(Flags, PartVT, /*isFixed=*/true, 0, 0));
+      Outs.push_back(ISD::OutputArg(Flags, PartVT, VT, /*isFixed=*/true, 0, 0));
   }
 }