Vector element extraction without stack operations on Power 8

This patch corresponds to review:
http://reviews.llvm.org/D12032

This patch builds onto the patch that provided scalar to vector conversions
without stack operations (D11471).
Included in this patch:

    - Vector element extraction for all vector types with constant element number
    - Vector element extraction for v16i8 and v8i16 with variable element number
    - Removal of some unnecessary COPY_TO_REGCLASS operations that ended up
      unnecessarily moving things around between registers

Not included in this patch (will be in upcoming patch):

    - Vector element extraction for v4i32, v4f32, v2i64 and v2f64 with
      variable element number
    - Vector element insertion for variable/constant element number

Testing is provided for all extractions. The extractions that are not
implemented yet are just placeholders.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249822 91177308-0d34-0410-b5e6-96231b3b80d8

Author: nemanjai

lib/Target/PowerPC/PPCISelLowering.cpp

@@ -543,14 +543,21 @@ PPCTargetLowering::PPCTargetLowering(const PPCTargetMachine &TM,
 
     if (Subtarget.hasVSX()) {
       setOperationAction(ISD::SCALAR_TO_VECTOR, MVT::v2f64, Legal);
-      if (Subtarget.hasP8Vector())
+      setOperationAction(ISD::EXTRACT_VECTOR_ELT, MVT::v2f64, Legal);
+      if (Subtarget.hasP8Vector()) {
         setOperationAction(ISD::SCALAR_TO_VECTOR, MVT::v4f32, Legal);
+        setOperationAction(ISD::EXTRACT_VECTOR_ELT, MVT::v4f32, Legal);
+      }
       if (Subtarget.hasDirectMove()) {
         setOperationAction(ISD::SCALAR_TO_VECTOR, MVT::v16i8, Legal);
         setOperationAction(ISD::SCALAR_TO_VECTOR, MVT::v8i16, Legal);
         setOperationAction(ISD::SCALAR_TO_VECTOR, MVT::v4i32, Legal);
         // FIXME: this is causing bootstrap failures, disable temporarily
         //setOperationAction(ISD::SCALAR_TO_VECTOR, MVT::v2i64, Legal);
+        setOperationAction(ISD::EXTRACT_VECTOR_ELT, MVT::v16i8, Legal);
+        setOperationAction(ISD::EXTRACT_VECTOR_ELT, MVT::v8i16, Legal);
+        setOperationAction(ISD::EXTRACT_VECTOR_ELT, MVT::v4i32, Legal);
+        setOperationAction(ISD::EXTRACT_VECTOR_ELT, MVT::v2i64, Legal);
       }
       setOperationAction(ISD::EXTRACT_VECTOR_ELT, MVT::v2f64, Legal);