[R600] Replicate old DAGCombiner behavior in target specific DAG combine.

build_vector is lowered to REG_SEQUENCE, which is something the register
allocator does a good job at optimizing.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187397 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/R600/R600ISelLowering.cpp

@@ -89,6 +89,7 @@ R600TargetLowering::R600TargetLowering(TargetMachine &TM) :
   setTargetDAGCombine(ISD::FP_TO_SINT);
   setTargetDAGCombine(ISD::EXTRACT_VECTOR_ELT);
   setTargetDAGCombine(ISD::SELECT_CC);
+  setTargetDAGCombine(ISD::INSERT_VECTOR_ELT);
 
   setOperationAction(ISD::GlobalAddress, MVT::i32, Custom);
 
@@ -1409,6 +1410,61 @@ SDValue R600TargetLowering::PerformDAGCombine(SDNode *N,
 
     break;
   }
+
+  // insert_vector_elt (build_vector elt0, …, eltN), NewEltIdx, idx
+  // => build_vector elt0, …, NewEltIdx, …, eltN
+  case ISD::INSERT_VECTOR_ELT: {
+    SDValue InVec = N->getOperand(0);
+    SDValue InVal = N->getOperand(1);
+    SDValue EltNo = N->getOperand(2);
+    SDLoc dl(N);
+
+    // If the inserted element is an UNDEF, just use the input vector.
+    if (InVal.getOpcode() == ISD::UNDEF)
+      return InVec;
+
+    EVT VT = InVec.getValueType();
+
+    // If we can't generate a legal BUILD_VECTOR, exit
+    if (!isOperationLegal(ISD::BUILD_VECTOR, VT))
+      return SDValue();
+
+    // Check that we know which element is being inserted
+    if (!isa<ConstantSDNode>(EltNo))
+      return SDValue();
+    unsigned Elt = cast<ConstantSDNode>(EltNo)->getZExtValue();
+
+    // Check that the operand is a BUILD_VECTOR (or UNDEF, which can essentially
+    // be converted to a BUILD_VECTOR).  Fill in the Ops vector with the
+    // vector elements.
+    SmallVector<SDValue, 8> Ops;
+    if (InVec.getOpcode() == ISD::BUILD_VECTOR) {
+      Ops.append(InVec.getNode()->op_begin(),
+                 InVec.getNode()->op_end());
+    } else if (InVec.getOpcode() == ISD::UNDEF) {
+      unsigned NElts = VT.getVectorNumElements();
+      Ops.append(NElts, DAG.getUNDEF(InVal.getValueType()));
+    } else {
+      return SDValue();
+    }
+
+    // Insert the element
+    if (Elt < Ops.size()) {
+      // All the operands of BUILD_VECTOR must have the same type;
+      // we enforce that here.
+      EVT OpVT = Ops[0].getValueType();
+      if (InVal.getValueType() != OpVT)
+        InVal = OpVT.bitsGT(InVal.getValueType()) ?
+          DAG.getNode(ISD::ANY_EXTEND, dl, OpVT, InVal) :
+          DAG.getNode(ISD::TRUNCATE, dl, OpVT, InVal);
+      Ops[Elt] = InVal;
+    }
+
+    // Return the new vector
+    return DAG.getNode(ISD::BUILD_VECTOR, dl,
+                       VT, &Ops[0], Ops.size());
+  }
+
   // Extract_vec (Build_vector) generated by custom lowering
   // also needs to be customly combined
   case ISD::EXTRACT_VECTOR_ELT: {

test/CodeGen/R600/swizzle-export.ll

@@ -1,5 +1,4 @@
 ; RUN: llc < %s -march=r600 -mcpu=redwood | FileCheck --check-prefix=EG-CHECK %s
-; XFAIL: *
 
 ;EG-CHECK: @main
 ;EG-CHECK: EXPORT T{{[0-9]+}}.XYXX