[SelectionDAG] Add FoldBUILD_VECTOR to simplify new BUILD_VECTOR nodes

	
Similar to FoldCONCAT_VECTORS, this patch adds FoldBUILD_VECTOR to simplify cases that can avoid the creation of the BUILD_VECTOR - if all the operands are UNDEF or if the BUILD_VECTOR simplifies to a copy.

This exposed an assumption in some AMDGPU code that getBuildVector was guaranteed to be a BUILD_VECTOR node that I've tried to handle.	
	
Differential Revision: https://reviews.llvm.org/D53760

llvm-svn: 345578

1 files changed, 18 insertions, 16 deletions

diff --git a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
index 8864aabb063..e2a0f05d2b3 100644
--- a/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
+++ b/llvm/lib/Target/AMDGPU/R600ISelLowering.cpp
@@ -1685,14 +1685,15 @@ bool R600TargetLowering::allowsMisalignedMemoryAccesses(EVT VT,
 static SDValue CompactSwizzlableVector(
   SelectionDAG &DAG, SDValue VectorEntry,
   DenseMap<unsigned, unsigned> &RemapSwizzle) {
-  assert(VectorEntry.getOpcode() == ISD::BUILD_VECTOR);
   assert(RemapSwizzle.empty());
-  SDValue NewBldVec[4] = {
-    VectorEntry.getOperand(0),
-    VectorEntry.getOperand(1),
-    VectorEntry.getOperand(2),
-    VectorEntry.getOperand(3)
-  };
+
+  SDLoc DL(VectorEntry);
+  EVT EltTy = VectorEntry.getValueType().getVectorElementType();
+
+  SDValue NewBldVec[4];
+  for (unsigned i = 0; i < 4; i++)
+    NewBldVec[i] = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, EltTy, VectorEntry,
+                               DAG.getIntPtrConstant(i, DL));
 
   for (unsigned i = 0; i < 4; i++) {
     if (NewBldVec[i].isUndef())
@@ -1727,15 +1728,17 @@ static SDValue CompactSwizzlableVector(
 
 static SDValue ReorganizeVector(SelectionDAG &DAG, SDValue VectorEntry,
                                 DenseMap<unsigned, unsigned> &RemapSwizzle) {
-  assert(VectorEntry.getOpcode() == ISD::BUILD_VECTOR);
   assert(RemapSwizzle.empty());
-  SDValue NewBldVec[4] = {
-      VectorEntry.getOperand(0),
-      VectorEntry.getOperand(1),
-      VectorEntry.getOperand(2),
-      VectorEntry.getOperand(3)
-  };
-  bool isUnmovable[4] = { false, false, false, false };
+
+  SDLoc DL(VectorEntry);
+  EVT EltTy = VectorEntry.getValueType().getVectorElementType();
+
+  SDValue NewBldVec[4];
+  bool isUnmovable[4] = {false, false, false, false};
+  for (unsigned i = 0; i < 4; i++)
+    NewBldVec[i] = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, DL, EltTy, VectorEntry,
+                               DAG.getIntPtrConstant(i, DL));
+
   for (unsigned i = 0; i < 4; i++) {
     RemapSwizzle[i] = i;
     if (NewBldVec[i].getOpcode() == ISD::EXTRACT_VECTOR_ELT) {
@@ -1766,7 +1769,6 @@ static SDValue ReorganizeVector(SelectionDAG &DAG, SDValue VectorEntry,
 SDValue R600TargetLowering::OptimizeSwizzle(SDValue BuildVector, SDValue Swz[4],
                                             SelectionDAG &DAG,
                                             const SDLoc &DL) const {
-  assert(BuildVector.getOpcode() == ISD::BUILD_VECTOR);
   // Old -> New swizzle values
   DenseMap<unsigned, unsigned> SwizzleRemap;