1 files changed, 84 insertions, 0 deletions

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 491c118fe3..2cf6dea0a3 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -990,6 +990,7 @@ X86TargetLowering::X86TargetLowering(X86TargetMachine &TM)
 
   // We have target-specific dag combine patterns for the following nodes:
   setTargetDAGCombine(ISD::VECTOR_SHUFFLE);
+  setTargetDAGCombine(ISD::EXTRACT_VECTOR_ELT);
   setTargetDAGCombine(ISD::BUILD_VECTOR);
   setTargetDAGCombine(ISD::SELECT);
   setTargetDAGCombine(ISD::SHL);
@@ -8853,6 +8854,87 @@ static SDValue PerformShuffleCombine(SDNode *N, SelectionDAG &DAG,
   return SDValue();
 }
 
+/// PerformShuffleCombine - Detect vector gather/scatter index generation
+/// and convert it from being a bunch of shuffles and extracts to a simple
+/// store and scalar loads to extract the elements.
+static SDValue PerformEXTRACT_VECTOR_ELTCombine(SDNode *N, SelectionDAG &DAG,
+                                                const TargetLowering &TLI) {
+  SDValue InputVector = N->getOperand(0);
+
+  // Only operate on vectors of 4 elements, where the alternative shuffling
+  // gets to be more expensive.
+  if (InputVector.getValueType() != MVT::v4i32)
+    return SDValue();
+
+  // Check whether every use of InputVector is an EXTRACT_VECTOR_ELT with a
+  // single use which is a sign-extend or zero-extend, and all elements are
+  // used.
+  SmallVector<SDNode *, 4> Uses;
+  unsigned ExtractedElements = 0;
+  for (SDNode::use_iterator UI = InputVector.getNode()->use_begin(),
+       UE = InputVector.getNode()->use_end(); UI != UE; ++UI) {
+    if (UI.getUse().getResNo() != InputVector.getResNo())
+      return SDValue();
+
+    SDNode *Extract = *UI;
+    if (Extract->getOpcode() != ISD::EXTRACT_VECTOR_ELT)
+      return SDValue();
+
+    if (Extract->getValueType(0) != MVT::i32)
+      return SDValue();
+    if (!Extract->hasOneUse())
+      return SDValue();
+    if (Extract->use_begin()->getOpcode() != ISD::SIGN_EXTEND &&
+        Extract->use_begin()->getOpcode() != ISD::ZERO_EXTEND)
+      return SDValue();
+    if (!isa<ConstantSDNode>(Extract->getOperand(1)))
+      return SDValue();
+
+    // Record which element was extracted.
+    ExtractedElements |=
+      1 << cast<ConstantSDNode>(Extract->getOperand(1))->getZExtValue();
+
+    Uses.push_back(Extract);
+  }
+
+  // If not all the elements were used, this may not be worthwhile.
+  if (ExtractedElements != 15)
+    return SDValue();
+
+  // Ok, we've now decided to do the transformation.
+  DebugLoc dl = InputVector.getDebugLoc();
+
+  // Store the value to a temporary stack slot.
+  SDValue StackPtr = DAG.CreateStackTemporary(InputVector.getValueType());
+  SDValue Ch = DAG.getStore(DAG.getEntryNode(), dl, InputVector, StackPtr, NULL, 0,
+                            false, false, 0);
+
+  // Replace each use (extract) with a load of the appropriate element.
+  for (SmallVectorImpl<SDNode *>::iterator UI = Uses.begin(),
+       UE = Uses.end(); UI != UE; ++UI) {
+    SDNode *Extract = *UI;
+
+    // Compute the element's address.
+    SDValue Idx = Extract->getOperand(1);
+    unsigned EltSize =
+        InputVector.getValueType().getVectorElementType().getSizeInBits()/8;
+    uint64_t Offset = EltSize * cast<ConstantSDNode>(Idx)->getZExtValue();
+    SDValue OffsetVal = DAG.getConstant(Offset, TLI.getPointerTy());
+
+    SDValue ScalarAddr = DAG.getNode(ISD::ADD, dl, Idx.getValueType(), OffsetVal, StackPtr);
+
+    // Load the scalar.
+    SDValue LoadScalar = DAG.getLoad(Extract->getValueType(0), dl, Ch, ScalarAddr,
+                          NULL, 0, false, false, 0);
+
+    // Replace the exact with the load.
+    DAG.ReplaceAllUsesOfValueWith(SDValue(Extract, 0), LoadScalar);
+  }
+
+  // The replacement was made in place; don't return anything.
+  return SDValue();
+}
+
 /// PerformSELECTCombine - Do target-specific dag combines on SELECT nodes.
 static SDValue PerformSELECTCombine(SDNode *N, SelectionDAG &DAG,
                                     const X86Subtarget *Subtarget) {
@@ -9742,6 +9824,8 @@ SDValue X86TargetLowering::PerformDAGCombine(SDNode *N,
   switch (N->getOpcode()) {
   default: break;
   case ISD::VECTOR_SHUFFLE: return PerformShuffleCombine(N, DAG, *this);
+  case ISD::EXTRACT_VECTOR_ELT:
+                        return PerformEXTRACT_VECTOR_ELTCombine(N, DAG, *this);
   case ISD::SELECT:         return PerformSELECTCombine(N, DAG, Subtarget);
   case X86ISD::CMOV:        return PerformCMOVCombine(N, DAG, DCI);
   case ISD::MUL:            return PerformMulCombine(N, DAG, DCI);