[DAGCombine] visitEXTRACT_SUBVECTOR - 'little to big' extract_subvector(bitcast()) support

This moves the X86 specific transform from rL364407
into DAGCombiner to generically handle 'little to big' cases
(for example: extract_subvector(v2i64 bitcast(v16i8))). This
allows us to remove both the x86 implementation and the aarch64
bitcast(extract_subvector(bitcast())) combine.

Earlier patches that dealt with regressions initially exposed
by this patch:
rG5e5e99c041e4
rG0b38af89e2c0

Patch by: @RKSimon (Simon Pilgrim)

Differential Revision: https://reviews.llvm.org/D63815

1 files changed, 0 insertions, 26 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 54a64052ebb..cd6821c16e8 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -45103,7 +45103,6 @@ static SDValue combineExtractSubvector(SDNode *N, SelectionDAG &DAG,
   SDValue InVec = N->getOperand(0);
   SDValue InVecBC = peekThroughBitcasts(InVec);
   EVT InVecVT = InVec.getValueType();
-  EVT InVecBCVT = InVecBC.getValueType();
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
 
   if (Subtarget.hasAVX() && !Subtarget.hasAVX2() &&
@@ -45147,31 +45146,6 @@ static SDValue combineExtractSubvector(SDNode *N, SelectionDAG &DAG,
         VT, SDLoc(N),
         InVec.getNode()->ops().slice(IdxVal, VT.getVectorNumElements()));
 
-  // Try to move vector bitcast after extract_subv by scaling extraction index:
-  // extract_subv (bitcast X), Index --> bitcast (extract_subv X, Index')
-  // TODO: Move this to DAGCombiner::visitEXTRACT_SUBVECTOR
-  if (InVec != InVecBC && InVecBCVT.isVector()) {
-    unsigned SrcNumElts = InVecBCVT.getVectorNumElements();
-    unsigned DestNumElts = InVecVT.getVectorNumElements();
-    if ((DestNumElts % SrcNumElts) == 0) {
-      unsigned DestSrcRatio = DestNumElts / SrcNumElts;
-      if ((VT.getVectorNumElements() % DestSrcRatio) == 0) {
-        unsigned NewExtNumElts = VT.getVectorNumElements() / DestSrcRatio;
-        EVT NewExtVT = EVT::getVectorVT(*DAG.getContext(),
-                                        InVecBCVT.getScalarType(), NewExtNumElts);
-        if ((N->getConstantOperandVal(1) % DestSrcRatio) == 0 &&
-            TLI.isOperationLegalOrCustom(ISD::EXTRACT_SUBVECTOR, NewExtVT)) {
-          unsigned IndexValScaled = N->getConstantOperandVal(1) / DestSrcRatio;
-          SDLoc DL(N);
-          SDValue NewIndex = DAG.getIntPtrConstant(IndexValScaled, DL);
-          SDValue NewExtract = DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, NewExtVT,
-                                           InVecBC, NewIndex);
-          return DAG.getBitcast(VT, NewExtract);
-        }
-      }
-    }
-  }
-
   // If we are extracting from an insert into a zero vector, replace with a
   // smaller insert into zero if we don't access less than the original
   // subvector. Don't do this for i1 vectors.