return V;
}
-/// Search for a combinable shuffle across a chain ending in pshuflw or
-/// pshufhw.
-///
-/// We walk up the chain, skipping shuffles of the other half and looking
-/// through shuffles which switch halves trying to find a shuffle of the same
-/// pair of dwords.
-static bool combineRedundantHalfShuffle(SDValue N, MutableArrayRef<int> Mask,
- SelectionDAG &DAG,
- TargetLowering::DAGCombinerInfo &DCI) {
- assert(
- (N.getOpcode() == X86ISD::PSHUFLW || N.getOpcode() == X86ISD::PSHUFHW) &&
- "Called with something other than an x86 128-bit half shuffle!");
- SDLoc DL(N);
- unsigned CombineOpcode = N.getOpcode();
-
- // Walk up a single-use chain looking for a combinable shuffle.
- SDValue V = N.getOperand(0);
- for (; V.hasOneUse(); V = V.getOperand(0)) {
- switch (V.getOpcode()) {
- default:
- return false; // Nothing combined!
-
- case ISD::BITCAST:
- // Skip bitcasts as we always know the type for the target specific
- // instructions.
- continue;
-
- case X86ISD::PSHUFLW:
- case X86ISD::PSHUFHW:
- if (V.getOpcode() == CombineOpcode)
- break;
-
- // Other-half shuffles are no-ops.
- continue;
- }
- // Break out of the loop if we break out of the switch.
- break;
- }
-
- if (!V.hasOneUse())
- // We fell out of the loop without finding a viable combining instruction.
- return false;
-
- // Combine away the bottom node as its shuffle will be accumulated into
- // a preceding shuffle.
- DCI.CombineTo(N.getNode(), N.getOperand(0), /*AddTo*/ true);
-
- // Record the old value.
- SDValue Old = V;
-
- // Merge this node's mask and our incoming mask (adjusted to account for all
- // the pshufd instructions encountered).
- SmallVector<int, 4> VMask = getPSHUFShuffleMask(V);
- for (int &M : Mask)
- M = VMask[M];
- V = DAG.getNode(V.getOpcode(), DL, MVT::v8i16, V.getOperand(0),
- getV4X86ShuffleImm8ForMask(Mask, DL, DAG));
-
- // Check that the shuffles didn't cancel each other out. If not, we need to
- // combine to the new one.
- if (Old != V)
- // Replace the combinable shuffle with the combined one, updating all users
- // so that we re-evaluate the chain here.
- DCI.CombineTo(Old.getNode(), V, /*AddTo*/ true);
-
- return true;
-}
-
/// Try to combine x86 target specific shuffles.
static SDValue combineTargetShuffle(SDValue N, SelectionDAG &DAG,
TargetLowering::DAGCombinerInfo &DCI,
case X86ISD::PSHUFHW:
assert(VT.getVectorElementType() == MVT::i16 && "Bad word shuffle type!");
- if (combineRedundantHalfShuffle(N, Mask, DAG, DCI))
- return SDValue(); // We combined away this shuffle, so we're done.
-
// See if this reduces to a PSHUFD which is no more expensive and can
// combine with more operations. Note that it has to at least flip the
// dwords as otherwise it would have been removed as a no-op.