[SelectionDAG] Improve scalarization of irregular vector types

Use a more general strategy when splitting a vector into scalar parts (and vice-versa) to correctly handle vector types whose element size is not a power of 2 (and a multiple of 8). Reviewed By: atanasyan Differential Revision: https://reviews.llvm.org/D98273
llvm · Mar 11, 2021 · cfe69c8 · cfe69c8
1 parent cc999c9
commit cfe69c8
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Showing 2 changed files with 239 additions and 539 deletions.
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -436,14 +436,11 @@ static SDValue getCopyFromPartsVector(SelectionDAG &DAG, const SDLoc &DL,
      if (ValueVT.getSizeInBits() == PartEVT.getSizeInBits()) {
        return DAG.getNode(ISD::BITCAST, DL, ValueVT, Val);
      } else if (ValueVT.bitsLT(PartEVT)) {
-       // Bitcast Val back the original type and extract the corresponding
-       // vector we want.
-       unsigned Elts = PartEVT.getSizeInBits() / ValueVT.getScalarSizeInBits();
-       EVT WiderVecType = EVT::getVectorVT(*DAG.getContext(),
-                                           ValueVT.getVectorElementType(), Elts);
-       Val = DAG.getBitcast(WiderVecType, Val);
-       return DAG.getNode(ISD::EXTRACT_SUBVECTOR, DL, ValueVT, Val,
-                          DAG.getVectorIdxConstant(0, DL));
+       const uint64_t ValueSize = ValueVT.getFixedSizeInBits();
+       EVT IntermediateType = EVT::getIntegerVT(*DAG.getContext(), ValueSize);
+       // Drop the extra bits.
+       Val = DAG.getNode(ISD::TRUNCATE, DL, IntermediateType, Val);
+       return DAG.getBitcast(ValueVT, Val);
      }
 
      diagnosePossiblyInvalidConstraint(
@@ -714,13 +711,25 @@ static void getCopyToPartsVector(SelectionDAG &DAG, const SDLoc &DL,
 
   EVT BuiltVectorTy = EVT::getVectorVT(
       *DAG.getContext(), IntermediateVT.getScalarType(), DestEltCnt.getValue());
-  if (ValueVT != BuiltVectorTy) {
-    if (SDValue Widened = widenVectorToPartType(DAG, Val, DL, BuiltVectorTy))
-      Val = Widened;
 
+  if (ValueVT == BuiltVectorTy) {
+    // Nothing to do.
+  } else if (ValueVT.getSizeInBits() == BuiltVectorTy.getSizeInBits()) {
+    // Bitconvert vector->vector case.
     Val = DAG.getNode(ISD::BITCAST, DL, BuiltVectorTy, Val);
+  } else if (SDValue Widened =
+                 widenVectorToPartType(DAG, Val, DL, BuiltVectorTy)) {
+    Val = Widened;
+  } else if (BuiltVectorTy.getVectorElementType().bitsGE(
+                 ValueVT.getVectorElementType()) &&
+             BuiltVectorTy.getVectorElementCount() ==
+                 ValueVT.getVectorElementCount()) {
+    // Promoted vector extract
+    Val = DAG.getAnyExtOrTrunc(Val, DL, BuiltVectorTy);
   }
 
+  assert(Val.getValueType() == BuiltVectorTy && "Unexpected vector value type");
+
   // Split the vector into intermediate operands.
   SmallVector<SDValue, 8> Ops(NumIntermediates);
   for (unsigned i = 0; i != NumIntermediates; ++i) {