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[CodeGen] Combine concat_vectors of scalars into build_vector.

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Combine something like:
  (v8i8 concat_vectors (v2i8 bitcast (i16)) x4)
into:
  (v8i8 (bitcast (v4i16 BUILD_VECTOR (i16) x4)))

If any of the scalars are floating point, use that throughout.

Differential Revision: http://reviews.llvm.org/D8948


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234809 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ahmed Bougacha
2015-04-13 22:57:21 +00:00
parent 8bdb7dbe57
commit 164cbefb85
2 changed files with 185 additions and 0 deletions
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60
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -11499,6 +11499,62 @@ SDValue DAGCombiner::visitBUILD_VECTOR(SDNode *N) {
return SDValue();
}
static SDValue combineConcatVectorOfScalars(SDNode *N, SelectionDAG &DAG) {
const TargetLowering &TLI = DAG.getTargetLoweringInfo();
EVT OpVT = N->getOperand(0).getValueType();
// If the operands are legal vectors, leave them alone.
if (TLI.isTypeLegal(OpVT))
return SDValue();
SDLoc DL(N);
EVT VT = N->getValueType(0);
SmallVector<SDValue, 8> Ops;
EVT SVT = EVT::getIntegerVT(*DAG.getContext(), OpVT.getSizeInBits());
SDValue ScalarUndef = DAG.getNode(ISD::UNDEF, DL, SVT);
// Keep track of what we encounter.
bool AnyInteger = false;
bool AnyFP = false;
for (const SDValue &Op : N->ops()) {
if (ISD::BITCAST == Op.getOpcode() &&
!Op.getOperand(0).getValueType().isVector())
Ops.push_back(Op.getOperand(0));
else if (ISD::UNDEF == Op.getOpcode())
Ops.push_back(ScalarUndef);
else
return SDValue();
if (Ops.back().getValueType().isFloatingPoint())
AnyFP = true;
else
AnyInteger = true;
}
// If any of the operands is a floating point scalar bitcast to a vector,
// use floating point types throughout, and bitcast everything.
// Replace UNDEFs by another scalar UNDEF node, of the final desired type.
if (AnyFP) {
SVT = EVT::getFloatingPointVT(OpVT.getSizeInBits());
ScalarUndef = DAG.getNode(ISD::UNDEF, DL, SVT);
if (AnyInteger) {
for (SDValue &Op : Ops) {
if (Op.getValueType() != SVT) {
Op = DAG.getNode(ISD::BITCAST, DL, SVT, Op);
if (Op.getOpcode() == ISD::UNDEF)
Op = ScalarUndef;
}
}
}
}
EVT VecVT = EVT::getVectorVT(*DAG.getContext(), SVT,
VT.getSizeInBits() / SVT.getSizeInBits());
return DAG.getNode(ISD::BITCAST, DL, VT,
DAG.getNode(ISD::BUILD_VECTOR, DL, VecVT, Ops));
}
SDValue DAGCombiner::visitCONCAT_VECTORS(SDNode *N) {
// TODO: Check to see if this is a CONCAT_VECTORS of a bunch of
// EXTRACT_SUBVECTOR operations. If so, and if the EXTRACT_SUBVECTOR vector
@ -11601,6 +11657,10 @@ SDValue DAGCombiner::visitCONCAT_VECTORS(SDNode *N) {
return DAG.getNode(ISD::BUILD_VECTOR, SDLoc(N), VT, Opnds);
}
// Fold CONCAT_VECTORS of only bitcast scalars (or undef) to BUILD_VECTOR.
if (SDValue V = combineConcatVectorOfScalars(N, DAG))
return V;
// Type legalization of vectors and DAG canonicalization of SHUFFLE_VECTOR
// nodes often generate nop CONCAT_VECTOR nodes.
// Scan the CONCAT_VECTOR operands and look for a CONCAT operations that