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Fix a bug in the cost calculation of vector casts. Detect situations where bitcasts cost zero.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167170 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem
2012-10-31 20:52:26 +00:00
parent 2932284f04
commit 0dba9a9a26
2 changed files with 90 additions and 27 deletions
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69
lib/Target/TargetTransformImpl.cpp
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@@ -211,40 +211,55 @@ unsigned VectorTargetTransformImpl::getCastInstrCost(unsigned Opcode, Type *Dst,
std::pair<unsigned, EVT> DstLT =
getTypeLegalizationCost(Dst->getContext(), TLI->getValueType(Dst));
// If the cast is between same-sized registers, then the check is simple.
if (SrcLT.first == DstLT.first &&
SrcLT.second.getSizeInBits() == DstLT.second.getSizeInBits()) {
// Just check the op cost:
if (!TLI->isOperationExpand(ISD, DstLT.second)) {
// The operation is legal. Assume it costs 1. Multiply
// by the type-legalization overhead.
return SrcLT.first * 1;
// Handle scalar conversions.
if (!Src->isVectorTy() && !Dst->isVectorTy()) {
// Just check the op cost. If the operation is legal then assume it costs 1.
if (!TLI->isOperationExpand(ISD, DstLT.second))
return 1;
// Assume that illegal scalar instruction are expensive.
return 4;
}
// Check vector-to-vector casts.
if (Dst->isVectorTy() && Src->isVectorTy()) {
// If the cast is between same-sized registers, then the check is simple.
if (SrcLT.first == DstLT.first &&
SrcLT.second.getSizeInBits() == DstLT.second.getSizeInBits()) {
// Bitcast between types that are legalized to the same type are free.
if (Opcode == Instruction::BitCast)
return 0;
// Just check the op cost. If the operation is legal then assume it costs
// 1 and multiply by the type-legalization overhead.
if (!TLI->isOperationExpand(ISD, DstLT.second))
return SrcLT.first * 1;
}
}
unsigned ScalarizationCost = 1;
// Otherwise, assume that the cast is scalarized.
if (Dst->isVectorTy()) {
// If we are converting vectors and the operation is illegal, or
// if the vectors are legalized to different types, estimate the
// scalarization costs.
unsigned Num = Dst->getVectorNumElements();
unsigned Cost = getCastInstrCost(Opcode, Src->getScalarType(),
Dst->getScalarType());
// return the cost of multiple scalar invocation plus the cost of inserting
// and extracting the values.
ScalarizationCost *= getScalarizationOverhead(Dst, true, true) + Num * Cost;
}
if (Src->isVectorTy()) {
unsigned Num = Src->getVectorNumElements();
unsigned Cost = getCastInstrCost(Opcode, Dst->getScalarType(),
Src->getScalarType());
// return the cost of multiple scalar invocation plus the cost of inserting
// and extracting the values.
ScalarizationCost *= getScalarizationOverhead(Src, true, true) + Num * Cost;
// Return the cost of multiple scalar invocation plus the cost of
// inserting and extracting the values.
return getScalarizationOverhead(Dst, true, true) + Num * Cost;
}
return ScalarizationCost;
}
// We already handled vector-to-vector and scalar-to-scalar conversions. This
// is where we handle bitcast between vectors and scalars. We need to assume
// that the conversion is scalarized in one way or another.
if (Opcode == Instruction::BitCast)
// Illegal bitcasts are done by storing and loading from a stack slot.
return (Src->isVectorTy()? getScalarizationOverhead(Src, false, true):0) +
(Dst->isVectorTy()? getScalarizationOverhead(Dst, true, false):0);
llvm_unreachable("Unhandled cast");
}
unsigned VectorTargetTransformImpl::getCFInstrCost(unsigned Opcode) const {
return 1;