Fix a bug in the cost calculation of vector casts. Detect situations where bitcasts cost zero.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167170 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/TargetTransformImpl.cpp b/lib/Target/TargetTransformImpl.cpp
index 38c704f..dbbf37a 100644
--- a/lib/Target/TargetTransformImpl.cpp
+++ b/lib/Target/TargetTransformImpl.cpp
@@ -211,40 +211,55 @@
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;