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llvm-project/llvm/lib/CodeGen/GlobalISel/LegacyLegalizerInfo.cpp

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//===- lib/CodeGen/GlobalISel/LegacyLegalizerInfo.cpp - Legalizer ---------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Implement an interface to specify and query how an illegal operation on a
// given type should be expanded.
//
// Issues to be resolved:
// + Make it fast.
// + Support weird types like i3, <7 x i3>, ...
// + Operations with more than one type (ICMP, CMPXCHG, intrinsics, ...)
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/GlobalISel/LegacyLegalizerInfo.h"
#include "llvm/CodeGen/GlobalISel/LegalizerInfo.h"
#include <map>
using namespace llvm;
using namespace LegacyLegalizeActions;
#define DEBUG_TYPE "legalizer-info"
raw_ostream &llvm::operator<<(raw_ostream &OS, LegacyLegalizeAction Action) {
switch (Action) {
case Legal:
OS << "Legal";
break;
case NarrowScalar:
OS << "NarrowScalar";
break;
case WidenScalar:
OS << "WidenScalar";
break;
case FewerElements:
OS << "FewerElements";
break;
case MoreElements:
OS << "MoreElements";
break;
case Bitcast:
OS << "Bitcast";
break;
case Lower:
OS << "Lower";
break;
case Libcall:
OS << "Libcall";
break;
case Custom:
OS << "Custom";
break;
case Unsupported:
OS << "Unsupported";
break;
case NotFound:
OS << "NotFound";
break;
}
return OS;
}
LegacyLegalizerInfo::LegacyLegalizerInfo() {
// Set defaults.
// FIXME: these two (G_ANYEXT and G_TRUNC?) can be legalized to the
// fundamental load/store Jakob proposed. Once loads & stores are supported.
setScalarAction(TargetOpcode::G_ANYEXT, 1, {{1, Legal}});
setScalarAction(TargetOpcode::G_ZEXT, 1, {{1, Legal}});
setScalarAction(TargetOpcode::G_SEXT, 1, {{1, Legal}});
setScalarAction(TargetOpcode::G_TRUNC, 0, {{1, Legal}});
setScalarAction(TargetOpcode::G_TRUNC, 1, {{1, Legal}});
setScalarAction(TargetOpcode::G_INTRINSIC, 0, {{1, Legal}});
setScalarAction(TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS, 0, {{1, Legal}});
setLegalizeScalarToDifferentSizeStrategy(
TargetOpcode::G_IMPLICIT_DEF, 0, narrowToSmallerAndUnsupportedIfTooSmall);
setLegalizeScalarToDifferentSizeStrategy(
TargetOpcode::G_ADD, 0, widenToLargerTypesAndNarrowToLargest);
setLegalizeScalarToDifferentSizeStrategy(
TargetOpcode::G_OR, 0, widenToLargerTypesAndNarrowToLargest);
setLegalizeScalarToDifferentSizeStrategy(
TargetOpcode::G_LOAD, 0, narrowToSmallerAndUnsupportedIfTooSmall);
setLegalizeScalarToDifferentSizeStrategy(
TargetOpcode::G_STORE, 0, narrowToSmallerAndUnsupportedIfTooSmall);
setLegalizeScalarToDifferentSizeStrategy(
TargetOpcode::G_BRCOND, 0, widenToLargerTypesUnsupportedOtherwise);
setLegalizeScalarToDifferentSizeStrategy(
TargetOpcode::G_INSERT, 0, narrowToSmallerAndUnsupportedIfTooSmall);
setLegalizeScalarToDifferentSizeStrategy(
TargetOpcode::G_EXTRACT, 0, narrowToSmallerAndUnsupportedIfTooSmall);
setLegalizeScalarToDifferentSizeStrategy(
TargetOpcode::G_EXTRACT, 1, narrowToSmallerAndUnsupportedIfTooSmall);
setScalarAction(TargetOpcode::G_FNEG, 0, {{1, Lower}});
}
void LegacyLegalizerInfo::computeTables() {
assert(TablesInitialized == false);
for (unsigned OpcodeIdx = 0; OpcodeIdx <= LastOp - FirstOp; ++OpcodeIdx) {
const unsigned Opcode = FirstOp + OpcodeIdx;
for (unsigned TypeIdx = 0; TypeIdx != SpecifiedActions[OpcodeIdx].size();
++TypeIdx) {
// 0. Collect information specified through the setAction API, i.e.
// for specific bit sizes.
// For scalar types:
SizeAndActionsVec ScalarSpecifiedActions;
// For pointer types:
std::map<uint16_t, SizeAndActionsVec> AddressSpace2SpecifiedActions;
// For vector types:
std::map<uint16_t, SizeAndActionsVec> ElemSize2SpecifiedActions;
for (auto LLT2Action : SpecifiedActions[OpcodeIdx][TypeIdx]) {
const LLT Type = LLT2Action.first;
const LegacyLegalizeAction Action = LLT2Action.second;
auto SizeAction = std::make_pair(Type.getSizeInBits(), Action);
if (Type.isPointer())
AddressSpace2SpecifiedActions[Type.getAddressSpace()].push_back(
SizeAction);
else if (Type.isVector())
ElemSize2SpecifiedActions[Type.getElementType().getSizeInBits()]
.push_back(SizeAction);
else
ScalarSpecifiedActions.push_back(SizeAction);
}
// 1. Handle scalar types
{
// Decide how to handle bit sizes for which no explicit specification
// was given.
SizeChangeStrategy S = &unsupportedForDifferentSizes;
if (TypeIdx < ScalarSizeChangeStrategies[OpcodeIdx].size() &&
ScalarSizeChangeStrategies[OpcodeIdx][TypeIdx] != nullptr)
S = ScalarSizeChangeStrategies[OpcodeIdx][TypeIdx];
llvm::sort(ScalarSpecifiedActions);
checkPartialSizeAndActionsVector(ScalarSpecifiedActions);
setScalarAction(Opcode, TypeIdx, S(ScalarSpecifiedActions));
}
// 2. Handle pointer types
for (auto PointerSpecifiedActions : AddressSpace2SpecifiedActions) {
llvm::sort(PointerSpecifiedActions.second);
checkPartialSizeAndActionsVector(PointerSpecifiedActions.second);
// For pointer types, we assume that there isn't a meaningfull way
// to change the number of bits used in the pointer.
setPointerAction(
Opcode, TypeIdx, PointerSpecifiedActions.first,
unsupportedForDifferentSizes(PointerSpecifiedActions.second));
}
// 3. Handle vector types
SizeAndActionsVec ElementSizesSeen;
for (auto VectorSpecifiedActions : ElemSize2SpecifiedActions) {
llvm::sort(VectorSpecifiedActions.second);
const uint16_t ElementSize = VectorSpecifiedActions.first;
ElementSizesSeen.push_back({ElementSize, Legal});
checkPartialSizeAndActionsVector(VectorSpecifiedActions.second);
// For vector types, we assume that the best way to adapt the number
// of elements is to the next larger number of elements type for which
// the vector type is legal, unless there is no such type. In that case,
// legalize towards a vector type with a smaller number of elements.
SizeAndActionsVec NumElementsActions;
for (SizeAndAction BitsizeAndAction : VectorSpecifiedActions.second) {
assert(BitsizeAndAction.first % ElementSize == 0);
const uint16_t NumElements = BitsizeAndAction.first / ElementSize;
NumElementsActions.push_back({NumElements, BitsizeAndAction.second});
}
setVectorNumElementAction(
Opcode, TypeIdx, ElementSize,
moreToWiderTypesAndLessToWidest(NumElementsActions));
}
llvm::sort(ElementSizesSeen);
SizeChangeStrategy VectorElementSizeChangeStrategy =
&unsupportedForDifferentSizes;
if (TypeIdx < VectorElementSizeChangeStrategies[OpcodeIdx].size() &&
VectorElementSizeChangeStrategies[OpcodeIdx][TypeIdx] != nullptr)
VectorElementSizeChangeStrategy =
VectorElementSizeChangeStrategies[OpcodeIdx][TypeIdx];
setScalarInVectorAction(
Opcode, TypeIdx, VectorElementSizeChangeStrategy(ElementSizesSeen));
}
}
TablesInitialized = true;
}
// FIXME: inefficient implementation for now. Without ComputeValueVTs we're
// probably going to need specialized lookup structures for various types before
// we have any hope of doing well with something like <13 x i3>. Even the common
// cases should do better than what we have now.
std::pair<LegacyLegalizeAction, LLT>
LegacyLegalizerInfo::getAspectAction(const InstrAspect &Aspect) const {
assert(TablesInitialized && "backend forgot to call computeTables");
// These *have* to be implemented for now, they're the fundamental basis of
// how everything else is transformed.
if (Aspect.Type.isScalar() || Aspect.Type.isPointer())
return findScalarLegalAction(Aspect);
assert(Aspect.Type.isVector());
return findVectorLegalAction(Aspect);
}
LegacyLegalizerInfo::SizeAndActionsVec
LegacyLegalizerInfo::increaseToLargerTypesAndDecreaseToLargest(
const SizeAndActionsVec &v, LegacyLegalizeAction IncreaseAction,
LegacyLegalizeAction DecreaseAction) {
SizeAndActionsVec result;
unsigned LargestSizeSoFar = 0;
if (v.size() >= 1 && v[0].first != 1)
result.push_back({1, IncreaseAction});
for (size_t i = 0; i < v.size(); ++i) {
result.push_back(v[i]);
LargestSizeSoFar = v[i].first;
if (i + 1 < v.size() && v[i + 1].first != v[i].first + 1) {
result.push_back({LargestSizeSoFar + 1, IncreaseAction});
LargestSizeSoFar = v[i].first + 1;
}
}
result.push_back({LargestSizeSoFar + 1, DecreaseAction});
return result;
}
LegacyLegalizerInfo::SizeAndActionsVec
LegacyLegalizerInfo::decreaseToSmallerTypesAndIncreaseToSmallest(
const SizeAndActionsVec &v, LegacyLegalizeAction DecreaseAction,
LegacyLegalizeAction IncreaseAction) {
SizeAndActionsVec result;
if (v.size() == 0 || v[0].first != 1)
result.push_back({1, IncreaseAction});
for (size_t i = 0; i < v.size(); ++i) {
result.push_back(v[i]);
if (i + 1 == v.size() || v[i + 1].first != v[i].first + 1) {
result.push_back({v[i].first + 1, DecreaseAction});
}
}
return result;
}
LegacyLegalizerInfo::SizeAndAction
LegacyLegalizerInfo::findAction(const SizeAndActionsVec &Vec, const uint32_t Size) {
assert(Size >= 1);
// Find the last element in Vec that has a bitsize equal to or smaller than
// the requested bit size.
// That is the element just before the first element that is bigger than Size.
auto It = partition_point(
Vec, [=](const SizeAndAction &A) { return A.first <= Size; });
assert(It != Vec.begin() && "Does Vec not start with size 1?");
int VecIdx = It - Vec.begin() - 1;
LegacyLegalizeAction Action = Vec[VecIdx].second;
switch (Action) {
case Legal:
case Bitcast:
case Lower:
case Libcall:
case Custom:
return {Size, Action};
case FewerElements:
// FIXME: is this special case still needed and correct?
// Special case for scalarization:
if (Vec == SizeAndActionsVec({{1, FewerElements}}))
return {1, FewerElements};
LLVM_FALLTHROUGH;
case NarrowScalar: {
// The following needs to be a loop, as for now, we do allow needing to
// go over "Unsupported" bit sizes before finding a legalizable bit size.
// e.g. (s8, WidenScalar), (s9, Unsupported), (s32, Legal). if Size==8,
// we need to iterate over s9, and then to s32 to return (s32, Legal).
// If we want to get rid of the below loop, we should have stronger asserts
// when building the SizeAndActionsVecs, probably not allowing
// "Unsupported" unless at the ends of the vector.
for (int i = VecIdx - 1; i >= 0; --i)
if (!needsLegalizingToDifferentSize(Vec[i].second) &&
Vec[i].second != Unsupported)
return {Vec[i].first, Action};
llvm_unreachable("");
}
case WidenScalar:
case MoreElements: {
// See above, the following needs to be a loop, at least for now.
for (std::size_t i = VecIdx + 1; i < Vec.size(); ++i)
if (!needsLegalizingToDifferentSize(Vec[i].second) &&
Vec[i].second != Unsupported)
return {Vec[i].first, Action};
llvm_unreachable("");
}
case Unsupported:
return {Size, Unsupported};
case NotFound:
llvm_unreachable("NotFound");
}
llvm_unreachable("Action has an unknown enum value");
}
std::pair<LegacyLegalizeAction, LLT>
LegacyLegalizerInfo::findScalarLegalAction(const InstrAspect &Aspect) const {
assert(Aspect.Type.isScalar() || Aspect.Type.isPointer());
if (Aspect.Opcode < FirstOp || Aspect.Opcode > LastOp)
return {NotFound, LLT()};
const unsigned OpcodeIdx = getOpcodeIdxForOpcode(Aspect.Opcode);
if (Aspect.Type.isPointer() &&
AddrSpace2PointerActions[OpcodeIdx].find(Aspect.Type.getAddressSpace()) ==
AddrSpace2PointerActions[OpcodeIdx].end()) {
return {NotFound, LLT()};
}
const SmallVector<SizeAndActionsVec, 1> &Actions =
Aspect.Type.isPointer()
? AddrSpace2PointerActions[OpcodeIdx]
.find(Aspect.Type.getAddressSpace())
->second
: ScalarActions[OpcodeIdx];
if (Aspect.Idx >= Actions.size())
return {NotFound, LLT()};
const SizeAndActionsVec &Vec = Actions[Aspect.Idx];
// FIXME: speed up this search, e.g. by using a results cache for repeated
// queries?
auto SizeAndAction = findAction(Vec, Aspect.Type.getSizeInBits());
return {SizeAndAction.second,
Aspect.Type.isScalar() ? LLT::scalar(SizeAndAction.first)
: LLT::pointer(Aspect.Type.getAddressSpace(),
SizeAndAction.first)};
}
std::pair<LegacyLegalizeAction, LLT>
LegacyLegalizerInfo::findVectorLegalAction(const InstrAspect &Aspect) const {
assert(Aspect.Type.isVector());
// First legalize the vector element size, then legalize the number of
// lanes in the vector.
if (Aspect.Opcode < FirstOp || Aspect.Opcode > LastOp)
return {NotFound, Aspect.Type};
const unsigned OpcodeIdx = getOpcodeIdxForOpcode(Aspect.Opcode);
const unsigned TypeIdx = Aspect.Idx;
if (TypeIdx >= ScalarInVectorActions[OpcodeIdx].size())
return {NotFound, Aspect.Type};
const SizeAndActionsVec &ElemSizeVec =
ScalarInVectorActions[OpcodeIdx][TypeIdx];
LLT IntermediateType;
auto ElementSizeAndAction =
findAction(ElemSizeVec, Aspect.Type.getScalarSizeInBits());
IntermediateType = LLT::fixed_vector(Aspect.Type.getNumElements(),
ElementSizeAndAction.first);
if (ElementSizeAndAction.second != Legal)
return {ElementSizeAndAction.second, IntermediateType};
auto i = NumElements2Actions[OpcodeIdx].find(
IntermediateType.getScalarSizeInBits());
if (i == NumElements2Actions[OpcodeIdx].end()) {
return {NotFound, IntermediateType};
}
const SizeAndActionsVec &NumElementsVec = (*i).second[TypeIdx];
auto NumElementsAndAction =
findAction(NumElementsVec, IntermediateType.getNumElements());
return {NumElementsAndAction.second,
LLT::fixed_vector(NumElementsAndAction.first,
IntermediateType.getScalarSizeInBits())};
}
unsigned LegacyLegalizerInfo::getOpcodeIdxForOpcode(unsigned Opcode) const {
assert(Opcode >= FirstOp && Opcode <= LastOp && "Unsupported opcode");
return Opcode - FirstOp;
}
LegacyLegalizeActionStep
LegacyLegalizerInfo::getAction(const LegalityQuery &Query) const {
for (unsigned i = 0; i < Query.Types.size(); ++i) {
auto Action = getAspectAction({Query.Opcode, i, Query.Types[i]});
if (Action.first != Legal) {
LLVM_DEBUG(dbgs() << ".. (legacy) Type " << i << " Action="
<< Action.first << ", " << Action.second << "\n");
return {Action.first, i, Action.second};
} else
LLVM_DEBUG(dbgs() << ".. (legacy) Type " << i << " Legal\n");
}
LLVM_DEBUG(dbgs() << ".. (legacy) Legal\n");
return {Legal, 0, LLT{}};
}
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