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

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//===- lib/CodeGen/GlobalISel/LegalizerInfo.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.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/GlobalISel/LegalizerInfo.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LowLevelTypeImpl.h"
#include <algorithm>
using namespace llvm;
using namespace LegalizeActions;
#define DEBUG_TYPE "legalizer-info"
cl::opt<bool> llvm::DisableGISelLegalityCheck(
"disable-gisel-legality-check",
cl::desc("Don't verify that MIR is fully legal between GlobalISel passes"),
cl::Hidden);
raw_ostream &llvm::operator<<(raw_ostream &OS, LegalizeAction 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;
case UseLegacyRules:
OS << "UseLegacyRules";
break;
}
return OS;
}
raw_ostream &LegalityQuery::print(raw_ostream &OS) const {
OS << Opcode << ", Tys={";
for (const auto &Type : Types) {
OS << Type << ", ";
}
OS << "}, Opcode=";
OS << Opcode << ", MMOs={";
for (const auto &MMODescr : MMODescrs) {
OS << MMODescr.MemoryTy << ", ";
}
OS << "}";
return OS;
}
#ifndef NDEBUG
// Make sure the rule won't (trivially) loop forever.
static bool hasNoSimpleLoops(const LegalizeRule &Rule, const LegalityQuery &Q,
const std::pair<unsigned, LLT> &Mutation) {
switch (Rule.getAction()) {
case Legal:
case Custom:
case Lower:
case MoreElements:
case FewerElements:
break;
default:
return Q.Types[Mutation.first] != Mutation.second;
}
return true;
}
// Make sure the returned mutation makes sense for the match type.
static bool mutationIsSane(const LegalizeRule &Rule,
const LegalityQuery &Q,
std::pair<unsigned, LLT> Mutation) {
// If the user wants a custom mutation, then we can't really say much about
// it. Return true, and trust that they're doing the right thing.
if (Rule.getAction() == Custom || Rule.getAction() == Legal)
return true;
const unsigned TypeIdx = Mutation.first;
const LLT OldTy = Q.Types[TypeIdx];
const LLT NewTy = Mutation.second;
switch (Rule.getAction()) {
case FewerElements:
if (!OldTy.isVector())
return false;
LLVM_FALLTHROUGH;
case MoreElements: {
// MoreElements can go from scalar to vector.
const ElementCount OldElts = OldTy.isVector() ?
OldTy.getElementCount() : ElementCount::getFixed(1);
if (NewTy.isVector()) {
if (Rule.getAction() == FewerElements) {
// Make sure the element count really decreased.
if (ElementCount::isKnownGE(NewTy.getElementCount(), OldElts))
return false;
} else {
// Make sure the element count really increased.
if (ElementCount::isKnownLE(NewTy.getElementCount(), OldElts))
return false;
}
} else if (Rule.getAction() == MoreElements)
return false;
// Make sure the element type didn't change.
return NewTy.getScalarType() == OldTy.getScalarType();
}
case NarrowScalar:
case WidenScalar: {
if (OldTy.isVector()) {
// Number of elements should not change.
if (!NewTy.isVector() || OldTy.getNumElements() != NewTy.getNumElements())
return false;
} else {
// Both types must be vectors
if (NewTy.isVector())
return false;
}
if (Rule.getAction() == NarrowScalar) {
// Make sure the size really decreased.
if (NewTy.getScalarSizeInBits() >= OldTy.getScalarSizeInBits())
return false;
} else {
// Make sure the size really increased.
if (NewTy.getScalarSizeInBits() <= OldTy.getScalarSizeInBits())
return false;
}
return true;
}
case Bitcast: {
return OldTy != NewTy && OldTy.getSizeInBits() == NewTy.getSizeInBits();
}
default:
return true;
}
}
#endif
LegalizeActionStep LegalizeRuleSet::apply(const LegalityQuery &Query) const {
LLVM_DEBUG(dbgs() << "Applying legalizer ruleset to: "; Query.print(dbgs());
dbgs() << "\n");
if (Rules.empty()) {
LLVM_DEBUG(dbgs() << ".. fallback to legacy rules (no rules defined)\n");
return {LegalizeAction::UseLegacyRules, 0, LLT{}};
}
for (const LegalizeRule &Rule : Rules) {
if (Rule.match(Query)) {
LLVM_DEBUG(dbgs() << ".. match\n");
std::pair<unsigned, LLT> Mutation = Rule.determineMutation(Query);
LLVM_DEBUG(dbgs() << ".. .. " << Rule.getAction() << ", "
<< Mutation.first << ", " << Mutation.second << "\n");
assert(mutationIsSane(Rule, Query, Mutation) &&
"legality mutation invalid for match");
assert(hasNoSimpleLoops(Rule, Query, Mutation) && "Simple loop detected");
return {Rule.getAction(), Mutation.first, Mutation.second};
} else
LLVM_DEBUG(dbgs() << ".. no match\n");
}
LLVM_DEBUG(dbgs() << ".. unsupported\n");
return {LegalizeAction::Unsupported, 0, LLT{}};
}
bool LegalizeRuleSet::verifyTypeIdxsCoverage(unsigned NumTypeIdxs) const {
#ifndef NDEBUG
if (Rules.empty()) {
LLVM_DEBUG(
dbgs() << ".. type index coverage check SKIPPED: no rules defined\n");
return true;
}
const int64_t FirstUncovered = TypeIdxsCovered.find_first_unset();
if (FirstUncovered < 0) {
LLVM_DEBUG(dbgs() << ".. type index coverage check SKIPPED:"
" user-defined predicate detected\n");
return true;
}
const bool AllCovered = (FirstUncovered >= NumTypeIdxs);
if (NumTypeIdxs > 0)
LLVM_DEBUG(dbgs() << ".. the first uncovered type index: " << FirstUncovered
<< ", " << (AllCovered ? "OK" : "FAIL") << "\n");
return AllCovered;
#else
return true;
#endif
}
bool LegalizeRuleSet::verifyImmIdxsCoverage(unsigned NumImmIdxs) const {
#ifndef NDEBUG
if (Rules.empty()) {
LLVM_DEBUG(
dbgs() << ".. imm index coverage check SKIPPED: no rules defined\n");
return true;
}
const int64_t FirstUncovered = ImmIdxsCovered.find_first_unset();
if (FirstUncovered < 0) {
LLVM_DEBUG(dbgs() << ".. imm index coverage check SKIPPED:"
" user-defined predicate detected\n");
return true;
}
const bool AllCovered = (FirstUncovered >= NumImmIdxs);
LLVM_DEBUG(dbgs() << ".. the first uncovered imm index: " << FirstUncovered
<< ", " << (AllCovered ? "OK" : "FAIL") << "\n");
return AllCovered;
#else
return true;
#endif
}
/// Helper function to get LLT for the given type index.
static LLT getTypeFromTypeIdx(const MachineInstr &MI,
const MachineRegisterInfo &MRI, unsigned OpIdx,
unsigned TypeIdx) {
assert(TypeIdx < MI.getNumOperands() && "Unexpected TypeIdx");
// G_UNMERGE_VALUES has variable number of operands, but there is only
// one source type and one destination type as all destinations must be the
// same type. So, get the last operand if TypeIdx == 1.
if (MI.getOpcode() == TargetOpcode::G_UNMERGE_VALUES && TypeIdx == 1)
return MRI.getType(MI.getOperand(MI.getNumOperands() - 1).getReg());
return MRI.getType(MI.getOperand(OpIdx).getReg());
}
unsigned LegalizerInfo::getOpcodeIdxForOpcode(unsigned Opcode) const {
assert(Opcode >= FirstOp && Opcode <= LastOp && "Unsupported opcode");
return Opcode - FirstOp;
}
unsigned LegalizerInfo::getActionDefinitionsIdx(unsigned Opcode) const {
unsigned OpcodeIdx = getOpcodeIdxForOpcode(Opcode);
if (unsigned Alias = RulesForOpcode[OpcodeIdx].getAlias()) {
LLVM_DEBUG(dbgs() << ".. opcode " << Opcode << " is aliased to " << Alias
<< "\n");
OpcodeIdx = getOpcodeIdxForOpcode(Alias);
assert(RulesForOpcode[OpcodeIdx].getAlias() == 0 && "Cannot chain aliases");
}
return OpcodeIdx;
}
const LegalizeRuleSet &
LegalizerInfo::getActionDefinitions(unsigned Opcode) const {
unsigned OpcodeIdx = getActionDefinitionsIdx(Opcode);
return RulesForOpcode[OpcodeIdx];
}
LegalizeRuleSet &LegalizerInfo::getActionDefinitionsBuilder(unsigned Opcode) {
unsigned OpcodeIdx = getActionDefinitionsIdx(Opcode);
auto &Result = RulesForOpcode[OpcodeIdx];
assert(!Result.isAliasedByAnother() && "Modifying this opcode will modify aliases");
return Result;
}
LegalizeRuleSet &LegalizerInfo::getActionDefinitionsBuilder(
std::initializer_list<unsigned> Opcodes) {
unsigned Representative = *Opcodes.begin();
assert(!llvm::empty(Opcodes) && Opcodes.begin() + 1 != Opcodes.end() &&
"Initializer list must have at least two opcodes");
for (unsigned Op : llvm::drop_begin(Opcodes))
aliasActionDefinitions(Representative, Op);
auto &Return = getActionDefinitionsBuilder(Representative);
Return.setIsAliasedByAnother();
return Return;
}
void LegalizerInfo::aliasActionDefinitions(unsigned OpcodeTo,
unsigned OpcodeFrom) {
assert(OpcodeTo != OpcodeFrom && "Cannot alias to self");
assert(OpcodeTo >= FirstOp && OpcodeTo <= LastOp && "Unsupported opcode");
const unsigned OpcodeFromIdx = getOpcodeIdxForOpcode(OpcodeFrom);
RulesForOpcode[OpcodeFromIdx].aliasTo(OpcodeTo);
}
LegalizeActionStep
LegalizerInfo::getAction(const LegalityQuery &Query) const {
LegalizeActionStep Step = getActionDefinitions(Query.Opcode).apply(Query);
if (Step.Action != LegalizeAction::UseLegacyRules) {
return Step;
}
return getLegacyLegalizerInfo().getAction(Query);
}
LegalizeActionStep
LegalizerInfo::getAction(const MachineInstr &MI,
const MachineRegisterInfo &MRI) const {
SmallVector<LLT, 8> Types;
SmallBitVector SeenTypes(8);
const MCOperandInfo *OpInfo = MI.getDesc().OpInfo;
// FIXME: probably we'll need to cache the results here somehow?
for (unsigned i = 0; i < MI.getDesc().getNumOperands(); ++i) {
if (!OpInfo[i].isGenericType())
continue;
// We must only record actions once for each TypeIdx; otherwise we'd
// try to legalize operands multiple times down the line.
unsigned TypeIdx = OpInfo[i].getGenericTypeIndex();
if (SeenTypes[TypeIdx])
continue;
SeenTypes.set(TypeIdx);
LLT Ty = getTypeFromTypeIdx(MI, MRI, i, TypeIdx);
Types.push_back(Ty);
}
SmallVector<LegalityQuery::MemDesc, 2> MemDescrs;
for (const auto &MMO : MI.memoperands())
MemDescrs.push_back({*MMO});
return getAction({MI.getOpcode(), Types, MemDescrs});
}
bool LegalizerInfo::isLegal(const MachineInstr &MI,
const MachineRegisterInfo &MRI) const {
return getAction(MI, MRI).Action == Legal;
}
bool LegalizerInfo::isLegalOrCustom(const MachineInstr &MI,
const MachineRegisterInfo &MRI) const {
auto Action = getAction(MI, MRI).Action;
// If the action is custom, it may not necessarily modify the instruction,
// so we have to assume it's legal.
return Action == Legal || Action == Custom;
}
unsigned LegalizerInfo::getExtOpcodeForWideningConstant(LLT SmallTy) const {
return SmallTy.isByteSized() ? TargetOpcode::G_SEXT : TargetOpcode::G_ZEXT;
}
/// \pre Type indices of every opcode form a dense set starting from 0.
void LegalizerInfo::verify(const MCInstrInfo &MII) const {
#ifndef NDEBUG
std::vector<unsigned> FailedOpcodes;
for (unsigned Opcode = FirstOp; Opcode <= LastOp; ++Opcode) {
const MCInstrDesc &MCID = MII.get(Opcode);
const unsigned NumTypeIdxs = std::accumulate(
MCID.opInfo_begin(), MCID.opInfo_end(), 0U,
[](unsigned Acc, const MCOperandInfo &OpInfo) {
return OpInfo.isGenericType()
? std::max(OpInfo.getGenericTypeIndex() + 1U, Acc)
: Acc;
});
const unsigned NumImmIdxs = std::accumulate(
MCID.opInfo_begin(), MCID.opInfo_end(), 0U,
[](unsigned Acc, const MCOperandInfo &OpInfo) {
return OpInfo.isGenericImm()
? std::max(OpInfo.getGenericImmIndex() + 1U, Acc)
: Acc;
});
LLVM_DEBUG(dbgs() << MII.getName(Opcode) << " (opcode " << Opcode
<< "): " << NumTypeIdxs << " type ind"
<< (NumTypeIdxs == 1 ? "ex" : "ices") << ", "
<< NumImmIdxs << " imm ind"
<< (NumImmIdxs == 1 ? "ex" : "ices") << "\n");
const LegalizeRuleSet &RuleSet = getActionDefinitions(Opcode);
if (!RuleSet.verifyTypeIdxsCoverage(NumTypeIdxs))
FailedOpcodes.push_back(Opcode);
else if (!RuleSet.verifyImmIdxsCoverage(NumImmIdxs))
FailedOpcodes.push_back(Opcode);
}
if (!FailedOpcodes.empty()) {
errs() << "The following opcodes have ill-defined legalization rules:";
for (unsigned Opcode : FailedOpcodes)
errs() << " " << MII.getName(Opcode);
errs() << "\n";
report_fatal_error("ill-defined LegalizerInfo"
", try -debug-only=legalizer-info for details");
}
#endif
}
#ifndef NDEBUG
// FIXME: This should be in the MachineVerifier, but it can't use the
// LegalizerInfo as it's currently in the separate GlobalISel library.
// Note that RegBankSelected property already checked in the verifier
// has the same layering problem, but we only use inline methods so
// end up not needing to link against the GlobalISel library.
const MachineInstr *llvm::machineFunctionIsIllegal(const MachineFunction &MF) {
if (const LegalizerInfo *MLI = MF.getSubtarget().getLegalizerInfo()) {
const MachineRegisterInfo &MRI = MF.getRegInfo();
for (const MachineBasicBlock &MBB : MF)
for (const MachineInstr &MI : MBB)
if (isPreISelGenericOpcode(MI.getOpcode()) &&
!MLI->isLegalOrCustom(MI, MRI))
return &MI;
}
return nullptr;
}
#endif
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