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llvm-project/llvm/lib/MCA/InstrBuilder.cpp

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//===--------------------- InstrBuilder.cpp ---------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
/// \file
///
/// This file implements the InstrBuilder interface.
///
//===----------------------------------------------------------------------===//
#include "llvm/MCA/InstrBuilder.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/MC/MCInst.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/WithColor.h"
#include "llvm/Support/raw_ostream.h"
#define DEBUG_TYPE "llvm-mca"
namespace llvm {
namespace mca {
InstrBuilder::InstrBuilder(const llvm::MCSubtargetInfo &sti,
const llvm::MCInstrInfo &mcii,
const llvm::MCRegisterInfo &mri,
const llvm::MCInstrAnalysis *mcia)
: STI(sti), MCII(mcii), MRI(mri), MCIA(mcia), FirstCallInst(true),
FirstReturnInst(true) {
computeProcResourceMasks(STI.getSchedModel(), ProcResourceMasks);
}
static void initializeUsedResources(InstrDesc &ID,
const MCSchedClassDesc &SCDesc,
const MCSubtargetInfo &STI,
ArrayRef<uint64_t> ProcResourceMasks) {
const MCSchedModel &SM = STI.getSchedModel();
// Populate resources consumed.
using ResourcePlusCycles = std::pair<uint64_t, ResourceUsage>;
std::vector<ResourcePlusCycles> Worklist;
// Track cycles contributed by resources that are in a "Super" relationship.
// This is required if we want to correctly match the behavior of method
// SubtargetEmitter::ExpandProcResource() in Tablegen. When computing the set
// of "consumed" processor resources and resource cycles, the logic in
// ExpandProcResource() doesn't update the number of resource cycles
// contributed by a "Super" resource to a group.
// We need to take this into account when we find that a processor resource is
// part of a group, and it is also used as the "Super" of other resources.
// This map stores the number of cycles contributed by sub-resources that are
// part of a "Super" resource. The key value is the "Super" resource mask ID.
DenseMap<uint64_t, unsigned> SuperResources;
unsigned NumProcResources = SM.getNumProcResourceKinds();
APInt Buffers(NumProcResources, 0);
bool AllInOrderResources = true;
bool AnyDispatchHazards = false;
for (unsigned I = 0, E = SCDesc.NumWriteProcResEntries; I < E; ++I) {
const MCWriteProcResEntry *PRE = STI.getWriteProcResBegin(&SCDesc) + I;
const MCProcResourceDesc &PR = *SM.getProcResource(PRE->ProcResourceIdx);
uint64_t Mask = ProcResourceMasks[PRE->ProcResourceIdx];
if (PR.BufferSize < 0) {
AllInOrderResources = false;
} else {
Buffers.setBit(PRE->ProcResourceIdx);
AnyDispatchHazards |= (PR.BufferSize == 0);
AllInOrderResources &= (PR.BufferSize <= 1);
}
CycleSegment RCy(0, PRE->Cycles, false);
Worklist.emplace_back(ResourcePlusCycles(Mask, ResourceUsage(RCy)));
if (PR.SuperIdx) {
uint64_t Super = ProcResourceMasks[PR.SuperIdx];
SuperResources[Super] += PRE->Cycles;
}
}
ID.MustIssueImmediately = AllInOrderResources && AnyDispatchHazards;
// Sort elements by mask popcount, so that we prioritize resource units over
// resource groups, and smaller groups over larger groups.
sort(Worklist, [](const ResourcePlusCycles &A, const ResourcePlusCycles &B) {
unsigned popcntA = countPopulation(A.first);
unsigned popcntB = countPopulation(B.first);
if (popcntA < popcntB)
return true;
if (popcntA > popcntB)
return false;
return A.first < B.first;
});
uint64_t UsedResourceUnits = 0;
// Remove cycles contributed by smaller resources.
for (unsigned I = 0, E = Worklist.size(); I < E; ++I) {
ResourcePlusCycles &A = Worklist[I];
if (!A.second.size()) {
A.second.NumUnits = 0;
A.second.setReserved();
ID.Resources.emplace_back(A);
continue;
}
ID.Resources.emplace_back(A);
uint64_t NormalizedMask = A.first;
if (countPopulation(A.first) == 1) {
UsedResourceUnits |= A.first;
} else {
// Remove the leading 1 from the resource group mask.
NormalizedMask ^= PowerOf2Floor(NormalizedMask);
}
for (unsigned J = I + 1; J < E; ++J) {
ResourcePlusCycles &B = Worklist[J];
if ((NormalizedMask & B.first) == NormalizedMask) {
B.second.CS.subtract(A.second.size() - SuperResources[A.first]);
if (countPopulation(B.first) > 1)
B.second.NumUnits++;
}
}
}
// A SchedWrite may specify a number of cycles in which a resource group
// is reserved. For example (on target x86; cpu Haswell):
//
// SchedWriteRes<[HWPort0, HWPort1, HWPort01]> {
// let ResourceCycles = [2, 2, 3];
// }
//
// This means:
// Resource units HWPort0 and HWPort1 are both used for 2cy.
// Resource group HWPort01 is the union of HWPort0 and HWPort1.
// Since this write touches both HWPort0 and HWPort1 for 2cy, HWPort01
// will not be usable for 2 entire cycles from instruction issue.
//
// On top of those 2cy, SchedWriteRes explicitly specifies an extra latency
// of 3 cycles for HWPort01. This tool assumes that the 3cy latency is an
// extra delay on top of the 2 cycles latency.
// During those extra cycles, HWPort01 is not usable by other instructions.
for (ResourcePlusCycles &RPC : ID.Resources) {
if (countPopulation(RPC.first) > 1 && !RPC.second.isReserved()) {
// Remove the leading 1 from the resource group mask.
uint64_t Mask = RPC.first ^ PowerOf2Floor(RPC.first);
if ((Mask & UsedResourceUnits) == Mask)
RPC.second.setReserved();
}
}
// Identify extra buffers that are consumed through super resources.
for (const std::pair<uint64_t, unsigned> &SR : SuperResources) {
for (unsigned I = 1, E = NumProcResources; I < E; ++I) {
const MCProcResourceDesc &PR = *SM.getProcResource(I);
if (PR.BufferSize == -1)
continue;
uint64_t Mask = ProcResourceMasks[I];
if (Mask != SR.first && ((Mask & SR.first) == SR.first))
Buffers.setBit(I);
}
}
// Now set the buffers.
if (unsigned NumBuffers = Buffers.countPopulation()) {
ID.Buffers.resize(NumBuffers);
for (unsigned I = 0, E = NumProcResources; I < E && NumBuffers; ++I) {
if (Buffers[I]) {
--NumBuffers;
ID.Buffers[NumBuffers] = ProcResourceMasks[I];
}
}
}
LLVM_DEBUG({
for (const std::pair<uint64_t, ResourceUsage> &R : ID.Resources)
dbgs() << "\t\tMask=" << R.first << ", cy=" << R.second.size() << '\n';
for (const uint64_t R : ID.Buffers)
dbgs() << "\t\tBuffer Mask=" << R << '\n';
});
}
static void computeMaxLatency(InstrDesc &ID, const MCInstrDesc &MCDesc,
const MCSchedClassDesc &SCDesc,
const MCSubtargetInfo &STI) {
if (MCDesc.isCall()) {
// We cannot estimate how long this call will take.
// Artificially set an arbitrarily high latency (100cy).
ID.MaxLatency = 100U;
return;
}
int Latency = MCSchedModel::computeInstrLatency(STI, SCDesc);
// If latency is unknown, then conservatively assume a MaxLatency of 100cy.
ID.MaxLatency = Latency < 0 ? 100U : static_cast<unsigned>(Latency);
}
static Error verifyOperands(const MCInstrDesc &MCDesc, const MCInst &MCI) {
// Count register definitions, and skip non register operands in the process.
unsigned I, E;
unsigned NumExplicitDefs = MCDesc.getNumDefs();
for (I = 0, E = MCI.getNumOperands(); NumExplicitDefs && I < E; ++I) {
const MCOperand &Op = MCI.getOperand(I);
if (Op.isReg())
--NumExplicitDefs;
}
if (NumExplicitDefs) {
return make_error<InstructionError<MCInst>>(
"Expected more register operand definitions.", MCI);
}
if (MCDesc.hasOptionalDef()) {
// Always assume that the optional definition is the last operand.
const MCOperand &Op = MCI.getOperand(MCDesc.getNumOperands() - 1);
if (I == MCI.getNumOperands() || !Op.isReg()) {
std::string Message =
"expected a register operand for an optional definition. Instruction "
"has not been correctly analyzed.";
return make_error<InstructionError<MCInst>>(Message, MCI);
}
}
return ErrorSuccess();
}
void InstrBuilder::populateWrites(InstrDesc &ID, const MCInst &MCI,
unsigned SchedClassID) {
const MCInstrDesc &MCDesc = MCII.get(MCI.getOpcode());
const MCSchedModel &SM = STI.getSchedModel();
const MCSchedClassDesc &SCDesc = *SM.getSchedClassDesc(SchedClassID);
// Assumptions made by this algorithm:
// 1. The number of explicit and implicit register definitions in a MCInst
// matches the number of explicit and implicit definitions according to
// the opcode descriptor (MCInstrDesc).
// 2. Uses start at index #(MCDesc.getNumDefs()).
// 3. There can only be a single optional register definition, an it is
// always the last operand of the sequence (excluding extra operands
// contributed by variadic opcodes).
//
// These assumptions work quite well for most out-of-order in-tree targets
// like x86. This is mainly because the vast majority of instructions is
// expanded to MCInst using a straightforward lowering logic that preserves
// the ordering of the operands.
//
// About assumption 1.
// The algorithm allows non-register operands between register operand
// definitions. This helps to handle some special ARM instructions with
// implicit operand increment (-mtriple=armv7):
//
// vld1.32 {d18, d19}, [r1]! @ <MCInst #1463 VLD1q32wb_fixed
// @ <MCOperand Reg:59>
// @ <MCOperand Imm:0> (!!)
// @ <MCOperand Reg:67>
// @ <MCOperand Imm:0>
// @ <MCOperand Imm:14>
// @ <MCOperand Reg:0>>
//
// MCDesc reports:
// 6 explicit operands.
// 1 optional definition
// 2 explicit definitions (!!)
//
// The presence of an 'Imm' operand between the two register definitions
// breaks the assumption that "register definitions are always at the
// beginning of the operand sequence".
//
// To workaround this issue, this algorithm ignores (i.e. skips) any
// non-register operands between register definitions. The optional
// definition is still at index #(NumOperands-1).
//
// According to assumption 2. register reads start at #(NumExplicitDefs-1).
// That means, register R1 from the example is both read and written.
unsigned NumExplicitDefs = MCDesc.getNumDefs();
unsigned NumImplicitDefs = MCDesc.getNumImplicitDefs();
unsigned NumWriteLatencyEntries = SCDesc.NumWriteLatencyEntries;
unsigned TotalDefs = NumExplicitDefs + NumImplicitDefs;
if (MCDesc.hasOptionalDef())
TotalDefs++;
unsigned NumVariadicOps = MCI.getNumOperands() - MCDesc.getNumOperands();
ID.Writes.resize(TotalDefs + NumVariadicOps);
// Iterate over the operands list, and skip non-register operands.
// The first NumExplictDefs register operands are expected to be register
// definitions.
unsigned CurrentDef = 0;
unsigned i = 0;
for (; i < MCI.getNumOperands() && CurrentDef < NumExplicitDefs; ++i) {
const MCOperand &Op = MCI.getOperand(i);
if (!Op.isReg())
continue;
WriteDescriptor &Write = ID.Writes[CurrentDef];
Write.OpIndex = i;
if (CurrentDef < NumWriteLatencyEntries) {
const MCWriteLatencyEntry &WLE =
*STI.getWriteLatencyEntry(&SCDesc, CurrentDef);
// Conservatively default to MaxLatency.
Write.Latency =
WLE.Cycles < 0 ? ID.MaxLatency : static_cast<unsigned>(WLE.Cycles);
Write.SClassOrWriteResourceID = WLE.WriteResourceID;
} else {
// Assign a default latency for this write.
Write.Latency = ID.MaxLatency;
Write.SClassOrWriteResourceID = 0;
}
Write.IsOptionalDef = false;
LLVM_DEBUG({
dbgs() << "\t\t[Def] OpIdx=" << Write.OpIndex
<< ", Latency=" << Write.Latency
<< ", WriteResourceID=" << Write.SClassOrWriteResourceID << '\n';
});
CurrentDef++;
}
assert(CurrentDef == NumExplicitDefs &&
"Expected more register operand definitions.");
for (CurrentDef = 0; CurrentDef < NumImplicitDefs; ++CurrentDef) {
unsigned Index = NumExplicitDefs + CurrentDef;
WriteDescriptor &Write = ID.Writes[Index];
Write.OpIndex = ~CurrentDef;
Write.RegisterID = MCDesc.getImplicitDefs()[CurrentDef];
if (Index < NumWriteLatencyEntries) {
const MCWriteLatencyEntry &WLE =
*STI.getWriteLatencyEntry(&SCDesc, Index);
// Conservatively default to MaxLatency.
Write.Latency =
WLE.Cycles < 0 ? ID.MaxLatency : static_cast<unsigned>(WLE.Cycles);
Write.SClassOrWriteResourceID = WLE.WriteResourceID;
} else {
// Assign a default latency for this write.
Write.Latency = ID.MaxLatency;
Write.SClassOrWriteResourceID = 0;
}
Write.IsOptionalDef = false;
assert(Write.RegisterID != 0 && "Expected a valid phys register!");
LLVM_DEBUG({
dbgs() << "\t\t[Def][I] OpIdx=" << ~Write.OpIndex
<< ", PhysReg=" << MRI.getName(Write.RegisterID)
<< ", Latency=" << Write.Latency
<< ", WriteResourceID=" << Write.SClassOrWriteResourceID << '\n';
});
}
if (MCDesc.hasOptionalDef()) {
WriteDescriptor &Write = ID.Writes[NumExplicitDefs + NumImplicitDefs];
Write.OpIndex = MCDesc.getNumOperands() - 1;
// Assign a default latency for this write.
Write.Latency = ID.MaxLatency;
Write.SClassOrWriteResourceID = 0;
Write.IsOptionalDef = true;
LLVM_DEBUG({
dbgs() << "\t\t[Def][O] OpIdx=" << Write.OpIndex
<< ", Latency=" << Write.Latency
<< ", WriteResourceID=" << Write.SClassOrWriteResourceID << '\n';
});
}
if (!NumVariadicOps)
return;
// FIXME: if an instruction opcode is flagged 'mayStore', and it has no
// "unmodeledSideEffects', then this logic optimistically assumes that any
// extra register operands in the variadic sequence is not a register
// definition.
//
// Otherwise, we conservatively assume that any register operand from the
// variadic sequence is both a register read and a register write.
bool AssumeUsesOnly = MCDesc.mayStore() && !MCDesc.mayLoad() &&
!MCDesc.hasUnmodeledSideEffects();
CurrentDef = NumExplicitDefs + NumImplicitDefs + MCDesc.hasOptionalDef();
for (unsigned I = 0, OpIndex = MCDesc.getNumOperands();
I < NumVariadicOps && !AssumeUsesOnly; ++I, ++OpIndex) {
const MCOperand &Op = MCI.getOperand(OpIndex);
if (!Op.isReg())
continue;
WriteDescriptor &Write = ID.Writes[CurrentDef];
Write.OpIndex = OpIndex;
// Assign a default latency for this write.
Write.Latency = ID.MaxLatency;
Write.SClassOrWriteResourceID = 0;
Write.IsOptionalDef = false;
++CurrentDef;
LLVM_DEBUG({
dbgs() << "\t\t[Def][V] OpIdx=" << Write.OpIndex
<< ", Latency=" << Write.Latency
<< ", WriteResourceID=" << Write.SClassOrWriteResourceID << '\n';
});
}
ID.Writes.resize(CurrentDef);
}
void InstrBuilder::populateReads(InstrDesc &ID, const MCInst &MCI,
unsigned SchedClassID) {
const MCInstrDesc &MCDesc = MCII.get(MCI.getOpcode());
unsigned NumExplicitUses = MCDesc.getNumOperands() - MCDesc.getNumDefs();
unsigned NumImplicitUses = MCDesc.getNumImplicitUses();
// Remove the optional definition.
if (MCDesc.hasOptionalDef())
--NumExplicitUses;
unsigned NumVariadicOps = MCI.getNumOperands() - MCDesc.getNumOperands();
unsigned TotalUses = NumExplicitUses + NumImplicitUses + NumVariadicOps;
ID.Reads.resize(TotalUses);
unsigned CurrentUse = 0;
for (unsigned I = 0, OpIndex = MCDesc.getNumDefs(); I < NumExplicitUses;
++I, ++OpIndex) {
const MCOperand &Op = MCI.getOperand(OpIndex);
if (!Op.isReg())
continue;
ReadDescriptor &Read = ID.Reads[CurrentUse];
Read.OpIndex = OpIndex;
Read.UseIndex = I;
Read.SchedClassID = SchedClassID;
++CurrentUse;
LLVM_DEBUG(dbgs() << "\t\t[Use] OpIdx=" << Read.OpIndex
<< ", UseIndex=" << Read.UseIndex << '\n');
}
// For the purpose of ReadAdvance, implicit uses come directly after explicit
// uses. The "UseIndex" must be updated according to that implicit layout.
for (unsigned I = 0; I < NumImplicitUses; ++I) {
ReadDescriptor &Read = ID.Reads[CurrentUse + I];
Read.OpIndex = ~I;
Read.UseIndex = NumExplicitUses + I;
Read.RegisterID = MCDesc.getImplicitUses()[I];
Read.SchedClassID = SchedClassID;
LLVM_DEBUG(dbgs() << "\t\t[Use][I] OpIdx=" << ~Read.OpIndex
<< ", UseIndex=" << Read.UseIndex << ", RegisterID="
<< MRI.getName(Read.RegisterID) << '\n');
}
CurrentUse += NumImplicitUses;
// FIXME: If an instruction opcode is marked as 'mayLoad', and it has no
// "unmodeledSideEffects", then this logic optimistically assumes that any
// extra register operands in the variadic sequence are not register
// definition.
bool AssumeDefsOnly = !MCDesc.mayStore() && MCDesc.mayLoad() &&
!MCDesc.hasUnmodeledSideEffects();
for (unsigned I = 0, OpIndex = MCDesc.getNumOperands();
I < NumVariadicOps && !AssumeDefsOnly; ++I, ++OpIndex) {
const MCOperand &Op = MCI.getOperand(OpIndex);
if (!Op.isReg())
continue;
ReadDescriptor &Read = ID.Reads[CurrentUse];
Read.OpIndex = OpIndex;
Read.UseIndex = NumExplicitUses + NumImplicitUses + I;
Read.SchedClassID = SchedClassID;
++CurrentUse;
LLVM_DEBUG(dbgs() << "\t\t[Use][V] OpIdx=" << Read.OpIndex
<< ", UseIndex=" << Read.UseIndex << '\n');
}
ID.Reads.resize(CurrentUse);
}
Error InstrBuilder::verifyInstrDesc(const InstrDesc &ID,
const MCInst &MCI) const {
if (ID.NumMicroOps != 0)
return ErrorSuccess();
bool UsesMemory = ID.MayLoad || ID.MayStore;
bool UsesBuffers = !ID.Buffers.empty();
bool UsesResources = !ID.Resources.empty();
if (!UsesMemory && !UsesBuffers && !UsesResources)
return ErrorSuccess();
StringRef Message;
if (UsesMemory) {
Message = "found an inconsistent instruction that decodes "
"into zero opcodes and that consumes load/store "
"unit resources.";
} else {
Message = "found an inconsistent instruction that decodes "
"to zero opcodes and that consumes scheduler "
"resources.";
}
return make_error<InstructionError<MCInst>>(Message, MCI);
}
Expected<const InstrDesc &>
InstrBuilder::createInstrDescImpl(const MCInst &MCI) {
assert(STI.getSchedModel().hasInstrSchedModel() &&
"Itineraries are not yet supported!");
// Obtain the instruction descriptor from the opcode.
unsigned short Opcode = MCI.getOpcode();
const MCInstrDesc &MCDesc = MCII.get(Opcode);
const MCSchedModel &SM = STI.getSchedModel();
// Then obtain the scheduling class information from the instruction.
unsigned SchedClassID = MCDesc.getSchedClass();
bool IsVariant = SM.getSchedClassDesc(SchedClassID)->isVariant();
// Try to solve variant scheduling classes.
if (IsVariant) {
unsigned CPUID = SM.getProcessorID();
while (SchedClassID && SM.getSchedClassDesc(SchedClassID)->isVariant())
SchedClassID = STI.resolveVariantSchedClass(SchedClassID, &MCI, CPUID);
if (!SchedClassID) {
return make_error<InstructionError<MCInst>>(
"unable to resolve scheduling class for write variant.", MCI);
}
}
// Check if this instruction is supported. Otherwise, report an error.
const MCSchedClassDesc &SCDesc = *SM.getSchedClassDesc(SchedClassID);
if (SCDesc.NumMicroOps == MCSchedClassDesc::InvalidNumMicroOps) {
return make_error<InstructionError<MCInst>>(
"found an unsupported instruction in the input assembly sequence.",
MCI);
}
// Create a new empty descriptor.
std::unique_ptr<InstrDesc> ID = llvm::make_unique<InstrDesc>();
ID->NumMicroOps = SCDesc.NumMicroOps;
if (MCDesc.isCall() && FirstCallInst) {
// We don't correctly model calls.
WithColor::warning() << "found a call in the input assembly sequence.\n";
WithColor::note() << "call instructions are not correctly modeled. "
<< "Assume a latency of 100cy.\n";
FirstCallInst = false;
}
if (MCDesc.isReturn() && FirstReturnInst) {
WithColor::warning() << "found a return instruction in the input"
<< " assembly sequence.\n";
WithColor::note() << "program counter updates are ignored.\n";
FirstReturnInst = false;
}
ID->MayLoad = MCDesc.mayLoad();
ID->MayStore = MCDesc.mayStore();
ID->HasSideEffects = MCDesc.hasUnmodeledSideEffects();
ID->BeginGroup = SCDesc.BeginGroup;
ID->EndGroup = SCDesc.EndGroup;
initializeUsedResources(*ID, SCDesc, STI, ProcResourceMasks);
computeMaxLatency(*ID, MCDesc, SCDesc, STI);
if (Error Err = verifyOperands(MCDesc, MCI))
return std::move(Err);
populateWrites(*ID, MCI, SchedClassID);
populateReads(*ID, MCI, SchedClassID);
LLVM_DEBUG(dbgs() << "\t\tMaxLatency=" << ID->MaxLatency << '\n');
LLVM_DEBUG(dbgs() << "\t\tNumMicroOps=" << ID->NumMicroOps << '\n');
// Sanity check on the instruction descriptor.
if (Error Err = verifyInstrDesc(*ID, MCI))
return std::move(Err);
// Now add the new descriptor.
SchedClassID = MCDesc.getSchedClass();
bool IsVariadic = MCDesc.isVariadic();
if (!IsVariadic && !IsVariant) {
Descriptors[MCI.getOpcode()] = std::move(ID);
return *Descriptors[MCI.getOpcode()];
}
VariantDescriptors[&MCI] = std::move(ID);
return *VariantDescriptors[&MCI];
}
Expected<const InstrDesc &>
InstrBuilder::getOrCreateInstrDesc(const MCInst &MCI) {
if (Descriptors.find_as(MCI.getOpcode()) != Descriptors.end())
return *Descriptors[MCI.getOpcode()];
if (VariantDescriptors.find(&MCI) != VariantDescriptors.end())
return *VariantDescriptors[&MCI];
return createInstrDescImpl(MCI);
}
Expected<std::unique_ptr<Instruction>>
InstrBuilder::createInstruction(const MCInst &MCI) {
Expected<const InstrDesc &> DescOrErr = getOrCreateInstrDesc(MCI);
if (!DescOrErr)
return DescOrErr.takeError();
const InstrDesc &D = *DescOrErr;
std::unique_ptr<Instruction> NewIS = llvm::make_unique<Instruction>(D);
// Check if this is a dependency breaking instruction.
APInt Mask;
bool IsZeroIdiom = false;
bool IsDepBreaking = false;
if (MCIA) {
unsigned ProcID = STI.getSchedModel().getProcessorID();
IsZeroIdiom = MCIA->isZeroIdiom(MCI, Mask, ProcID);
IsDepBreaking =
IsZeroIdiom || MCIA->isDependencyBreaking(MCI, Mask, ProcID);
if (MCIA->isOptimizableRegisterMove(MCI, ProcID))
NewIS->setOptimizableMove();
}
// Initialize Reads first.
for (const ReadDescriptor &RD : D.Reads) {
int RegID = -1;
if (!RD.isImplicitRead()) {
// explicit read.
const MCOperand &Op = MCI.getOperand(RD.OpIndex);
// Skip non-register operands.
if (!Op.isReg())
continue;
RegID = Op.getReg();
} else {
// Implicit read.
RegID = RD.RegisterID;
}
// Skip invalid register operands.
if (!RegID)
continue;
// Okay, this is a register operand. Create a ReadState for it.
assert(RegID > 0 && "Invalid register ID found!");
NewIS->getUses().emplace_back(RD, RegID);
ReadState &RS = NewIS->getUses().back();
if (IsDepBreaking) {
// A mask of all zeroes means: explicit input operands are not
// independent.
if (Mask.isNullValue()) {
if (!RD.isImplicitRead())
RS.setIndependentFromDef();
} else {
// Check if this register operand is independent according to `Mask`.
// Note that Mask may not have enough bits to describe all explicit and
// implicit input operands. If this register operand doesn't have a
// corresponding bit in Mask, then conservatively assume that it is
// dependent.
if (Mask.getBitWidth() > RD.UseIndex) {
// Okay. This map describe register use `RD.UseIndex`.
if (Mask[RD.UseIndex])
RS.setIndependentFromDef();
}
}
}
}
// Early exit if there are no writes.
if (D.Writes.empty())
return std::move(NewIS);
// Track register writes that implicitly clear the upper portion of the
// underlying super-registers using an APInt.
APInt WriteMask(D.Writes.size(), 0);
// Now query the MCInstrAnalysis object to obtain information about which
// register writes implicitly clear the upper portion of a super-register.
if (MCIA)
MCIA->clearsSuperRegisters(MRI, MCI, WriteMask);
// Initialize writes.
unsigned WriteIndex = 0;
for (const WriteDescriptor &WD : D.Writes) {
unsigned RegID = WD.isImplicitWrite() ? WD.RegisterID
: MCI.getOperand(WD.OpIndex).getReg();
// Check if this is a optional definition that references NoReg.
if (WD.IsOptionalDef && !RegID) {
++WriteIndex;
continue;
}
assert(RegID && "Expected a valid register ID!");
NewIS->getDefs().emplace_back(WD, RegID,
/* ClearsSuperRegs */ WriteMask[WriteIndex],
/* WritesZero */ IsZeroIdiom);
++WriteIndex;
}
return std::move(NewIS);
}
} // namespace mca
} // namespace llvm
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