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llvm-project/llvm/lib/CodeGen/StackMaps.cpp

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//===- StackMaps.cpp ------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/ADT/DenseMapInfo.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <iterator>
#include <utility>
using namespace llvm;
#define DEBUG_TYPE "stackmaps"
static cl::opt<int> StackMapVersion(
"stackmap-version", cl::init(3), cl::Hidden,
cl::desc("Specify the stackmap encoding version (default = 3)"));
const char *StackMaps::WSMP = "Stack Maps: ";
StackMapOpers::StackMapOpers(const MachineInstr *MI)
: MI(MI) {
assert(getVarIdx() <= MI->getNumOperands() &&
"invalid stackmap definition");
}
PatchPointOpers::PatchPointOpers(const MachineInstr *MI)
: MI(MI), HasDef(MI->getOperand(0).isReg() && MI->getOperand(0).isDef() &&
!MI->getOperand(0).isImplicit()) {
#ifndef NDEBUG
unsigned CheckStartIdx = 0, e = MI->getNumOperands();
while (CheckStartIdx < e && MI->getOperand(CheckStartIdx).isReg() &&
MI->getOperand(CheckStartIdx).isDef() &&
!MI->getOperand(CheckStartIdx).isImplicit())
++CheckStartIdx;
assert(getMetaIdx() == CheckStartIdx &&
"Unexpected additional definition in Patchpoint intrinsic.");
#endif
}
unsigned PatchPointOpers::getNextScratchIdx(unsigned StartIdx) const {
if (!StartIdx)
StartIdx = getVarIdx();
// Find the next scratch register (implicit def and early clobber)
unsigned ScratchIdx = StartIdx, e = MI->getNumOperands();
while (ScratchIdx < e &&
!(MI->getOperand(ScratchIdx).isReg() &&
MI->getOperand(ScratchIdx).isDef() &&
MI->getOperand(ScratchIdx).isImplicit() &&
MI->getOperand(ScratchIdx).isEarlyClobber()))
++ScratchIdx;
assert(ScratchIdx != e && "No scratch register available");
return ScratchIdx;
}
StackMaps::StackMaps(AsmPrinter &AP) : AP(AP) {
if (StackMapVersion != 3)
llvm_unreachable("Unsupported stackmap version!");
}
/// Go up the super-register chain until we hit a valid dwarf register number.
static unsigned getDwarfRegNum(unsigned Reg, const TargetRegisterInfo *TRI) {
int RegNum = TRI->getDwarfRegNum(Reg, false);
for (MCSuperRegIterator SR(Reg, TRI); SR.isValid() && RegNum < 0; ++SR)
RegNum = TRI->getDwarfRegNum(*SR, false);
assert(RegNum >= 0 && "Invalid Dwarf register number.");
return (unsigned)RegNum;
}
MachineInstr::const_mop_iterator
StackMaps::parseOperand(MachineInstr::const_mop_iterator MOI,
MachineInstr::const_mop_iterator MOE, LocationVec &Locs,
LiveOutVec &LiveOuts) const {
const TargetRegisterInfo *TRI = AP.MF->getSubtarget().getRegisterInfo();
if (MOI->isImm()) {
switch (MOI->getImm()) {
default:
llvm_unreachable("Unrecognized operand type.");
case StackMaps::DirectMemRefOp: {
auto &DL = AP.MF->getDataLayout();
unsigned Size = DL.getPointerSizeInBits();
assert((Size % 8) == 0 && "Need pointer size in bytes.");
Size /= 8;
Register Reg = (++MOI)->getReg();
int64_t Imm = (++MOI)->getImm();
Locs.emplace_back(StackMaps::Location::Direct, Size,
getDwarfRegNum(Reg, TRI), Imm);
break;
}
case StackMaps::IndirectMemRefOp: {
int64_t Size = (++MOI)->getImm();
assert(Size > 0 && "Need a valid size for indirect memory locations.");
Register Reg = (++MOI)->getReg();
int64_t Imm = (++MOI)->getImm();
Locs.emplace_back(StackMaps::Location::Indirect, Size,
getDwarfRegNum(Reg, TRI), Imm);
break;
}
case StackMaps::ConstantOp: {
++MOI;
assert(MOI->isImm() && "Expected constant operand.");
int64_t Imm = MOI->getImm();
Locs.emplace_back(Location::Constant, sizeof(int64_t), 0, Imm);
break;
}
}
return ++MOI;
}
// The physical register number will ultimately be encoded as a DWARF regno.
// The stack map also records the size of a spill slot that can hold the
// register content. (The runtime can track the actual size of the data type
// if it needs to.)
if (MOI->isReg()) {
// Skip implicit registers (this includes our scratch registers)
if (MOI->isImplicit())
return ++MOI;
assert(Register::isPhysicalRegister(MOI->getReg()) &&
"Virtreg operands should have been rewritten before now.");
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(MOI->getReg());
assert(!MOI->getSubReg() && "Physical subreg still around.");
unsigned Offset = 0;
unsigned DwarfRegNum = getDwarfRegNum(MOI->getReg(), TRI);
unsigned LLVMRegNum = *TRI->getLLVMRegNum(DwarfRegNum, false);
unsigned SubRegIdx = TRI->getSubRegIndex(LLVMRegNum, MOI->getReg());
if (SubRegIdx)
Offset = TRI->getSubRegIdxOffset(SubRegIdx);
Locs.emplace_back(Location::Register, TRI->getSpillSize(*RC),
DwarfRegNum, Offset);
return ++MOI;
}
if (MOI->isRegLiveOut())
LiveOuts = parseRegisterLiveOutMask(MOI->getRegLiveOut());
return ++MOI;
}
void StackMaps::print(raw_ostream &OS) {
const TargetRegisterInfo *TRI =
AP.MF ? AP.MF->getSubtarget().getRegisterInfo() : nullptr;
OS << WSMP << "callsites:\n";
for (const auto &CSI : CSInfos) {
const LocationVec &CSLocs = CSI.Locations;
const LiveOutVec &LiveOuts = CSI.LiveOuts;
OS << WSMP << "callsite " << CSI.ID << "\n";
OS << WSMP << " has " << CSLocs.size() << " locations\n";
unsigned Idx = 0;
for (const auto &Loc : CSLocs) {
OS << WSMP << "\t\tLoc " << Idx << ": ";
switch (Loc.Type) {
case Location::Unprocessed:
OS << "<Unprocessed operand>";
break;
case Location::Register:
OS << "Register ";
if (TRI)
OS << printReg(Loc.Reg, TRI);
else
OS << Loc.Reg;
break;
case Location::Direct:
OS << "Direct ";
if (TRI)
OS << printReg(Loc.Reg, TRI);
else
OS << Loc.Reg;
if (Loc.Offset)
OS << " + " << Loc.Offset;
break;
case Location::Indirect:
OS << "Indirect ";
if (TRI)
OS << printReg(Loc.Reg, TRI);
else
OS << Loc.Reg;
OS << "+" << Loc.Offset;
break;
case Location::Constant:
OS << "Constant " << Loc.Offset;
break;
case Location::ConstantIndex:
OS << "Constant Index " << Loc.Offset;
break;
}
OS << "\t[encoding: .byte " << Loc.Type << ", .byte 0"
<< ", .short " << Loc.Size << ", .short " << Loc.Reg << ", .short 0"
<< ", .int " << Loc.Offset << "]\n";
Idx++;
}
OS << WSMP << "\thas " << LiveOuts.size() << " live-out registers\n";
Idx = 0;
for (const auto &LO : LiveOuts) {
OS << WSMP << "\t\tLO " << Idx << ": ";
if (TRI)
OS << printReg(LO.Reg, TRI);
else
OS << LO.Reg;
OS << "\t[encoding: .short " << LO.DwarfRegNum << ", .byte 0, .byte "
<< LO.Size << "]\n";
Idx++;
}
}
}
/// Create a live-out register record for the given register Reg.
StackMaps::LiveOutReg
StackMaps::createLiveOutReg(unsigned Reg, const TargetRegisterInfo *TRI) const {
unsigned DwarfRegNum = getDwarfRegNum(Reg, TRI);
unsigned Size = TRI->getSpillSize(*TRI->getMinimalPhysRegClass(Reg));
return LiveOutReg(Reg, DwarfRegNum, Size);
}
/// Parse the register live-out mask and return a vector of live-out registers
/// that need to be recorded in the stackmap.
StackMaps::LiveOutVec
StackMaps::parseRegisterLiveOutMask(const uint32_t *Mask) const {
assert(Mask && "No register mask specified");
const TargetRegisterInfo *TRI = AP.MF->getSubtarget().getRegisterInfo();
LiveOutVec LiveOuts;
// Create a LiveOutReg for each bit that is set in the register mask.
for (unsigned Reg = 0, NumRegs = TRI->getNumRegs(); Reg != NumRegs; ++Reg)
if ((Mask[Reg / 32] >> (Reg % 32)) & 1)
LiveOuts.push_back(createLiveOutReg(Reg, TRI));
// We don't need to keep track of a register if its super-register is already
// in the list. Merge entries that refer to the same dwarf register and use
// the maximum size that needs to be spilled.
llvm::sort(LiveOuts, [](const LiveOutReg &LHS, const LiveOutReg &RHS) {
// Only sort by the dwarf register number.
return LHS.DwarfRegNum < RHS.DwarfRegNum;
});
for (auto I = LiveOuts.begin(), E = LiveOuts.end(); I != E; ++I) {
for (auto II = std::next(I); II != E; ++II) {
if (I->DwarfRegNum != II->DwarfRegNum) {
// Skip all the now invalid entries.
I = --II;
break;
}
I->Size = std::max(I->Size, II->Size);
if (TRI->isSuperRegister(I->Reg, II->Reg))
I->Reg = II->Reg;
II->Reg = 0; // mark for deletion.
}
}
LiveOuts.erase(
llvm::remove_if(LiveOuts,
[](const LiveOutReg &LO) { return LO.Reg == 0; }),
LiveOuts.end());
return LiveOuts;
}
void StackMaps::recordStackMapOpers(const MCSymbol &MILabel,
const MachineInstr &MI, uint64_t ID,
MachineInstr::const_mop_iterator MOI,
MachineInstr::const_mop_iterator MOE,
bool recordResult) {
MCContext &OutContext = AP.OutStreamer->getContext();
LocationVec Locations;
LiveOutVec LiveOuts;
if (recordResult) {
assert(PatchPointOpers(&MI).hasDef() && "Stackmap has no return value.");
parseOperand(MI.operands_begin(), std::next(MI.operands_begin()), Locations,
LiveOuts);
}
// Parse operands.
while (MOI != MOE) {
MOI = parseOperand(MOI, MOE, Locations, LiveOuts);
}
// Move large constants into the constant pool.
for (auto &Loc : Locations) {
// Constants are encoded as sign-extended integers.
// -1 is directly encoded as .long 0xFFFFFFFF with no constant pool.
if (Loc.Type == Location::Constant && !isInt<32>(Loc.Offset)) {
Loc.Type = Location::ConstantIndex;
// ConstPool is intentionally a MapVector of 'uint64_t's (as
// opposed to 'int64_t's). We should never be in a situation
// where we have to insert either the tombstone or the empty
// keys into a map, and for a DenseMap<uint64_t, T> these are
// (uint64_t)0 and (uint64_t)-1. They can be and are
// represented using 32 bit integers.
assert((uint64_t)Loc.Offset != DenseMapInfo<uint64_t>::getEmptyKey() &&
(uint64_t)Loc.Offset !=
DenseMapInfo<uint64_t>::getTombstoneKey() &&
"empty and tombstone keys should fit in 32 bits!");
auto Result = ConstPool.insert(std::make_pair(Loc.Offset, Loc.Offset));
Loc.Offset = Result.first - ConstPool.begin();
}
}
// Create an expression to calculate the offset of the callsite from function
// entry.
const MCExpr *CSOffsetExpr = MCBinaryExpr::createSub(
MCSymbolRefExpr::create(&MILabel, OutContext),
MCSymbolRefExpr::create(AP.CurrentFnSymForSize, OutContext), OutContext);
CSInfos.emplace_back(CSOffsetExpr, ID, std::move(Locations),
std::move(LiveOuts));
// Record the stack size of the current function and update callsite count.
const MachineFrameInfo &MFI = AP.MF->getFrameInfo();
const TargetRegisterInfo *RegInfo = AP.MF->getSubtarget().getRegisterInfo();
bool HasDynamicFrameSize =
MFI.hasVarSizedObjects() || RegInfo->needsStackRealignment(*(AP.MF));
uint64_t FrameSize = HasDynamicFrameSize ? UINT64_MAX : MFI.getStackSize();
auto CurrentIt = FnInfos.find(AP.CurrentFnSym);
if (CurrentIt != FnInfos.end())
CurrentIt->second.RecordCount++;
else
FnInfos.insert(std::make_pair(AP.CurrentFnSym, FunctionInfo(FrameSize)));
}
void StackMaps::recordStackMap(const MCSymbol &L, const MachineInstr &MI) {
assert(MI.getOpcode() == TargetOpcode::STACKMAP && "expected stackmap");
StackMapOpers opers(&MI);
const int64_t ID = MI.getOperand(PatchPointOpers::IDPos).getImm();
recordStackMapOpers(L, MI, ID, std::next(MI.operands_begin(),
opers.getVarIdx()),
MI.operands_end());
}
void StackMaps::recordPatchPoint(const MCSymbol &L, const MachineInstr &MI) {
assert(MI.getOpcode() == TargetOpcode::PATCHPOINT && "expected patchpoint");
PatchPointOpers opers(&MI);
const int64_t ID = opers.getID();
auto MOI = std::next(MI.operands_begin(), opers.getStackMapStartIdx());
recordStackMapOpers(L, MI, ID, MOI, MI.operands_end(),
opers.isAnyReg() && opers.hasDef());
#ifndef NDEBUG
// verify anyregcc
auto &Locations = CSInfos.back().Locations;
if (opers.isAnyReg()) {
unsigned NArgs = opers.getNumCallArgs();
for (unsigned i = 0, e = (opers.hasDef() ? NArgs + 1 : NArgs); i != e; ++i)
assert(Locations[i].Type == Location::Register &&
"anyreg arg must be in reg.");
}
#endif
}
void StackMaps::recordStatepoint(const MCSymbol &L, const MachineInstr &MI) {
assert(MI.getOpcode() == TargetOpcode::STATEPOINT && "expected statepoint");
StatepointOpers opers(&MI);
// Record all the deopt and gc operands (they're contiguous and run from the
// initial index to the end of the operand list)
const unsigned StartIdx = opers.getVarIdx();
recordStackMapOpers(L, MI, opers.getID(), MI.operands_begin() + StartIdx,
MI.operands_end(), false);
}
/// Emit the stackmap header.
///
/// Header {
/// uint8 : Stack Map Version (currently 2)
/// uint8 : Reserved (expected to be 0)
/// uint16 : Reserved (expected to be 0)
/// }
/// uint32 : NumFunctions
/// uint32 : NumConstants
/// uint32 : NumRecords
void StackMaps::emitStackmapHeader(MCStreamer &OS) {
// Header.
OS.emitIntValue(StackMapVersion, 1); // Version.
OS.emitIntValue(0, 1); // Reserved.
OS.emitInt16(0); // Reserved.
// Num functions.
LLVM_DEBUG(dbgs() << WSMP << "#functions = " << FnInfos.size() << '\n');
OS.emitInt32(FnInfos.size());
// Num constants.
LLVM_DEBUG(dbgs() << WSMP << "#constants = " << ConstPool.size() << '\n');
OS.emitInt32(ConstPool.size());
// Num callsites.
LLVM_DEBUG(dbgs() << WSMP << "#callsites = " << CSInfos.size() << '\n');
OS.emitInt32(CSInfos.size());
}
/// Emit the function frame record for each function.
///
/// StkSizeRecord[NumFunctions] {
/// uint64 : Function Address
/// uint64 : Stack Size
/// uint64 : Record Count
/// }
void StackMaps::emitFunctionFrameRecords(MCStreamer &OS) {
// Function Frame records.
LLVM_DEBUG(dbgs() << WSMP << "functions:\n");
for (auto const &FR : FnInfos) {
LLVM_DEBUG(dbgs() << WSMP << "function addr: " << FR.first
<< " frame size: " << FR.second.StackSize
<< " callsite count: " << FR.second.RecordCount << '\n');
OS.emitSymbolValue(FR.first, 8);
OS.emitIntValue(FR.second.StackSize, 8);
OS.emitIntValue(FR.second.RecordCount, 8);
}
}
/// Emit the constant pool.
///
/// int64 : Constants[NumConstants]
void StackMaps::emitConstantPoolEntries(MCStreamer &OS) {
// Constant pool entries.
LLVM_DEBUG(dbgs() << WSMP << "constants:\n");
for (const auto &ConstEntry : ConstPool) {
LLVM_DEBUG(dbgs() << WSMP << ConstEntry.second << '\n');
OS.emitIntValue(ConstEntry.second, 8);
}
}
/// Emit the callsite info for each callsite.
///
/// StkMapRecord[NumRecords] {
/// uint64 : PatchPoint ID
/// uint32 : Instruction Offset
/// uint16 : Reserved (record flags)
/// uint16 : NumLocations
/// Location[NumLocations] {
/// uint8 : Register | Direct | Indirect | Constant | ConstantIndex
/// uint8 : Size in Bytes
/// uint16 : Dwarf RegNum
/// int32 : Offset
/// }
/// uint16 : Padding
/// uint16 : NumLiveOuts
/// LiveOuts[NumLiveOuts] {
/// uint16 : Dwarf RegNum
/// uint8 : Reserved
/// uint8 : Size in Bytes
/// }
/// uint32 : Padding (only if required to align to 8 byte)
/// }
///
/// Location Encoding, Type, Value:
/// 0x1, Register, Reg (value in register)
/// 0x2, Direct, Reg + Offset (frame index)
/// 0x3, Indirect, [Reg + Offset] (spilled value)
/// 0x4, Constant, Offset (small constant)
/// 0x5, ConstIndex, Constants[Offset] (large constant)
void StackMaps::emitCallsiteEntries(MCStreamer &OS) {
LLVM_DEBUG(print(dbgs()));
// Callsite entries.
for (const auto &CSI : CSInfos) {
const LocationVec &CSLocs = CSI.Locations;
const LiveOutVec &LiveOuts = CSI.LiveOuts;
// Verify stack map entry. It's better to communicate a problem to the
// runtime than crash in case of in-process compilation. Currently, we do
// simple overflow checks, but we may eventually communicate other
// compilation errors this way.
if (CSLocs.size() > UINT16_MAX || LiveOuts.size() > UINT16_MAX) {
OS.emitIntValue(UINT64_MAX, 8); // Invalid ID.
OS.emitValue(CSI.CSOffsetExpr, 4);
OS.emitInt16(0); // Reserved.
OS.emitInt16(0); // 0 locations.
OS.emitInt16(0); // padding.
OS.emitInt16(0); // 0 live-out registers.
OS.emitInt32(0); // padding.
continue;
}
OS.emitIntValue(CSI.ID, 8);
OS.emitValue(CSI.CSOffsetExpr, 4);
// Reserved for flags.
OS.emitInt16(0);
OS.emitInt16(CSLocs.size());
for (const auto &Loc : CSLocs) {
OS.emitIntValue(Loc.Type, 1);
OS.emitIntValue(0, 1); // Reserved
OS.emitInt16(Loc.Size);
OS.emitInt16(Loc.Reg);
OS.emitInt16(0); // Reserved
OS.emitInt32(Loc.Offset);
}
// Emit alignment to 8 byte.
OS.emitValueToAlignment(8);
// Num live-out registers and padding to align to 4 byte.
OS.emitInt16(0);
OS.emitInt16(LiveOuts.size());
for (const auto &LO : LiveOuts) {
OS.emitInt16(LO.DwarfRegNum);
OS.emitIntValue(0, 1);
OS.emitIntValue(LO.Size, 1);
}
// Emit alignment to 8 byte.
OS.emitValueToAlignment(8);
}
}
/// Serialize the stackmap data.
void StackMaps::serializeToStackMapSection() {
(void)WSMP;
// Bail out if there's no stack map data.
assert((!CSInfos.empty() || ConstPool.empty()) &&
"Expected empty constant pool too!");
assert((!CSInfos.empty() || FnInfos.empty()) &&
"Expected empty function record too!");
if (CSInfos.empty())
return;
MCContext &OutContext = AP.OutStreamer->getContext();
MCStreamer &OS = *AP.OutStreamer;
// Create the section.
MCSection *StackMapSection =
OutContext.getObjectFileInfo()->getStackMapSection();
OS.SwitchSection(StackMapSection);
// Emit a dummy symbol to force section inclusion.
OS.emitLabel(OutContext.getOrCreateSymbol(Twine("__LLVM_StackMaps")));
// Serialize data.
LLVM_DEBUG(dbgs() << "********** Stack Map Output **********\n");
emitStackmapHeader(OS);
emitFunctionFrameRecords(OS);
emitConstantPoolEntries(OS);
emitCallsiteEntries(OS);
OS.AddBlankLine();
// Clean up.
CSInfos.clear();
ConstPool.clear();
}
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