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//===- AsmPrinter.cpp - Common AsmPrinter code ----------------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file implements the AsmPrinter class.
#include "llvm/CodeGen/AsmPrinter.h"
#include "CodeViewDebug.h"
#include "DwarfDebug.h"
#include "DwarfException.h"
#include "PseudoProbePrinter.h"
#include "WasmException.h"
#include "WinCFGuard.h"
#include "WinException.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/BinaryFormat/COFF.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/CodeGen/GCMetadata.h"
#include "llvm/CodeGen/GCMetadataPrinter.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBundle.h"
#include "llvm/CodeGen/MachineJumpTableInfo.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineModuleInfoImpls.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
#include "llvm/CodeGen/StackMaps.h"
#include "llvm/CodeGen/TargetFrameLowering.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/Config/config.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Comdat.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GCStrategy.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalIFunc.h"
#include "llvm/IR/GlobalObject.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"
#include "llvm/IR/PseudoProbe.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Value.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSectionXCOFF.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCSymbolELF.h"
#include "llvm/MC/MCSymbolXCOFF.h"
#include "llvm/MC/MCTargetOptions.h"
#include "llvm/MC/MCValue.h"
#include "llvm/MC/SectionKind.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Pass.h"
#include "llvm/Remarks/Remark.h"
#include "llvm/Remarks/RemarkFormat.h"
#include "llvm/Remarks/RemarkStreamer.h"
#include "llvm/Remarks/RemarkStringTable.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include <algorithm>
#include <cassert>
#include <cinttypes>
#include <cstdint>
#include <iterator>
#include <limits>
#include <memory>
#include <string>
#include <utility>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "asm-printer"
// FIXME: this option currently only applies to DWARF, and not CodeView, tables
static cl::opt<bool>
DisableDebugInfoPrinting("disable-debug-info-print", cl::Hidden,
cl::desc("Disable debug info printing"));
const char DWARFGroupName[] = "dwarf";
const char DWARFGroupDescription[] = "DWARF Emission";
const char DbgTimerName[] = "emit";
const char DbgTimerDescription[] = "Debug Info Emission";
const char EHTimerName[] = "write_exception";
const char EHTimerDescription[] = "DWARF Exception Writer";
const char CFGuardName[] = "Control Flow Guard";
const char CFGuardDescription[] = "Control Flow Guard";
const char CodeViewLineTablesGroupName[] = "linetables";
const char CodeViewLineTablesGroupDescription[] = "CodeView Line Tables";
const char PPTimerName[] = "emit";
const char PPTimerDescription[] = "Pseudo Probe Emission";
const char PPGroupName[] = "pseudo probe";
const char PPGroupDescription[] = "Pseudo Probe Emission";
STATISTIC(EmittedInsts, "Number of machine instrs printed");
char AsmPrinter::ID = 0;
using gcp_map_type = DenseMap<GCStrategy *, std::unique_ptr<GCMetadataPrinter>>;
static gcp_map_type &getGCMap(void *&P) {
if (!P)
P = new gcp_map_type();
return *(gcp_map_type*)P;
/// getGVAlignment - Return the alignment to use for the specified global
/// value. This rounds up to the preferred alignment if possible and legal.
Align AsmPrinter::getGVAlignment(const GlobalObject *GV, const DataLayout &DL,
Align InAlign) {
Align Alignment;
if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV))
Alignment = DL.getPreferredAlign(GVar);
// If InAlign is specified, round it to it.
if (InAlign > Alignment)
Alignment = InAlign;
// If the GV has a specified alignment, take it into account.
const MaybeAlign GVAlign(GV->getAlignment());
if (!GVAlign)
return Alignment;
assert(GVAlign && "GVAlign must be set");
// If the GVAlign is larger than NumBits, or if we are required to obey
// NumBits because the GV has an assigned section, obey it.
if (*GVAlign > Alignment || GV->hasSection())
Alignment = *GVAlign;
return Alignment;
AsmPrinter::AsmPrinter(TargetMachine &tm, std::unique_ptr<MCStreamer> Streamer)
: MachineFunctionPass(ID), TM(tm), MAI(tm.getMCAsmInfo()),
OutContext(Streamer->getContext()), OutStreamer(std::move(Streamer)) {
VerboseAsm = OutStreamer->isVerboseAsm();
AsmPrinter::~AsmPrinter() {
assert(!DD && Handlers.size() == NumUserHandlers &&
"Debug/EH info didn't get finalized");
if (GCMetadataPrinters) {
gcp_map_type &GCMap = getGCMap(GCMetadataPrinters);
delete &GCMap;
GCMetadataPrinters = nullptr;
bool AsmPrinter::isPositionIndependent() const {
return TM.isPositionIndependent();
/// getFunctionNumber - Return a unique ID for the current function.
unsigned AsmPrinter::getFunctionNumber() const {
return MF->getFunctionNumber();
const TargetLoweringObjectFile &AsmPrinter::getObjFileLowering() const {
return *TM.getObjFileLowering();
const DataLayout &AsmPrinter::getDataLayout() const {
return MMI->getModule()->getDataLayout();
// Do not use the cached DataLayout because some client use it without a Module
// (dsymutil, llvm-dwarfdump).
unsigned AsmPrinter::getPointerSize() const {
return TM.getPointerSize(0); // FIXME: Default address space
const MCSubtargetInfo &AsmPrinter::getSubtargetInfo() const {
assert(MF && "getSubtargetInfo requires a valid MachineFunction!");
return MF->getSubtarget<MCSubtargetInfo>();
void AsmPrinter::EmitToStreamer(MCStreamer &S, const MCInst &Inst) {
S.emitInstruction(Inst, getSubtargetInfo());
void AsmPrinter::emitInitialRawDwarfLocDirective(const MachineFunction &MF) {
if (DD) {
assert(OutStreamer->hasRawTextSupport() &&
"Expected assembly output mode.");
(void)DD->emitInitialLocDirective(MF, /*CUID=*/0);
/// getCurrentSection() - Return the current section we are emitting to.
const MCSection *AsmPrinter::getCurrentSection() const {
return OutStreamer->getCurrentSectionOnly();
void AsmPrinter::getAnalysisUsage(AnalysisUsage &AU) const {
bool AsmPrinter::doInitialization(Module &M) {
auto *MMIWP = getAnalysisIfAvailable<MachineModuleInfoWrapperPass>();
MMI = MMIWP ? &MMIWP->getMMI() : nullptr;
// Initialize TargetLoweringObjectFile.
.Initialize(OutContext, TM);
const_cast<TargetLoweringObjectFile &>(getObjFileLowering())
OutStreamer->initSections(false, *TM.getMCSubtargetInfo());
if (DisableDebugInfoPrinting)
// Emit the version-min deployment target directive if needed.
// FIXME: If we end up with a collection of these sorts of Darwin-specific
// or ELF-specific things, it may make sense to have a platform helper class
// that will work with the target helper class. For now keep it here, as the
// alternative is duplicated code in each of the target asm printers that
// use the directive, where it would need the same conditionalization
// anyway.
const Triple &Target = TM.getTargetTriple();
OutStreamer->emitVersionForTarget(Target, M.getSDKVersion());
// Allow the target to emit any magic that it wants at the start of the file.
// Very minimal debug info. It is ignored if we emit actual debug info. If we
// don't, this at least helps the user find where a global came from.
if (MAI->hasSingleParameterDotFile()) {
// .file "foo.c"
SmallString<128> FileName;
if (MAI->hasBasenameOnlyForFileDirective())
FileName = llvm::sys::path::filename(M.getSourceFileName());
FileName = M.getSourceFileName();
if (MAI->hasFourStringsDotFile()) {
const char VerStr[] =
const char VerStr[] = PACKAGE_NAME " version " PACKAGE_VERSION;
// TODO: Add timestamp and description.
OutStreamer->emitFileDirective(FileName, VerStr, "", "");
} else {
GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
assert(MI && "AsmPrinter didn't require GCModuleInfo?");
for (auto &I : *MI)
if (GCMetadataPrinter *MP = GetOrCreateGCPrinter(*I))
MP->beginAssembly(M, *MI, *this);
// Emit module-level inline asm if it exists.
if (!M.getModuleInlineAsm().empty()) {
OutStreamer->AddComment("Start of file scope inline assembly");
emitInlineAsm(M.getModuleInlineAsm() + "\n", *TM.getMCSubtargetInfo(),
OutStreamer->AddComment("End of file scope inline assembly");
if (MAI->doesSupportDebugInformation()) {
bool EmitCodeView = M.getCodeViewFlag();
if (EmitCodeView && TM.getTargetTriple().isOSWindows()) {
DbgTimerName, DbgTimerDescription,
if (!EmitCodeView || M.getDwarfVersion()) {
if (!DisableDebugInfoPrinting) {
DD = new DwarfDebug(this);
Handlers.emplace_back(std::unique_ptr<DwarfDebug>(DD), DbgTimerName,
DbgTimerDescription, DWARFGroupName,
if (M.getNamedMetadata(PseudoProbeDescMetadataName)) {
PP = new PseudoProbeHandler(this);
Handlers.emplace_back(std::unique_ptr<PseudoProbeHandler>(PP), PPTimerName,
PPTimerDescription, PPGroupName, PPGroupDescription);
switch (MAI->getExceptionHandlingType()) {
case ExceptionHandling::None:
// We may want to emit CFI for debug.
case ExceptionHandling::SjLj:
case ExceptionHandling::DwarfCFI:
case ExceptionHandling::ARM:
for (auto &F : M.getFunctionList()) {
if (getFunctionCFISectionType(F) != CFISection::None)
ModuleCFISection = getFunctionCFISectionType(F);
// If any function needsUnwindTableEntry(), it needs .eh_frame and hence
// the module needs .eh_frame. If we have found that case, we are done.
if (ModuleCFISection == CFISection::EH)
assert(MAI->getExceptionHandlingType() == ExceptionHandling::DwarfCFI ||
ModuleCFISection != CFISection::EH);
EHStreamer *ES = nullptr;
switch (MAI->getExceptionHandlingType()) {
case ExceptionHandling::None:
if (!needsCFIForDebug())
case ExceptionHandling::SjLj:
case ExceptionHandling::DwarfCFI:
ES = new DwarfCFIException(this);
case ExceptionHandling::ARM:
ES = new ARMException(this);
case ExceptionHandling::WinEH:
switch (MAI->getWinEHEncodingType()) {
default: llvm_unreachable("unsupported unwinding information encoding");
case WinEH::EncodingType::Invalid:
case WinEH::EncodingType::X86:
case WinEH::EncodingType::Itanium:
ES = new WinException(this);
case ExceptionHandling::Wasm:
ES = new WasmException(this);
case ExceptionHandling::AIX:
ES = new AIXException(this);
if (ES)
Handlers.emplace_back(std::unique_ptr<EHStreamer>(ES), EHTimerName,
EHTimerDescription, DWARFGroupName,
// Emit tables for any value of cfguard flag (i.e. cfguard=1 or cfguard=2).
if (mdconst::extract_or_null<ConstantInt>(M.getModuleFlag("cfguard")))
Handlers.emplace_back(std::make_unique<WinCFGuard>(this), CFGuardName,
CFGuardDescription, DWARFGroupName,
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription, HI.TimerGroupName,
HI.TimerGroupDescription, TimePassesIsEnabled);
return false;
static bool canBeHidden(const GlobalValue *GV, const MCAsmInfo &MAI) {
if (!MAI.hasWeakDefCanBeHiddenDirective())
return false;
return GV->canBeOmittedFromSymbolTable();
void AsmPrinter::emitLinkage(const GlobalValue *GV, MCSymbol *GVSym) const {
GlobalValue::LinkageTypes Linkage = GV->getLinkage();
switch (Linkage) {
case GlobalValue::CommonLinkage:
case GlobalValue::LinkOnceAnyLinkage:
case GlobalValue::LinkOnceODRLinkage:
case GlobalValue::WeakAnyLinkage:
case GlobalValue::WeakODRLinkage:
if (MAI->hasWeakDefDirective()) {
// .globl _foo
OutStreamer->emitSymbolAttribute(GVSym, MCSA_Global);
if (!canBeHidden(GV, *MAI))
// .weak_definition _foo
OutStreamer->emitSymbolAttribute(GVSym, MCSA_WeakDefinition);
OutStreamer->emitSymbolAttribute(GVSym, MCSA_WeakDefAutoPrivate);
} else if (MAI->avoidWeakIfComdat() && GV->hasComdat()) {
// .globl _foo
OutStreamer->emitSymbolAttribute(GVSym, MCSA_Global);
//NOTE: linkonce is handled by the section the symbol was assigned to.
} else {
// .weak _foo
OutStreamer->emitSymbolAttribute(GVSym, MCSA_Weak);
case GlobalValue::ExternalLinkage:
OutStreamer->emitSymbolAttribute(GVSym, MCSA_Global);
case GlobalValue::PrivateLinkage:
case GlobalValue::InternalLinkage:
case GlobalValue::ExternalWeakLinkage:
case GlobalValue::AvailableExternallyLinkage:
case GlobalValue::AppendingLinkage:
llvm_unreachable("Should never emit this");
llvm_unreachable("Unknown linkage type!");
void AsmPrinter::getNameWithPrefix(SmallVectorImpl<char> &Name,
const GlobalValue *GV) const {
TM.getNameWithPrefix(Name, GV, getObjFileLowering().getMangler());
MCSymbol *AsmPrinter::getSymbol(const GlobalValue *GV) const {
return TM.getSymbol(GV);
MCSymbol *AsmPrinter::getSymbolPreferLocal(const GlobalValue &GV) const {
// On ELF, use .Lfoo$local if GV is a non-interposable GlobalObject with an
// exact definion (intersection of GlobalValue::hasExactDefinition() and
// !isInterposable()). These linkages include: external, appending, internal,
// private. It may be profitable to use a local alias for external. The
// assembler would otherwise be conservative and assume a global default
// visibility symbol can be interposable, even if the code generator already
// assumed it.
if (TM.getTargetTriple().isOSBinFormatELF() && GV.canBenefitFromLocalAlias()) {
const Module &M = *GV.getParent();
if (TM.getRelocationModel() != Reloc::Static &&
M.getPIELevel() == PIELevel::Default && GV.isDSOLocal())
return getSymbolWithGlobalValueBase(&GV, "$local");
return TM.getSymbol(&GV);
/// EmitGlobalVariable - Emit the specified global variable to the .s file.
void AsmPrinter::emitGlobalVariable(const GlobalVariable *GV) {
bool IsEmuTLSVar = TM.useEmulatedTLS() && GV->isThreadLocal();
assert(!(IsEmuTLSVar && GV->hasCommonLinkage()) &&
"No emulated TLS variables in the common section");
// Never emit TLS variable xyz in emulated TLS model.
// The initialization value is in instead of xyz.
if (IsEmuTLSVar)
if (GV->hasInitializer()) {
// Check to see if this is a special global used by LLVM, if so, emit it.
if (emitSpecialLLVMGlobal(GV))
// Skip the emission of global equivalents. The symbol can be emitted later
// on by emitGlobalGOTEquivs in case it turns out to be needed.
if (GlobalGOTEquivs.count(getSymbol(GV)))
if (isVerbose()) {
// When printing the control variable __emutls_v.*,
// we don't need to print the original TLS variable name.
/*PrintType=*/false, GV->getParent());
OutStreamer->GetCommentOS() << '\n';
MCSymbol *GVSym = getSymbol(GV);
MCSymbol *EmittedSym = GVSym;
// getOrCreateEmuTLSControlSym only creates the symbol with name and default
// attributes.
// GV's or GVSym's attributes will be used for the EmittedSym.
emitVisibility(EmittedSym, GV->getVisibility(), !GV->isDeclaration());
if (!GV->hasInitializer()) // External globals require no extra code.
if (GVSym->isDefined() || GVSym->isVariable())
OutContext.reportError(SMLoc(), "symbol '" + Twine(GVSym->getName()) +
"' is already defined");
if (MAI->hasDotTypeDotSizeDirective())
OutStreamer->emitSymbolAttribute(EmittedSym, MCSA_ELF_TypeObject);
SectionKind GVKind = TargetLoweringObjectFile::getKindForGlobal(GV, TM);
const DataLayout &DL = GV->getParent()->getDataLayout();
uint64_t Size = DL.getTypeAllocSize(GV->getValueType());
// If the alignment is specified, we *must* obey it. Overaligning a global
// with a specified alignment is a prompt way to break globals emitted to
// sections and expected to be contiguous (e.g. ObjC metadata).
const Align Alignment = getGVAlignment(GV, DL);
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription,
HI.TimerGroupName, HI.TimerGroupDescription,
HI.Handler->setSymbolSize(GVSym, Size);
// Handle common symbols
if (GVKind.isCommon()) {
if (Size == 0) Size = 1; // .comm Foo, 0 is undefined, avoid it.
// .comm _foo, 42, 4
const bool SupportsAlignment =
OutStreamer->emitCommonSymbol(GVSym, Size,
SupportsAlignment ? Alignment.value() : 0);
// Determine to which section this global should be emitted.
MCSection *TheSection = getObjFileLowering().SectionForGlobal(GV, GVKind, TM);
// If we have a bss global going to a section that supports the
// zerofill directive, do so here.
if (GVKind.isBSS() && MAI->hasMachoZeroFillDirective() &&
TheSection->isVirtualSection()) {
if (Size == 0)
Size = 1; // zerofill of 0 bytes is undefined.
emitLinkage(GV, GVSym);
// .zerofill __DATA, __bss, _foo, 400, 5
OutStreamer->emitZerofill(TheSection, GVSym, Size, Alignment.value());
// If this is a BSS local symbol and we are emitting in the BSS
// section use .lcomm/.comm directive.
if (GVKind.isBSSLocal() &&
getObjFileLowering().getBSSSection() == TheSection) {
if (Size == 0)
Size = 1; // .comm Foo, 0 is undefined, avoid it.
// Use .lcomm only if it supports user-specified alignment.
// Otherwise, while it would still be correct to use .lcomm in some
// cases (e.g. when Align == 1), the external assembler might enfore
// some -unknown- default alignment behavior, which could cause
// spurious differences between external and integrated assembler.
// Prefer to simply fall back to .local / .comm in this case.
if (MAI->getLCOMMDirectiveAlignmentType() != LCOMM::NoAlignment) {
// .lcomm _foo, 42
OutStreamer->emitLocalCommonSymbol(GVSym, Size, Alignment.value());
// .local _foo
OutStreamer->emitSymbolAttribute(GVSym, MCSA_Local);
// .comm _foo, 42, 4
const bool SupportsAlignment =
OutStreamer->emitCommonSymbol(GVSym, Size,
SupportsAlignment ? Alignment.value() : 0);
// Handle thread local data for mach-o which requires us to output an
// additional structure of data and mangle the original symbol so that we
// can reference it later.
// TODO: This should become an "emit thread local global" method on TLOF.
// All of this macho specific stuff should be sunk down into TLOFMachO and
// stuff like "TLSExtraDataSection" should no longer be part of the parent
// TLOF class. This will also make it more obvious that stuff like
// MCStreamer::EmitTBSSSymbol is macho specific and only called from macho
// specific code.
if (GVKind.isThreadLocal() && MAI->hasMachoTBSSDirective()) {
// Emit the .tbss symbol
MCSymbol *MangSym =
OutContext.getOrCreateSymbol(GVSym->getName() + Twine("$tlv$init"));
if (GVKind.isThreadBSS()) {
TheSection = getObjFileLowering().getTLSBSSSection();
OutStreamer->emitTBSSSymbol(TheSection, MangSym, Size, Alignment.value());
} else if (GVKind.isThreadData()) {
emitAlignment(Alignment, GV);
// Emit the variable struct for the runtime.
MCSection *TLVSect = getObjFileLowering().getTLSExtraDataSection();
// Emit the linkage here.
emitLinkage(GV, GVSym);
// Three pointers in size:
// - __tlv_bootstrap - used to make sure support exists
// - spare pointer, used when mapped by the runtime
// - pointer to mangled symbol above with initializer
unsigned PtrSize = DL.getPointerTypeSize(GV->getType());
OutStreamer->emitIntValue(0, PtrSize);
OutStreamer->emitSymbolValue(MangSym, PtrSize);
MCSymbol *EmittedInitSym = GVSym;
emitLinkage(GV, EmittedInitSym);
emitAlignment(Alignment, GV);
MCSymbol *LocalAlias = getSymbolPreferLocal(*GV);
if (LocalAlias != EmittedInitSym)
emitGlobalConstant(GV->getParent()->getDataLayout(), GV->getInitializer());
if (MAI->hasDotTypeDotSizeDirective())
// .size foo, 42
MCConstantExpr::create(Size, OutContext));
/// Emit the directive and value for debug thread local expression
/// \p Value - The value to emit.
/// \p Size - The size of the integer (in bytes) to emit.
void AsmPrinter::emitDebugValue(const MCExpr *Value, unsigned Size) const {
OutStreamer->emitValue(Value, Size);
void AsmPrinter::emitFunctionHeaderComment() {}
/// EmitFunctionHeader - This method emits the header for the current
/// function.
void AsmPrinter::emitFunctionHeader() {
const Function &F = MF->getFunction();
if (isVerbose())
<< "-- Begin function "
<< GlobalValue::dropLLVMManglingEscape(F.getName()) << '\n';
// Print out constants referenced by the function
// Print the 'header' of function.
// If basic block sections are desired, explicitly request a unique section
// for this function's entry block.
if (MF->front().isBeginSection())
MF->setSection(getObjFileLowering().getUniqueSectionForFunction(F, TM));
MF->setSection(getObjFileLowering().SectionForGlobal(&F, TM));
if (!MAI->hasVisibilityOnlyWithLinkage())
emitVisibility(CurrentFnSym, F.getVisibility());
if (MAI->needsFunctionDescriptors())
emitLinkage(&F, CurrentFnDescSym);
emitLinkage(&F, CurrentFnSym);
if (MAI->hasFunctionAlignment())
emitAlignment(MF->getAlignment(), &F);
if (MAI->hasDotTypeDotSizeDirective())
OutStreamer->emitSymbolAttribute(CurrentFnSym, MCSA_ELF_TypeFunction);
if (F.hasFnAttribute(Attribute::Cold))
OutStreamer->emitSymbolAttribute(CurrentFnSym, MCSA_Cold);
if (isVerbose()) {
/*PrintType=*/false, F.getParent());
OutStreamer->GetCommentOS() << '\n';
// Emit the prefix data.
if (F.hasPrefixData()) {
if (MAI->hasSubsectionsViaSymbols()) {
// Preserving prefix data on platforms which use subsections-via-symbols
// is a bit tricky. Here we introduce a symbol for the prefix data
// and use the .alt_entry attribute to mark the function's real entry point
// as an alternative entry point to the prefix-data symbol.
MCSymbol *PrefixSym = OutContext.createLinkerPrivateTempSymbol();
emitGlobalConstant(F.getParent()->getDataLayout(), F.getPrefixData());
// Emit an .alt_entry directive for the actual function symbol.
OutStreamer->emitSymbolAttribute(CurrentFnSym, MCSA_AltEntry);
} else {
emitGlobalConstant(F.getParent()->getDataLayout(), F.getPrefixData());
// Emit M NOPs for -fpatchable-function-entry=N,M where M>0. We arbitrarily
// place prefix data before NOPs.
unsigned PatchableFunctionPrefix = 0;
unsigned PatchableFunctionEntry = 0;
.getAsInteger(10, PatchableFunctionPrefix);
.getAsInteger(10, PatchableFunctionEntry);
if (PatchableFunctionPrefix) {
CurrentPatchableFunctionEntrySym =
} else if (PatchableFunctionEntry) {
// May be reassigned when emitting the body, to reference the label after
// the initial BTI (AArch64) or endbr32/endbr64 (x86).
CurrentPatchableFunctionEntrySym = CurrentFnBegin;
// Emit the function descriptor. This is a virtual function to allow targets
// to emit their specific function descriptor. Right now it is only used by
// the AIX target. The PowerPC 64-bit V1 ELF target also uses function
// descriptors and should be converted to use this hook as well.
if (MAI->needsFunctionDescriptors())
// Emit the CurrentFnSym. This is a virtual function to allow targets to do
// their wild and crazy things as required.
// If the function had address-taken blocks that got deleted, then we have
// references to the dangling symbols. Emit them at the start of the function
// so that we don't get references to undefined symbols.
std::vector<MCSymbol*> DeadBlockSyms;
MMI->takeDeletedSymbolsForFunction(&F, DeadBlockSyms);
for (MCSymbol *DeadBlockSym : DeadBlockSyms) {
OutStreamer->AddComment("Address taken block that was later removed");
if (CurrentFnBegin) {
if (MAI->useAssignmentForEHBegin()) {
MCSymbol *CurPos = OutContext.createTempSymbol();
MCSymbolRefExpr::create(CurPos, OutContext));
} else {
// Emit pre-function debug and/or EH information.
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription, HI.TimerGroupName,
HI.TimerGroupDescription, TimePassesIsEnabled);
// Emit the prologue data.
if (F.hasPrologueData())
emitGlobalConstant(F.getParent()->getDataLayout(), F.getPrologueData());
/// EmitFunctionEntryLabel - Emit the label that is the entrypoint for the
/// function. This can be overridden by targets as required to do custom stuff.
void AsmPrinter::emitFunctionEntryLabel() {
// The function label could have already been emitted if two symbols end up
// conflicting due to asm renaming. Detect this and emit an error.
if (CurrentFnSym->isVariable())
report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
"' is a protected alias");
if (TM.getTargetTriple().isOSBinFormatELF()) {
MCSymbol *Sym = getSymbolPreferLocal(MF->getFunction());
if (Sym != CurrentFnSym)
/// emitComments - Pretty-print comments for instructions.
static void emitComments(const MachineInstr &MI, raw_ostream &CommentOS) {
const MachineFunction *MF = MI.getMF();
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
// Check for spills and reloads
// We assume a single instruction only has a spill or reload, not
// both.
Optional<unsigned> Size;
if ((Size = MI.getRestoreSize(TII))) {
CommentOS << *Size << "-byte Reload\n";
} else if ((Size = MI.getFoldedRestoreSize(TII))) {
if (*Size) {
if (*Size == unsigned(MemoryLocation::UnknownSize))
CommentOS << "Unknown-size Folded Reload\n";
CommentOS << *Size << "-byte Folded Reload\n";
} else if ((Size = MI.getSpillSize(TII))) {
CommentOS << *Size << "-byte Spill\n";
} else if ((Size = MI.getFoldedSpillSize(TII))) {
if (*Size) {
if (*Size == unsigned(MemoryLocation::UnknownSize))
CommentOS << "Unknown-size Folded Spill\n";
CommentOS << *Size << "-byte Folded Spill\n";
// Check for spill-induced copies
if (MI.getAsmPrinterFlag(MachineInstr::ReloadReuse))
CommentOS << " Reload Reuse\n";
/// emitImplicitDef - This method emits the specified machine instruction
/// that is an implicit def.
void AsmPrinter::emitImplicitDef(const MachineInstr *MI) const {
Register RegNo = MI->getOperand(0).getReg();
SmallString<128> Str;
raw_svector_ostream OS(Str);
OS << "implicit-def: "
<< printReg(RegNo, MF->getSubtarget().getRegisterInfo());
static void emitKill(const MachineInstr *MI, AsmPrinter &AP) {
std::string Str;
raw_string_ostream OS(Str);
OS << "kill:";
for (const MachineOperand &Op : MI->operands()) {
assert(Op.isReg() && "KILL instruction must have only register operands");
OS << ' ' << (Op.isDef() ? "def " : "killed ")
<< printReg(Op.getReg(), AP.MF->getSubtarget().getRegisterInfo());
/// emitDebugValueComment - This method handles the target-independent form
/// of DBG_VALUE, returning true if it was able to do so. A false return
/// means the target will need to handle MI in EmitInstruction.
static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
// This code handles only the 4-operand target-independent form.
if (MI->isNonListDebugValue() && MI->getNumOperands() != 4)
return false;
SmallString<128> Str;
raw_svector_ostream OS(Str);
const DILocalVariable *V = MI->getDebugVariable();
if (auto *SP = dyn_cast<DISubprogram>(V->getScope())) {
StringRef Name = SP->getName();
if (!Name.empty())
OS << Name << ":";
OS << V->getName();
OS << " <- ";
const DIExpression *Expr = MI->getDebugExpression();
if (Expr->getNumElements()) {
OS << '[';
ListSeparator LS;
for (auto Op : Expr->expr_ops()) {
OS << LS << dwarf::OperationEncodingString(Op.getOp());
for (unsigned I = 0; I < Op.getNumArgs(); ++I)
OS << ' ' << Op.getArg(I);
OS << "] ";
// Register or immediate value. Register 0 means undef.
for (const MachineOperand &Op : MI->debug_operands()) {
if (&Op != MI->debug_operands().begin())
OS << ", ";
switch (Op.getType()) {
case MachineOperand::MO_FPImmediate: {
APFloat APF = APFloat(Op.getFPImm()->getValueAPF());
Type *ImmTy = Op.getFPImm()->getType();
if (ImmTy->isBFloatTy() || ImmTy->isHalfTy() || ImmTy->isFloatTy() ||
ImmTy->isDoubleTy()) {
OS << APF.convertToDouble();
} else {
// There is no good way to print long double. Convert a copy to
// double. Ah well, it's only a comment.
bool ignored;
APF.convert(APFloat::IEEEdouble(), APFloat::rmNearestTiesToEven,
OS << "(long double) " << APF.convertToDouble();
case MachineOperand::MO_Immediate: {
OS << Op.getImm();
case MachineOperand::MO_CImmediate: {
Op.getCImm()->getValue().print(OS, false /*isSigned*/);
case MachineOperand::MO_TargetIndex: {
OS << "!target-index(" << Op.getIndex() << "," << Op.getOffset() << ")";
// NOTE: Want this comment at start of line, don't emit with AddComment.
case MachineOperand::MO_Register:
case MachineOperand::MO_FrameIndex: {
Register Reg;
Optional<StackOffset> Offset;
if (Op.isReg()) {
Reg = Op.getReg();
} else {
const TargetFrameLowering *TFI =
Offset = TFI->getFrameIndexReference(*AP.MF, Op.getIndex(), Reg);
if (!Reg) {
// Suppress offset, it is not meaningful here.
OS << "undef";
// The second operand is only an offset if it's an immediate.
if (MI->isIndirectDebugValue())
Offset = StackOffset::getFixed(MI->getDebugOffset().getImm());
if (Offset)
OS << '[';
OS << printReg(Reg, AP.MF->getSubtarget().getRegisterInfo());
if (Offset)
OS << '+' << Offset->getFixed() << ']';
llvm_unreachable("Unknown operand type");
// NOTE: Want this comment at start of line, don't emit with AddComment.
return true;
/// This method handles the target-independent form of DBG_LABEL, returning
/// true if it was able to do so. A false return means the target will need
/// to handle MI in EmitInstruction.
static bool emitDebugLabelComment(const MachineInstr *MI, AsmPrinter &AP) {
if (MI->getNumOperands() != 1)
return false;
SmallString<128> Str;
raw_svector_ostream OS(Str);
const DILabel *V = MI->getDebugLabel();
if (auto *SP = dyn_cast<DISubprogram>(
V->getScope()->getNonLexicalBlockFileScope())) {
StringRef Name = SP->getName();
if (!Name.empty())
OS << Name << ":";
OS << V->getName();
// NOTE: Want this comment at start of line, don't emit with AddComment.
return true;
AsmPrinter::getFunctionCFISectionType(const Function &F) const {
// Ignore functions that won't get emitted.
if (F.isDeclarationForLinker())
return CFISection::None;
if (MAI->getExceptionHandlingType() == ExceptionHandling::DwarfCFI &&
return CFISection::EH;
if (MMI->hasDebugInfo() || TM.Options.ForceDwarfFrameSection)
return CFISection::Debug;
return CFISection::None;
AsmPrinter::getFunctionCFISectionType(const MachineFunction &MF) const {
return getFunctionCFISectionType(MF.getFunction());
bool AsmPrinter::needsSEHMoves() {
return MAI->usesWindowsCFI() && MF->getFunction().needsUnwindTableEntry();
bool AsmPrinter::needsCFIForDebug() const {
return MAI->getExceptionHandlingType() == ExceptionHandling::None &&
MAI->doesUseCFIForDebug() && ModuleCFISection == CFISection::Debug;
void AsmPrinter::emitCFIInstruction(const MachineInstr &MI) {
ExceptionHandling ExceptionHandlingType = MAI->getExceptionHandlingType();
if (!needsCFIForDebug() &&
ExceptionHandlingType != ExceptionHandling::DwarfCFI &&
ExceptionHandlingType != ExceptionHandling::ARM)
if (getFunctionCFISectionType(*MF) == CFISection::None)
// If there is no "real" instruction following this CFI instruction, skip
// emitting it; it would be beyond the end of the function's FDE range.
auto *MBB = MI.getParent();
auto I = std::next(MI.getIterator());
while (I != MBB->end() && I->isTransient())
if (I == MBB->instr_end() &&
MBB->getReverseIterator() == MBB->getParent()->rbegin())
const std::vector<MCCFIInstruction> &Instrs = MF->getFrameInstructions();
unsigned CFIIndex = MI.getOperand(0).getCFIIndex();
const MCCFIInstruction &CFI = Instrs[CFIIndex];
void AsmPrinter::emitFrameAlloc(const MachineInstr &MI) {
// The operands are the MCSymbol and the frame offset of the allocation.
MCSymbol *FrameAllocSym = MI.getOperand(0).getMCSymbol();
int FrameOffset = MI.getOperand(1).getImm();
// Emit a symbol assignment.
MCConstantExpr::create(FrameOffset, OutContext));
/// Returns the BB metadata to be emitted in the .llvm_bb_addr_map section for a
/// given basic block. This can be used to capture more precise profile
/// information. We use the last 4 bits (LSBs) to encode the following
/// information:
/// * (1): set if return block (ret or tail call).
/// * (2): set if ends with a tail call.
/// * (3): set if exception handling (EH) landing pad.
/// * (4): set if the block can fall through to its next.
/// The remaining bits are zero.
static unsigned getBBAddrMapMetadata(const MachineBasicBlock &MBB) {
const TargetInstrInfo *TII = MBB.getParent()->getSubtarget().getInstrInfo();
return ((unsigned)MBB.isReturnBlock()) |
((!MBB.empty() && TII->isTailCall(MBB.back())) << 1) |
(MBB.isEHPad() << 2) |
(const_cast<MachineBasicBlock &>(MBB).canFallThrough() << 3);
void AsmPrinter::emitBBAddrMapSection(const MachineFunction &MF) {
MCSection *BBAddrMapSection =
assert(BBAddrMapSection && ".llvm_bb_addr_map section is not initialized.");
const MCSymbol *FunctionSymbol = getFunctionBegin();
OutStreamer->emitSymbolValue(FunctionSymbol, getPointerSize());
// Emit the total number of basic blocks in this function.
// Emit BB Information for each basic block in the funciton.
for (const MachineBasicBlock &MBB : MF) {
const MCSymbol *MBBSymbol =
MBB.isEntryBlock() ? FunctionSymbol : MBB.getSymbol();
// Emit the basic block offset.
emitLabelDifferenceAsULEB128(MBBSymbol, FunctionSymbol);
// Emit the basic block size. When BBs have alignments, their size cannot
// always be computed from their offsets.
emitLabelDifferenceAsULEB128(MBB.getEndSymbol(), MBBSymbol);
void AsmPrinter::emitPseudoProbe(const MachineInstr &MI) {
auto GUID = MI.getOperand(0).getImm();
auto Index = MI.getOperand(1).getImm();
auto Type = MI.getOperand(2).getImm();
auto Attr = MI.getOperand(3).getImm();
DILocation *DebugLoc = MI.getDebugLoc();
PP->emitPseudoProbe(GUID, Index, Type, Attr, DebugLoc);
void AsmPrinter::emitStackSizeSection(const MachineFunction &MF) {
if (!MF.getTarget().Options.EmitStackSizeSection)
MCSection *StackSizeSection =
if (!StackSizeSection)
const MachineFrameInfo &FrameInfo = MF.getFrameInfo();
// Don't emit functions with dynamic stack allocations.
if (FrameInfo.hasVarSizedObjects())
const MCSymbol *FunctionSymbol = getFunctionBegin();
uint64_t StackSize = FrameInfo.getStackSize();
OutStreamer->emitSymbolValue(FunctionSymbol, TM.getProgramPointerSize());
void AsmPrinter::emitStackUsage(const MachineFunction &MF) {
const std::string &OutputFilename = MF.getTarget().Options.StackUsageOutput;
// OutputFilename empty implies -fstack-usage is not passed.
if (OutputFilename.empty())
const MachineFrameInfo &FrameInfo = MF.getFrameInfo();
uint64_t StackSize = FrameInfo.getStackSize();
if (StackUsageStream == nullptr) {
std::error_code EC;
StackUsageStream =
std::make_unique<raw_fd_ostream>(OutputFilename, EC, sys::fs::OF_Text);
if (EC) {
errs() << "Could not open file: " << EC.message();
*StackUsageStream << MF.getFunction().getParent()->getName();
if (const DISubprogram *DSP = MF.getFunction().getSubprogram())
*StackUsageStream << ':' << DSP->getLine();
*StackUsageStream << ':' << MF.getName() << '\t' << StackSize << '\t';
if (FrameInfo.hasVarSizedObjects())
*StackUsageStream << "dynamic\n";
*StackUsageStream << "static\n";
static bool needFuncLabelsForEHOrDebugInfo(const MachineFunction &MF) {
MachineModuleInfo &MMI = MF.getMMI();
if (!MF.getLandingPads().empty() || MF.hasEHFunclets() || MMI.hasDebugInfo())
return true;
// We might emit an EH table that uses function begin and end labels even if
// we don't have any landingpads.
if (!MF.getFunction().hasPersonalityFn())
return false;
return !isNoOpWithoutInvoke(
/// EmitFunctionBody - This method emits the body and trailer for a
/// function.
void AsmPrinter::emitFunctionBody() {
// Emit target-specific gunk before the function body.
if (isVerbose()) {
// Get MachineDominatorTree or compute it on the fly if it's unavailable
MDT = getAnalysisIfAvailable<MachineDominatorTree>();
if (!MDT) {
OwnedMDT = std::make_unique<MachineDominatorTree>();
MDT = OwnedMDT.get();
// Get MachineLoopInfo or compute it on the fly if it's unavailable
MLI = getAnalysisIfAvailable<MachineLoopInfo>();
if (!MLI) {
OwnedMLI = std::make_unique<MachineLoopInfo>();
MLI = OwnedMLI.get();
// Print out code for the function.
bool HasAnyRealCode = false;
int NumInstsInFunction = 0;
bool CanDoExtraAnalysis = ORE->allowExtraAnalysis(DEBUG_TYPE);
for (auto &MBB : *MF) {
// Print a label for the basic block.
DenseMap<StringRef, unsigned> MnemonicCounts;
for (auto &MI : MBB) {
// Print the assembly for the instruction.
if (!MI.isPosition() && !MI.isImplicitDef() && !MI.isKill() &&
!MI.isDebugInstr()) {
HasAnyRealCode = true;
// If there is a pre-instruction symbol, emit a label for it here.
if (MCSymbol *S = MI.getPreInstrSymbol())
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription, HI.TimerGroupName,
HI.TimerGroupDescription, TimePassesIsEnabled);
if (isVerbose())
emitComments(MI, OutStreamer->GetCommentOS());
switch (MI.getOpcode()) {
case TargetOpcode::CFI_INSTRUCTION:
case TargetOpcode::LOCAL_ESCAPE:
case TargetOpcode::ANNOTATION_LABEL:
case TargetOpcode::EH_LABEL:
case TargetOpcode::GC_LABEL:
case TargetOpcode::INLINEASM:
case TargetOpcode::INLINEASM_BR:
case TargetOpcode::DBG_VALUE:
case TargetOpcode::DBG_VALUE_LIST:
if (isVerbose()) {
if (!emitDebugValueComment(&MI, *this))
case TargetOpcode::DBG_INSTR_REF:
// This instruction reference will have been resolved to a machine
// location, and a nearby DBG_VALUE created. We can safely ignore
// the instruction reference.
case TargetOpcode::DBG_PHI:
// This instruction is only used to label a program point, it's purely
// meta information.
case TargetOpcode::DBG_LABEL:
if (isVerbose()) {
if (!emitDebugLabelComment(&MI, *this))
case TargetOpcode::IMPLICIT_DEF:
if (isVerbose()) emitImplicitDef(&MI);
case TargetOpcode::KILL:
if (isVerbose()) emitKill(&MI, *this);
case TargetOpcode::PSEUDO_PROBE:
case TargetOpcode::ARITH_FENCE:
if (isVerbose())
if (CanDoExtraAnalysis) {
auto Name = OutStreamer->getMnemonic(MCI);
auto I = MnemonicCounts.insert({Name, 0u});
// If there is a post-instruction symbol, emit a label for it here.
if (MCSymbol *S = MI.getPostInstrSymbol())
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription, HI.TimerGroupName,
HI.TimerGroupDescription, TimePassesIsEnabled);
// We must emit temporary symbol for the end of this basic block, if either
// we have BBLabels enabled or if this basic blocks marks the end of a
// section.
if (MF->hasBBLabels() ||
(MAI->hasDotTypeDotSizeDirective() && MBB.isEndSection()))
if (MBB.isEndSection()) {
// The size directive for the section containing the entry block is
// handled separately by the function section.
if (!MBB.sameSection(&MF->front())) {
if (MAI->hasDotTypeDotSizeDirective()) {
// Emit the size directive for the basic block section.
const MCExpr *SizeExp = MCBinaryExpr::createSub(
MCSymbolRefExpr::create(MBB.getEndSymbol(), OutContext),
MCSymbolRefExpr::create(CurrentSectionBeginSym, OutContext),
OutStreamer->emitELFSize(CurrentSectionBeginSym, SizeExp);
MBBSectionRanges[MBB.getSectionIDNum()] =
MBBSectionRange{CurrentSectionBeginSym, MBB.getEndSymbol()};
if (CanDoExtraAnalysis) {
// Skip empty blocks.
if (MBB.empty())
MachineOptimizationRemarkAnalysis R(DEBUG_TYPE, "InstructionMix",
MBB.begin()->getDebugLoc(), &MBB);
// Generate instruction mix remark. First, sort counts in descending order
// by count and name.
SmallVector<std::pair<StringRef, unsigned>, 128> MnemonicVec;
for (auto &KV : MnemonicCounts)
MnemonicVec.emplace_back(KV.first, KV.second);
sort(MnemonicVec, [](const std::pair<StringRef, unsigned> &A,
const std::pair<StringRef, unsigned> &B) {
if (A.second > B.second)
return true;
if (A.second == B.second)
return StringRef(A.first) < StringRef(B.first);
return false;
R << "BasicBlock: " << ore::NV("BasicBlock", MBB.getName()) << "\n";
for (auto &KV : MnemonicVec) {
auto Name = (Twine("INST_") + getToken(KV.first.trim()).first).str();
R << KV.first << ": " << ore::NV(Name, KV.second) << "\n";
EmittedInsts += NumInstsInFunction;
MachineOptimizationRemarkAnalysis R(DEBUG_TYPE, "InstructionCount",
R << ore::NV("NumInstructions", NumInstsInFunction)
<< " instructions in function";
// If the function is empty and the object file uses .subsections_via_symbols,
// then we need to emit *something* to the function body to prevent the
// labels from collapsing together. Just emit a noop.
// Similarly, don't emit empty functions on Windows either. It can lead to
// duplicate entries (two functions with the same RVA) in the Guard CF Table
// after linking, causing the kernel not to load the binary:
// FIXME: Hide this behind some API in e.g. MCAsmInfo or MCTargetStreamer.
const Triple &TT = TM.getTargetTriple();
if (!HasAnyRealCode && (MAI->hasSubsectionsViaSymbols() ||
(TT.isOSWindows() && TT.isOSBinFormatCOFF()))) {
MCInst Noop = MF->getSubtarget().getInstrInfo()->getNop();
// Targets can opt-out of emitting the noop here by leaving the opcode
// unspecified.
if (Noop.getOpcode()) {
OutStreamer->AddComment("avoids zero-length function");
// Switch to the original section in case basic block sections was used.
const Function &F = MF->getFunction();
for (const auto &BB : F) {
if (!BB.hasAddressTaken())
MCSymbol *Sym = GetBlockAddressSymbol(&BB);
if (Sym->isDefined())
OutStreamer->AddComment("Address of block that was removed by CodeGen");
// Emit target-specific gunk after the function body.
if (needFuncLabelsForEHOrDebugInfo(*MF) ||
MAI->hasDotTypeDotSizeDirective()) {
// Create a symbol for the end of function.
CurrentFnEnd = createTempSymbol("func_end");
// If the target wants a .size directive for the size of the function, emit
// it.
if (MAI->hasDotTypeDotSizeDirective()) {
// We can get the size as difference between the function label and the
// temp label.
const MCExpr *SizeExp = MCBinaryExpr::createSub(
MCSymbolRefExpr::create(CurrentFnEnd, OutContext),
MCSymbolRefExpr::create(CurrentFnSymForSize, OutContext), OutContext);
OutStreamer->emitELFSize(CurrentFnSym, SizeExp);
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription, HI.TimerGroupName,
HI.TimerGroupDescription, TimePassesIsEnabled);
MBBSectionRanges[MF->front().getSectionIDNum()] =
MBBSectionRange{CurrentFnBegin, CurrentFnEnd};
// Print out jump tables referenced by the function.
// Emit post-function debug and/or EH information.
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription, HI.TimerGroupName,
HI.TimerGroupDescription, TimePassesIsEnabled);
// Emit section containing BB address offsets and their metadata, when
// BB labels are requested for this function. Skip empty functions.
if (MF->hasBBLabels() && HasAnyRealCode)
// Emit section containing stack size metadata.
// Emit .su file containing function stack size information.
if (isVerbose())
OutStreamer->GetCommentOS() << "-- End function\n";
/// Compute the number of Global Variables that uses a Constant.
static unsigned getNumGlobalVariableUses(const Constant *C) {
if (!C)
return 0;
if (isa<GlobalVariable>(C))
return 1;
unsigned NumUses = 0;
for (auto *CU : C->users())
NumUses += getNumGlobalVariableUses(dyn_cast<Constant>(CU));
return NumUses;
/// Only consider global GOT equivalents if at least one user is a
/// cstexpr inside an initializer of another global variables. Also, don't
/// handle cstexpr inside instructions. During global variable emission,
/// candidates are skipped and are emitted later in case at least one cstexpr
/// isn't replaced by a PC relative GOT entry access.
static bool isGOTEquivalentCandidate(const GlobalVariable *GV,
unsigned &NumGOTEquivUsers) {
// Global GOT equivalents are unnamed private globals with a constant
// pointer initializer to another global symbol. They must point to a
// GlobalVariable or Function, i.e., as GlobalValue.
if (!GV->hasGlobalUnnamedAddr() || !GV->hasInitializer() ||
!GV->isConstant() || !GV->isDiscardableIfUnused() ||
return false;
// To be a got equivalent, at least one of its users need to be a constant
// expression used by another global variable.
for (auto *U : GV->users())
NumGOTEquivUsers += getNumGlobalVariableUses(dyn_cast<Constant>(U));
return NumGOTEquivUsers > 0;
/// Unnamed constant global variables solely contaning a pointer to
/// another globals variable is equivalent to a GOT table entry; it contains the
/// the address of another symbol. Optimize it and replace accesses to these
/// "GOT equivalents" by using the GOT entry for the final global instead.
/// Compute GOT equivalent candidates among all global variables to avoid
/// emitting them if possible later on, after it use is replaced by a GOT entry
/// access.
void AsmPrinter::computeGlobalGOTEquivs(Module &M) {
if (!getObjFileLowering().supportIndirectSymViaGOTPCRel())
for (const auto &G : M.globals()) {
unsigned NumGOTEquivUsers = 0;
if (!isGOTEquivalentCandidate(&G, NumGOTEquivUsers))
const MCSymbol *GOTEquivSym = getSymbol(&G);
GlobalGOTEquivs[GOTEquivSym] = std::make_pair(&G, NumGOTEquivUsers);
/// Constant expressions using GOT equivalent globals may not be eligible
/// for PC relative GOT entry conversion, in such cases we need to emit such
/// globals we previously omitted in EmitGlobalVariable.
void AsmPrinter::emitGlobalGOTEquivs() {
if (!getObjFileLowering().supportIndirectSymViaGOTPCRel())
SmallVector<const GlobalVariable *, 8> FailedCandidates;
for (auto &I : GlobalGOTEquivs) {
const GlobalVariable *GV = I.second.first;
unsigned Cnt = I.second.second;
if (Cnt)
for (auto *GV : FailedCandidates)
void AsmPrinter::emitGlobalAlias(Module &M, const GlobalAlias &GA) {
MCSymbol *Name = getSymbol(&GA);
bool IsFunction = GA.getValueType()->isFunctionTy();
// Treat bitcasts of functions as functions also. This is important at least
// on WebAssembly where object and function addresses can't alias each other.
if (!IsFunction)
if (auto *CE = dyn_cast<ConstantExpr>(GA.getAliasee()))
if (CE->getOpcode() == Instruction::BitCast)
IsFunction =
// AIX's assembly directive `.set` is not usable for aliasing purpose,
// so AIX has to use the extra-label-at-definition strategy. At this
// point, all the extra label is emitted, we just have to emit linkage for
// those labels.
if (TM.getTargetTriple().isOSBinFormatXCOFF()) {
assert(MAI->hasVisibilityOnlyWithLinkage() &&
"Visibility should be handled with emitLinkage() on AIX.");
emitLinkage(&GA, Name);
// If it's a function, also emit linkage for aliases of function entry
// point.
if (IsFunction)
getObjFileLowering().getFunctionEntryPointSymbol(&GA, TM));
if (GA.hasExternalLinkage() || !MAI->getWeakRefDirective())
OutStreamer->emitSymbolAttribute(Name, MCSA_Global);
else if (GA.hasWeakLinkage() || GA.hasLinkOnceLinkage())
OutStreamer->emitSymbolAttribute(Name, MCSA_WeakReference);
assert(GA.hasLocalLinkage() && "Invalid alias linkage");
// Set the symbol type to function if the alias has a function type.
// This affects codegen when the aliasee is not a function.
if (IsFunction)
OutStreamer->emitSymbolAttribute(Name, MCSA_ELF_TypeFunction);
emitVisibility(Name, GA.getVisibility());
const MCExpr *Expr = lowerConstant(GA.getAliasee());
if (MAI->hasAltEntry() && isa<MCBinaryExpr>(Expr))
OutStreamer->emitSymbolAttribute(Name, MCSA_AltEntry);
// Emit the directives as assignments aka .set:
OutStreamer->emitAssignment(Name, Expr);
MCSymbol *LocalAlias = getSymbolPreferLocal(GA);
if (LocalAlias != Name)
OutStreamer->emitAssignment(LocalAlias, Expr);
// If the aliasee does not correspond to a symbol in the output, i.e. the
// alias is not of an object or the aliased object is private, then set the
// size of the alias symbol from the type of the alias. We don't do this in
// other situations as the alias and aliasee having differing types but same
// size may be intentional.
const GlobalObject *BaseObject = GA.getAliaseeObject();
if (MAI->hasDotTypeDotSizeDirective() && GA.getValueType()->isSized() &&
(!BaseObject || BaseObject->hasPrivateLinkage())) {
const DataLayout &DL = M.getDataLayout();
uint64_t Size = DL.getTypeAllocSize(GA.getValueType());
OutStreamer->emitELFSize(Name, MCConstantExpr::create(Size, OutContext));
void AsmPrinter::emitGlobalIFunc(Module &M, const GlobalIFunc &GI) {
assert(!TM.getTargetTriple().isOSBinFormatXCOFF() &&
"IFunc is not supported on AIX.");
MCSymbol *Name = getSymbol(&GI);
if (GI.hasExternalLinkage() || !MAI->getWeakRefDirective())
OutStreamer->emitSymbolAttribute(Name, MCSA_Global);
else if (GI.hasWeakLinkage() || GI.hasLinkOnceLinkage())
OutStreamer->emitSymbolAttribute(Name, MCSA_WeakReference);
assert(GI.hasLocalLinkage() && "Invalid ifunc linkage");
OutStreamer->emitSymbolAttribute(Name, MCSA_ELF_TypeIndFunction);
emitVisibility(Name, GI.getVisibility());
// Emit the directives as assignments aka .set:
const MCExpr *Expr = lowerConstant(GI.getResolver());
OutStreamer->emitAssignment(Name, Expr);
MCSymbol *LocalAlias = getSymbolPreferLocal(GI);
if (LocalAlias != Name)
OutStreamer->emitAssignment(LocalAlias, Expr);
void AsmPrinter::emitRemarksSection(remarks::RemarkStreamer &RS) {
if (!RS.needsSection())
remarks::RemarkSerializer &RemarkSerializer = RS.getSerializer();
Optional<SmallString<128>> Filename;
if (Optional<StringRef> FilenameRef = RS.getFilename()) {
Filename = *FilenameRef;
assert(!Filename->empty() && "The filename can't be empty.");
std::string Buf;
raw_string_ostream OS(Buf);
std::unique_ptr<remarks::MetaSerializer> MetaSerializer =
Filename ? RemarkSerializer.metaSerializer(OS, Filename->str())
: RemarkSerializer.metaSerializer(OS);
// Switch to the remarks section.
MCSection *RemarksSection =
bool AsmPrinter::doFinalization(Module &M) {
// Set the MachineFunction to nullptr so that we can catch attempted
// accesses to MF specific features at the module level and so that
// we can conditionalize accesses based on whether or not it is nullptr.
MF = nullptr;
// Gather all GOT equivalent globals in the module. We really need two
// passes over the globals: one to compute and another to avoid its emission
// in EmitGlobalVariable, otherwise we would not be able to handle cases
// where the got equivalent shows up before its use.
// Emit global variables.
for (const auto &G : M.globals())
// Emit remaining GOT equivalent globals.
const TargetLoweringObjectFile &TLOF = getObjFileLowering();
// Emit linkage(XCOFF) and visibility info for declarations
for (const Function &F : M) {
if (!F.isDeclarationForLinker())
MCSymbol *Name = getSymbol(&F);
// Function getSymbol gives us the function descriptor symbol for XCOFF.
if (!TM.getTargetTriple().isOSBinFormatXCOFF()) {
GlobalValue::VisibilityTypes V = F.getVisibility();
if (V == GlobalValue::DefaultVisibility)
emitVisibility(Name, V, false);
if (F.isIntrinsic())
// Handle the XCOFF case.
// Variable `Name` is the function descriptor symbol (see above). Get the
// function entry point symbol.
MCSymbol *FnEntryPointSym = TLOF.getFunctionEntryPointSymbol(&F, TM);
// Emit linkage for the function entry point.
emitLinkage(&F, FnEntryPointSym);
// Emit linkage for the function descriptor.
emitLinkage(&F, Name);
// Emit the remarks section contents.
// FIXME: Figure out when is the safest time to emit this section. It should
// not come after debug info.
if (remarks::RemarkStreamer *RS = M.getContext().getMainRemarkStreamer())
TLOF.emitModuleMetadata(*OutStreamer, M);
if (TM.getTargetTriple().isOSBinFormatELF()) {
MachineModuleInfoELF &MMIELF = MMI->getObjFileInfo<MachineModuleInfoELF>();
// Output stubs for external and common global variables.
MachineModuleInfoELF::SymbolListTy Stubs = MMIELF.GetGVStubList();
if (!Stubs.empty()) {
const DataLayout &DL = M.getDataLayout();
for (const auto &Stub : Stubs) {
if (TM.getTargetTriple().isOSBinFormatCOFF()) {
MachineModuleInfoCOFF &MMICOFF =
// Output stubs for external and common global variables.
MachineModuleInfoCOFF::SymbolListTy Stubs = MMICOFF.GetGVStubList();
if (!Stubs.empty()) {
const DataLayout &DL = M.getDataLayout();
for (const auto &Stub : Stubs) {
SmallString<256> SectionName = StringRef(".rdata$");
SectionName += Stub.first->getName();
SectionKind::getReadOnly(), Stub.first->getName(),
OutStreamer->emitSymbolAttribute(Stub.first, MCSA_Global);
// This needs to happen before emitting debug information since that can end
// arbitrary sections.
if (auto *TS = OutStreamer->getTargetStreamer())
// Finalize debug and EH information.
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription, HI.TimerGroupName,
HI.TimerGroupDescription, TimePassesIsEnabled);
// This deletes all the ephemeral handlers that AsmPrinter added, while
// keeping all the user-added handlers alive until the AsmPrinter is
// destroyed.
Handlers.erase(Handlers.begin() + NumUserHandlers, Handlers.end());
DD = nullptr;
// If the target wants to know about weak references, print them all.
if (MAI->getWeakRefDirective()) {
// FIXME: This is not lazy, it would be nice to only print weak references
// to stuff that is actually used. Note that doing so would require targets
// to notice uses in operands (due to constant exprs etc). This should
// happen with the MC stuff eventually.
// Print out module-level global objects here.
for (const auto &GO : M.global_objects()) {
if (!GO.hasExternalWeakLinkage())
OutStreamer->emitSymbolAttribute(getSymbol(&GO), MCSA_WeakReference);
// Print aliases in topological order, that is, for each alias a = b,
// b must be printed before a.
// This is because on some targets (e.g. PowerPC) linker expects aliases in
// such an order to generate correct TOC information.
SmallVector<const GlobalAlias *, 16> AliasStack;
SmallPtrSet<const GlobalAlias *, 16> AliasVisited;
for (const auto &Alias : M.aliases()) {
for (const GlobalAlias *Cur = &Alias; Cur;
Cur = dyn_cast<GlobalAlias>(Cur->getAliasee())) {
if (!AliasVisited.insert(Cur).second)
for (const GlobalAlias *AncestorAlias : llvm::reverse(AliasStack))
emitGlobalAlias(M, *AncestorAlias);
for (const auto &IFunc : M.ifuncs())
emitGlobalIFunc(M, IFunc);
GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
assert(MI && "AsmPrinter didn't require GCModuleInfo?");
for (GCModuleInfo::iterator I = MI->end(), E = MI->begin(); I != E; )
if (GCMetadataPrinter *MP = GetOrCreateGCPrinter(**--I))
MP->finishAssembly(M, *MI, *this);
// Emit llvm.ident metadata in an '.ident' directive.
// Emit bytes for llvm.commandline metadata.
// Emit __morestack address if needed for indirect calls.
if (MMI->usesMorestackAddr()) {
Align Alignment(1);
MCSection *ReadOnlySection = getObjFileLowering().getSectionForConstant(
getDataLayout(), SectionKind::getReadOnly(),
/*C=*/nullptr, Alignment);
MCSymbol *AddrSymbol =
unsigned PtrSize = MAI->getCodePointerSize();
// Emit .note.GNU-split-stack and .note.GNU-no-split-stack sections if
// split-stack is used.
if (TM.getTargetTriple().isOSBinFormatELF() && MMI->hasSplitStack()) {
OutContext.getELFSection(".note.GNU-split-stack", ELF::SHT_PROGBITS, 0));
if (MMI->hasNosplitStack())
OutContext.getELFSection(".note.GNU-no-split-stack", ELF::SHT_PROGBITS, 0));
// If we don't have any trampolines, then we don't require stack memory
// to be executable. Some targets have a directive to declare this.
Function *InitTrampolineIntrinsic = M.getFunction("llvm.init.trampoline");
if (!InitTrampolineIntrinsic || InitTrampolineIntrinsic->use_empty())
if (MCSection *S = MAI->getNonexecutableStackSection(OutContext))
if (TM.Options.EmitAddrsig) {
// Emit address-significance attributes for all globals.
for (const GlobalValue &GV : M.global_values()) {
if (!GV.use_empty() && !GV.isTransitiveUsedByMetadataOnly() &&
!GV.isThreadLocal() && !GV.hasDLLImportStorageClass() &&
!GV.getName().startswith("llvm.") && !GV.hasAtLeastLocalUnnamedAddr())
// Emit symbol partition specifications (ELF only).
if (TM.getTargetTriple().isOSBinFormatELF()) {
unsigned UniqueID = 0;
for (const GlobalValue &GV : M.global_values()) {
if (!GV.hasPartition() || GV.isDeclarationForLinker() ||
GV.getVisibility() != GlobalValue::DefaultVisibility)
OutContext.getELFSection(".llvm_sympart", ELF::SHT_LLVM_SYMPART, 0, 0,
"", false, ++UniqueID, nullptr));
MCSymbolRefExpr::create(getSymbol(&GV), OutContext),
// Allow the target to emit any magic that it wants at the end of the file,
// after everything else has gone out.
MMI = nullptr;
return false;
MCSymbol *AsmPrinter::getMBBExceptionSym(const MachineBasicBlock &MBB) {
auto Res = MBBSectionExceptionSyms.try_emplace(MBB.getSectionIDNum());
if (Res.second)
Res.first->second = createTempSymbol("exception");
return Res.first->second;
void AsmPrinter::SetupMachineFunction(MachineFunction &MF) {
this->MF = &MF;
const Function &F = MF.getFunction();
// Get the function symbol.
if (!MAI->needsFunctionDescriptors()) {
CurrentFnSym = getSymbol(&MF.getFunction());
} else {
assert(TM.getTargetTriple().isOSAIX() &&
"Only AIX uses the function descriptor hooks.");
// AIX is unique here in that the name of the symbol emitted for the
// function body does not have the same name as the source function's
// C-linkage name.
assert(CurrentFnDescSym && "The function descriptor symbol needs to be"
" initalized first.");
// Get the function entry point symbol.
CurrentFnSym = getObjFileLowering().getFunctionEntryPointSymbol(&F, TM);
CurrentFnSymForSize = CurrentFnSym;
CurrentFnBegin = nullptr;
CurrentSectionBeginSym = nullptr;
bool NeedsLocalForSize = MAI->needsLocalForSize();
if (F.hasFnAttribute("patchable-function-entry") ||
F.hasFnAttribute("function-instrument") ||
F.hasFnAttribute("xray-instruction-threshold") ||
needFuncLabelsForEHOrDebugInfo(MF) || NeedsLocalForSize ||
MF.getTarget().Options.EmitStackSizeSection || MF.hasBBLabels()) {
CurrentFnBegin = createTempSymbol("func_begin");
if (NeedsLocalForSize)
CurrentFnSymForSize = CurrentFnBegin;
ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE();
namespace {
// Keep track the alignment, constpool entries per Section.
struct SectionCPs {
MCSection *S;
Align Alignment;
SmallVector<unsigned, 4> CPEs;
SectionCPs(MCSection *s, Align a) : S(s), Alignment(a) {}
} // end anonymous namespace
/// EmitConstantPool - Print to the current output stream assembly
/// representations of the constants in the constant pool MCP. This is
/// used to print out constants which have been "spilled to memory" by
/// the code generator.
void AsmPrinter::emitConstantPool() {
const MachineConstantPool *MCP = MF->getConstantPool();
const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants();
if (CP.empty()) return;
// Calculate sections for constant pool entries. We collect entries to go into
// the same section together to reduce amount of section switch statements.
SmallVector<SectionCPs, 4> CPSections;
for (unsigned i = 0, e = CP.size(); i != e; ++i) {
const MachineConstantPoolEntry &CPE = CP[i];
Align Alignment = CPE.getAlign();
SectionKind Kind = CPE.getSectionKind(&getDataLayout());
const Constant *C = nullptr;
if (!CPE.isMachineConstantPoolEntry())
C = CPE.Val.ConstVal;
MCSection *S = getObjFileLowering().getSectionForConstant(
getDataLayout(), Kind, C, Alignment);
// The number of sections are small, just do a linear search from the
// last section to the first.
bool Found = false;
unsigned SecIdx = CPSections.size();
while (SecIdx != 0) {
if (CPSections[--SecIdx].S == S) {
Found = true;
if (!Found) {
SecIdx = CPSections.size();
CPSections.push_back(SectionCPs(S, Alignment));
if (Alignment > CPSections[SecIdx].Alignment)
CPSections[SecIdx].Alignment = Alignment;
// Now print stuff into the calculated sections.
const MCSection *CurSection = nullptr;
unsigned Offset = 0;
for (unsigned i = 0, e = CPSections.size(); i != e; ++i) {
for (unsigned j = 0, ee = CPSections[i].CPEs.size(); j != ee; ++j) {
unsigned CPI = CPSections[i].CPEs[j];
MCSymbol *Sym = GetCPISymbol(CPI);
if (!Sym->isUndefined())
if (CurSection != CPSections[i].S) {
CurSection = CPSections[i].S;
Offset = 0;
MachineConstantPoolEntry CPE = CP[CPI];
// Emit inter-object padding for alignment.
unsigned NewOffset = alignTo(Offset, CPE.getAlign());
OutStreamer->emitZeros(NewOffset - Offset);
Offset = NewOffset + CPE.getSizeInBytes(getDataLayout());
if (CPE.isMachineConstantPoolEntry())
emitGlobalConstant(getDataLayout(), CPE.Val.ConstVal);
// Print assembly representations of the jump tables used by the current
// function.
void AsmPrinter::emitJumpTableInfo() {
const DataLayout &DL = MF->getDataLayout();
const MachineJumpTableInfo *MJTI = MF->getJumpTableInfo();
if (!MJTI) return;
if (MJTI->getEntryKind() == MachineJumpTableInfo::EK_Inline) return;
const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
if (JT.empty()) return;
// Pick the directive to use to print the jump table entries, and switch to
// the appropriate section.
const Function &F = MF->getFunction();
const TargetLoweringObjectFile &TLOF = getObjFileLowering();
bool JTInDiffSection = !TLOF.shouldPutJumpTableInFunctionSection(
MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32,
if (JTInDiffSection) {
// Drop it in the readonly section.
MCSection *ReadOnlySection = TLOF.getSectionForJumpTable(F, TM);
// Jump tables in code sections are marked with a data_region directive
// where that's supported.
if (!JTInDiffSection)
for (unsigned JTI = 0, e = JT.size(); JTI != e; ++JTI) {
const std::vector<MachineBasicBlock*> &JTBBs = JT[JTI].MBBs;
// If this jump table was deleted, ignore it.
if (JTBBs.empty()) continue;
// For the EK_LabelDifference32 entry, if using .set avoids a relocation,
/// emit a .set directive for each unique entry.
if (MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 &&
MAI->doesSetDirectiveSuppressReloc()) {
SmallPtrSet<const MachineBasicBlock*, 16> EmittedSets;
const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
const MCExpr *Base = TLI->getPICJumpTableRelocBaseExpr(MF,JTI,OutContext);
for (const MachineBasicBlock *MBB : JTBBs) {
if (!EmittedSets.insert(MBB).second)
// .set LJTSet, LBB32-base
const MCExpr *LHS =
MCSymbolRefExpr::create(MBB->getSymbol(), OutContext);
OutStreamer->emitAssignment(GetJTSetSymbol(JTI, MBB->getNumber()),
MCBinaryExpr::createSub(LHS, Base,
// On some targets (e.g. Darwin) we want to emit two consecutive labels
// before each jump table. The first label is never referenced, but tells
// the assembler and linker the extents of the jump table object. The
// second label is actually referenced by the code.
if (JTInDiffSection && DL.hasLinkerPrivateGlobalPrefix())
// FIXME: This doesn't have to have any specific name, just any randomly
// named and numbered local label started with 'l' would work. Simplify
// GetJTISymbol.
OutStreamer->emitLabel(GetJTISymbol(JTI, true));
MCSymbol* JTISymbol = GetJTISymbol(JTI);
for (const MachineBasicBlock *MBB : JTBBs)
emitJumpTableEntry(MJTI, MBB, JTI);
if (!JTInDiffSection)
/// EmitJumpTableEntry - Emit a jump table entry for the specified MBB to the
/// current stream.
void AsmPrinter::emitJumpTableEntry(const MachineJumpTableInfo *MJTI,
const MachineBasicBlock *MBB,
unsigned UID) const {
assert(MBB && MBB->getNumber() >= 0 && "Invalid basic block");
const MCExpr *Value = nullptr;
switch (MJTI->getEntryKind()) {
case MachineJumpTableInfo::EK_Inline:
llvm_unreachable("Cannot emit EK_Inline jump table entry");
case MachineJumpTableInfo::EK_Custom32:
Value = MF->getSubtarget().getTargetLowering()->LowerCustomJumpTableEntry(
MJTI, MBB, UID, OutContext);
case MachineJumpTableInfo::EK_BlockAddress:
// EK_BlockAddress - Each entry is a plain address of block, e.g.:
// .word LBB123
Value = MCSymbolRefExpr::create(MBB->getSymbol(), OutContext);
case MachineJumpTableInfo::EK_GPRel32BlockAddress: {
// EK_GPRel32BlockAddress - Each entry is an address of block, encoded
// with a relocation as gp-relative, e.g.:
// .gprel32 LBB123
MCSymbol *MBBSym = MBB->getSymbol();
OutStreamer->emitGPRel32Value(MCSymbolRefExpr::create(MBBSym, OutContext));
case MachineJumpTableInfo::EK_GPRel64BlockAddress: {
// EK_GPRel64BlockAddress - Each entry is an address of block, encoded
// with a relocation as gp-relative, e.g.:
// .gpdword LBB123
MCSymbol *MBBSym = MBB->getSymbol();
OutStreamer->emitGPRel64Value(MCSymbolRefExpr::create(MBBSym, OutContext));
case MachineJumpTableInfo::EK_LabelDifference32: {
// Each entry is the address of the block minus the address of the jump
// table. This is used for PIC jump tables where gprel32 is not supported.
// e.g.:
// .word LBB123 - LJTI1_2
// If the .set directive avoids relocations, this is emitted as:
// .set L4_5_set_123, LBB123 - LJTI1_2
// .word L4_5_set_123
if (MAI->doesSetDirectiveSuppressReloc()) {
Value = MCSymbolRefExpr::create(GetJTSetSymbol(UID, MBB->getNumber()),
Value = MCSymbolRefExpr::create(MBB->getSymbol(), OutContext);
const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
const MCExpr *Base = TLI->getPICJumpTableRelocBaseExpr(MF, UID, OutContext);
Value = MCBinaryExpr::createSub(Value, Base, OutContext);
assert(Value && "Unknown entry kind!");
unsigned EntrySize = MJTI->getEntrySize(getDataLayout());
OutStreamer->emitValue(Value, EntrySize);
/// EmitSpecialLLVMGlobal - Check to see if the specified global is a
/// special global used by LLVM. If so, emit it and return true, otherwise
/// do nothing and return false.
bool AsmPrinter::emitSpecialLLVMGlobal(const GlobalVariable *GV) {
if (GV->getName() == "llvm.used") {
if (MAI->hasNoDeadStrip()) // No need to emit this at all.
return true;
// Ignore debug and non-emitted data. This handles llvm.compiler.used.
if (GV->getSection() == "llvm.metadata" ||
return true;
if (!GV->hasAppendingLinkage()) return false;
assert(GV->hasInitializer() && "Not a special LLVM global!");
if (GV->getName() == "llvm.global_ctors") {
emitXXStructorList(GV->getParent()->getDataLayout(), GV->getInitializer(),
/* isCtor */ true);
return true;
if (GV->getName() == "llvm.global_dtors") {
emitXXStructorList(GV->getParent()->getDataLayout(), GV->getInitializer(),
/* isCtor */ false);
return true;
report_fatal_error("unknown special variable");
/// EmitLLVMUsedList - For targets that define a MAI::UsedDirective, mark each
/// global in the specified llvm.used list.
void AsmPrinter::emitLLVMUsedList(const ConstantArray *InitList) {
// Should be an array of 'i8*'.
for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
const GlobalValue *GV =
if (GV)
OutStreamer->emitSymbolAttribute(getSymbol(GV), MCSA_NoDeadStrip);
void AsmPrinter::preprocessXXStructorList(const DataLayout &DL,
const Constant *List,
SmallVector<Structor, 8> &Structors) {
// Should be an array of '{ i32, void ()*, i8* }' structs. The first value is
// the init priority.
if (!isa<ConstantArray>(List))
// Gather the structors in a form that's convenient for sorting by priority.
for (Value *O : cast<ConstantArray>(List)->operands()) {
auto *CS = cast<ConstantStruct>(O);
if (CS->getOperand(1)->isNullValue())
break; // Found a null terminator, skip the rest.
ConstantInt *Priority = dyn_cast<ConstantInt>(CS->getOperand(0));
if (!Priority)
continue; // Malformed.
Structor &S = Structors.back();
S.Priority = Priority->getLimitedValue(65535);
S.Func = CS->getOperand(1);
if (!CS->getOperand(2)->isNullValue()) {
if (TM.getTargetTriple().isOSAIX())
"associated data of XXStructor list is not yet supported on AIX");
S.ComdatKey =
// Emit the function pointers in the target-specific order
llvm::stable_sort(Structors, [](const Structor &L, const Structor &R) {
return L.Priority < R.Priority;
/// EmitXXStructorList - Emit the ctor or dtor list taking into account the init
/// priority.
void AsmPrinter::emitXXStructorList(const DataLayout &DL, const Constant *List,
bool IsCtor) {
SmallVector<Structor, 8> Structors;
preprocessXXStructorList(DL, List, Structors);
if (Structors.empty())
// Emit the structors in reverse order if we are using the .ctor/.dtor
// initialization scheme.
if (!TM.Options.UseInitArray)
std::reverse(Structors.begin(), Structors.end());
const Align Align = DL.getPointerPrefAlignment();
for (Structor &S : Structors) {
const TargetLoweringObjectFile &Obj = getObjFileLowering();
const MCSymbol *KeySym = nullptr;
if (GlobalValue *GV = S.ComdatKey) {
if (GV->isDeclarationForLinker())
// If the associated variable is not defined in this module
// (it might be available_externally, or have been an
// available_externally definition that was dropped by the
// EliminateAvailableExternally pass), some other TU
// will provide its dynamic initializer.
KeySym = getSymbol(GV);
MCSection *OutputSection =
(IsCtor ? Obj.getStaticCtorSection(S.Priority, KeySym)
: Obj.getStaticDtorSection(S.Priority, KeySym));
if (OutStreamer->getCurrentSection() != OutStreamer->getPreviousSection())
emitXXStructor(DL, S.Func);
void AsmPrinter::emitModuleIdents(Module &M) {
if (!MAI->hasIdentDirective())
if (const NamedMDNode *NMD = M.getNamedMetadata("llvm.ident")) {
for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i) {
const MDNode *N = NMD->getOperand(i);
assert(N->getNumOperands() == 1 &&
"llvm.ident metadata entry can have only one operand");
const MDString *S = cast<MDString>(N->getOperand(0));
void AsmPrinter::emitModuleCommandLines(Module &M) {
MCSection *CommandLine = getObjFileLowering().getSectionForCommandLines();
if (!CommandLine)
const NamedMDNode *NMD = M.getNamedMetadata("llvm.commandline");
if (!NMD || !NMD->getNumOperands())
for (unsigned i = 0, e = NMD->getNumOperands(); i != e; ++i) {
const MDNode *N = NMD->getOperand(i);
assert(N->getNumOperands() == 1 &&
"llvm.commandline metadata entry can have only one operand");
const MDString *S = cast<MDString>(N->getOperand(0));
// Emission and print routines
/// Emit a byte directive and value.
void AsmPrinter::emitInt8(int Value) const { OutStreamer->emitInt8(Value); }
/// Emit a short directive and value.
void AsmPrinter::emitInt16(int Value) const { OutStreamer->emitInt16(Value); }
/// Emit a long directive and value.
void AsmPrinter::emitInt32(int Value) const { OutStreamer->emitInt32(Value); }
/// Emit a long long directive and value.
void AsmPrinter::emitInt64(uint64_t Value) const {
/// Emit something like ".long Hi-Lo" where the size in bytes of the directive
/// is specified by Size and Hi/Lo specify the labels. This implicitly uses
/// .set if it avoids relocations.
void AsmPrinter::emitLabelDifference(const MCSymbol *Hi, const MCSymbol *Lo,
unsigned Size) const {
OutStreamer->emitAbsoluteSymbolDiff(Hi, Lo, Size);
/// EmitLabelPlusOffset - Emit something like ".long Label+Offset"
/// where the size in bytes of the directive is specified by Size and Label
/// specifies the label. This implicitly uses .set if it is available.
void AsmPrinter::emitLabelPlusOffset(const MCSymbol *Label, uint64_t Offset,
unsigned Size,
bool IsSectionRelative) const {
if (MAI->needsDwarfSectionOffsetDirective() && IsSectionRelative) {
OutStreamer->EmitCOFFSecRel32(Label, Offset);
if (Size > 4)
OutStreamer->emitZeros(Size - 4);
// Emit Label+Offset (or just Label if Offset is zero)
const MCExpr *Expr = MCSymbolRefExpr::create(Label, OutContext);
if (Offset)
Expr = MCBinaryExpr::createAdd(
Expr, MCConstantExpr::create(Offset, OutContext), OutContext);
OutStreamer->emitValue(Expr, Size);
// EmitAlignment - Emit an alignment directive to the specified power of
// two boundary. If a global value is specified, and if that global has
// an explicit alignment requested, it will override the alignment request
// if required for correctness.
void AsmPrinter::emitAlignment(Align Alignment, const GlobalObject *GV) const {
if (GV)
Alignment = getGVAlignment(GV, GV->getParent()->getDataLayout(), Alignment);
if (Alignment == Align(1))
return; // 1-byte aligned: no need to emit alignment.
if (getCurrentSection()->getKind().isText()) {
const MCSubtargetInfo *STI = nullptr;
if (this->MF)
STI = &getSubtargetInfo();
STI = TM.getMCSubtargetInfo();
OutStreamer->emitCodeAlignment(Alignment.value(), STI);
} else
// Constant emission.
const MCExpr *AsmPrinter::lowerConstant(const Constant *CV) {
MCContext &Ctx = OutContext;
if (CV->isNullValue() || isa<UndefValue>(CV))
return MCConstantExpr::create(0, Ctx);
if (const ConstantInt *CI = dyn_cast<ConstantInt>(CV))
return MCConstantExpr::create(CI->getZExtValue(), Ctx);
if (const GlobalValue *GV = dyn_cast<GlobalValue>(CV))
return MCSymbolRefExpr::create(getSymbol(GV), Ctx);
if (const BlockAddress *BA = dyn_cast<BlockAddress>(CV))
return MCSymbolRefExpr::create(GetBlockAddressSymbol(BA), Ctx);
if (const auto *Equiv = dyn_cast<DSOLocalEquivalent>(CV))
return getObjFileLowering().lowerDSOLocalEquivalent(Equiv, TM);
const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
if (!CE) {
llvm_unreachable("Unknown constant value to lower!");
switch (CE->getOpcode()) {
case Instruction::AddrSpaceCast: {
const Constant *Op = CE->getOperand(0);
unsigned DstAS = CE->getType()->getPointerAddressSpace();
unsigned SrcAS = Op->getType()->getPointerAddressSpace();
if (TM.isNoopAddrSpaceCast(SrcAS, DstAS))
return lowerConstant(Op);
// Fallthrough to error.
default: {
// If the code isn't optimized, there may be outstanding folding
// opportunities. Attempt to fold the expression using DataLayout as a
// last resort before giving up.
Constant *C = ConstantFoldConstant(CE, getDataLayout());
if (C != CE)
return lowerConstant(C);
// Otherwise report the problem to the user.
std::string S;
raw_string_ostream OS(S);
OS << "Unsupported expression in static initializer: ";
CE->printAsOperand(OS, /*PrintType=*/false,
!MF ? nullptr : MF->getFunction().getParent());
case Instruction::GetElementPtr: {
// Generate a symbolic expression for the byte address
APInt OffsetAI(getDataLayout().getPointerTypeSizeInBits(CE->getType()), 0);
cast<GEPOperator>(CE)->accumulateConstantOffset(getDataLayout(), OffsetAI);
const MCExpr *Base = lowerConstant(CE->getOperand(0));
if (!OffsetAI)
return Base;
int64_t Offset = OffsetAI.getSExtValue();
return MCBinaryExpr::createAdd(Base, MCConstantExpr::create(Offset, Ctx),
case Instruction::Trunc:
// We emit the value and depend on the assembler to truncate the generated
// expression properly. This is important for differences between
// blockaddress labels. Since the two labels are in the same function, it
// is reasonable to treat their delta as a 32-bit value.
case Instruction::BitCast:
return lowerConstant(CE->getOperand(0));
case Instruction::IntToPtr: {
const DataLayout &DL = getDataLayout();
// Handle casts to pointers by changing them into casts to the appropriate
// integer type. This promotes constant folding and simplifies this code.
Constant *Op = CE->getOperand(0);
Op = ConstantExpr::getIntegerCast(Op, DL.getIntPtrType(CV->getType()),
return lowerConstant(Op);
case Instruction::PtrToInt: {
const DataLayout &DL = getDataLayout();
// Support only foldable casts to/from pointers that can be eliminated by
// changing the pointer to the appropriately sized integer type.
Constant *Op = CE->getOperand(0);
Type *Ty = CE->getType();
const MCExpr *OpExpr = lowerConstant(Op);
// We can emit the pointer value into this slot if the slot is an
// integer slot equal to the size of the pointer.
// If the pointer is larger than the resultant integer, then
// as with Trunc just depend on the assembler to truncate it.
if (DL.getTypeAllocSize(Ty).getFixedSize() <=
return OpExpr;
// Otherwise the pointer is smaller than the resultant integer, mask off
// the high bits so we are sure to get a proper truncation if the input is
// a constant expr.
unsigned InBits = DL.getTypeAllocSizeInBits(Op->getType());
const MCExpr *MaskExpr = MCConstantExpr::create(~0ULL >> (64-InBits), Ctx);
return MCBinaryExpr::createAnd(OpExpr, MaskExpr, Ctx);
case Instruction::Sub: {
GlobalValue *LHSGV;
APInt LHSOffset;
DSOLocalEquivalent *DSOEquiv;
if (IsConstantOffsetFromGlobal(CE->getOperand(0), LHSGV, LHSOffset,
getDataLayout(), &DSOEquiv)) {
GlobalValue *RHSGV;
APInt RHSOffset;
if (IsConstantOffsetFromGlobal(CE->getOperand(1), RHSGV, RHSOffset,
getDataLayout())) {
const MCExpr *RelocExpr =
getObjFileLowering().lowerRelativeReference(LHSGV, RHSGV, TM);
if (!RelocExpr) {
const MCExpr *LHSExpr =
MCSymbolRefExpr::create(getSymbol(LHSGV), Ctx);
if (DSOEquiv &&
LHSExpr =
getObjFileLowering().lowerDSOLocalEquivalent(DSOEquiv, TM);
RelocExpr = MCBinaryExpr::createSub(
LHSExpr, MCSymbolRefExpr::create(getSymbol(RHSGV), Ctx), Ctx);
int64_t Addend = (LHSOffset - RHSOffset).getSExtValue();
if (Addend != 0)
RelocExpr = MCBinaryExpr::createAdd(
RelocExpr, MCConstantExpr::create(Addend, Ctx), Ctx);
return RelocExpr;
// else fallthrough
// The MC library also has a right-shift operator, but it isn't consistently
// signed or unsigned between different targets.
case Instruction::Add:
case Instruction::Mul:
case Instruction::SDiv:
case Instruction::SRem:
case Instruction::Shl:
case Instruction::And:
case Instruction::Or:
case Instruction::Xor: {
const MCExpr *LHS = lowerConstant(CE->getOperand(0));
const MCExpr *RHS = lowerConstant(CE->getOperand(1));
switch (CE->getOpcode()) {
default: llvm_unreachable("Unknown binary operator constant cast expr");
case Instruction::Add: return MCBinaryExpr::createAdd(LHS, RHS, Ctx);
case Instruction::Sub: return MCBinaryExpr::createSub(LHS, RHS, Ctx);
case Instruction::Mul: return MCBinaryExpr::createMul(LHS, RHS, Ctx);
case Instruction::SDiv: return MCBinaryExpr::createDiv(LHS, RHS, Ctx);
case Instruction::SRem: return MCBinaryExpr::createMod(LHS, RHS, Ctx);
case Instruction::Shl: return MCBinaryExpr::createShl(LHS, RHS, Ctx);
case Instruction::And: return MCBinaryExpr::createAnd(LHS, RHS, Ctx);
case Instruction::Or: return MCBinaryExpr::createOr (LHS, RHS, Ctx);
case Instruction::Xor: return MCBinaryExpr::createXor(LHS, RHS, Ctx);
static void emitGlobalConstantImpl(const DataLayout &DL, const Constant *C,
AsmPrinter &AP,
const Constant *BaseCV = nullptr,
uint64_t Offset = 0);
static void emitGlobalConstantFP(const ConstantFP *CFP, AsmPrinter &AP);
static void emitGlobalConstantFP(APFloat APF, Type *ET, AsmPrinter &AP);
/// isRepeatedByteSequence - Determine whether the given value is
/// composed of a repeated sequence of identical bytes and return the
/// byte value. If it is not a repeated sequence, return -1.
static int isRepeatedByteSequence(const ConstantDataSequential *V) {
StringRef Data = V->getRawDataValues();
assert(!Data.empty() && "Empty aggregates should be CAZ node");
char C = Data[0];
for (unsigned i = 1, e = Data.size(); i != e; ++i)
if (Data[i] != C) return -1;
return static_cast<uint8_t>(C); // Ensure 255 is not returned as -1.
/// isRepeatedByteSequence - Determine whether the given value is
/// composed of a repeated sequence of identical bytes and return the
/// byte value. If it is not a repeated sequence, return -1.
static int isRepeatedByteSequence(const Value *V, const DataLayout &DL) {
if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
uint64_t Size = DL.getTypeAllocSizeInBits(V->getType());
assert(Size % 8 == 0);
// Extend the element to take zero padding into account.
APInt Value = CI->getValue().zextOrSelf(Size);
if (!Value.isSplat(8))
return -1;
return Value.zextOrTrunc(8).getZExtValue();
if (const ConstantArray *CA = dyn_cast<ConstantArray>(V)) {
// Make sure all array elements are sequences of the same repeated
// byte.
assert(CA->getNumOperands() != 0 && "Should be a CAZ");
Constant *Op0 = CA->getOperand(0);
int Byte = isRepeatedByteSequence(Op0, DL);
if (Byte == -1)
return -1;
// All array elements must be equal.
for (unsigned i = 1, e = CA->getNumOperands(); i != e; ++i)
if (CA->getOperand(i) != Op0)
return -1;
return Byte;
if (const ConstantDataSequential *CDS = dyn_cast<ConstantDataSequential>(V))
return isRepeatedByteSequence(CDS);
return -1;
static void emitGlobalConstantDataSequential(const DataLayout &DL,
const ConstantDataSequential *CDS,
AsmPrinter &AP) {
// See if we can aggregate this into a .fill, if so, emit it as such.
int Value = isRepeatedByteSequence(CDS, DL);
if (Value != -1) {
uint64_t Bytes = DL.getTypeAllocSize(CDS->getType());
// Don't emit a 1-byte object as a .fill.
if (Bytes > 1)
return AP.OutStreamer->emitFill(Bytes, Value);
// If this can be emitted with .ascii/.asciz, emit it as such.
if (CDS->isString())
return AP.OutStreamer->emitBytes(CDS->getAsString());
// Otherwise, emit the values in successive locations.
unsigned ElementByteSize = CDS->getElementByteSize();
if (isa<IntegerType>(CDS->getElementType())) {
for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
if (AP.isVerbose())
AP.OutStreamer->GetCommentOS() << format("0x%" PRIx64 "\n",
} else {
Type *ET = CDS->getElementType();
for (unsigned I = 0, E = CDS->getNumElements(); I != E; ++I)
emitGlobalConstantFP(CDS->getElementAsAPFloat(I), ET, AP);