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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 "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/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/ProfileSummaryInfo.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/GCStrategy.h"
#include "llvm/CodeGen/LazyMachineBlockFrequencyInfo.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineBlockFrequencyInfo.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/MachineSizeOpts.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/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/GlobalAlias.h"
#include "llvm/IR/GlobalIFunc.h"
#include "llvm/IR/GlobalIndirectSymbol.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/RemarkStreamer.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/Pass.h"
#include "llvm/Remarks/Remark.h"
#include "llvm/Remarks/RemarkFormat.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/Format.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/TargetRegistry.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"
static const char *const DWARFGroupName = "dwarf";
static const char *const DWARFGroupDescription = "DWARF Emission";
static const char *const DbgTimerName = "emit";
static const char *const DbgTimerDescription = "Debug Info Emission";
static const char *const EHTimerName = "write_exception";
static const char *const EHTimerDescription = "DWARF Exception Writer";
static const char *const CFGuardName = "Control Flow Guard";
static const char *const CFGuardDescription = "Control Flow Guard";
static const char *const CodeViewLineTablesGroupName = "linetables";
static const char *const CodeViewLineTablesGroupDescription =
"CodeView Line Tables";
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 GlobalValue *GV, const DataLayout &DL,
Align InAlign) {
Align Alignment;
if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV))
Alignment = Align(DL.getPreferredAlignment(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.empty() && "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) {
assert(DD && "Dwarf debug file is not defined.");
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())
// 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"
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()) {
// We're at the module level. Construct MCSubtarget from the default CPU
// and target triple.
std::unique_ptr<MCSubtargetInfo> STI(TM.getTarget().createMCSubtargetInfo(
TM.getTargetTriple().str(), TM.getTargetCPU(),
OutStreamer->AddComment("Start of file scope inline assembly");
OutContext.getSubtargetCopy(*STI), TM.Options.MCOptions);
OutStreamer->AddComment("End of file scope inline assembly");
if (MAI->doesSupportDebugInformation()) {
bool EmitCodeView = MMI->getModule()->getCodeViewFlag();
if (EmitCodeView && TM.getTargetTriple().isOSWindows()) {
DbgTimerName, DbgTimerDescription,
if (!EmitCodeView || MMI->getModule()->getDwarfVersion()) {
DD = new DwarfDebug(this, &M);
Handlers.emplace_back(std::unique_ptr<DwarfDebug>(DD), DbgTimerName,
DbgTimerDescription, DWARFGroupName,
switch (MAI->getExceptionHandlingType()) {
case ExceptionHandling::SjLj:
case ExceptionHandling::DwarfCFI:
case ExceptionHandling::ARM:
isCFIMoveForDebugging = true;
if (MAI->getExceptionHandlingType() != ExceptionHandling::DwarfCFI)
for (auto &F: M.getFunctionList()) {
// If the module contains any function with unwind data,
// .eh_frame has to be emitted.
// Ignore functions that won't get emitted.
if (!F.isDeclarationForLinker() && F.needsUnwindTableEntry()) {
isCFIMoveForDebugging = false;
isCFIMoveForDebugging = false;
EHStreamer *ES = nullptr;
switch (MAI->getExceptionHandlingType()) {
case ExceptionHandling::None:
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);
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>(
Handlers.emplace_back(std::make_unique<WinCFGuard>(this), CFGuardName,
CFGuardDescription, DWARFGroupName,
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->hasLinkOnceDirective()) {
// .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:
// If external, declare as a global symbol: .globl _foo
OutStreamer->EmitSymbolAttribute(GVSym, MCSA_Global);
case GlobalValue::PrivateLinkage:
case GlobalValue::InternalLinkage:
if (MAI->hasDotLGloblDirective())
OutStreamer->EmitSymbolAttribute(GVSym, MCSA_LGlobal);
case GlobalValue::AppendingLinkage:
case GlobalValue::AvailableExternallyLinkage:
case GlobalValue::ExternalWeakLinkage:
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);
/// 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())
report_fatal_error("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);
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);
/// 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.
OutStreamer->SwitchSection(getObjFileLowering().SectionForGlobal(&F, TM));
EmitVisibility(CurrentFnSym, F.getVisibility());
if (MAI->needsFunctionDescriptors() &&
F.getLinkage() != GlobalValue::InternalLinkage)
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.
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 (unsigned i = 0, e = DeadBlockSyms.size(); i != e; ++i) {
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 (CurrentFnSym->isDefined())
report_fatal_error("'" + Twine(CurrentFnSym->getName()) +
"' label emitted multiple times to assembly file");
return OutStreamer->EmitLabel(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)
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)
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 (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &Op = MI->getOperand(i);
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->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 << " <- ";
// The second operand is only an offset if it's an immediate.
bool MemLoc = MI->getOperand(0).isReg() && MI->getOperand(1).isImm();
int64_t Offset = MemLoc ? MI->getOperand(1).getImm() : 0;
const DIExpression *Expr = MI->getDebugExpression();
if (Expr->getNumElements()) {
OS << '[';
bool NeedSep = false;
for (auto Op : Expr->expr_ops()) {
if (NeedSep)
OS << ", ";
NeedSep = true;
OS << 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.
if (MI->getOperand(0).isFPImm()) {
APFloat APF = APFloat(MI->getOperand(0).getFPImm()->getValueAPF());
if (MI->getOperand(0).getFPImm()->getType()->isFloatTy()) {
OS << (double)APF.convertToFloat();
} else if (MI->getOperand(0).getFPImm()->getType()->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();
} else if (MI->getOperand(0).isImm()) {
OS << MI->getOperand(0).getImm();
} else if (MI->getOperand(0).isCImm()) {
MI->getOperand(0).getCImm()->getValue().print(OS, false /*isSigned*/);
} else if (MI->getOperand(0).isTargetIndex()) {
auto Op = MI->getOperand(0);
OS << "!target-index(" << Op.getIndex() << "," << Op.getOffset() << ")";
return true;
} else {
unsigned Reg;
if (MI->getOperand(0).isReg()) {
Reg = MI->getOperand(0).getReg();
} else {
assert(MI->getOperand(0).isFI() && "Unknown operand type");
const TargetFrameLowering *TFI = AP.MF->getSubtarget().getFrameLowering();
Offset += TFI->getFrameIndexReference(*AP.MF,
MI->getOperand(0).getIndex(), Reg);
MemLoc = true;
if (Reg == 0) {
// Suppress offset, it is not meaningful here.
OS << "undef";
// NOTE: Want this comment at start of line, don't emit with AddComment.
return true;
if (MemLoc)
OS << '[';
OS << printReg(Reg, AP.MF->getSubtarget().getRegisterInfo());
if (MemLoc)
OS << '+' << Offset << ']';
// 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::CFIMoveType AsmPrinter::needsCFIMoves() const {
if (MAI->getExceptionHandlingType() == ExceptionHandling::DwarfCFI &&
return CFI_M_EH;
if (MMI->hasDebugInfo() || MF->getTarget().Options.ForceDwarfFrameSection)
return CFI_M_Debug;
return CFI_M_None;
bool AsmPrinter::needsSEHMoves() {
return MAI->usesWindowsCFI() && MF->getFunction().needsUnwindTableEntry();
void AsmPrinter::emitCFIInstruction(const MachineInstr &MI) {
ExceptionHandling ExceptionHandlingType = MAI->getExceptionHandlingType();
if (ExceptionHandlingType != ExceptionHandling::DwarfCFI &&
ExceptionHandlingType != ExceptionHandling::ARM)
if (needsCFIMoves() == CFI_M_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));
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());
static bool needFuncLabelsForEHOrDebugInfo(const MachineFunction &MF,
MachineModuleInfo *MMI) {
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.
bool ShouldPrintDebugScopes = MMI->hasDebugInfo();
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;
for (auto &MBB : *MF) {
// Print a label for the basic block.
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())
if (ShouldPrintDebugScopes) {
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription,
HI.TimerGroupName, HI.TimerGroupDescription,
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:
if (isVerbose()) {
if (!emitDebugValueComment(&MI, *this))
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);
// If there is a post-instruction symbol, emit a label for it here.
if (MCSymbol *S = MI.getPostInstrSymbol())
if (ShouldPrintDebugScopes) {
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription,
HI.TimerGroupName, HI.TimerGroupDescription,
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;
// Targets can opt-out of emitting the noop here by leaving the opcode
// unspecified.
if (Noop.getOpcode()) {
OutStreamer->AddComment("avoids zero-length function");
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, MMI) ||
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);
// 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 stack size metadata.
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::emitGlobalIndirectSymbol(Module &M,
const GlobalIndirectSymbol& GIS) {
MCSymbol *Name = getSymbol(&GIS);
if (GIS.hasExternalLinkage() || !MAI->getWeakRefDirective())
OutStreamer->EmitSymbolAttribute(Name, MCSA_Global);
else if (GIS.hasWeakLinkage() || GIS.hasLinkOnceLinkage())
OutStreamer->EmitSymbolAttribute(Name, MCSA_WeakReference);
assert(GIS.hasLocalLinkage() && "Invalid alias or ifunc linkage");
bool IsFunction = GIS.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>(GIS.getIndirectSymbol()))
if (CE->getOpcode() == Instruction::BitCast)
IsFunction =
// 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, isa<GlobalIFunc>(GIS)
? MCSA_ELF_TypeIndFunction
: MCSA_ELF_TypeFunction);
EmitVisibility(Name, GIS.getVisibility());
const MCExpr *Expr = lowerConstant(GIS.getIndirectSymbol());
if (isa<GlobalAlias>(&GIS) && MAI->hasAltEntry() && isa<MCBinaryExpr>(Expr))
OutStreamer->EmitSymbolAttribute(Name, MCSA_AltEntry);
// Emit the directives as assignments aka .set:
OutStreamer->EmitAssignment(Name, Expr);
if (auto *GA = dyn_cast<GlobalAlias>(&GIS)) {
// 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->getBaseObject();
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::emitRemarksSection(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, StringRef(*Filename))
: 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.
// Emit visibility info for declarations
for (const Function &F : M) {
if (!F.isDeclarationForLinker())
GlobalValue::VisibilityTypes V = F.getVisibility();
if (V == GlobalValue::DefaultVisibility)
MCSymbol *Name = getSymbol(&F);
EmitVisibility(Name, V, false);
// 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 (RemarkStreamer *RS = M.getContext().getRemarkStreamer())
const TargetLoweringObjectFile &TLOF = getObjFileLowering();
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);
// Finalize debug and EH information.
for (const HandlerInfo &HI : Handlers) {
NamedRegionTimer T(HI.TimerName, HI.TimerDescription, HI.TimerGroupName,
HI.TimerGroupDescription, TimePassesIsEnabled);
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))
emitGlobalIndirectSymbol(M, *AncestorAlias);
for (const auto &IFunc : M.ifuncs())
emitGlobalIndirectSymbol(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()) {
unsigned Align = 1;
MCSection *ReadOnlySection = getObjFileLowering().getSectionForConstant(
getDataLayout(), SectionKind::getReadOnly(),
/*C=*/nullptr, Align);
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.getTargetTriple().isOSBinFormatCOFF()) {
// Emit /EXPORT: flags for each exported global as necessary.
const auto &TLOF = getObjFileLowering();
std::string Flags;
for (const GlobalValue &GV : M.global_values()) {
raw_string_ostream OS(Flags);
TLOF.emitLinkerFlagsForGlobal(OS, &GV);
if (!Flags.empty()) {
// Emit /INCLUDE: flags for each used global as necessary.
if (const auto *LU = M.getNamedGlobal("llvm.used")) {
assert(LU->hasInitializer() &&
"expected llvm.used to have an initializer");
assert(isa<ArrayType>(LU->getValueType()) &&
"expected llvm.used to be an array type");
if (const auto *A = cast<ConstantArray>(LU->getInitializer())) {
for (const Value *Op : A->operands()) {
const auto *GV = cast<GlobalValue>(Op->stripPointerCasts());
// Global symbols with internal or private linkage are not visible to
// the linker, and thus would cause an error when the linker tried to
// preserve the symbol due to the `/include:` directive.
if (GV->hasLocalLinkage())
raw_string_ostream OS(Flags);
TLOF.emitLinkerFlagsForUsed(OS, GV);
if (!Flags.empty()) {
if (TM.Options.EmitAddrsig) {
// Emit address-significance attributes for all globals.
for (const GlobalValue &GV : M.global_values())
if (!GV.use_empty() && !GV.isThreadLocal() &&
!GV.hasDLLImportStorageClass() && !GV.getName().startswith("llvm.") &&
// 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)
".llvm_sympart", ELF::SHT_LLVM_SYMPART, 0, 0, "", ++UniqueID));
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::getCurExceptionSym() {
if (!CurExceptionSym)
CurExceptionSym = createTempSymbol("exception");
return CurExceptionSym;
void AsmPrinter::SetupMachineFunction(MachineFunction &MF) {
this->MF = &MF;
const Function &F = MF.getFunction();
// Get the function symbol.
if (MAI->needsFunctionDescriptors()) {
assert(TM.getTargetTriple().isOSAIX() && "Function descriptor is only"
" supported on AIX.");
assert(CurrentFnDescSym && "The function descriptor symbol needs to be"
" initalized first.");
// Get the function entry point symbol.
CurrentFnSym =
OutContext.getOrCreateSymbol("." + CurrentFnDescSym->getName());
MCSectionXCOFF *FnEntryPointSec =
cast<MCSectionXCOFF>(getObjFileLowering().SectionForGlobal(&F, TM));
// Set the containing csect.
} else {
CurrentFnSym = getSymbol(&MF.getFunction());
CurrentFnSymForSize = CurrentFnSym;
CurrentFnBegin = nullptr;
CurExceptionSym = nullptr;
bool NeedsLocalForSize = MAI->needsLocalForSize();
if (F.hasFnAttribute("patchable-function-entry") ||
needFuncLabelsForEHOrDebugInfo(MF, MMI) || NeedsLocalForSize ||
MF.getTarget().Options.EmitStackSizeSection) {
CurrentFnBegin = createTempSymbol("func_begin");
if (NeedsLocalForSize)
CurrentFnSymForSize = CurrentFnBegin;
ORE = &getAnalysis<MachineOptimizationRemarkEmitterPass>().getORE();
PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
MBFI = (PSI && PSI->hasProfileSummary()) ?
// ORE conditionally computes MBFI. If available, use it, otherwise
// request it.
(ORE->getBFI() ? ORE->getBFI() :
&getAnalysis<LazyMachineBlockFrequencyInfoPass>().getBFI()) :
namespace {
// Keep track the alignment, constpool entries per Section.
struct SectionCPs {
MCSection *S;
unsigned Alignment;
SmallVector<unsigned, 4> CPEs;
SectionCPs(MCSection *s, unsigned 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];
unsigned Align = CPE.getAlignment();
SectionKind Kind = CPE.getSectionKind(&getDataLayout());
const Constant *C = nullptr;
if (!CPE.isMachineConstantPoolEntry())
C = CPE.Val.ConstVal;
MCSection *S = getObjFileLowering().getSectionForConstant(getDataLayout(),
Kind, C, Align);
// 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, Align));
if (Align > CPSections[SecIdx].Alignment)
CPSections[SecIdx].Alignment = Align;
// 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 (TM.getTargetTriple().isOSBinFormatXCOFF()) {
if (CurSection != CPSections[i].S) {
CurSection = CPSections[i].S;
Offset = 0;
MachineConstantPoolEntry CPE = CP[CPI];
// Emit inter-object padding for alignment.
unsigned AlignMask = CPE.getAlignment() - 1;
unsigned NewOffset = (Offset + AlignMask) & ~AlignMask;
OutStreamer->EmitZeros(NewOffset - Offset);
Type *Ty = CPE.getType();
Offset = NewOffset + getDataLayout().getTypeAllocSize(Ty);
if (CPE.isMachineConstantPoolEntry())
EmitGlobalConstant(getDataLayout(), CPE.Val.ConstVal);
/// EmitJumpTableInfo - Print assembly representations of the jump tables used
/// by the current function to the current output stream.
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 (unsigned ii = 0, ee = JTBBs.size(); ii != ee; ++ii) {
const MachineBasicBlock *MBB = JTBBs[ii];
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);
if (TM.getTargetTriple().isOSBinFormatXCOFF()) {
cast<MCSectionXCOFF>(TLOF.getSectionForJumpTable(F, TM)));
for (unsigned ii = 0, ee = JTBBs.size(); ii != ee; ++ii)
EmitJumpTableEntry(MJTI, JTBBs[ii], 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);
namespace {
struct Structor {
int Priority = 0;
Constant *Func = nullptr;
GlobalValue *ComdatKey = nullptr;
Structor() = default;
} // end anonymous namespace
/// EmitXXStructorList - Emit the ctor or dtor list taking into account the init
/// priority.
void AsmPrinter::EmitXXStructorList(const DataLayout &DL, const Constant *List,
bool isCtor) {
// Should be an array of '{ i32, void ()*, i8* }' structs. The first value is the
// init priority.
if (!isa<ConstantArray>(List)) return;
// Sanity check the structors list.
const ConstantArray *InitList = dyn_cast<ConstantArray>(List);
if (!InitList) return; // Not an array!
StructType *ETy = dyn_cast<StructType>(InitList->getType()->getElementType());
if (!ETy || ETy->getNumElements() != 3 ||
!isa<IntegerType>(ETy->getTypeAtIndex(0U)) ||
!isa<PointerType>(ETy->getTypeAtIndex(1U)) ||
return; // Not (int, ptr, ptr).
// Gather the structors in a form that's convenient for sorting by priority.
SmallVector<Structor, 8> Structors;
for (Value *O : InitList->operands()) {
ConstantStruct *CS = dyn_cast<ConstantStruct>(O);
if (!CS) continue; // Malformed.
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())
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;
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->EmitIntValue(Value, 1);
/// Emit a short directive and value.
void AsmPrinter::emitInt16(int Value) const {
OutStreamer->EmitIntValue(Value, 2);
/// Emit a long directive and value.
void AsmPrinter::emitInt32(int Value) const {
OutStreamer->EmitIntValue(Value, 4);
/// Emit a long long directive and value.
void AsmPrinter::emitInt64(uint64_t Value) const {
OutStreamer->EmitIntValue(Value, 8);
/// 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::None())
return; // 1-byte aligned: no need to emit alignment.
if (getCurrentSection()->getKind().isText())
// 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);
const ConstantExpr *CE = dyn_cast<ConstantExpr>(CV);
if (!CE) {
llvm_unreachable("Unknown constant value to lower!");
switch (CE->getOpcode()) {
// 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.
if (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) <= DL.getTypeAllocSize(Op->getType()))
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;
if (IsConstantOffsetFromGlobal(CE->getOperand(0), LHSGV, LHSOffset,
getDataLayout())) {
GlobalValue *RHSGV;
APInt RHSOffset;
if (IsConstantOffsetFromGlobal(CE->getOperand(1), RHSGV, RHSOffset,
getDataLayout())) {
const MCExpr *RelocExpr =
getObjFileLowering().lowerRelativeReference(LHSGV, RHSGV, TM);
if (!RelocExpr)
RelocExpr = MCBinaryExpr::createSub(
MCSymbolRefExpr::create(getSymbol(LHSGV), Ctx),
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);
unsigned Size = DL.getTypeAllocSize(CDS->getType());
unsigned EmittedSize = DL.getTypeAllocSize(CDS->getType()->getElementType()) *
assert(EmittedSize <= Size && "Size cannot be less than EmittedSize!");
if (unsigned Padding = Size - EmittedSize)
static void emitGlobalConstantArray(const DataLayout &DL,
const ConstantArray *CA, AsmPrinter &AP,
const Constant *BaseCV, uint64_t Offset) {
// See if we can aggregate some values. Make sure it can be
// represented as a series of bytes of the constant value.
int Value = isRepeatedByteSequence(CA, DL);
if (Value != -1) {
uint64_t Bytes = DL.getTypeAllocSize(CA->getType());
AP.OutStreamer->emitFill(Bytes, Value);
else {
for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) {
emitGlobalConstantImpl(DL, CA->getOperand(i), AP, BaseCV, Offset);
Offset += DL.getTypeAllocSize(CA->getOperand(i)->getType());
static void emitGlobalConstantVector(const DataLayout &DL,
const ConstantVector *CV, AsmPrinter &AP) {