105 lines · cpp
1//===- lib/MC/MCSymbol.cpp - MCSymbol implementation ----------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#include "llvm/MC/MCSymbol.h"10#include "llvm/ADT/StringRef.h"11#include "llvm/Config/llvm-config.h"12#include "llvm/MC/MCAsmInfo.h"13#include "llvm/MC/MCContext.h"14#include "llvm/Support/Compiler.h"15#include "llvm/Support/Debug.h"16#include "llvm/Support/ErrorHandling.h"17#include "llvm/Support/raw_ostream.h"18#include <cassert>19#include <cstddef>20 21using namespace llvm;22 23// There are numerous MCSymbol objects, so keeping sizeof(MCSymbol) small is24// crucial for minimizing peak memory usage.25static_assert(sizeof(MCSymbol) <= 24, "Keep the base symbol small");26 27// Only the address of this fragment is ever actually used.28static MCFragment SentinelFragment;29 30// Sentinel value for the absolute pseudo fragment.31MCFragment *MCSymbol::AbsolutePseudoFragment = &SentinelFragment;32 33void *MCSymbol::operator new(size_t s, const MCSymbolTableEntry *Name,34 MCContext &Ctx) {35 // We may need more space for a Name to account for alignment. So allocate36 // space for the storage type and not the name pointer.37 size_t Size = s + (Name ? sizeof(NameEntryStorageTy) : 0);38 39 // For safety, ensure that the alignment of a pointer is enough for an40 // MCSymbol. This also ensures we don't need padding between the name and41 // symbol.42 static_assert((unsigned)alignof(MCSymbol) <= alignof(NameEntryStorageTy),43 "Bad alignment of MCSymbol");44 void *Storage = Ctx.allocate(Size, alignof(NameEntryStorageTy));45 NameEntryStorageTy *Start = static_cast<NameEntryStorageTy*>(Storage);46 NameEntryStorageTy *End = Start + (Name ? 1 : 0);47 return End;48}49 50void MCSymbol::setVariableValue(const MCExpr *Value) {51 assert(Value && "Invalid equated expression");52 assert((kind == Kind::Regular || kind == Kind::Equated) &&53 "Cannot equate a common symbol");54 this->Value = Value;55 kind = Kind::Equated;56 Fragment = nullptr;57}58 59void MCSymbol::print(raw_ostream &OS, const MCAsmInfo *MAI) const {60 // The name for this MCSymbol is required to be a valid target name. However,61 // some targets support quoting names with funny characters. If the name62 // contains a funny character, then print it quoted.63 StringRef Name = getName();64 if (!MAI || MAI->isValidUnquotedName(Name)) {65 OS << Name;66 return;67 }68 69 if (MAI && !MAI->supportsNameQuoting())70 report_fatal_error("Symbol name with unsupported characters");71 72 OS << '"';73 for (char C : Name) {74 if (C == '\n')75 OS << "\\n";76 else if (C == '"')77 OS << "\\\"";78 else if (C == '\\')79 OS << "\\\\";80 else81 OS << C;82 }83 OS << '"';84}85 86#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)87LLVM_DUMP_METHOD void MCSymbol::dump() const { dbgs() << *this; }88#endif89 90// Determine whether the offset between two labels can change at link time.91// Currently, this function is used only in DWARF info emission logic, where it92// helps generate more optimal debug info when the offset between labels is93// constant at link time.94bool llvm::isRangeRelaxable(const MCSymbol *Begin, const MCSymbol *End) {95 assert(Begin && "Range without a begin symbol?");96 assert(End && "Range without an end symbol?");97 for (const auto *Fragment = Begin->getFragment();98 Fragment != End->getFragment(); Fragment = Fragment->getNext()) {99 assert(Fragment);100 if (Fragment->isLinkerRelaxable())101 return true;102 }103 return false;104}105