llvm-6502/include/llvm/MC/MCSymbol.h
Daniel Dunbar 525a3a67c1 llvm-mc: Support reassignment of variables in one special case, when the
variable has not yet been used in an expression. This allows us to support a few
cases that show up in real code (mostly because gcc generates it for Objective-C
on Darwin), without giving up a reasonable semantic model for assignment.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103950 91177308-0d34-0410-b5e6-96231b3b80d8
2010-05-17 17:46:23 +00:00

159 lines
4.8 KiB
C++

//===- MCSymbol.h - Machine Code Symbols ------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the declaration of the MCSymbol class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_MC_MCSYMBOL_H
#define LLVM_MC_MCSYMBOL_H
#include "llvm/ADT/StringRef.h"
namespace llvm {
class MCExpr;
class MCSection;
class MCContext;
class raw_ostream;
/// MCSymbol - Instances of this class represent a symbol name in the MC file,
/// and MCSymbols are created and unique'd by the MCContext class. MCSymbols
/// should only be constructed with valid names for the object file.
///
/// If the symbol is defined/emitted into the current translation unit, the
/// Section member is set to indicate what section it lives in. Otherwise, if
/// it is a reference to an external entity, it has a null section.
class MCSymbol {
// Special sentinal value for the absolute pseudo section.
//
// FIXME: Use a PointerInt wrapper for this?
static const MCSection *AbsolutePseudoSection;
/// Name - The name of the symbol. The referred-to string data is actually
/// held by the StringMap that lives in MCContext.
StringRef Name;
/// Section - The section the symbol is defined in. This is null for
/// undefined symbols, and the special AbsolutePseudoSection value for
/// absolute symbols.
const MCSection *Section;
/// Value - If non-null, the value for a variable symbol.
const MCExpr *Value;
/// IsTemporary - True if this is an assembler temporary label, which
/// typically does not survive in the .o file's symbol table. Usually
/// "Lfoo" or ".foo".
unsigned IsTemporary : 1;
/// IsUsedInExpr - True if this symbol has been used in an expression and
/// cannot be redefined.
unsigned IsUsedInExpr : 1;
private: // MCContext creates and uniques these.
friend class MCContext;
MCSymbol(StringRef name, bool isTemporary)
: Name(name), Section(0), Value(0),
IsTemporary(isTemporary), IsUsedInExpr(false) {}
MCSymbol(const MCSymbol&); // DO NOT IMPLEMENT
void operator=(const MCSymbol&); // DO NOT IMPLEMENT
public:
/// getName - Get the symbol name.
StringRef getName() const { return Name; }
/// @name Accessors
/// @{
/// isTemporary - Check if this is an assembler temporary symbol.
bool isTemporary() const { return IsTemporary; }
/// isUsedInExpr - Check if this is an assembler temporary symbol.
bool isUsedInExpr() const { return IsUsedInExpr; }
void setUsedInExpr(bool Value) { IsUsedInExpr = Value; }
/// @}
/// @name Associated Sections
/// @{
/// isDefined - Check if this symbol is defined (i.e., it has an address).
///
/// Defined symbols are either absolute or in some section.
bool isDefined() const {
return Section != 0;
}
/// isInSection - Check if this symbol is defined in some section (i.e., it
/// is defined but not absolute).
bool isInSection() const {
return isDefined() && !isAbsolute();
}
/// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
bool isUndefined() const {
return !isDefined();
}
/// isAbsolute - Check if this is an absolute symbol.
bool isAbsolute() const {
return Section == AbsolutePseudoSection;
}
/// getSection - Get the section associated with a defined, non-absolute
/// symbol.
const MCSection &getSection() const {
assert(isInSection() && "Invalid accessor!");
return *Section;
}
/// setSection - Mark the symbol as defined in the section \arg S.
void setSection(const MCSection &S) { Section = &S; }
/// setUndefined - Mark the symbol as undefined.
void setUndefined() {
Section = 0;
}
/// setAbsolute - Mark the symbol as absolute.
void setAbsolute() { Section = AbsolutePseudoSection; }
/// @}
/// @name Variable Symbols
/// @{
/// isVariable - Check if this is a variable symbol.
bool isVariable() const {
return Value != 0;
}
/// getValue() - Get the value for variable symbols.
const MCExpr *getVariableValue() const {
assert(isVariable() && "Invalid accessor!");
return Value;
}
void setVariableValue(const MCExpr *Value);
/// @}
/// print - Print the value to the stream \arg OS.
void print(raw_ostream &OS) const;
/// dump - Print the value to stderr.
void dump() const;
};
inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
Sym.print(OS);
return OS;
}
} // end namespace llvm
#endif