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//===- MCExpr.cpp - Assembly Level Expression Implementation --------------===//
// 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
#include "llvm/MC/MCExpr.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Config/llvm-config.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstdint>
using namespace llvm;
#define DEBUG_TYPE "mcexpr"
namespace {
namespace stats {
STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations");
} // end namespace stats
} // end anonymous namespace
void MCExpr::print(raw_ostream &OS, const MCAsmInfo *MAI, bool InParens) const {
switch (getKind()) {
case MCExpr::Target:
return cast<MCTargetExpr>(this)->printImpl(OS, MAI);
case MCExpr::Constant: {
auto Value = cast<MCConstantExpr>(*this).getValue();
auto PrintInHex = cast<MCConstantExpr>(*this).useHexFormat();
auto SizeInBytes = cast<MCConstantExpr>(*this).getSizeInBytes();
if (Value < 0 && MAI && !MAI->supportsSignedData())
PrintInHex = true;
if (PrintInHex)
switch (SizeInBytes) {
OS << "0x" << Twine::utohexstr(Value);
case 1:
OS << format("0x%02" PRIx64, Value);
case 2:
OS << format("0x%04" PRIx64, Value);
case 4:
OS << format("0x%08" PRIx64, Value);
case 8:
OS << format("0x%016" PRIx64, Value);
OS << Value;
case MCExpr::SymbolRef: {
const MCSymbolRefExpr &SRE = cast<MCSymbolRefExpr>(*this);
const MCSymbol &Sym = SRE.getSymbol();
// Parenthesize names that start with $ so that they don't look like
// absolute names.
bool UseParens =
!InParens && !Sym.getName().empty() && Sym.getName()[0] == '$';
if (UseParens) {
OS << '(';
Sym.print(OS, MAI);
OS << ')';
} else
Sym.print(OS, MAI);
const MCSymbolRefExpr::VariantKind Kind = SRE.getKind();
if (Kind != MCSymbolRefExpr::VK_None) {
if (MAI && MAI->useParensForSymbolVariant()) // ARM
OS << '(' << MCSymbolRefExpr::getVariantKindName(Kind) << ')';
OS << '@' << MCSymbolRefExpr::getVariantKindName(Kind);
case MCExpr::Unary: {
const MCUnaryExpr &UE = cast<MCUnaryExpr>(*this);
switch (UE.getOpcode()) {
case MCUnaryExpr::LNot: OS << '!'; break;
case MCUnaryExpr::Minus: OS << '-'; break;
case MCUnaryExpr::Not: OS << '~'; break;
case MCUnaryExpr::Plus: OS << '+'; break;
bool Binary = UE.getSubExpr()->getKind() == MCExpr::Binary;
if (Binary) OS << "(";
UE.getSubExpr()->print(OS, MAI);
if (Binary) OS << ")";
case MCExpr::Binary: {
const MCBinaryExpr &BE = cast<MCBinaryExpr>(*this);
// Only print parens around the LHS if it is non-trivial.
if (isa<MCConstantExpr>(BE.getLHS()) || isa<MCSymbolRefExpr>(BE.getLHS())) {
BE.getLHS()->print(OS, MAI);
} else {
OS << '(';
BE.getLHS()->print(OS, MAI);
OS << ')';
switch (BE.getOpcode()) {
case MCBinaryExpr::Add:
// Print "X-42" instead of "X+-42".
if (const MCConstantExpr *RHSC = dyn_cast<MCConstantExpr>(BE.getRHS())) {
if (RHSC->getValue() < 0) {
OS << RHSC->getValue();
OS << '+';
case MCBinaryExpr::AShr: OS << ">>"; break;
case MCBinaryExpr::And: OS << '&'; break;
case MCBinaryExpr::Div: OS << '/'; break;
case MCBinaryExpr::EQ: OS << "=="; break;
case MCBinaryExpr::GT: OS << '>'; break;
case MCBinaryExpr::GTE: OS << ">="; break;
case MCBinaryExpr::LAnd: OS << "&&"; break;
case MCBinaryExpr::LOr: OS << "||"; break;
case MCBinaryExpr::LShr: OS << ">>"; break;
case MCBinaryExpr::LT: OS << '<'; break;
case MCBinaryExpr::LTE: OS << "<="; break;
case MCBinaryExpr::Mod: OS << '%'; break;
case MCBinaryExpr::Mul: OS << '*'; break;
case MCBinaryExpr::NE: OS << "!="; break;
case MCBinaryExpr::Or: OS << '|'; break;
case MCBinaryExpr::OrNot: OS << '!'; break;
case MCBinaryExpr::Shl: OS << "<<"; break;
case MCBinaryExpr::Sub: OS << '-'; break;
case MCBinaryExpr::Xor: OS << '^'; break;
// Only print parens around the LHS if it is non-trivial.
if (isa<MCConstantExpr>(BE.getRHS()) || isa<MCSymbolRefExpr>(BE.getRHS())) {
BE.getRHS()->print(OS, MAI);
} else {
OS << '(';
BE.getRHS()->print(OS, MAI);
OS << ')';
llvm_unreachable("Invalid expression kind!");
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void MCExpr::dump() const {
dbgs() << *this;
dbgs() << '\n';
/* *** */
const MCBinaryExpr *MCBinaryExpr::create(Opcode Opc, const MCExpr *LHS,
const MCExpr *RHS, MCContext &Ctx,
SMLoc Loc) {
return new (Ctx) MCBinaryExpr(Opc, LHS, RHS, Loc);
const MCUnaryExpr *MCUnaryExpr::create(Opcode Opc, const MCExpr *Expr,
MCContext &Ctx, SMLoc Loc) {
return new (Ctx) MCUnaryExpr(Opc, Expr, Loc);
const MCConstantExpr *MCConstantExpr::create(int64_t Value, MCContext &Ctx,
bool PrintInHex,
unsigned SizeInBytes) {
return new (Ctx) MCConstantExpr(Value, PrintInHex, SizeInBytes);
/* *** */
MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind,
const MCAsmInfo *MAI, SMLoc Loc)
: MCExpr(MCExpr::SymbolRef, Loc,
encodeSubclassData(Kind, MAI->hasSubsectionsViaSymbols())),
Symbol(Symbol) {
const MCSymbolRefExpr *MCSymbolRefExpr::create(const MCSymbol *Sym,
VariantKind Kind,
MCContext &Ctx, SMLoc Loc) {
return new (Ctx) MCSymbolRefExpr(Sym, Kind, Ctx.getAsmInfo(), Loc);
const MCSymbolRefExpr *MCSymbolRefExpr::create(StringRef Name, VariantKind Kind,
MCContext &Ctx) {
return create(Ctx.getOrCreateSymbol(Name), Kind, Ctx);
StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
switch (Kind) {
case VK_Invalid: return "<<invalid>>";
case VK_None: return "<<none>>";
case VK_DTPOFF: return "DTPOFF";
case VK_DTPREL: return "DTPREL";
case VK_GOT: return "GOT";
case VK_GOTOFF: return "GOTOFF";
case VK_GOTREL: return "GOTREL";
case VK_PCREL: return "PCREL";
case VK_GOTPCREL: return "GOTPCREL";
case VK_GOTTPOFF: return "GOTTPOFF";
case VK_NTPOFF: return "NTPOFF";
case VK_PLT: return "PLT";
case VK_TLSGD: return "TLSGD";
case VK_TLSLD: return "TLSLD";
case VK_TLSLDM: return "TLSLDM";
case VK_TPOFF: return "TPOFF";
case VK_TPREL: return "TPREL";
case VK_TLSCALL: return "tlscall";
case VK_TLSDESC: return "tlsdesc";
case VK_TLVP: return "TLVP";
case VK_TLVPPAGE: return "TLVPPAGE";
case VK_PAGE: return "PAGE";
case VK_PAGEOFF: return "PAGEOFF";
case VK_GOTPAGE: return "GOTPAGE";
case VK_SECREL: return "SECREL32";
case VK_SIZE: return "SIZE";
case VK_WEAKREF: return "WEAKREF";
case VK_X86_ABS8: return "ABS8";
case VK_X86_PLTOFF: return "PLTOFF";
case VK_ARM_NONE: return "none";
case VK_ARM_GOT_PREL: return "GOT_PREL";
case VK_ARM_TARGET1: return "target1";
case VK_ARM_TARGET2: return "target2";
case VK_ARM_PREL31: return "prel31";
case VK_ARM_SBREL: return "sbrel";
case VK_ARM_TLSLDO: return "tlsldo";
case VK_ARM_TLSDESCSEQ: return "tlsdescseq";
case VK_AVR_NONE: return "none";
case VK_AVR_LO8: return "lo8";
case VK_AVR_HI8: return "hi8";
case VK_AVR_HLO8: return "hlo8";
case VK_AVR_DIFF8: return "diff8";
case VK_AVR_DIFF16: return "diff16";
case VK_AVR_DIFF32: return "diff32";
case VK_AVR_PM: return "pm";
case VK_PPC_LO: return "l";
case VK_PPC_HI: return "h";
case VK_PPC_HA: return "ha";
case VK_PPC_HIGH: return "high";
case VK_PPC_HIGHA: return "higha";
case VK_PPC_HIGHER: return "higher";
case VK_PPC_HIGHERA: return "highera";
case VK_PPC_HIGHEST: return "highest";
case VK_PPC_HIGHESTA: return "highesta";
case VK_PPC_GOT_LO: return "got@l";
case VK_PPC_GOT_HI: return "got@h";
case VK_PPC_GOT_HA: return "got@ha";
case VK_PPC_TOCBASE: return "tocbase";
case VK_PPC_TOC: return "toc";
case VK_PPC_TOC_LO: return "toc@l";
case VK_PPC_TOC_HI: return "toc@h";
case VK_PPC_TOC_HA: return "toc@ha";
case VK_PPC_U: return "u";
case VK_PPC_L: return "l";
case VK_PPC_DTPMOD: return "dtpmod";
case VK_PPC_TPREL_LO: return "tprel@l";
case VK_PPC_TPREL_HI: return "tprel@h";
case VK_PPC_TPREL_HA: return "tprel@ha";
case VK_PPC_TPREL_HIGH: return "tprel@high";
case VK_PPC_TPREL_HIGHA: return "tprel@higha";
case VK_PPC_TPREL_HIGHER: return "tprel@higher";
case VK_PPC_TPREL_HIGHERA: return "tprel@highera";
case VK_PPC_TPREL_HIGHEST: return "tprel@highest";
case VK_PPC_TPREL_HIGHESTA: return "tprel@highesta";
case VK_PPC_DTPREL_LO: return "dtprel@l";
case VK_PPC_DTPREL_HI: return "dtprel@h";
case VK_PPC_DTPREL_HA: return "dtprel@ha";
case VK_PPC_DTPREL_HIGH: return "dtprel@high";
case VK_PPC_DTPREL_HIGHA: return "dtprel@higha";
case VK_PPC_DTPREL_HIGHER: return "dtprel@higher";
case VK_PPC_DTPREL_HIGHERA: return "dtprel@highera";
case VK_PPC_DTPREL_HIGHEST: return "dtprel@highest";
case VK_PPC_DTPREL_HIGHESTA: return "dtprel@highesta";
case VK_PPC_GOT_TPREL: return "got@tprel";
case VK_PPC_GOT_TPREL_LO: return "got@tprel@l";
case VK_PPC_GOT_TPREL_HI: return "got@tprel@h";
case VK_PPC_GOT_TPREL_HA: return "got@tprel@ha";
case VK_PPC_GOT_DTPREL: return "got@dtprel";
case VK_PPC_GOT_DTPREL_LO: return "got@dtprel@l";
case VK_PPC_GOT_DTPREL_HI: return "got@dtprel@h";
case VK_PPC_GOT_DTPREL_HA: return "got@dtprel@ha";
case VK_PPC_TLS: return "tls";
case VK_PPC_GOT_TLSGD: return "got@tlsgd";
case VK_PPC_GOT_TLSGD_LO: return "got@tlsgd@l";
case VK_PPC_GOT_TLSGD_HI: return "got@tlsgd@h";
case VK_PPC_GOT_TLSGD_HA: return "got@tlsgd@ha";
case VK_PPC_TLSGD: return "tlsgd";
case VK_PPC_GOT_TLSLD: return "got@tlsld";
case VK_PPC_GOT_TLSLD_LO: return "got@tlsld@l";
case VK_PPC_GOT_TLSLD_HI: return "got@tlsld@h";
case VK_PPC_GOT_TLSLD_HA: return "got@tlsld@ha";
return "got@pcrel";
return "got@tlsgd@pcrel";
return "got@tlsld@pcrel";
return "got@tprel@pcrel";
return "tls@pcrel";
case VK_PPC_TLSLD: return "tlsld";
case VK_PPC_LOCAL: return "local";
case VK_PPC_NOTOC: return "notoc";
case VK_PPC_PCREL_OPT: return "<<invalid>>";
case VK_COFF_IMGREL32: return "IMGREL";
case VK_Hexagon_LO16: return "LO16";
case VK_Hexagon_HI16: return "HI16";
case VK_Hexagon_GPREL: return "GPREL";
case VK_Hexagon_GD_GOT: return "GDGOT";
case VK_Hexagon_LD_GOT: return "LDGOT";
case VK_Hexagon_GD_PLT: return "GDPLT";
case VK_Hexagon_LD_PLT: return "LDPLT";
case VK_Hexagon_IE: return "IE";
case VK_Hexagon_IE_GOT: return "IEGOT";
case VK_WASM_MBREL: return "MBREL";
case VK_WASM_TLSREL: return "TLSREL";
case VK_WASM_TBREL: return "TBREL";
case VK_AMDGPU_GOTPCREL32_LO: return "gotpcrel32@lo";
case VK_AMDGPU_GOTPCREL32_HI: return "gotpcrel32@hi";
case VK_AMDGPU_REL32_LO: return "rel32@lo";
case VK_AMDGPU_REL32_HI: return "rel32@hi";
case VK_AMDGPU_REL64: return "rel64";
case VK_AMDGPU_ABS32_LO: return "abs32@lo";
case VK_AMDGPU_ABS32_HI: return "abs32@hi";
case VK_VE_HI32: return "hi";
case VK_VE_LO32: return "lo";
case VK_VE_PC_HI32: return "pc_hi";
case VK_VE_PC_LO32: return "pc_lo";
case VK_VE_GOT_HI32: return "got_hi";
case VK_VE_GOT_LO32: return "got_lo";
case VK_VE_GOTOFF_HI32: return "gotoff_hi";
case VK_VE_GOTOFF_LO32: return "gotoff_lo";
case VK_VE_PLT_HI32: return "plt_hi";
case VK_VE_PLT_LO32: return "plt_lo";
case VK_VE_TLS_GD_HI32: return "tls_gd_hi";
case VK_VE_TLS_GD_LO32: return "tls_gd_lo";
case VK_VE_TPOFF_HI32: return "tpoff_hi";
case VK_VE_TPOFF_LO32: return "tpoff_lo";
llvm_unreachable("Invalid variant kind");
MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
return StringSwitch<VariantKind>(Name.lower())
.Case("dtprel", VK_DTPREL)
.Case("dtpoff", VK_DTPOFF)
.Case("got", VK_GOT)
.Case("gotoff", VK_GOTOFF)
.Case("gotrel", VK_GOTREL)
.Case("pcrel", VK_PCREL)
.Case("gotpcrel", VK_GOTPCREL)
.Case("gottpoff", VK_GOTTPOFF)
.Case("indntpoff", VK_INDNTPOFF)
.Case("ntpoff", VK_NTPOFF)
.Case("gotntpoff", VK_GOTNTPOFF)
.Case("plt", VK_PLT)
.Case("tlscall", VK_TLSCALL)
.Case("tlsdesc", VK_TLSDESC)
.Case("tlsgd", VK_TLSGD)
.Case("tlsld", VK_TLSLD)
.Case("tlsldm", VK_TLSLDM)
.Case("tpoff", VK_TPOFF)
.Case("tprel", VK_TPREL)
.Case("tlvp", VK_TLVP)
.Case("tlvppage", VK_TLVPPAGE)
.Case("tlvppageoff", VK_TLVPPAGEOFF)
.Case("page", VK_PAGE)
.Case("pageoff", VK_PAGEOFF)
.Case("gotpage", VK_GOTPAGE)
.Case("gotpageoff", VK_GOTPAGEOFF)
.Case("imgrel", VK_COFF_IMGREL32)
.Case("secrel32", VK_SECREL)
.Case("size", VK_SIZE)
.Case("abs8", VK_X86_ABS8)
.Case("pltoff", VK_X86_PLTOFF)
.Case("l", VK_PPC_LO)
.Case("h", VK_PPC_HI)
.Case("ha", VK_PPC_HA)
.Case("high", VK_PPC_HIGH)
.Case("higha", VK_PPC_HIGHA)
.Case("higher", VK_PPC_HIGHER)
.Case("highera", VK_PPC_HIGHERA)
.Case("highest", VK_PPC_HIGHEST)
.Case("highesta", VK_PPC_HIGHESTA)
.Case("got@l", VK_PPC_GOT_LO)
.Case("got@h", VK_PPC_GOT_HI)
.Case("got@ha", VK_PPC_GOT_HA)
.Case("local", VK_PPC_LOCAL)
.Case("tocbase", VK_PPC_TOCBASE)
.Case("toc", VK_PPC_TOC)
.Case("toc@l", VK_PPC_TOC_LO)
.Case("toc@h", VK_PPC_TOC_HI)
.Case("toc@ha", VK_PPC_TOC_HA)
.Case("u", VK_PPC_U)
.Case("l", VK_PPC_L)
.Case("tls", VK_PPC_TLS)
.Case("dtpmod", VK_PPC_DTPMOD)
.Case("tprel@l", VK_PPC_TPREL_LO)
.Case("tprel@h", VK_PPC_TPREL_HI)
.Case("tprel@ha", VK_PPC_TPREL_HA)
.Case("tprel@high", VK_PPC_TPREL_HIGH)
.Case("tprel@higha", VK_PPC_TPREL_HIGHA)
.Case("tprel@higher", VK_PPC_TPREL_HIGHER)
.Case("tprel@highera", VK_PPC_TPREL_HIGHERA)
.Case("tprel@highest", VK_PPC_TPREL_HIGHEST)
.Case("tprel@highesta", VK_PPC_TPREL_HIGHESTA)
.Case("dtprel@l", VK_PPC_DTPREL_LO)
.Case("dtprel@h", VK_PPC_DTPREL_HI)
.Case("dtprel@ha", VK_PPC_DTPREL_HA)
.Case("dtprel@high", VK_PPC_DTPREL_HIGH)
.Case("dtprel@higha", VK_PPC_DTPREL_HIGHA)
.Case("dtprel@higher", VK_PPC_DTPREL_HIGHER)
.Case("dtprel@highera", VK_PPC_DTPREL_HIGHERA)
.Case("dtprel@highest", VK_PPC_DTPREL_HIGHEST)
.Case("dtprel@highesta", VK_PPC_DTPREL_HIGHESTA)
.Case("got@tprel", VK_PPC_GOT_TPREL)
.Case("got@tprel@l", VK_PPC_GOT_TPREL_LO)
.Case("got@tprel@h", VK_PPC_GOT_TPREL_HI)
.Case("got@tprel@ha", VK_PPC_GOT_TPREL_HA)
.Case("got@dtprel", VK_PPC_GOT_DTPREL)
.Case("got@dtprel@l", VK_PPC_GOT_DTPREL_LO)
.Case("got@dtprel@h", VK_PPC_GOT_DTPREL_HI)
.Case("got@dtprel@ha", VK_PPC_GOT_DTPREL_HA)
.Case("got@tlsgd", VK_PPC_GOT_TLSGD)
.Case("got@tlsgd@l", VK_PPC_GOT_TLSGD_LO)
.Case("got@tlsgd@h", VK_PPC_GOT_TLSGD_HI)
.Case("got@tlsgd@ha", VK_PPC_GOT_TLSGD_HA)
.Case("got@tlsld", VK_PPC_GOT_TLSLD)
.Case("got@tlsld@l", VK_PPC_GOT_TLSLD_LO)
.Case("got@tlsld@h", VK_PPC_GOT_TLSLD_HI)
.Case("got@tlsld@ha", VK_PPC_GOT_TLSLD_HA)
.Case("got@pcrel", VK_PPC_GOT_PCREL)
.Case("got@tlsgd@pcrel", VK_PPC_GOT_TLSGD_PCREL)
.Case("got@tlsld@pcrel", VK_PPC_GOT_TLSLD_PCREL)
.Case("got@tprel@pcrel", VK_PPC_GOT_TPREL_PCREL)
.Case("tls@pcrel", VK_PPC_TLS_PCREL)
.Case("notoc", VK_PPC_NOTOC)
.Case("gdgot", VK_Hexagon_GD_GOT)
.Case("gdplt", VK_Hexagon_GD_PLT)
.Case("iegot", VK_Hexagon_IE_GOT)
.Case("ie", VK_Hexagon_IE)
.Case("ldgot", VK_Hexagon_LD_GOT)
.Case("ldplt", VK_Hexagon_LD_PLT)
.Case("none", VK_ARM_NONE)
.Case("got_prel", VK_ARM_GOT_PREL)
.Case("target1", VK_ARM_TARGET1)
.Case("target2", VK_ARM_TARGET2)
.Case("prel31", VK_ARM_PREL31)
.Case("sbrel", VK_ARM_SBREL)
.Case("tlsldo", VK_ARM_TLSLDO)
.Case("lo8", VK_AVR_LO8)
.Case("hi8", VK_AVR_HI8)
.Case("hlo8", VK_AVR_HLO8)
.Case("typeindex", VK_WASM_TYPEINDEX)
.Case("tbrel", VK_WASM_TBREL)
.Case("mbrel", VK_WASM_MBREL)
.Case("tlsrel", VK_WASM_TLSREL)
.Case("gotpcrel32@lo", VK_AMDGPU_GOTPCREL32_LO)
.Case("gotpcrel32@hi", VK_AMDGPU_GOTPCREL32_HI)
.Case("rel32@lo", VK_AMDGPU_REL32_LO)
.Case("rel32@hi", VK_AMDGPU_REL32_HI)
.Case("rel64", VK_AMDGPU_REL64)
.Case("abs32@lo", VK_AMDGPU_ABS32_LO)
.Case("abs32@hi", VK_AMDGPU_ABS32_HI)
.Case("hi", VK_VE_HI32)
.Case("lo", VK_VE_LO32)
.Case("pc_hi", VK_VE_PC_HI32)
.Case("pc_lo", VK_VE_PC_LO32)
.Case("got_hi", VK_VE_GOT_HI32)
.Case("got_lo", VK_VE_GOT_LO32)
.Case("gotoff_hi", VK_VE_GOTOFF_HI32)
.Case("gotoff_lo", VK_VE_GOTOFF_LO32)
.Case("plt_hi", VK_VE_PLT_HI32)
.Case("plt_lo", VK_VE_PLT_LO32)
.Case("tls_gd_hi", VK_VE_TLS_GD_HI32)
.Case("tls_gd_lo", VK_VE_TLS_GD_LO32)
.Case("tpoff_hi", VK_VE_TPOFF_HI32)
.Case("tpoff_lo", VK_VE_TPOFF_LO32)
/* *** */
void MCTargetExpr::anchor() {}
/* *** */
bool MCExpr::evaluateAsAbsolute(int64_t &Res) const {
return evaluateAsAbsolute(Res, nullptr, nullptr, nullptr, false);
bool MCExpr::evaluateAsAbsolute(int64_t &Res,
const MCAsmLayout &Layout) const {
return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr, false);
bool MCExpr::evaluateAsAbsolute(int64_t &Res,
const MCAsmLayout &Layout,
const SectionAddrMap &Addrs) const {
// Setting InSet causes us to absolutize differences across sections and that
// is what the MachO writer uses Addrs for.
return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs, true);
bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const {
return evaluateAsAbsolute(Res, &Asm, nullptr, nullptr, false);
bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm) const {
return evaluateAsAbsolute(Res, Asm, nullptr, nullptr, false);
bool MCExpr::evaluateKnownAbsolute(int64_t &Res,
const MCAsmLayout &Layout) const {
return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr,
bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
const MCAsmLayout *Layout,
const SectionAddrMap *Addrs, bool InSet) const {
MCValue Value;
// Fast path constants.
if (const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(this)) {
Res = CE->getValue();
return true;
bool IsRelocatable =
evaluateAsRelocatableImpl(Value, Asm, Layout, nullptr, Addrs, InSet);
// Record the current value.
Res = Value.getConstant();
return IsRelocatable && Value.isAbsolute();
/// Helper method for \see EvaluateSymbolAdd().
static void AttemptToFoldSymbolOffsetDifference(
const MCAssembler *Asm, const MCAsmLayout *Layout,
const SectionAddrMap *Addrs, bool InSet, const MCSymbolRefExpr *&A,
const MCSymbolRefExpr *&B, int64_t &Addend) {
if (!A || !B)
const MCSymbol &SA = A->getSymbol();
const MCSymbol &SB = B->getSymbol();
if (SA.isUndefined() || SB.isUndefined())
if (!Asm->getWriter().isSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet))
auto FinalizeFolding = [&]() {
// Pointers to Thumb symbols need to have their low-bit set to allow
// for interworking.
if (Asm->isThumbFunc(&SA))
Addend |= 1;
// If symbol is labeled as micromips, we set low-bit to ensure
// correct offset in .gcc_except_table
if (Asm->getBackend().isMicroMips(&SA))
Addend |= 1;
// Clear the symbol expr pointers to indicate we have folded these
// operands.
A = B = nullptr;
const MCFragment *FA = SA.getFragment();
const MCFragment *FB = SB.getFragment();
// If both symbols are in the same fragment, return the difference of their
// offsets
if (FA == FB && !SA.isVariable() && !SA.isUnset() && !SB.isVariable() &&
!SB.isUnset()) {
Addend += SA.getOffset() - SB.getOffset();
return FinalizeFolding();
const MCSection &SecA = *FA->getParent();
const MCSection &SecB = *FB->getParent();
if ((&SecA != &SecB) && !Addrs)
if (Layout) {
// One of the symbol involved is part of a fragment being laid out. Quit now
// to avoid a self loop.
if (!Layout->canGetFragmentOffset(FA) || !Layout->canGetFragmentOffset(FB))
// Eagerly evaluate when layout is finalized.
Addend += Layout->getSymbolOffset(A->getSymbol()) -
if (Addrs && (&SecA != &SecB))
Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB));
} else {
// When layout is not finalized, our ability to resolve differences between
// symbols is limited to specific cases where the fragments between two
// symbols (including the fragments the symbols are defined in) are
// fixed-size fragments so the difference can be calculated. For example,
// this is important when the Subtarget is changed and a new MCDataFragment
// is created in the case of foo: instr; .arch_extension ext; instr .if . -
// foo.
if (SA.isVariable() || SA.isUnset() || SB.isVariable() || SB.isUnset() ||
FA->getKind() != MCFragment::FT_Data ||
FB->getKind() != MCFragment::FT_Data ||
FA->getSubsectionNumber() != FB->getSubsectionNumber())
// Try to find a constant displacement from FA to FB, add the displacement
// between the offset in FA of SA and the offset in FB of SB.
int64_t Displacement = SA.getOffset() - SB.getOffset();
for (auto FI = FB->getIterator(), FE = SecA.end(); FI != FE; ++FI) {
if (&*FI == FA) {
Addend += Displacement;
return FinalizeFolding();
if (FI->getKind() != MCFragment::FT_Data)
Displacement += cast<MCDataFragment>(FI)->getContents().size();
static bool canFold(const MCAssembler *Asm, const MCSymbolRefExpr *A,
const MCSymbolRefExpr *B, bool InSet) {
if (InSet)
return true;
if (!Asm->getBackend().requiresDiffExpressionRelocations())
return true;
const MCSymbol &CheckSym = A ? A->getSymbol() : B->getSymbol();
if (!CheckSym.isInSection())
return true;
if (!CheckSym.getSection().hasInstructions())
return true;
return false;
/// Evaluate the result of an add between (conceptually) two MCValues.
/// This routine conceptually attempts to construct an MCValue:
/// Result = (Result_A - Result_B + Result_Cst)
/// from two MCValue's LHS and RHS where
/// Result = LHS + RHS
/// and
/// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
/// This routine attempts to aggressively fold the operands such that the result
/// is representable in an MCValue, but may not always succeed.
/// \returns True on success, false if the result is not representable in an
/// MCValue.
/// NOTE: It is really important to have both the Asm and Layout arguments.
/// They might look redundant, but this function can be used before layout
/// is done (see the object streamer for example) and having the Asm argument
/// lets us avoid relaxations early.
static bool
EvaluateSymbolicAdd(const MCAssembler *Asm, const MCAsmLayout *Layout,
const SectionAddrMap *Addrs, bool InSet, const MCValue &LHS,
const MCSymbolRefExpr *RHS_A, const MCSymbolRefExpr *RHS_B,
int64_t RHS_Cst, MCValue &Res) {
// FIXME: This routine (and other evaluation parts) are *incredibly* sloppy
// about dealing with modifiers. This will ultimately bite us, one day.
const MCSymbolRefExpr *LHS_A = LHS.getSymA();
const MCSymbolRefExpr *LHS_B = LHS.getSymB();
int64_t LHS_Cst = LHS.getConstant();
// Fold the result constant immediately.
int64_t Result_Cst = LHS_Cst + RHS_Cst;
assert((!Layout || Asm) &&
"Must have an assembler object if layout is given!");
// If we have a layout, we can fold resolved differences. Do not do this if
// the backend requires this to be emitted as individual relocations, unless
// the InSet flag is set to get the current difference anyway (used for
// example to calculate symbol sizes).
if (Asm && canFold(Asm, LHS_A, LHS_B, InSet)) {
// First, fold out any differences which are fully resolved. By
// reassociating terms in
// Result = (LHS_A - LHS_B + LHS_Cst) + (RHS_A - RHS_B + RHS_Cst).
// we have the four possible differences:
// (LHS_A - LHS_B),
// (LHS_A - RHS_B),
// (RHS_A - LHS_B),
// (RHS_A - RHS_B).
// Since we are attempting to be as aggressive as possible about folding, we
// attempt to evaluate each possible alternative.
AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, LHS_B,
AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B,
AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B,
AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B,
// We can't represent the addition or subtraction of two symbols.
if ((LHS_A && RHS_A) || (LHS_B && RHS_B))
return false;
// At this point, we have at most one additive symbol and one subtractive
// symbol -- find them.
const MCSymbolRefExpr *A = LHS_A ? LHS_A : RHS_A;
const MCSymbolRefExpr *B = LHS_B ? LHS_B : RHS_B;
Res = MCValue::get(A, B, Result_Cst);
return true;
bool MCExpr::evaluateAsRelocatable(MCValue &Res,
const MCAsmLayout *Layout,
const MCFixup *Fixup) const {
MCAssembler *Assembler = Layout ? &Layout->getAssembler() : nullptr;
return evaluateAsRelocatableImpl(Res, Assembler, Layout, Fixup, nullptr,
bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const {
MCAssembler *Assembler = &Layout.getAssembler();
return evaluateAsRelocatableImpl(Res, Assembler, &Layout, nullptr, nullptr,
static bool canExpand(const MCSymbol &Sym, bool InSet) {
const MCExpr *Expr = Sym.getVariableValue();
const auto *Inner = dyn_cast<MCSymbolRefExpr>(Expr);
if (Inner) {
if (Inner->getKind() == MCSymbolRefExpr::VK_WEAKREF)
return false;
if (InSet)
return true;
return !Sym.isInSection();
bool MCExpr::evaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm,
const MCAsmLayout *Layout,
const MCFixup *Fixup,
const SectionAddrMap *Addrs,
bool InSet) const {
switch (getKind()) {
case Target:
return cast<MCTargetExpr>(this)->evaluateAsRelocatableImpl(Res, Layout,
case Constant:
Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
return true;
case SymbolRef: {
const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
const MCSymbol &Sym = SRE->getSymbol();
const auto Kind = SRE->getKind();
// Evaluate recursively if this is a variable.
if (Sym.isVariable() && (Kind == MCSymbolRefExpr::VK_None || Layout) &&
canExpand(Sym, InSet)) {
bool IsMachO = SRE->hasSubsectionsViaSymbols();
if (Sym.getVariableValue()->evaluateAsRelocatableImpl(
Res, Asm, Layout, Fixup, Addrs, InSet || IsMachO)) {
if (Kind != MCSymbolRefExpr::VK_None) {
if (Res.isAbsolute()) {
Res = MCValue::get(SRE, nullptr, 0);
return true;
// If the reference has a variant kind, we can only handle expressions
// which evaluate exactly to a single unadorned symbol. Attach the
// original VariantKind to SymA of the result.
if (Res.getRefKind() != MCSymbolRefExpr::VK_None || !Res.getSymA() ||
Res.getSymB() || Res.getConstant())
return false;
Res =
Kind, Asm->getContext()),
Res.getSymB(), Res.getConstant(), Res.getRefKind());
if (!IsMachO)
return true;
const MCSymbolRefExpr *A = Res.getSymA();
const MCSymbolRefExpr *B = Res.getSymB();
// FIXME: This is small hack. Given
// a = b + 4
// .long a
// the OS X assembler will completely drop the 4. We should probably
// include it in the relocation or produce an error if that is not
// possible.
// Allow constant expressions.
if (!A && !B)
return true;
// Allows aliases with zero offset.
if (Res.getConstant() == 0 && (!A || !B))
return true;
Res = MCValue::get(SRE, nullptr, 0);
return true;
case Unary: {
const MCUnaryExpr *AUE = cast<MCUnaryExpr>(this);
MCValue Value;
if (!AUE->getSubExpr()->evaluateAsRelocatableImpl(Value, Asm, Layout, Fixup,
Addrs, InSet))
return false;
switch (AUE->getOpcode()) {
case MCUnaryExpr::LNot:
if (!Value.isAbsolute())
return false;
Res = MCValue::get(!Value.getConstant());
case MCUnaryExpr::Minus:
/// -(a - b + const) ==> (b - a - const)
if (Value.getSymA() && !Value.getSymB())
return false;
// The cast avoids undefined behavior if the constant is INT64_MIN.
Res = MCValue::get(Value.getSymB(), Value.getSymA(),
case MCUnaryExpr::Not:
if (!Value.isAbsolute())
return false;
Res = MCValue::get(~Value.getConstant());
case MCUnaryExpr::Plus:
Res = Value;
return true;
case Binary: {
const MCBinaryExpr *ABE = cast<MCBinaryExpr>(this);
MCValue LHSValue, RHSValue;
if (!ABE->getLHS()->evaluateAsRelocatableImpl(LHSValue, Asm, Layout, Fixup,
Addrs, InSet) ||
!ABE->getRHS()->evaluateAsRelocatableImpl(RHSValue, Asm, Layout, Fixup,
Addrs, InSet)) {
// Check if both are Target Expressions, see if we can compare them.
if (const MCTargetExpr *L = dyn_cast<MCTargetExpr>(ABE->getLHS()))
if (const MCTargetExpr *R = cast<MCTargetExpr>(ABE->getRHS())) {
switch (ABE->getOpcode()) {
case MCBinaryExpr::EQ:
Res = MCValue::get((L->isEqualTo(R)) ? -1 : 0);
return true;
case MCBinaryExpr::NE:
Res = MCValue::get((R->isEqualTo(R)) ? 0 : -1);
return true;
default: break;
return false;
// We only support a few operations on non-constant expressions, handle
// those first.
if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
switch (ABE->getOpcode()) {
return false;
case MCBinaryExpr::Sub:
// Negate RHS and add.
// The cast avoids undefined behavior if the constant is INT64_MIN.
return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
RHSValue.getSymB(), RHSValue.getSymA(),
-(uint64_t)RHSValue.getConstant(), Res);
case MCBinaryExpr::Add:
return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
RHSValue.getSymA(), RHSValue.getSymB(),
RHSValue.getConstant(), Res);
// FIXME: We need target hooks for the evaluation. It may be limited in
// width, and gas defines the result of comparisons differently from
// Apple as.
int64_t LHS = LHSValue.getConstant(), RHS = RHSValue.getConstant();
int64_t Result = 0;
auto Op = ABE->getOpcode();
switch (Op) {
case MCBinaryExpr::AShr: Result = LHS >> RHS; break;
case MCBinaryExpr::Add: Result = LHS + RHS; break;
case MCBinaryExpr::And: Result = LHS & RHS; break;
case MCBinaryExpr::Div:
case MCBinaryExpr::Mod:
// Handle division by zero. gas just emits a warning and keeps going,
// we try to be stricter.
// FIXME: Currently the caller of this function has no way to understand
// we're bailing out because of 'division by zero'. Therefore, it will
// emit a 'expected relocatable expression' error. It would be nice to
// change this code to emit a better diagnostic.
if (RHS == 0)
return false;
if (ABE->getOpcode() == MCBinaryExpr::Div)
Result = LHS / RHS;
Result = LHS % RHS;
case MCBinaryExpr::EQ: Result = LHS == RHS; break;
case MCBinaryExpr::GT: Result = LHS > RHS; break;
case MCBinaryExpr::GTE: Result = LHS >= RHS; break;
case MCBinaryExpr::LAnd: Result = LHS && RHS; break;
case MCBinaryExpr::LOr: Result = LHS || RHS; break;
case MCBinaryExpr::LShr: Result = uint64_t(LHS) >> uint64_t(RHS); break;
case MCBinaryExpr::LT: Result = LHS < RHS; break;
case MCBinaryExpr::LTE: Result = LHS <= RHS; break;
case MCBinaryExpr::Mul: Result = LHS * RHS; break;
case MCBinaryExpr::NE: Result = LHS != RHS; break;
case MCBinaryExpr::Or: Result = LHS | RHS; break;
case MCBinaryExpr::OrNot: Result = LHS | ~RHS; break;
case MCBinaryExpr::Shl: Result = uint64_t(LHS) << uint64_t(RHS); break;
case MCBinaryExpr::Sub: Result = LHS - RHS; break;
case MCBinaryExpr::Xor: Result = LHS ^ RHS; break;
switch (Op) {
Res = MCValue::get(Result);
case MCBinaryExpr::EQ:
case MCBinaryExpr::GT:
case MCBinaryExpr::GTE:
case MCBinaryExpr::LT:
case MCBinaryExpr::LTE:
case MCBinaryExpr::NE:
// A comparison operator returns a -1 if true and 0 if false.
Res = MCValue::get(Result ? -1 : 0);
return true;
llvm_unreachable("Invalid assembly expression kind!");
MCFragment *MCExpr::findAssociatedFragment() const {
switch (getKind()) {
case Target:
// We never look through target specific expressions.
return cast<MCTargetExpr>(this)->findAssociatedFragment();
case Constant:
return MCSymbol::AbsolutePseudoFragment;
case SymbolRef: {
const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
const MCSymbol &Sym = SRE->getSymbol();
return Sym.getFragment();
case Unary:
return cast<MCUnaryExpr>(this)->getSubExpr()->findAssociatedFragment();
case Binary: {
const MCBinaryExpr *BE = cast<MCBinaryExpr>(this);
MCFragment *LHS_F = BE->getLHS()->findAssociatedFragment();
MCFragment *RHS_F = BE->getRHS()->findAssociatedFragment();
// If either is absolute, return the other.
if (LHS_F == MCSymbol::AbsolutePseudoFragment)
return RHS_F;
if (RHS_F == MCSymbol::AbsolutePseudoFragment)
return LHS_F;
// Not always correct, but probably the best we can do without more context.
if (BE->getOpcode() == MCBinaryExpr::Sub)
return MCSymbol::AbsolutePseudoFragment;
// Otherwise, return the first non-null fragment.
return LHS_F ? LHS_F : RHS_F;
llvm_unreachable("Invalid assembly expression kind!");