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llvm-6502/lib/MC/MCExpr.cpp
Rafael Espindola 7521964d28 Move alignment from MCSectionData to MCSection. 
This starts merging MCSection and MCSectionData.

There are a few issues with the current split between MCSection and
MCSectionData.

* It optimizes the the not as important case. We want the production
of .o files to be really fast, but the split puts the information used
for .o emission in a separate data structure.

* The ELF/COFF/MachO hierarchy is not represented in MCSectionData,
leading to some ad-hoc ways to represent the various flags.

* It makes it harder to remember where each item is.

The attached patch starts merging the two by moving the alignment from
MCSectionData to MCSection.

Most of the patch is actually just dropping 'const', since
MCSectionData is mutable, but MCSection was not.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237936 91177308-0d34-0410-b5e6-96231b3b80d8
2015-05-21 19:20:38 +00:00

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//===- MCExpr.cpp - Assembly Level Expression Implementation --------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCExpr.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringSwitch.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/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
#define DEBUG_TYPE "mcexpr"
namespace {
namespace stats {
STATISTIC(MCExprEvaluate, "Number of MCExpr evaluations");
}
}
void MCExpr::print(raw_ostream &OS) const {
switch (getKind()) {
case MCExpr::Target:
return cast<MCTargetExpr>(this)->PrintImpl(OS);
case MCExpr::Constant:
OS << cast<MCConstantExpr>(*this).getValue();
return;
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 = Sym.getName()[0] == '$';
if (UseParens)
OS << '(' << Sym << ')';
else
OS << Sym;
if (SRE.getKind() != MCSymbolRefExpr::VK_None)
SRE.printVariantKind(OS);
return;
}
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;
}
OS << *UE.getSubExpr();
return;
}
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())) {
OS << *BE.getLHS();
} else {
OS << '(' << *BE.getLHS() << ')';
}
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();
return;
}
}
OS << '+';
break;
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::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())) {
OS << *BE.getRHS();
} else {
OS << '(' << *BE.getRHS() << ')';
}
return;
}
}
llvm_unreachable("Invalid expression kind!");
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void MCExpr::dump() const {
print(dbgs());
dbgs() << '\n';
}
#endif
/* *** */
const MCBinaryExpr *MCBinaryExpr::Create(Opcode Opc, const MCExpr *LHS,
const MCExpr *RHS, MCContext &Ctx) {
return new (Ctx) MCBinaryExpr(Opc, LHS, RHS);
}
const MCUnaryExpr *MCUnaryExpr::Create(Opcode Opc, const MCExpr *Expr,
MCContext &Ctx) {
return new (Ctx) MCUnaryExpr(Opc, Expr);
}
const MCConstantExpr *MCConstantExpr::Create(int64_t Value, MCContext &Ctx) {
return new (Ctx) MCConstantExpr(Value);
}
/* *** */
MCSymbolRefExpr::MCSymbolRefExpr(const MCSymbol *Symbol, VariantKind Kind,
const MCAsmInfo *MAI)
: MCExpr(MCExpr::SymbolRef), Kind(Kind),
UseParensForSymbolVariant(MAI->useParensForSymbolVariant()),
HasSubsectionsViaSymbols(MAI->hasSubsectionsViaSymbols()),
Symbol(Symbol) {
assert(Symbol);
}
const MCSymbolRefExpr *MCSymbolRefExpr::Create(const MCSymbol *Sym,
VariantKind Kind,
MCContext &Ctx) {
return new (Ctx) MCSymbolRefExpr(Sym, Kind, Ctx.getAsmInfo());
}
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_GOT: return "GOT";
case VK_GOTOFF: return "GOTOFF";
case VK_GOTPCREL: return "GOTPCREL";
case VK_GOTTPOFF: return "GOTTPOFF";
case VK_INDNTPOFF: return "INDNTPOFF";
case VK_NTPOFF: return "NTPOFF";
case VK_GOTNTPOFF: return "GOTNTPOFF";
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_DTPOFF: return "DTPOFF";
case VK_TLVP: return "TLVP";
case VK_TLVPPAGE: return "TLVPPAGE";
case VK_TLVPPAGEOFF: return "TLVPPAGEOFF";
case VK_PAGE: return "PAGE";
case VK_PAGEOFF: return "PAGEOFF";
case VK_GOTPAGE: return "GOTPAGE";
case VK_GOTPAGEOFF: return "GOTPAGEOFF";
case VK_SECREL: return "SECREL32";
case VK_SIZE: return "SIZE";
case VK_WEAKREF: return "WEAKREF";
case VK_ARM_NONE: return "none";
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_TLSCALL: return "tlscall";
case VK_ARM_TLSDESC: return "tlsdesc";
case VK_ARM_TLSDESCSEQ: return "tlsdescseq";
case VK_PPC_LO: return "l";
case VK_PPC_HI: return "h";
case VK_PPC_HA: return "ha";
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_DTPMOD: return "dtpmod";
case VK_PPC_TPREL: return "tprel";
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_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: return "dtprel";
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_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";
case VK_PPC_TLSLD: return "tlsld";
case VK_PPC_LOCAL: return "local";
case VK_Mips_GPREL: return "GPREL";
case VK_Mips_GOT_CALL: return "GOT_CALL";
case VK_Mips_GOT16: return "GOT16";
case VK_Mips_GOT: return "GOT";
case VK_Mips_ABS_HI: return "ABS_HI";
case VK_Mips_ABS_LO: return "ABS_LO";
case VK_Mips_TLSGD: return "TLSGD";
case VK_Mips_TLSLDM: return "TLSLDM";
case VK_Mips_DTPREL_HI: return "DTPREL_HI";
case VK_Mips_DTPREL_LO: return "DTPREL_LO";
case VK_Mips_GOTTPREL: return "GOTTPREL";
case VK_Mips_TPREL_HI: return "TPREL_HI";
case VK_Mips_TPREL_LO: return "TPREL_LO";
case VK_Mips_GPOFF_HI: return "GPOFF_HI";
case VK_Mips_GPOFF_LO: return "GPOFF_LO";
case VK_Mips_GOT_DISP: return "GOT_DISP";
case VK_Mips_GOT_PAGE: return "GOT_PAGE";
case VK_Mips_GOT_OFST: return "GOT_OFST";
case VK_Mips_HIGHER: return "HIGHER";
case VK_Mips_HIGHEST: return "HIGHEST";
case VK_Mips_GOT_HI16: return "GOT_HI16";
case VK_Mips_GOT_LO16: return "GOT_LO16";
case VK_Mips_CALL_HI16: return "CALL_HI16";
case VK_Mips_CALL_LO16: return "CALL_LO16";
case VK_Mips_PCREL_HI16: return "PCREL_HI16";
case VK_Mips_PCREL_LO16: return "PCREL_LO16";
case VK_COFF_IMGREL32: return "IMGREL";
case VK_Hexagon_PCREL: return "PCREL";
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_TPREL: return "tprel";
case VK_DTPREL: return "dtprel";
}
llvm_unreachable("Invalid variant kind");
}
MCSymbolRefExpr::VariantKind
MCSymbolRefExpr::getVariantKindForName(StringRef Name) {
return StringSwitch<VariantKind>(Name.lower())
.Case("got", VK_GOT)
.Case("gotoff", VK_GOTOFF)
.Case("gotpcrel", VK_GOTPCREL)
.Case("got_prel", VK_GOTPCREL)
.Case("gottpoff", VK_GOTTPOFF)
.Case("indntpoff", VK_INDNTPOFF)
.Case("ntpoff", VK_NTPOFF)
.Case("gotntpoff", VK_GOTNTPOFF)
.Case("plt", VK_PLT)
.Case("tlsgd", VK_TLSGD)
.Case("tlsld", VK_TLSLD)
.Case("tlsldm", VK_TLSLDM)
.Case("tpoff", VK_TPOFF)
.Case("dtpoff", VK_DTPOFF)
.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("l", VK_PPC_LO)
.Case("h", VK_PPC_HI)
.Case("ha", VK_PPC_HA)
.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("tls", VK_PPC_TLS)
.Case("dtpmod", VK_PPC_DTPMOD)
.Case("tprel", VK_PPC_TPREL)
.Case("tprel@l", VK_PPC_TPREL_LO)
.Case("tprel@h", VK_PPC_TPREL_HI)
.Case("tprel@ha", VK_PPC_TPREL_HA)
.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", VK_PPC_DTPREL)
.Case("dtprel@l", VK_PPC_DTPREL_LO)
.Case("dtprel@h", VK_PPC_DTPREL_HI)
.Case("dtprel@ha", VK_PPC_DTPREL_HA)
.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("none", VK_ARM_NONE)
.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("tlscall", VK_ARM_TLSCALL)
.Case("tlsdesc", VK_ARM_TLSDESC)
.Default(VK_Invalid);
}
void MCSymbolRefExpr::printVariantKind(raw_ostream &OS) const {
if (UseParensForSymbolVariant)
OS << '(' << MCSymbolRefExpr::getVariantKindName(getKind()) << ')';
else
OS << '@' << MCSymbolRefExpr::getVariantKindName(getKind());
}
/* *** */
void MCTargetExpr::anchor() {}
/* *** */
bool MCExpr::EvaluateAsAbsolute(int64_t &Res) const {
return EvaluateAsAbsolute(Res, nullptr, nullptr, nullptr);
}
bool MCExpr::EvaluateAsAbsolute(int64_t &Res,
const MCAsmLayout &Layout) const {
return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr);
}
bool MCExpr::EvaluateAsAbsolute(int64_t &Res,
const MCAsmLayout &Layout,
const SectionAddrMap &Addrs) const {
return EvaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, &Addrs);
}
bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const {
return EvaluateAsAbsolute(Res, &Asm, nullptr, nullptr);
}
bool MCExpr::evaluateKnownAbsolute(int64_t &Res,
const MCAsmLayout &Layout) const {
return evaluateAsAbsolute(Res, &Layout.getAssembler(), &Layout, nullptr,
true);
}
bool MCExpr::EvaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm,
const MCAsmLayout *Layout,
const SectionAddrMap *Addrs) const {
// FIXME: The use if InSet = Addrs is a hack. Setting InSet causes us
// absolutize differences across sections and that is what the MachO writer
// uses Addrs for.
return evaluateAsAbsolute(Res, Asm, Layout, Addrs, Addrs);
}
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();
}
/// \brief 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)
return;
const MCSymbol &SA = A->getSymbol();
const MCSymbol &SB = B->getSymbol();
if (SA.isUndefined() || SB.isUndefined())
return;
if (!Asm->getWriter().IsSymbolRefDifferenceFullyResolved(*Asm, A, B, InSet))
return;
const MCSymbolData &AD = Asm->getSymbolData(SA);
const MCSymbolData &BD = Asm->getSymbolData(SB);
if (AD.getFragment() == BD.getFragment()) {
Addend += (AD.getOffset() - BD.getOffset());
// Pointers to Thumb symbols need to have their low-bit set to allow
// for interworking.
if (Asm->isThumbFunc(&SA))
Addend |= 1;
// Clear the symbol expr pointers to indicate we have folded these
// operands.
A = B = nullptr;
return;
}
if (!Layout)
return;
const MCSectionData &SecA = *AD.getFragment()->getParent();
const MCSectionData &SecB = *BD.getFragment()->getParent();
if ((&SecA != &SecB) && !Addrs)
return;
// Eagerly evaluate.
Addend += Layout->getSymbolOffset(A->getSymbol()) -
Layout->getSymbolOffset(B->getSymbol());
if (Addrs && (&SecA != &SecB))
Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB));
// Pointers to Thumb symbols need to have their low-bit set to allow
// for interworking.
if (Asm->isThumbFunc(&SA))
Addend |= 1;
// Clear the symbol expr pointers to indicate we have folded these
// operands.
A = B = nullptr;
}
/// \brief 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 aggresively 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.
if (Asm) {
// 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,
Result_Cst);
AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, LHS_A, RHS_B,
Result_Cst);
AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, LHS_B,
Result_Cst);
AttemptToFoldSymbolOffsetDifference(Asm, Layout, Addrs, InSet, RHS_A, RHS_B,
Result_Cst);
}
// 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;
// If we have a negated symbol, then we must have also have a non-negated
// symbol in order to encode the expression.
if (B && !A)
return false;
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,
false);
}
bool MCExpr::evaluateAsValue(MCValue &Res, const MCAsmLayout &Layout) const {
MCAssembler *Assembler = &Layout.getAssembler();
return EvaluateAsRelocatableImpl(Res, Assembler, &Layout, nullptr, nullptr,
true);
}
static bool canExpand(const MCSymbol &Sym, const MCAssembler *Asm, bool InSet) {
if (InSet)
return true;
if (!Asm)
return false;
return !Asm->getWriter().isWeak(Sym);
}
bool MCExpr::EvaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm,
const MCAsmLayout *Layout,
const MCFixup *Fixup,
const SectionAddrMap *Addrs,
bool InSet) const {
++stats::MCExprEvaluate;
switch (getKind()) {
case Target:
return cast<MCTargetExpr>(this)->EvaluateAsRelocatableImpl(Res, Layout,
Fixup);
case Constant:
Res = MCValue::get(cast<MCConstantExpr>(this)->getValue());
return true;
case SymbolRef: {
const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
const MCSymbol &Sym = SRE->getSymbol();
// Evaluate recursively if this is a variable.
if (Sym.isVariable() && SRE->getKind() == MCSymbolRefExpr::VK_None &&
canExpand(Sym, Asm, InSet)) {
bool IsMachO = SRE->hasSubsectionsViaSymbols();
if (Sym.getVariableValue()->EvaluateAsRelocatableImpl(
Res, Asm, Layout, Fixup, Addrs, InSet || IsMachO)) {
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.
if (!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());
break;
case MCUnaryExpr::Minus:
/// -(a - b + const) ==> (b - a - const)
if (Value.getSymA() && !Value.getSymB())
return false;
Res = MCValue::get(Value.getSymB(), Value.getSymA(),
-Value.getConstant());
break;
case MCUnaryExpr::Not:
if (!Value.isAbsolute())
return false;
Res = MCValue::get(~Value.getConstant());
break;
case MCUnaryExpr::Plus:
Res = Value;
break;
}
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))
return false;
// We only support a few operations on non-constant expressions, handle
// those first.
if (!LHSValue.isAbsolute() || !RHSValue.isAbsolute()) {
switch (ABE->getOpcode()) {
default:
return false;
case MCBinaryExpr::Sub:
// Negate RHS and add.
return EvaluateSymbolicAdd(Asm, Layout, Addrs, InSet, LHSValue,
RHSValue.getSymB(), RHSValue.getSymA(),
-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;
switch (ABE->getOpcode()) {
case MCBinaryExpr::AShr: Result = LHS >> RHS; break;
case MCBinaryExpr::Add: Result = LHS + RHS; break;
case MCBinaryExpr::And: Result = LHS & RHS; break;
case MCBinaryExpr::Div: Result = LHS / RHS; break;
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::Mod: 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::Shl: Result = LHS << RHS; break;
case MCBinaryExpr::Sub: Result = LHS - RHS; break;
case MCBinaryExpr::Xor: Result = LHS ^ RHS; break;
}
Res = MCValue::get(Result);
return true;
}
}
llvm_unreachable("Invalid assembly expression kind!");
}
MCSection *MCExpr::FindAssociatedSection() const {
switch (getKind()) {
case Target:
// We never look through target specific expressions.
return cast<MCTargetExpr>(this)->FindAssociatedSection();
case Constant:
return MCSymbol::AbsolutePseudoSection;
case SymbolRef: {
const MCSymbolRefExpr *SRE = cast<MCSymbolRefExpr>(this);
const MCSymbol &Sym = SRE->getSymbol();
if (Sym.isDefined())
return &Sym.getSection();
return nullptr;
}
case Unary:
return cast<MCUnaryExpr>(this)->getSubExpr()->FindAssociatedSection();
case Binary: {
const MCBinaryExpr *BE = cast<MCBinaryExpr>(this);
MCSection *LHS_S = BE->getLHS()->FindAssociatedSection();
MCSection *RHS_S = BE->getRHS()->FindAssociatedSection();
// If either section is absolute, return the other.
if (LHS_S == MCSymbol::AbsolutePseudoSection)
return RHS_S;
if (RHS_S == MCSymbol::AbsolutePseudoSection)
return LHS_S;
// Not always correct, but probably the best we can do without more context.
if (BE->getOpcode() == MCBinaryExpr::Sub)
return MCSymbol::AbsolutePseudoSection;
// Otherwise, return the first non-null section.
return LHS_S ? LHS_S : RHS_S;
}
}
llvm_unreachable("Invalid assembly expression kind!");
}
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