| //===- MCExpr.cpp - Assembly Level Expression Implementation --------------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt 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/StringSwitch.h" |
| #include "llvm/Config/llvm-config.h" |
| #include "llvm/MC/MCAsmBackend.h" |
| #include "llvm/MC/MCAsmInfo.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 |
| |
| // VariantKind printing and formatting utilize MAI. operator<< (dump and some |
| // target code) specifies MAI as nullptr and should be avoided when MAI is |
| // needed. |
| 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) { |
| default: |
| OS << "0x" << Twine::utohexstr(Value); |
| break; |
| case 1: |
| OS << format("0x%02" PRIx64, Value); |
| break; |
| case 2: |
| OS << format("0x%04" PRIx64, Value); |
| break; |
| case 4: |
| OS << format("0x%08" PRIx64, Value); |
| break; |
| case 8: |
| OS << format("0x%016" PRIx64, Value); |
| break; |
| } |
| else |
| OS << Value; |
| 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 = MAI && MAI->useParensForDollarSignNames() && !InParens && |
| Sym.getName().starts_with('$'); |
| |
| 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) // should only be used by dump() |
| OS << "@<variant " << Kind << '>'; |
| else if (MAI->useParensForSymbolVariant()) // ARM |
| OS << '(' << MAI->getVariantKindName(Kind) << ')'; |
| else |
| OS << '@' << MAI->getVariantKindName(Kind); |
| } |
| |
| 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; |
| } |
| bool Binary = UE.getSubExpr()->getKind() == MCExpr::Binary; |
| if (Binary) OS << "("; |
| UE.getSubExpr()->print(OS, MAI); |
| if (Binary) OS << ")"; |
| 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())) { |
| 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(); |
| 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::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 << ')'; |
| } |
| return; |
| } |
| } |
| |
| llvm_unreachable("Invalid expression kind!"); |
| } |
| |
| #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) |
| LLVM_DUMP_METHOD void MCExpr::dump() const { |
| dbgs() << *this; |
| dbgs() << '\n'; |
| } |
| #endif |
| |
| bool MCExpr::isSymbolUsedInExpression(const MCSymbol *Sym) const { |
| switch (getKind()) { |
| case MCExpr::Binary: { |
| const MCBinaryExpr *BE = static_cast<const MCBinaryExpr *>(this); |
| return BE->getLHS()->isSymbolUsedInExpression(Sym) || |
| BE->getRHS()->isSymbolUsedInExpression(Sym); |
| } |
| case MCExpr::Target: { |
| const MCTargetExpr *TE = static_cast<const MCTargetExpr *>(this); |
| return TE->isSymbolUsedInExpression(Sym); |
| } |
| case MCExpr::Constant: |
| return false; |
| case MCExpr::SymbolRef: { |
| const MCSymbol &S = static_cast<const MCSymbolRefExpr *>(this)->getSymbol(); |
| if (S.isVariable() && !S.isWeakExternal()) |
| return S.getVariableValue()->isSymbolUsedInExpression(Sym); |
| return &S == Sym; |
| } |
| case MCExpr::Unary: { |
| const MCExpr *SubExpr = |
| static_cast<const MCUnaryExpr *>(this)->getSubExpr(); |
| return SubExpr->isSymbolUsedInExpression(Sym); |
| } |
| } |
| |
| llvm_unreachable("Unknown expr kind!"); |
| } |
| |
| /* *** */ |
| |
| 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) { |
| assert(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); |
| } |
| |
| /* *** */ |
| |
| void MCTargetExpr::anchor() {} |
| |
| /* *** */ |
| |
| bool MCExpr::evaluateAsAbsolute(int64_t &Res) const { |
| return evaluateAsAbsolute(Res, nullptr, nullptr, false); |
| } |
| |
| bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm, |
| 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, &Asm, &Addrs, true); |
| } |
| |
| bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler &Asm) const { |
| return evaluateAsAbsolute(Res, &Asm, nullptr, false); |
| } |
| |
| bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm) const { |
| return evaluateAsAbsolute(Res, Asm, nullptr, false); |
| } |
| |
| bool MCExpr::evaluateKnownAbsolute(int64_t &Res, const MCAssembler &Asm) const { |
| return evaluateAsAbsolute(Res, &Asm, nullptr, true); |
| } |
| |
| bool MCExpr::evaluateAsAbsolute(int64_t &Res, const MCAssembler *Asm, |
| 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, 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 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; |
| |
| auto FinalizeFolding = [&]() { |
| // 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; |
| }; |
| |
| const MCFragment *FA = SA.getFragment(); |
| const MCFragment *FB = SB.getFragment(); |
| const MCSection &SecA = *FA->getParent(); |
| const MCSection &SecB = *FB->getParent(); |
| if ((&SecA != &SecB) && !Addrs) |
| return; |
| |
| // When layout is available, we can generally compute the difference using the |
| // getSymbolOffset path, which also avoids the possible slow fragment walk. |
| // However, linker relaxation may cause incorrect fold of A-B if A and B are |
| // separated by a linker-relaxable instruction. If the section contains |
| // instructions and InSet is false (not expressions in directive like |
| // .size/.fill), disable the fast path. |
| bool Layout = Asm->hasLayout(); |
| if (Layout && (InSet || !SecA.hasInstructions() || |
| !Asm->getBackend().allowLinkerRelaxation())) { |
| // If both symbols are in the same fragment, return the difference of their |
| // offsets. canGetFragmentOffset(FA) may be false. |
| if (FA == FB && !SA.isVariable() && !SB.isVariable()) { |
| Addend += SA.getOffset() - SB.getOffset(); |
| return FinalizeFolding(); |
| } |
| |
| // Eagerly evaluate when layout is finalized. |
| Addend += Asm->getSymbolOffset(A->getSymbol()) - |
| Asm->getSymbolOffset(B->getSymbol()); |
| if (Addrs && (&SecA != &SecB)) |
| Addend += (Addrs->lookup(&SecA) - Addrs->lookup(&SecB)); |
| |
| FinalizeFolding(); |
| } 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() || SB.isVariable()) |
| return; |
| |
| // 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. |
| bool Reverse = false; |
| if (FA == FB) |
| Reverse = SA.getOffset() < SB.getOffset(); |
| else |
| Reverse = FA->getLayoutOrder() < FB->getLayoutOrder(); |
| |
| uint64_t SAOffset = SA.getOffset(), SBOffset = SB.getOffset(); |
| int64_t Displacement = SA.getOffset() - SB.getOffset(); |
| if (Reverse) { |
| std::swap(FA, FB); |
| std::swap(SAOffset, SBOffset); |
| Displacement *= -1; |
| } |
| |
| // Track whether B is before a relaxable instruction and whether A is after |
| // a relaxable instruction. If SA and SB are separated by a linker-relaxable |
| // instruction, the difference cannot be resolved as it may be changed by |
| // the linker. |
| bool BBeforeRelax = false, AAfterRelax = false; |
| for (auto FI = FB; FI; FI = FI->getNext()) { |
| auto DF = dyn_cast<MCDataFragment>(FI); |
| if (DF && DF->isLinkerRelaxable()) { |
| if (&*FI != FB || SBOffset != DF->getContents().size()) |
| BBeforeRelax = true; |
| if (&*FI != FA || SAOffset == DF->getContents().size()) |
| AAfterRelax = true; |
| if (BBeforeRelax && AAfterRelax) |
| return; |
| } |
| if (&*FI == FA) { |
| // If FA and FB belong to the same subsection, the loop will find FA and |
| // we can resolve the difference. |
| Addend += Reverse ? -Displacement : Displacement; |
| FinalizeFolding(); |
| return; |
| } |
| |
| int64_t Num; |
| unsigned Count; |
| if (DF) { |
| Displacement += DF->getContents().size(); |
| } else if (auto *AF = dyn_cast<MCAlignFragment>(FI); |
| AF && Layout && AF->hasEmitNops() && |
| !Asm->getBackend().shouldInsertExtraNopBytesForCodeAlign( |
| *AF, Count)) { |
| Displacement += Asm->computeFragmentSize(*AF); |
| } else if (auto *FF = dyn_cast<MCFillFragment>(FI); |
| FF && FF->getNumValues().evaluateAsAbsolute(Num)) { |
| Displacement += Num * FF->getValueSize(); |
| } else { |
| return; |
| } |
| } |
| } |
| } |
| |
| /// 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 SectionAddrMap *Addrs, bool InSet, |
| const MCValue &LHS, const MCValue &RHS, |
| 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(); |
| |
| const MCSymbolRefExpr *RHS_A = RHS.getSymA(); |
| const MCSymbolRefExpr *RHS_B = RHS.getSymB(); |
| int64_t RHS_Cst = RHS.getConstant(); |
| |
| if (LHS.getRefKind() != RHS.getRefKind()) |
| return false; |
| |
| // Fold the result constant immediately. |
| int64_t Result_Cst = LHS_Cst + RHS_Cst; |
| |
| // 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, Addrs, InSet, LHS_A, LHS_B, |
| Result_Cst); |
| AttemptToFoldSymbolOffsetDifference(Asm, Addrs, InSet, LHS_A, RHS_B, |
| Result_Cst); |
| AttemptToFoldSymbolOffsetDifference(Asm, Addrs, InSet, RHS_A, LHS_B, |
| Result_Cst); |
| AttemptToFoldSymbolOffsetDifference(Asm, 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; |
| |
| Res = MCValue::get(A, B, Result_Cst); |
| return true; |
| } |
| |
| bool MCExpr::evaluateAsRelocatable(MCValue &Res, const MCAssembler *Asm, |
| const MCFixup *Fixup) const { |
| return evaluateAsRelocatableImpl(Res, Asm, Fixup, nullptr, false); |
| } |
| |
| bool MCExpr::evaluateAsValue(MCValue &Res, const MCAssembler &Asm) const { |
| return evaluateAsRelocatableImpl(Res, &Asm, nullptr, nullptr, true); |
| } |
| |
| static bool canExpand(const MCSymbol &Sym, bool InSet) { |
| if (Sym.isWeakExternal()) |
| return false; |
| |
| 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 MCFixup *Fixup, |
| const SectionAddrMap *Addrs, |
| bool InSet) const { |
| ++stats::MCExprEvaluate; |
| switch (getKind()) { |
| case Target: |
| return cast<MCTargetExpr>(this)->evaluateAsRelocatableImpl(Res, Asm, 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(); |
| const auto Kind = SRE->getKind(); |
| bool Layout = Asm && Asm->hasLayout(); |
| |
| // 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, 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 = |
| MCValue::get(MCSymbolRefExpr::create(&Res.getSymA()->getSymbol(), |
| 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, 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; |
| |
| // The cast avoids undefined behavior if the constant is INT64_MIN. |
| Res = MCValue::get(Value.getSymB(), Value.getSymA(), |
| -(uint64_t)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, Fixup, Addrs, |
| InSet) || |
| !ABE->getRHS()->evaluateAsRelocatableImpl(RHSValue, Asm, 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 = dyn_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(L->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()) { |
| default: |
| return false; |
| case MCBinaryExpr::Sub: |
| // Negate RHS and add. |
| // The cast avoids undefined behavior if the constant is INT64_MIN. |
| return evaluateSymbolicAdd( |
| Asm, Addrs, InSet, LHSValue, |
| MCValue::get(RHSValue.getSymB(), RHSValue.getSymA(), |
| -(uint64_t)RHSValue.getConstant(), |
| RHSValue.getRefKind()), |
| Res); |
| |
| case MCBinaryExpr::Add: |
| return evaluateSymbolicAdd( |
| Asm, Addrs, InSet, LHSValue, |
| MCValue::get(RHSValue.getSymA(), RHSValue.getSymB(), |
| RHSValue.getConstant(), RHSValue.getRefKind()), |
| 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; |
| else |
| 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::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) { |
| default: |
| Res = MCValue::get(Result); |
| break; |
| 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); |
| break; |
| } |
| |
| 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!"); |
| } |
