forked from OSchip/llvm-project
1155 lines
40 KiB
C++
1155 lines
40 KiB
C++
//===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/StringRef.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCAsmLayout.h"
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#include "llvm/MC/MCCodeEmitter.h"
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#include "llvm/MC/MCCodeView.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCDwarf.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCFixup.h"
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#include "llvm/MC/MCFixupKindInfo.h"
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#include "llvm/MC/MCFragment.h"
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#include "llvm/MC/MCInst.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/MC/MCSection.h"
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#include "llvm/MC/MCSectionELF.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/LEB128.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/raw_ostream.h"
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#include <cassert>
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#include <cstdint>
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#include <cstring>
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#include <tuple>
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#include <utility>
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using namespace llvm;
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#define DEBUG_TYPE "assembler"
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namespace {
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namespace stats {
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STATISTIC(EmittedFragments, "Number of emitted assembler fragments - total");
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STATISTIC(EmittedRelaxableFragments,
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"Number of emitted assembler fragments - relaxable");
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STATISTIC(EmittedDataFragments,
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"Number of emitted assembler fragments - data");
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STATISTIC(EmittedCompactEncodedInstFragments,
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"Number of emitted assembler fragments - compact encoded inst");
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STATISTIC(EmittedAlignFragments,
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"Number of emitted assembler fragments - align");
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STATISTIC(EmittedFillFragments,
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"Number of emitted assembler fragments - fill");
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STATISTIC(EmittedOrgFragments,
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"Number of emitted assembler fragments - org");
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STATISTIC(evaluateFixup, "Number of evaluated fixups");
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STATISTIC(FragmentLayouts, "Number of fragment layouts");
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STATISTIC(ObjectBytes, "Number of emitted object file bytes");
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STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
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STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
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STATISTIC(PaddingFragmentsRelaxations,
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"Number of Padding Fragments relaxations");
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STATISTIC(PaddingFragmentsBytes,
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"Total size of all padding from adding Fragments");
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} // end namespace stats
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} // end anonymous namespace
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// FIXME FIXME FIXME: There are number of places in this file where we convert
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// what is a 64-bit assembler value used for computation into a value in the
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// object file, which may truncate it. We should detect that truncation where
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// invalid and report errors back.
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/* *** */
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MCAssembler::MCAssembler(MCContext &Context,
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std::unique_ptr<MCAsmBackend> Backend,
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std::unique_ptr<MCCodeEmitter> Emitter,
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std::unique_ptr<MCObjectWriter> Writer)
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: Context(Context), Backend(std::move(Backend)),
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Emitter(std::move(Emitter)), Writer(std::move(Writer)),
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BundleAlignSize(0), RelaxAll(false), SubsectionsViaSymbols(false),
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IncrementalLinkerCompatible(false), ELFHeaderEFlags(0) {
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VersionInfo.Major = 0; // Major version == 0 for "none specified"
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}
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MCAssembler::~MCAssembler() = default;
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void MCAssembler::reset() {
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Sections.clear();
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Symbols.clear();
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IndirectSymbols.clear();
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DataRegions.clear();
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LinkerOptions.clear();
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FileNames.clear();
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ThumbFuncs.clear();
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BundleAlignSize = 0;
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RelaxAll = false;
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SubsectionsViaSymbols = false;
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IncrementalLinkerCompatible = false;
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ELFHeaderEFlags = 0;
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LOHContainer.reset();
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VersionInfo.Major = 0;
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VersionInfo.SDKVersion = VersionTuple();
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// reset objects owned by us
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if (getBackendPtr())
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getBackendPtr()->reset();
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if (getEmitterPtr())
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getEmitterPtr()->reset();
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if (getWriterPtr())
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getWriterPtr()->reset();
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getLOHContainer().reset();
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}
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bool MCAssembler::registerSection(MCSection &Section) {
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if (Section.isRegistered())
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return false;
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Sections.push_back(&Section);
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Section.setIsRegistered(true);
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return true;
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}
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bool MCAssembler::isThumbFunc(const MCSymbol *Symbol) const {
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if (ThumbFuncs.count(Symbol))
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return true;
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if (!Symbol->isVariable())
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return false;
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const MCExpr *Expr = Symbol->getVariableValue();
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MCValue V;
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if (!Expr->evaluateAsRelocatable(V, nullptr, nullptr))
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return false;
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if (V.getSymB() || V.getRefKind() != MCSymbolRefExpr::VK_None)
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return false;
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const MCSymbolRefExpr *Ref = V.getSymA();
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if (!Ref)
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return false;
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if (Ref->getKind() != MCSymbolRefExpr::VK_None)
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return false;
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const MCSymbol &Sym = Ref->getSymbol();
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if (!isThumbFunc(&Sym))
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return false;
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ThumbFuncs.insert(Symbol); // Cache it.
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return true;
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}
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bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
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// Non-temporary labels should always be visible to the linker.
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if (!Symbol.isTemporary())
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return true;
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// Absolute temporary labels are never visible.
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if (!Symbol.isInSection())
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return false;
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if (Symbol.isUsedInReloc())
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return true;
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return false;
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}
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const MCSymbol *MCAssembler::getAtom(const MCSymbol &S) const {
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// Linker visible symbols define atoms.
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if (isSymbolLinkerVisible(S))
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return &S;
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// Absolute and undefined symbols have no defining atom.
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if (!S.isInSection())
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return nullptr;
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// Non-linker visible symbols in sections which can't be atomized have no
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// defining atom.
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if (!getContext().getAsmInfo()->isSectionAtomizableBySymbols(
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*S.getFragment()->getParent()))
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return nullptr;
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// Otherwise, return the atom for the containing fragment.
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return S.getFragment()->getAtom();
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}
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bool MCAssembler::evaluateFixup(const MCAsmLayout &Layout,
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const MCFixup &Fixup, const MCFragment *DF,
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MCValue &Target, uint64_t &Value,
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bool &WasForced) const {
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++stats::evaluateFixup;
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// FIXME: This code has some duplication with recordRelocation. We should
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// probably merge the two into a single callback that tries to evaluate a
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// fixup and records a relocation if one is needed.
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// On error claim to have completely evaluated the fixup, to prevent any
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// further processing from being done.
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const MCExpr *Expr = Fixup.getValue();
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MCContext &Ctx = getContext();
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Value = 0;
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WasForced = false;
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if (!Expr->evaluateAsRelocatable(Target, &Layout, &Fixup)) {
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Ctx.reportError(Fixup.getLoc(), "expected relocatable expression");
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return true;
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}
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if (const MCSymbolRefExpr *RefB = Target.getSymB()) {
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if (RefB->getKind() != MCSymbolRefExpr::VK_None) {
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Ctx.reportError(Fixup.getLoc(),
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"unsupported subtraction of qualified symbol");
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return true;
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}
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}
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assert(getBackendPtr() && "Expected assembler backend");
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bool IsPCRel = getBackendPtr()->getFixupKindInfo(Fixup.getKind()).Flags &
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MCFixupKindInfo::FKF_IsPCRel;
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bool IsResolved = false;
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if (IsPCRel) {
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if (Target.getSymB()) {
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IsResolved = false;
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} else if (!Target.getSymA()) {
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IsResolved = false;
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} else {
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const MCSymbolRefExpr *A = Target.getSymA();
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const MCSymbol &SA = A->getSymbol();
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if (A->getKind() != MCSymbolRefExpr::VK_None || SA.isUndefined()) {
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IsResolved = false;
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} else if (auto *Writer = getWriterPtr()) {
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IsResolved = Writer->isSymbolRefDifferenceFullyResolvedImpl(
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*this, SA, *DF, false, true);
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}
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}
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} else {
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IsResolved = Target.isAbsolute();
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}
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Value = Target.getConstant();
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if (const MCSymbolRefExpr *A = Target.getSymA()) {
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const MCSymbol &Sym = A->getSymbol();
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if (Sym.isDefined())
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Value += Layout.getSymbolOffset(Sym);
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}
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if (const MCSymbolRefExpr *B = Target.getSymB()) {
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const MCSymbol &Sym = B->getSymbol();
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if (Sym.isDefined())
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Value -= Layout.getSymbolOffset(Sym);
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}
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bool ShouldAlignPC = getBackend().getFixupKindInfo(Fixup.getKind()).Flags &
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MCFixupKindInfo::FKF_IsAlignedDownTo32Bits;
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assert((ShouldAlignPC ? IsPCRel : true) &&
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"FKF_IsAlignedDownTo32Bits is only allowed on PC-relative fixups!");
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if (IsPCRel) {
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uint32_t Offset = Layout.getFragmentOffset(DF) + Fixup.getOffset();
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// A number of ARM fixups in Thumb mode require that the effective PC
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// address be determined as the 32-bit aligned version of the actual offset.
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if (ShouldAlignPC) Offset &= ~0x3;
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Value -= Offset;
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}
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// Let the backend force a relocation if needed.
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if (IsResolved && getBackend().shouldForceRelocation(*this, Fixup, Target)) {
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IsResolved = false;
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WasForced = true;
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}
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return IsResolved;
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}
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uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
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const MCFragment &F) const {
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assert(getBackendPtr() && "Requires assembler backend");
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switch (F.getKind()) {
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case MCFragment::FT_Data:
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return cast<MCDataFragment>(F).getContents().size();
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case MCFragment::FT_Relaxable:
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return cast<MCRelaxableFragment>(F).getContents().size();
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case MCFragment::FT_CompactEncodedInst:
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return cast<MCCompactEncodedInstFragment>(F).getContents().size();
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case MCFragment::FT_Fill: {
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auto &FF = cast<MCFillFragment>(F);
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int64_t NumValues = 0;
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if (!FF.getNumValues().evaluateAsAbsolute(NumValues, Layout)) {
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getContext().reportError(FF.getLoc(),
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"expected assembly-time absolute expression");
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return 0;
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}
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int64_t Size = NumValues * FF.getValueSize();
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if (Size < 0) {
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getContext().reportError(FF.getLoc(), "invalid number of bytes");
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return 0;
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}
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return Size;
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}
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case MCFragment::FT_LEB:
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return cast<MCLEBFragment>(F).getContents().size();
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case MCFragment::FT_Padding:
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return cast<MCPaddingFragment>(F).getSize();
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case MCFragment::FT_SymbolId:
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return 4;
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case MCFragment::FT_Align: {
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const MCAlignFragment &AF = cast<MCAlignFragment>(F);
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unsigned Offset = Layout.getFragmentOffset(&AF);
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unsigned Size = OffsetToAlignment(Offset, AF.getAlignment());
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// Insert extra Nops for code alignment if the target define
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// shouldInsertExtraNopBytesForCodeAlign target hook.
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if (AF.getParent()->UseCodeAlign() && AF.hasEmitNops() &&
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getBackend().shouldInsertExtraNopBytesForCodeAlign(AF, Size))
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return Size;
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// If we are padding with nops, force the padding to be larger than the
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// minimum nop size.
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if (Size > 0 && AF.hasEmitNops()) {
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while (Size % getBackend().getMinimumNopSize())
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Size += AF.getAlignment();
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}
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if (Size > AF.getMaxBytesToEmit())
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return 0;
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return Size;
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}
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case MCFragment::FT_Org: {
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const MCOrgFragment &OF = cast<MCOrgFragment>(F);
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MCValue Value;
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if (!OF.getOffset().evaluateAsValue(Value, Layout)) {
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getContext().reportError(OF.getLoc(),
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"expected assembly-time absolute expression");
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return 0;
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}
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uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
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int64_t TargetLocation = Value.getConstant();
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if (const MCSymbolRefExpr *A = Value.getSymA()) {
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uint64_t Val;
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if (!Layout.getSymbolOffset(A->getSymbol(), Val)) {
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getContext().reportError(OF.getLoc(), "expected absolute expression");
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return 0;
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}
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TargetLocation += Val;
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}
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int64_t Size = TargetLocation - FragmentOffset;
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if (Size < 0 || Size >= 0x40000000) {
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getContext().reportError(
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OF.getLoc(), "invalid .org offset '" + Twine(TargetLocation) +
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"' (at offset '" + Twine(FragmentOffset) + "')");
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return 0;
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}
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return Size;
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}
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case MCFragment::FT_Dwarf:
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return cast<MCDwarfLineAddrFragment>(F).getContents().size();
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case MCFragment::FT_DwarfFrame:
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return cast<MCDwarfCallFrameFragment>(F).getContents().size();
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case MCFragment::FT_CVInlineLines:
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return cast<MCCVInlineLineTableFragment>(F).getContents().size();
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case MCFragment::FT_CVDefRange:
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return cast<MCCVDefRangeFragment>(F).getContents().size();
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case MCFragment::FT_Dummy:
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llvm_unreachable("Should not have been added");
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}
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llvm_unreachable("invalid fragment kind");
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}
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void MCAsmLayout::layoutFragment(MCFragment *F) {
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MCFragment *Prev = F->getPrevNode();
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// We should never try to recompute something which is valid.
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assert(!isFragmentValid(F) && "Attempt to recompute a valid fragment!");
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// We should never try to compute the fragment layout if its predecessor
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// isn't valid.
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assert((!Prev || isFragmentValid(Prev)) &&
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"Attempt to compute fragment before its predecessor!");
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++stats::FragmentLayouts;
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// Compute fragment offset and size.
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if (Prev)
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F->Offset = Prev->Offset + getAssembler().computeFragmentSize(*this, *Prev);
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else
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F->Offset = 0;
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LastValidFragment[F->getParent()] = F;
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// If bundling is enabled and this fragment has instructions in it, it has to
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// obey the bundling restrictions. With padding, we'll have:
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//
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//
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// BundlePadding
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// |||
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// -------------------------------------
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// Prev |##########| F |
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// -------------------------------------
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// ^
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// |
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// F->Offset
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//
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// The fragment's offset will point to after the padding, and its computed
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// size won't include the padding.
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//
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// When the -mc-relax-all flag is used, we optimize bundling by writting the
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// padding directly into fragments when the instructions are emitted inside
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// the streamer. When the fragment is larger than the bundle size, we need to
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// ensure that it's bundle aligned. This means that if we end up with
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// multiple fragments, we must emit bundle padding between fragments.
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//
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// ".align N" is an example of a directive that introduces multiple
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// fragments. We could add a special case to handle ".align N" by emitting
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// within-fragment padding (which would produce less padding when N is less
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// than the bundle size), but for now we don't.
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//
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if (Assembler.isBundlingEnabled() && F->hasInstructions()) {
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assert(isa<MCEncodedFragment>(F) &&
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"Only MCEncodedFragment implementations have instructions");
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MCEncodedFragment *EF = cast<MCEncodedFragment>(F);
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uint64_t FSize = Assembler.computeFragmentSize(*this, *EF);
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if (!Assembler.getRelaxAll() && FSize > Assembler.getBundleAlignSize())
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report_fatal_error("Fragment can't be larger than a bundle size");
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uint64_t RequiredBundlePadding =
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computeBundlePadding(Assembler, EF, EF->Offset, FSize);
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if (RequiredBundlePadding > UINT8_MAX)
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report_fatal_error("Padding cannot exceed 255 bytes");
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EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
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EF->Offset += RequiredBundlePadding;
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}
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}
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void MCAssembler::registerSymbol(const MCSymbol &Symbol, bool *Created) {
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bool New = !Symbol.isRegistered();
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if (Created)
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*Created = New;
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if (New) {
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Symbol.setIsRegistered(true);
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Symbols.push_back(&Symbol);
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}
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}
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void MCAssembler::writeFragmentPadding(raw_ostream &OS,
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const MCEncodedFragment &EF,
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uint64_t FSize) const {
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assert(getBackendPtr() && "Expected assembler backend");
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// Should NOP padding be written out before this fragment?
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unsigned BundlePadding = EF.getBundlePadding();
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if (BundlePadding > 0) {
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assert(isBundlingEnabled() &&
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"Writing bundle padding with disabled bundling");
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assert(EF.hasInstructions() &&
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"Writing bundle padding for a fragment without instructions");
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unsigned TotalLength = BundlePadding + static_cast<unsigned>(FSize);
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if (EF.alignToBundleEnd() && TotalLength > getBundleAlignSize()) {
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// If the padding itself crosses a bundle boundary, it must be emitted
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// in 2 pieces, since even nop instructions must not cross boundaries.
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// v--------------v <- BundleAlignSize
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// v---------v <- BundlePadding
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// ----------------------------
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// | Prev |####|####| F |
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// ----------------------------
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// ^-------------------^ <- TotalLength
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unsigned DistanceToBoundary = TotalLength - getBundleAlignSize();
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if (!getBackend().writeNopData(OS, DistanceToBoundary))
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report_fatal_error("unable to write NOP sequence of " +
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Twine(DistanceToBoundary) + " bytes");
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BundlePadding -= DistanceToBoundary;
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}
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if (!getBackend().writeNopData(OS, BundlePadding))
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report_fatal_error("unable to write NOP sequence of " +
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Twine(BundlePadding) + " bytes");
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}
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}
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|
/// Write the fragment \p F to the output file.
|
|
static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
|
|
const MCAsmLayout &Layout, const MCFragment &F) {
|
|
// FIXME: Embed in fragments instead?
|
|
uint64_t FragmentSize = Asm.computeFragmentSize(Layout, F);
|
|
|
|
support::endianness Endian = Asm.getBackend().Endian;
|
|
|
|
if (const MCEncodedFragment *EF = dyn_cast<MCEncodedFragment>(&F))
|
|
Asm.writeFragmentPadding(OS, *EF, FragmentSize);
|
|
|
|
// This variable (and its dummy usage) is to participate in the assert at
|
|
// the end of the function.
|
|
uint64_t Start = OS.tell();
|
|
(void) Start;
|
|
|
|
++stats::EmittedFragments;
|
|
|
|
switch (F.getKind()) {
|
|
case MCFragment::FT_Align: {
|
|
++stats::EmittedAlignFragments;
|
|
const MCAlignFragment &AF = cast<MCAlignFragment>(F);
|
|
assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
|
|
|
|
uint64_t Count = FragmentSize / AF.getValueSize();
|
|
|
|
// FIXME: This error shouldn't actually occur (the front end should emit
|
|
// multiple .align directives to enforce the semantics it wants), but is
|
|
// severe enough that we want to report it. How to handle this?
|
|
if (Count * AF.getValueSize() != FragmentSize)
|
|
report_fatal_error("undefined .align directive, value size '" +
|
|
Twine(AF.getValueSize()) +
|
|
"' is not a divisor of padding size '" +
|
|
Twine(FragmentSize) + "'");
|
|
|
|
// See if we are aligning with nops, and if so do that first to try to fill
|
|
// the Count bytes. Then if that did not fill any bytes or there are any
|
|
// bytes left to fill use the Value and ValueSize to fill the rest.
|
|
// If we are aligning with nops, ask that target to emit the right data.
|
|
if (AF.hasEmitNops()) {
|
|
if (!Asm.getBackend().writeNopData(OS, Count))
|
|
report_fatal_error("unable to write nop sequence of " +
|
|
Twine(Count) + " bytes");
|
|
break;
|
|
}
|
|
|
|
// Otherwise, write out in multiples of the value size.
|
|
for (uint64_t i = 0; i != Count; ++i) {
|
|
switch (AF.getValueSize()) {
|
|
default: llvm_unreachable("Invalid size!");
|
|
case 1: OS << char(AF.getValue()); break;
|
|
case 2:
|
|
support::endian::write<uint16_t>(OS, AF.getValue(), Endian);
|
|
break;
|
|
case 4:
|
|
support::endian::write<uint32_t>(OS, AF.getValue(), Endian);
|
|
break;
|
|
case 8:
|
|
support::endian::write<uint64_t>(OS, AF.getValue(), Endian);
|
|
break;
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
|
|
case MCFragment::FT_Data:
|
|
++stats::EmittedDataFragments;
|
|
OS << cast<MCDataFragment>(F).getContents();
|
|
break;
|
|
|
|
case MCFragment::FT_Relaxable:
|
|
++stats::EmittedRelaxableFragments;
|
|
OS << cast<MCRelaxableFragment>(F).getContents();
|
|
break;
|
|
|
|
case MCFragment::FT_CompactEncodedInst:
|
|
++stats::EmittedCompactEncodedInstFragments;
|
|
OS << cast<MCCompactEncodedInstFragment>(F).getContents();
|
|
break;
|
|
|
|
case MCFragment::FT_Fill: {
|
|
++stats::EmittedFillFragments;
|
|
const MCFillFragment &FF = cast<MCFillFragment>(F);
|
|
uint64_t V = FF.getValue();
|
|
unsigned VSize = FF.getValueSize();
|
|
const unsigned MaxChunkSize = 16;
|
|
char Data[MaxChunkSize];
|
|
// Duplicate V into Data as byte vector to reduce number of
|
|
// writes done. As such, do endian conversion here.
|
|
for (unsigned I = 0; I != VSize; ++I) {
|
|
unsigned index = Endian == support::little ? I : (VSize - I - 1);
|
|
Data[I] = uint8_t(V >> (index * 8));
|
|
}
|
|
for (unsigned I = VSize; I < MaxChunkSize; ++I)
|
|
Data[I] = Data[I - VSize];
|
|
|
|
// Set to largest multiple of VSize in Data.
|
|
const unsigned NumPerChunk = MaxChunkSize / VSize;
|
|
// Set ChunkSize to largest multiple of VSize in Data
|
|
const unsigned ChunkSize = VSize * NumPerChunk;
|
|
|
|
// Do copies by chunk.
|
|
StringRef Ref(Data, ChunkSize);
|
|
for (uint64_t I = 0, E = FragmentSize / ChunkSize; I != E; ++I)
|
|
OS << Ref;
|
|
|
|
// do remainder if needed.
|
|
unsigned TrailingCount = FragmentSize % ChunkSize;
|
|
if (TrailingCount)
|
|
OS.write(Data, TrailingCount);
|
|
break;
|
|
}
|
|
|
|
case MCFragment::FT_LEB: {
|
|
const MCLEBFragment &LF = cast<MCLEBFragment>(F);
|
|
OS << LF.getContents();
|
|
break;
|
|
}
|
|
|
|
case MCFragment::FT_Padding: {
|
|
if (!Asm.getBackend().writeNopData(OS, FragmentSize))
|
|
report_fatal_error("unable to write nop sequence of " +
|
|
Twine(FragmentSize) + " bytes");
|
|
break;
|
|
}
|
|
|
|
case MCFragment::FT_SymbolId: {
|
|
const MCSymbolIdFragment &SF = cast<MCSymbolIdFragment>(F);
|
|
support::endian::write<uint32_t>(OS, SF.getSymbol()->getIndex(), Endian);
|
|
break;
|
|
}
|
|
|
|
case MCFragment::FT_Org: {
|
|
++stats::EmittedOrgFragments;
|
|
const MCOrgFragment &OF = cast<MCOrgFragment>(F);
|
|
|
|
for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
|
|
OS << char(OF.getValue());
|
|
|
|
break;
|
|
}
|
|
|
|
case MCFragment::FT_Dwarf: {
|
|
const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
|
|
OS << OF.getContents();
|
|
break;
|
|
}
|
|
case MCFragment::FT_DwarfFrame: {
|
|
const MCDwarfCallFrameFragment &CF = cast<MCDwarfCallFrameFragment>(F);
|
|
OS << CF.getContents();
|
|
break;
|
|
}
|
|
case MCFragment::FT_CVInlineLines: {
|
|
const auto &OF = cast<MCCVInlineLineTableFragment>(F);
|
|
OS << OF.getContents();
|
|
break;
|
|
}
|
|
case MCFragment::FT_CVDefRange: {
|
|
const auto &DRF = cast<MCCVDefRangeFragment>(F);
|
|
OS << DRF.getContents();
|
|
break;
|
|
}
|
|
case MCFragment::FT_Dummy:
|
|
llvm_unreachable("Should not have been added");
|
|
}
|
|
|
|
assert(OS.tell() - Start == FragmentSize &&
|
|
"The stream should advance by fragment size");
|
|
}
|
|
|
|
void MCAssembler::writeSectionData(raw_ostream &OS, const MCSection *Sec,
|
|
const MCAsmLayout &Layout) const {
|
|
assert(getBackendPtr() && "Expected assembler backend");
|
|
|
|
// Ignore virtual sections.
|
|
if (Sec->isVirtualSection()) {
|
|
assert(Layout.getSectionFileSize(Sec) == 0 && "Invalid size for section!");
|
|
|
|
// Check that contents are only things legal inside a virtual section.
|
|
for (const MCFragment &F : *Sec) {
|
|
switch (F.getKind()) {
|
|
default: llvm_unreachable("Invalid fragment in virtual section!");
|
|
case MCFragment::FT_Data: {
|
|
// Check that we aren't trying to write a non-zero contents (or fixups)
|
|
// into a virtual section. This is to support clients which use standard
|
|
// directives to fill the contents of virtual sections.
|
|
const MCDataFragment &DF = cast<MCDataFragment>(F);
|
|
if (DF.fixup_begin() != DF.fixup_end())
|
|
report_fatal_error("cannot have fixups in virtual section!");
|
|
for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
|
|
if (DF.getContents()[i]) {
|
|
if (auto *ELFSec = dyn_cast<const MCSectionELF>(Sec))
|
|
report_fatal_error("non-zero initializer found in section '" +
|
|
ELFSec->getSectionName() + "'");
|
|
else
|
|
report_fatal_error("non-zero initializer found in virtual section");
|
|
}
|
|
break;
|
|
}
|
|
case MCFragment::FT_Align:
|
|
// Check that we aren't trying to write a non-zero value into a virtual
|
|
// section.
|
|
assert((cast<MCAlignFragment>(F).getValueSize() == 0 ||
|
|
cast<MCAlignFragment>(F).getValue() == 0) &&
|
|
"Invalid align in virtual section!");
|
|
break;
|
|
case MCFragment::FT_Fill:
|
|
assert((cast<MCFillFragment>(F).getValue() == 0) &&
|
|
"Invalid fill in virtual section!");
|
|
break;
|
|
}
|
|
}
|
|
|
|
return;
|
|
}
|
|
|
|
uint64_t Start = OS.tell();
|
|
(void)Start;
|
|
|
|
for (const MCFragment &F : *Sec)
|
|
writeFragment(OS, *this, Layout, F);
|
|
|
|
assert(OS.tell() - Start == Layout.getSectionAddressSize(Sec));
|
|
}
|
|
|
|
std::tuple<MCValue, uint64_t, bool>
|
|
MCAssembler::handleFixup(const MCAsmLayout &Layout, MCFragment &F,
|
|
const MCFixup &Fixup) {
|
|
// Evaluate the fixup.
|
|
MCValue Target;
|
|
uint64_t FixedValue;
|
|
bool WasForced;
|
|
bool IsResolved = evaluateFixup(Layout, Fixup, &F, Target, FixedValue,
|
|
WasForced);
|
|
if (!IsResolved) {
|
|
// The fixup was unresolved, we need a relocation. Inform the object
|
|
// writer of the relocation, and give it an opportunity to adjust the
|
|
// fixup value if need be.
|
|
if (Target.getSymA() && Target.getSymB() &&
|
|
getBackend().requiresDiffExpressionRelocations()) {
|
|
// The fixup represents the difference between two symbols, which the
|
|
// backend has indicated must be resolved at link time. Split up the fixup
|
|
// into two relocations, one for the add, and one for the sub, and emit
|
|
// both of these. The constant will be associated with the add half of the
|
|
// expression.
|
|
MCFixup FixupAdd = MCFixup::createAddFor(Fixup);
|
|
MCValue TargetAdd =
|
|
MCValue::get(Target.getSymA(), nullptr, Target.getConstant());
|
|
getWriter().recordRelocation(*this, Layout, &F, FixupAdd, TargetAdd,
|
|
FixedValue);
|
|
MCFixup FixupSub = MCFixup::createSubFor(Fixup);
|
|
MCValue TargetSub = MCValue::get(Target.getSymB());
|
|
getWriter().recordRelocation(*this, Layout, &F, FixupSub, TargetSub,
|
|
FixedValue);
|
|
} else {
|
|
getWriter().recordRelocation(*this, Layout, &F, Fixup, Target,
|
|
FixedValue);
|
|
}
|
|
}
|
|
return std::make_tuple(Target, FixedValue, IsResolved);
|
|
}
|
|
|
|
void MCAssembler::layout(MCAsmLayout &Layout) {
|
|
assert(getBackendPtr() && "Expected assembler backend");
|
|
DEBUG_WITH_TYPE("mc-dump", {
|
|
errs() << "assembler backend - pre-layout\n--\n";
|
|
dump(); });
|
|
|
|
// Create dummy fragments and assign section ordinals.
|
|
unsigned SectionIndex = 0;
|
|
for (MCSection &Sec : *this) {
|
|
// Create dummy fragments to eliminate any empty sections, this simplifies
|
|
// layout.
|
|
if (Sec.getFragmentList().empty())
|
|
new MCDataFragment(&Sec);
|
|
|
|
Sec.setOrdinal(SectionIndex++);
|
|
}
|
|
|
|
// Assign layout order indices to sections and fragments.
|
|
for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
|
|
MCSection *Sec = Layout.getSectionOrder()[i];
|
|
Sec->setLayoutOrder(i);
|
|
|
|
unsigned FragmentIndex = 0;
|
|
for (MCFragment &Frag : *Sec)
|
|
Frag.setLayoutOrder(FragmentIndex++);
|
|
}
|
|
|
|
// Layout until everything fits.
|
|
while (layoutOnce(Layout))
|
|
if (getContext().hadError())
|
|
return;
|
|
|
|
DEBUG_WITH_TYPE("mc-dump", {
|
|
errs() << "assembler backend - post-relaxation\n--\n";
|
|
dump(); });
|
|
|
|
// Finalize the layout, including fragment lowering.
|
|
finishLayout(Layout);
|
|
|
|
DEBUG_WITH_TYPE("mc-dump", {
|
|
errs() << "assembler backend - final-layout\n--\n";
|
|
dump(); });
|
|
|
|
// Allow the object writer a chance to perform post-layout binding (for
|
|
// example, to set the index fields in the symbol data).
|
|
getWriter().executePostLayoutBinding(*this, Layout);
|
|
|
|
// Evaluate and apply the fixups, generating relocation entries as necessary.
|
|
for (MCSection &Sec : *this) {
|
|
for (MCFragment &Frag : Sec) {
|
|
// Data and relaxable fragments both have fixups. So only process
|
|
// those here.
|
|
// FIXME: Is there a better way to do this? MCEncodedFragmentWithFixups
|
|
// being templated makes this tricky.
|
|
if (isa<MCEncodedFragment>(&Frag) &&
|
|
isa<MCCompactEncodedInstFragment>(&Frag))
|
|
continue;
|
|
if (!isa<MCEncodedFragment>(&Frag) && !isa<MCCVDefRangeFragment>(&Frag) &&
|
|
!isa<MCAlignFragment>(&Frag))
|
|
continue;
|
|
ArrayRef<MCFixup> Fixups;
|
|
MutableArrayRef<char> Contents;
|
|
const MCSubtargetInfo *STI = nullptr;
|
|
if (auto *FragWithFixups = dyn_cast<MCDataFragment>(&Frag)) {
|
|
Fixups = FragWithFixups->getFixups();
|
|
Contents = FragWithFixups->getContents();
|
|
STI = FragWithFixups->getSubtargetInfo();
|
|
assert(!FragWithFixups->hasInstructions() || STI != nullptr);
|
|
} else if (auto *FragWithFixups = dyn_cast<MCRelaxableFragment>(&Frag)) {
|
|
Fixups = FragWithFixups->getFixups();
|
|
Contents = FragWithFixups->getContents();
|
|
STI = FragWithFixups->getSubtargetInfo();
|
|
assert(!FragWithFixups->hasInstructions() || STI != nullptr);
|
|
} else if (auto *FragWithFixups = dyn_cast<MCCVDefRangeFragment>(&Frag)) {
|
|
Fixups = FragWithFixups->getFixups();
|
|
Contents = FragWithFixups->getContents();
|
|
} else if (auto *FragWithFixups = dyn_cast<MCDwarfLineAddrFragment>(&Frag)) {
|
|
Fixups = FragWithFixups->getFixups();
|
|
Contents = FragWithFixups->getContents();
|
|
} else if (auto *AF = dyn_cast<MCAlignFragment>(&Frag)) {
|
|
// Insert fixup type for code alignment if the target define
|
|
// shouldInsertFixupForCodeAlign target hook.
|
|
if (Sec.UseCodeAlign() && AF->hasEmitNops()) {
|
|
getBackend().shouldInsertFixupForCodeAlign(*this, Layout, *AF);
|
|
}
|
|
continue;
|
|
} else if (auto *FragWithFixups =
|
|
dyn_cast<MCDwarfCallFrameFragment>(&Frag)) {
|
|
Fixups = FragWithFixups->getFixups();
|
|
Contents = FragWithFixups->getContents();
|
|
} else
|
|
llvm_unreachable("Unknown fragment with fixups!");
|
|
for (const MCFixup &Fixup : Fixups) {
|
|
uint64_t FixedValue;
|
|
bool IsResolved;
|
|
MCValue Target;
|
|
std::tie(Target, FixedValue, IsResolved) =
|
|
handleFixup(Layout, Frag, Fixup);
|
|
getBackend().applyFixup(*this, Fixup, Target, Contents, FixedValue,
|
|
IsResolved, STI);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
void MCAssembler::Finish() {
|
|
// Create the layout object.
|
|
MCAsmLayout Layout(*this);
|
|
layout(Layout);
|
|
|
|
// Write the object file.
|
|
stats::ObjectBytes += getWriter().writeObject(*this, Layout);
|
|
}
|
|
|
|
bool MCAssembler::fixupNeedsRelaxation(const MCFixup &Fixup,
|
|
const MCRelaxableFragment *DF,
|
|
const MCAsmLayout &Layout) const {
|
|
assert(getBackendPtr() && "Expected assembler backend");
|
|
MCValue Target;
|
|
uint64_t Value;
|
|
bool WasForced;
|
|
bool Resolved = evaluateFixup(Layout, Fixup, DF, Target, Value, WasForced);
|
|
if (Target.getSymA() &&
|
|
Target.getSymA()->getKind() == MCSymbolRefExpr::VK_X86_ABS8 &&
|
|
Fixup.getKind() == FK_Data_1)
|
|
return false;
|
|
return getBackend().fixupNeedsRelaxationAdvanced(Fixup, Resolved, Value, DF,
|
|
Layout, WasForced);
|
|
}
|
|
|
|
bool MCAssembler::fragmentNeedsRelaxation(const MCRelaxableFragment *F,
|
|
const MCAsmLayout &Layout) const {
|
|
assert(getBackendPtr() && "Expected assembler backend");
|
|
// If this inst doesn't ever need relaxation, ignore it. This occurs when we
|
|
// are intentionally pushing out inst fragments, or because we relaxed a
|
|
// previous instruction to one that doesn't need relaxation.
|
|
if (!getBackend().mayNeedRelaxation(F->getInst(), *F->getSubtargetInfo()))
|
|
return false;
|
|
|
|
for (const MCFixup &Fixup : F->getFixups())
|
|
if (fixupNeedsRelaxation(Fixup, F, Layout))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
|
|
MCRelaxableFragment &F) {
|
|
assert(getEmitterPtr() &&
|
|
"Expected CodeEmitter defined for relaxInstruction");
|
|
if (!fragmentNeedsRelaxation(&F, Layout))
|
|
return false;
|
|
|
|
++stats::RelaxedInstructions;
|
|
|
|
// FIXME-PERF: We could immediately lower out instructions if we can tell
|
|
// they are fully resolved, to avoid retesting on later passes.
|
|
|
|
// Relax the fragment.
|
|
|
|
MCInst Relaxed;
|
|
getBackend().relaxInstruction(F.getInst(), *F.getSubtargetInfo(), Relaxed);
|
|
|
|
// Encode the new instruction.
|
|
//
|
|
// FIXME-PERF: If it matters, we could let the target do this. It can
|
|
// probably do so more efficiently in many cases.
|
|
SmallVector<MCFixup, 4> Fixups;
|
|
SmallString<256> Code;
|
|
raw_svector_ostream VecOS(Code);
|
|
getEmitter().encodeInstruction(Relaxed, VecOS, Fixups, *F.getSubtargetInfo());
|
|
|
|
// Update the fragment.
|
|
F.setInst(Relaxed);
|
|
F.getContents() = Code;
|
|
F.getFixups() = Fixups;
|
|
|
|
return true;
|
|
}
|
|
|
|
bool MCAssembler::relaxPaddingFragment(MCAsmLayout &Layout,
|
|
MCPaddingFragment &PF) {
|
|
assert(getBackendPtr() && "Expected assembler backend");
|
|
uint64_t OldSize = PF.getSize();
|
|
if (!getBackend().relaxFragment(&PF, Layout))
|
|
return false;
|
|
uint64_t NewSize = PF.getSize();
|
|
|
|
++stats::PaddingFragmentsRelaxations;
|
|
stats::PaddingFragmentsBytes += NewSize;
|
|
stats::PaddingFragmentsBytes -= OldSize;
|
|
return true;
|
|
}
|
|
|
|
bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
|
|
uint64_t OldSize = LF.getContents().size();
|
|
int64_t Value;
|
|
bool Abs = LF.getValue().evaluateKnownAbsolute(Value, Layout);
|
|
if (!Abs)
|
|
report_fatal_error("sleb128 and uleb128 expressions must be absolute");
|
|
SmallString<8> &Data = LF.getContents();
|
|
Data.clear();
|
|
raw_svector_ostream OSE(Data);
|
|
// The compiler can generate EH table assembly that is impossible to assemble
|
|
// without either adding padding to an LEB fragment or adding extra padding
|
|
// to a later alignment fragment. To accommodate such tables, relaxation can
|
|
// only increase an LEB fragment size here, not decrease it. See PR35809.
|
|
if (LF.isSigned())
|
|
encodeSLEB128(Value, OSE, OldSize);
|
|
else
|
|
encodeULEB128(Value, OSE, OldSize);
|
|
return OldSize != LF.getContents().size();
|
|
}
|
|
|
|
bool MCAssembler::relaxDwarfLineAddr(MCAsmLayout &Layout,
|
|
MCDwarfLineAddrFragment &DF) {
|
|
MCContext &Context = Layout.getAssembler().getContext();
|
|
uint64_t OldSize = DF.getContents().size();
|
|
int64_t AddrDelta;
|
|
bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
|
|
assert(Abs && "We created a line delta with an invalid expression");
|
|
(void)Abs;
|
|
int64_t LineDelta;
|
|
LineDelta = DF.getLineDelta();
|
|
SmallVectorImpl<char> &Data = DF.getContents();
|
|
Data.clear();
|
|
raw_svector_ostream OSE(Data);
|
|
DF.getFixups().clear();
|
|
|
|
if (!getBackend().requiresDiffExpressionRelocations()) {
|
|
MCDwarfLineAddr::Encode(Context, getDWARFLinetableParams(), LineDelta,
|
|
AddrDelta, OSE);
|
|
} else {
|
|
uint32_t Offset;
|
|
uint32_t Size;
|
|
bool SetDelta = MCDwarfLineAddr::FixedEncode(Context,
|
|
getDWARFLinetableParams(),
|
|
LineDelta, AddrDelta,
|
|
OSE, &Offset, &Size);
|
|
// Add Fixups for address delta or new address.
|
|
const MCExpr *FixupExpr;
|
|
if (SetDelta) {
|
|
FixupExpr = &DF.getAddrDelta();
|
|
} else {
|
|
const MCBinaryExpr *ABE = cast<MCBinaryExpr>(&DF.getAddrDelta());
|
|
FixupExpr = ABE->getLHS();
|
|
}
|
|
DF.getFixups().push_back(
|
|
MCFixup::create(Offset, FixupExpr,
|
|
MCFixup::getKindForSize(Size, false /*isPCRel*/)));
|
|
}
|
|
|
|
return OldSize != Data.size();
|
|
}
|
|
|
|
bool MCAssembler::relaxDwarfCallFrameFragment(MCAsmLayout &Layout,
|
|
MCDwarfCallFrameFragment &DF) {
|
|
MCContext &Context = Layout.getAssembler().getContext();
|
|
uint64_t OldSize = DF.getContents().size();
|
|
int64_t AddrDelta;
|
|
bool Abs = DF.getAddrDelta().evaluateKnownAbsolute(AddrDelta, Layout);
|
|
assert(Abs && "We created call frame with an invalid expression");
|
|
(void) Abs;
|
|
SmallVectorImpl<char> &Data = DF.getContents();
|
|
Data.clear();
|
|
raw_svector_ostream OSE(Data);
|
|
DF.getFixups().clear();
|
|
|
|
if (getBackend().requiresDiffExpressionRelocations()) {
|
|
uint32_t Offset;
|
|
uint32_t Size;
|
|
MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE, &Offset,
|
|
&Size);
|
|
if (Size) {
|
|
DF.getFixups().push_back(MCFixup::create(
|
|
Offset, &DF.getAddrDelta(),
|
|
MCFixup::getKindForSizeInBits(Size /*In bits.*/, false /*isPCRel*/)));
|
|
}
|
|
} else {
|
|
MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OSE);
|
|
}
|
|
|
|
return OldSize != Data.size();
|
|
}
|
|
|
|
bool MCAssembler::relaxCVInlineLineTable(MCAsmLayout &Layout,
|
|
MCCVInlineLineTableFragment &F) {
|
|
unsigned OldSize = F.getContents().size();
|
|
getContext().getCVContext().encodeInlineLineTable(Layout, F);
|
|
return OldSize != F.getContents().size();
|
|
}
|
|
|
|
bool MCAssembler::relaxCVDefRange(MCAsmLayout &Layout,
|
|
MCCVDefRangeFragment &F) {
|
|
unsigned OldSize = F.getContents().size();
|
|
getContext().getCVContext().encodeDefRange(Layout, F);
|
|
return OldSize != F.getContents().size();
|
|
}
|
|
|
|
bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) {
|
|
// Holds the first fragment which needed relaxing during this layout. It will
|
|
// remain NULL if none were relaxed.
|
|
// When a fragment is relaxed, all the fragments following it should get
|
|
// invalidated because their offset is going to change.
|
|
MCFragment *FirstRelaxedFragment = nullptr;
|
|
|
|
// Attempt to relax all the fragments in the section.
|
|
for (MCSection::iterator I = Sec.begin(), IE = Sec.end(); I != IE; ++I) {
|
|
// Check if this is a fragment that needs relaxation.
|
|
bool RelaxedFrag = false;
|
|
switch(I->getKind()) {
|
|
default:
|
|
break;
|
|
case MCFragment::FT_Relaxable:
|
|
assert(!getRelaxAll() &&
|
|
"Did not expect a MCRelaxableFragment in RelaxAll mode");
|
|
RelaxedFrag = relaxInstruction(Layout, *cast<MCRelaxableFragment>(I));
|
|
break;
|
|
case MCFragment::FT_Dwarf:
|
|
RelaxedFrag = relaxDwarfLineAddr(Layout,
|
|
*cast<MCDwarfLineAddrFragment>(I));
|
|
break;
|
|
case MCFragment::FT_DwarfFrame:
|
|
RelaxedFrag =
|
|
relaxDwarfCallFrameFragment(Layout,
|
|
*cast<MCDwarfCallFrameFragment>(I));
|
|
break;
|
|
case MCFragment::FT_LEB:
|
|
RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
|
|
break;
|
|
case MCFragment::FT_Padding:
|
|
RelaxedFrag = relaxPaddingFragment(Layout, *cast<MCPaddingFragment>(I));
|
|
break;
|
|
case MCFragment::FT_CVInlineLines:
|
|
RelaxedFrag =
|
|
relaxCVInlineLineTable(Layout, *cast<MCCVInlineLineTableFragment>(I));
|
|
break;
|
|
case MCFragment::FT_CVDefRange:
|
|
RelaxedFrag = relaxCVDefRange(Layout, *cast<MCCVDefRangeFragment>(I));
|
|
break;
|
|
}
|
|
if (RelaxedFrag && !FirstRelaxedFragment)
|
|
FirstRelaxedFragment = &*I;
|
|
}
|
|
if (FirstRelaxedFragment) {
|
|
Layout.invalidateFragmentsFrom(FirstRelaxedFragment);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
bool MCAssembler::layoutOnce(MCAsmLayout &Layout) {
|
|
++stats::RelaxationSteps;
|
|
|
|
bool WasRelaxed = false;
|
|
for (iterator it = begin(), ie = end(); it != ie; ++it) {
|
|
MCSection &Sec = *it;
|
|
while (layoutSectionOnce(Layout, Sec))
|
|
WasRelaxed = true;
|
|
}
|
|
|
|
return WasRelaxed;
|
|
}
|
|
|
|
void MCAssembler::finishLayout(MCAsmLayout &Layout) {
|
|
assert(getBackendPtr() && "Expected assembler backend");
|
|
// The layout is done. Mark every fragment as valid.
|
|
for (unsigned int i = 0, n = Layout.getSectionOrder().size(); i != n; ++i) {
|
|
MCSection &Section = *Layout.getSectionOrder()[i];
|
|
Layout.getFragmentOffset(&*Section.rbegin());
|
|
computeFragmentSize(Layout, *Section.rbegin());
|
|
}
|
|
getBackend().finishLayout(*this, Layout);
|
|
}
|
|
|
|
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
|
|
LLVM_DUMP_METHOD void MCAssembler::dump() const{
|
|
raw_ostream &OS = errs();
|
|
|
|
OS << "<MCAssembler\n";
|
|
OS << " Sections:[\n ";
|
|
for (const_iterator it = begin(), ie = end(); it != ie; ++it) {
|
|
if (it != begin()) OS << ",\n ";
|
|
it->dump();
|
|
}
|
|
OS << "],\n";
|
|
OS << " Symbols:[";
|
|
|
|
for (const_symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
|
|
if (it != symbol_begin()) OS << ",\n ";
|
|
OS << "(";
|
|
it->dump();
|
|
OS << ", Index:" << it->getIndex() << ", ";
|
|
OS << ")";
|
|
}
|
|
OS << "]>\n";
|
|
}
|
|
#endif
|