forked from OSchip/llvm-project
482 lines
16 KiB
C++
482 lines
16 KiB
C++
//===--------- JITLinkGeneric.cpp - Generic JIT linker utilities ----------===//
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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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//
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// Generic JITLinker utility class.
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//
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//===----------------------------------------------------------------------===//
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#include "JITLinkGeneric.h"
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#include "EHFrameSupportImpl.h"
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#include "llvm/Support/BinaryStreamReader.h"
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#include "llvm/Support/MemoryBuffer.h"
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#define DEBUG_TYPE "jitlink"
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namespace llvm {
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namespace jitlink {
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JITLinkerBase::~JITLinkerBase() {}
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void JITLinkerBase::linkPhase1(std::unique_ptr<JITLinkerBase> Self) {
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// Build the atom graph.
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if (auto GraphOrErr = buildGraph(Ctx->getObjectBuffer()))
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G = std::move(*GraphOrErr);
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else
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return Ctx->notifyFailed(GraphOrErr.takeError());
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assert(G && "Graph should have been created by buildGraph above");
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// Prune and optimize the graph.
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if (auto Err = runPasses(Passes.PrePrunePasses, *G))
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return Ctx->notifyFailed(std::move(Err));
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LLVM_DEBUG({
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dbgs() << "Atom graph \"" << G->getName() << "\" pre-pruning:\n";
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dumpGraph(dbgs());
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});
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prune(*G);
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LLVM_DEBUG({
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dbgs() << "Atom graph \"" << G->getName() << "\" post-pruning:\n";
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dumpGraph(dbgs());
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});
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// Run post-pruning passes.
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if (auto Err = runPasses(Passes.PostPrunePasses, *G))
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return Ctx->notifyFailed(std::move(Err));
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// Sort atoms into segments.
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layOutAtoms();
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// Allocate memory for segments.
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if (auto Err = allocateSegments(Layout))
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return Ctx->notifyFailed(std::move(Err));
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// Notify client that the defined atoms have been assigned addresses.
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Ctx->notifyResolved(*G);
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auto ExternalSymbols = getExternalSymbolNames();
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// We're about to hand off ownership of ourself to the continuation. Grab a
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// pointer to the context so that we can call it to initiate the lookup.
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//
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// FIXME: Once callee expressions are defined to be sequenced before argument
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// expressions (c++17) we can simplify all this to:
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//
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// Ctx->lookup(std::move(UnresolvedExternals),
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// [Self=std::move(Self)](Expected<AsyncLookupResult> Result) {
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// Self->linkPhase2(std::move(Self), std::move(Result));
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// });
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//
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// FIXME: Use move capture once we have c++14.
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auto *TmpCtx = Ctx.get();
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auto *UnownedSelf = Self.release();
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auto Phase2Continuation =
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[UnownedSelf](Expected<AsyncLookupResult> LookupResult) {
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std::unique_ptr<JITLinkerBase> Self(UnownedSelf);
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UnownedSelf->linkPhase2(std::move(Self), std::move(LookupResult));
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};
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TmpCtx->lookup(std::move(ExternalSymbols), std::move(Phase2Continuation));
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}
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void JITLinkerBase::linkPhase2(std::unique_ptr<JITLinkerBase> Self,
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Expected<AsyncLookupResult> LR) {
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// If the lookup failed, bail out.
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if (!LR)
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return deallocateAndBailOut(LR.takeError());
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// Assign addresses to external atoms.
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applyLookupResult(*LR);
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LLVM_DEBUG({
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dbgs() << "Atom graph \"" << G->getName() << "\" before copy-and-fixup:\n";
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dumpGraph(dbgs());
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});
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// Copy atom content to working memory and fix up.
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if (auto Err = copyAndFixUpAllAtoms(Layout, *Alloc))
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return deallocateAndBailOut(std::move(Err));
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LLVM_DEBUG({
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dbgs() << "Atom graph \"" << G->getName() << "\" after copy-and-fixup:\n";
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dumpGraph(dbgs());
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});
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if (auto Err = runPasses(Passes.PostFixupPasses, *G))
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return deallocateAndBailOut(std::move(Err));
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// FIXME: Use move capture once we have c++14.
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auto *UnownedSelf = Self.release();
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auto Phase3Continuation = [UnownedSelf](Error Err) {
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std::unique_ptr<JITLinkerBase> Self(UnownedSelf);
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UnownedSelf->linkPhase3(std::move(Self), std::move(Err));
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};
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Alloc->finalizeAsync(std::move(Phase3Continuation));
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}
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void JITLinkerBase::linkPhase3(std::unique_ptr<JITLinkerBase> Self, Error Err) {
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if (Err)
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return deallocateAndBailOut(std::move(Err));
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Ctx->notifyFinalized(std::move(Alloc));
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}
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Error JITLinkerBase::runPasses(AtomGraphPassList &Passes, AtomGraph &G) {
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for (auto &P : Passes)
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if (auto Err = P(G))
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return Err;
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return Error::success();
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}
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void JITLinkerBase::layOutAtoms() {
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// Group sections by protections, and whether or not they're zero-fill.
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for (auto &S : G->sections()) {
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// Skip empty sections.
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if (S.atoms_empty())
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continue;
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auto &SL = Layout[S.getProtectionFlags()];
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if (S.isZeroFill())
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SL.ZeroFillSections.push_back(SegmentLayout::SectionLayout(S));
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else
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SL.ContentSections.push_back(SegmentLayout::SectionLayout(S));
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}
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// Sort sections within the layout by ordinal.
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{
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auto CompareByOrdinal = [](const SegmentLayout::SectionLayout &LHS,
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const SegmentLayout::SectionLayout &RHS) {
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return LHS.S->getSectionOrdinal() < RHS.S->getSectionOrdinal();
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};
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for (auto &KV : Layout) {
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auto &SL = KV.second;
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std::sort(SL.ContentSections.begin(), SL.ContentSections.end(),
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CompareByOrdinal);
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std::sort(SL.ZeroFillSections.begin(), SL.ZeroFillSections.end(),
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CompareByOrdinal);
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}
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}
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// Add atoms to the sections.
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for (auto &KV : Layout) {
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auto &SL = KV.second;
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for (auto *SIList : {&SL.ContentSections, &SL.ZeroFillSections}) {
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for (auto &SI : *SIList) {
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// First build the set of layout-heads (i.e. "heads" of layout-next
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// chains) by copying the section atoms, then eliminating any that
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// appear as layout-next targets.
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DenseSet<DefinedAtom *> LayoutHeads;
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for (auto *DA : SI.S->atoms())
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LayoutHeads.insert(DA);
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for (auto *DA : SI.S->atoms())
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if (DA->hasLayoutNext())
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LayoutHeads.erase(&DA->getLayoutNext());
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// Next, sort the layout heads by address order.
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std::vector<DefinedAtom *> OrderedLayoutHeads;
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OrderedLayoutHeads.reserve(LayoutHeads.size());
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for (auto *DA : LayoutHeads)
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OrderedLayoutHeads.push_back(DA);
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// Now sort the list of layout heads by address.
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std::sort(OrderedLayoutHeads.begin(), OrderedLayoutHeads.end(),
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[](const DefinedAtom *LHS, const DefinedAtom *RHS) {
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return LHS->getAddress() < RHS->getAddress();
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});
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// Now populate the SI.Atoms field by appending each of the chains.
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for (auto *DA : OrderedLayoutHeads) {
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SI.Atoms.push_back(DA);
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while (DA->hasLayoutNext()) {
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auto &Next = DA->getLayoutNext();
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SI.Atoms.push_back(&Next);
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DA = &Next;
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}
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}
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}
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}
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}
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LLVM_DEBUG({
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dbgs() << "Segment ordering:\n";
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for (auto &KV : Layout) {
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dbgs() << " Segment "
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<< static_cast<sys::Memory::ProtectionFlags>(KV.first) << ":\n";
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auto &SL = KV.second;
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for (auto &SIEntry :
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{std::make_pair(&SL.ContentSections, "content sections"),
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std::make_pair(&SL.ZeroFillSections, "zero-fill sections")}) {
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auto &SIList = *SIEntry.first;
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dbgs() << " " << SIEntry.second << ":\n";
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for (auto &SI : SIList) {
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dbgs() << " " << SI.S->getName() << ":\n";
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for (auto *DA : SI.Atoms)
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dbgs() << " " << *DA << "\n";
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}
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}
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}
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});
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}
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Error JITLinkerBase::allocateSegments(const SegmentLayoutMap &Layout) {
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// Compute segment sizes and allocate memory.
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LLVM_DEBUG(dbgs() << "JIT linker requesting: { ");
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JITLinkMemoryManager::SegmentsRequestMap Segments;
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for (auto &KV : Layout) {
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auto &Prot = KV.first;
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auto &SegLayout = KV.second;
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// Calculate segment content size.
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size_t SegContentSize = 0;
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for (auto &SI : SegLayout.ContentSections) {
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assert(!SI.S->atoms_empty() && "Sections in layout must not be empty");
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assert(!SI.Atoms.empty() && "Section layouts must not be empty");
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// Bump to section alignment before processing atoms.
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SegContentSize = alignTo(SegContentSize, SI.S->getAlignment());
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for (auto *DA : SI.Atoms) {
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SegContentSize = alignTo(SegContentSize, DA->getAlignment());
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SegContentSize += DA->getSize();
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}
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}
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// Get segment content alignment.
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unsigned SegContentAlign = 1;
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if (!SegLayout.ContentSections.empty()) {
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auto &FirstContentSection = SegLayout.ContentSections.front();
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SegContentAlign =
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std::max(FirstContentSection.S->getAlignment(),
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FirstContentSection.Atoms.front()->getAlignment());
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}
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// Calculate segment zero-fill size.
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uint64_t SegZeroFillSize = 0;
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for (auto &SI : SegLayout.ZeroFillSections) {
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assert(!SI.S->atoms_empty() && "Sections in layout must not be empty");
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assert(!SI.Atoms.empty() && "Section layouts must not be empty");
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// Bump to section alignment before processing atoms.
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SegZeroFillSize = alignTo(SegZeroFillSize, SI.S->getAlignment());
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for (auto *DA : SI.Atoms) {
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SegZeroFillSize = alignTo(SegZeroFillSize, DA->getAlignment());
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SegZeroFillSize += DA->getSize();
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}
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}
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// Calculate segment zero-fill alignment.
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uint32_t SegZeroFillAlign = 1;
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if (!SegLayout.ZeroFillSections.empty()) {
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auto &FirstZeroFillSection = SegLayout.ZeroFillSections.front();
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SegZeroFillAlign =
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std::max(FirstZeroFillSection.S->getAlignment(),
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FirstZeroFillSection.Atoms.front()->getAlignment());
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}
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if (SegContentSize == 0)
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SegContentAlign = SegZeroFillAlign;
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if (SegContentAlign % SegZeroFillAlign != 0)
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return make_error<JITLinkError>("First content atom alignment does not "
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"accommodate first zero-fill atom "
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"alignment");
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Segments[Prot] = {SegContentSize, SegContentAlign, SegZeroFillSize,
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SegZeroFillAlign};
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LLVM_DEBUG({
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dbgs() << (&KV == &*Layout.begin() ? "" : "; ")
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<< static_cast<sys::Memory::ProtectionFlags>(Prot) << ": "
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<< SegContentSize << " content bytes (alignment "
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<< SegContentAlign << ") + " << SegZeroFillSize
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<< " zero-fill bytes (alignment " << SegZeroFillAlign << ")";
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});
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}
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LLVM_DEBUG(dbgs() << " }\n");
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if (auto AllocOrErr = Ctx->getMemoryManager().allocate(Segments))
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Alloc = std::move(*AllocOrErr);
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else
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return AllocOrErr.takeError();
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LLVM_DEBUG({
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dbgs() << "JIT linker got working memory:\n";
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for (auto &KV : Layout) {
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auto Prot = static_cast<sys::Memory::ProtectionFlags>(KV.first);
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dbgs() << " " << Prot << ": "
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<< (const void *)Alloc->getWorkingMemory(Prot).data() << "\n";
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}
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});
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// Update atom target addresses.
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for (auto &KV : Layout) {
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auto &Prot = KV.first;
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auto &SL = KV.second;
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JITTargetAddress AtomTargetAddr =
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Alloc->getTargetMemory(static_cast<sys::Memory::ProtectionFlags>(Prot));
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for (auto *SIList : {&SL.ContentSections, &SL.ZeroFillSections})
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for (auto &SI : *SIList) {
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AtomTargetAddr = alignTo(AtomTargetAddr, SI.S->getAlignment());
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for (auto *DA : SI.Atoms) {
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AtomTargetAddr = alignTo(AtomTargetAddr, DA->getAlignment());
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DA->setAddress(AtomTargetAddr);
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AtomTargetAddr += DA->getSize();
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}
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}
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}
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return Error::success();
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}
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DenseSet<StringRef> JITLinkerBase::getExternalSymbolNames() const {
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// Identify unresolved external atoms.
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DenseSet<StringRef> UnresolvedExternals;
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for (auto *DA : G->external_atoms()) {
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assert(DA->getAddress() == 0 &&
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"External has already been assigned an address");
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assert(DA->getName() != StringRef() && DA->getName() != "" &&
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"Externals must be named");
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UnresolvedExternals.insert(DA->getName());
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}
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return UnresolvedExternals;
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}
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void JITLinkerBase::applyLookupResult(AsyncLookupResult Result) {
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for (auto &KV : Result) {
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Atom &A = G->getAtomByName(KV.first);
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assert(A.getAddress() == 0 && "Atom already resolved");
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A.setAddress(KV.second.getAddress());
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}
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LLVM_DEBUG({
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dbgs() << "Externals after applying lookup result:\n";
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for (auto *A : G->external_atoms())
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dbgs() << " " << A->getName() << ": "
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<< formatv("{0:x16}", A->getAddress()) << "\n";
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});
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assert(llvm::all_of(G->external_atoms(),
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[](Atom *A) { return A->getAddress() != 0; }) &&
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"All atoms should have been resolved by this point");
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}
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void JITLinkerBase::deallocateAndBailOut(Error Err) {
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assert(Err && "Should not be bailing out on success value");
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assert(Alloc && "can not call deallocateAndBailOut before allocation");
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Ctx->notifyFailed(joinErrors(std::move(Err), Alloc->deallocate()));
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}
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void JITLinkerBase::dumpGraph(raw_ostream &OS) {
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assert(G && "Graph is not set yet");
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G->dump(dbgs(), [this](Edge::Kind K) { return getEdgeKindName(K); });
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}
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void prune(AtomGraph &G) {
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std::vector<DefinedAtom *> Worklist;
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DenseMap<DefinedAtom *, std::vector<Edge *>> EdgesToUpdate;
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// Build the initial worklist from all atoms initially live.
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for (auto *DA : G.defined_atoms()) {
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if (!DA->isLive() || DA->shouldDiscard())
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continue;
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for (auto &E : DA->edges()) {
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if (!E.getTarget().isDefined())
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continue;
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auto &EDT = static_cast<DefinedAtom &>(E.getTarget());
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if (EDT.shouldDiscard())
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EdgesToUpdate[&EDT].push_back(&E);
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else if (E.isKeepAlive() && !EDT.isLive())
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Worklist.push_back(&EDT);
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}
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}
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// Propagate live flags to all atoms reachable from the initial live set.
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while (!Worklist.empty()) {
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DefinedAtom &NextLive = *Worklist.back();
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Worklist.pop_back();
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assert(!NextLive.shouldDiscard() &&
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"should-discard nodes should never make it into the worklist");
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// If this atom has already been marked as live, or is marked to be
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// discarded, then skip it.
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if (NextLive.isLive())
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continue;
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// Otherwise set it as live and add any non-live atoms that it points to
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// to the worklist.
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NextLive.setLive(true);
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for (auto &E : NextLive.edges()) {
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if (!E.getTarget().isDefined())
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continue;
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auto &EDT = static_cast<DefinedAtom &>(E.getTarget());
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if (EDT.shouldDiscard())
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EdgesToUpdate[&EDT].push_back(&E);
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else if (E.isKeepAlive() && !EDT.isLive())
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Worklist.push_back(&EDT);
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}
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}
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// Collect atoms to remove, then remove them from the graph.
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std::vector<DefinedAtom *> AtomsToRemove;
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for (auto *DA : G.defined_atoms())
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if (DA->shouldDiscard() || !DA->isLive())
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AtomsToRemove.push_back(DA);
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LLVM_DEBUG(dbgs() << "Pruning atoms:\n");
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for (auto *DA : AtomsToRemove) {
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LLVM_DEBUG(dbgs() << " " << *DA << "... ");
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// Check whether we need to replace this atom with an external atom.
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//
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// We replace if all of the following hold:
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// (1) The atom is marked should-discard,
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// (2) it has live edges (i.e. edges from live atoms) pointing to it.
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//
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// Otherwise we simply delete the atom.
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G.removeDefinedAtom(*DA);
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auto EdgesToUpdateItr = EdgesToUpdate.find(DA);
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if (EdgesToUpdateItr != EdgesToUpdate.end()) {
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auto &ExternalReplacement = G.addExternalAtom(DA->getName());
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for (auto *EdgeToUpdate : EdgesToUpdateItr->second)
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EdgeToUpdate->setTarget(ExternalReplacement);
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LLVM_DEBUG(dbgs() << "replaced with " << ExternalReplacement << "\n");
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} else
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LLVM_DEBUG(dbgs() << "deleted\n");
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}
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// Finally, discard any absolute symbols that were marked should-discard.
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{
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std::vector<Atom *> AbsoluteAtomsToRemove;
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for (auto *A : G.absolute_atoms())
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if (A->shouldDiscard() || A->isLive())
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AbsoluteAtomsToRemove.push_back(A);
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for (auto *A : AbsoluteAtomsToRemove)
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G.removeAbsoluteAtom(*A);
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}
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}
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} // end namespace jitlink
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} // end namespace llvm
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