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425dda76e9
The gold linker veneers are written between functions without symbols, so we to handle it specially in BOLT. Vladislav Khmelevsky, Advanced Software Technology Lab, Huawei Differential Revision: https://reviews.llvm.org/D128082
103 lines
3.2 KiB
C++
103 lines
3.2 KiB
C++
//===- bolt/Passes/VeneerElimination.cpp ----------------------------------===//
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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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// This class implements a pass that removes linker-inserted veneers from the
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// code and redirects veneer callers to call to veneers destinations
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//
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//===----------------------------------------------------------------------===//
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#include "bolt/Passes/VeneerElimination.h"
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#define DEBUG_TYPE "veneer-elim"
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using namespace llvm;
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namespace opts {
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extern cl::OptionCategory BoltOptCategory;
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static llvm::cl::opt<bool>
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EliminateVeneers("elim-link-veneers",
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cl::desc("run veneer elimination pass"), cl::init(true),
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cl::Hidden, cl::cat(BoltOptCategory));
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} // namespace opts
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namespace llvm {
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namespace bolt {
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void VeneerElimination::runOnFunctions(BinaryContext &BC) {
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if (!opts::EliminateVeneers || !BC.isAArch64())
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return;
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auto &BFs = BC.getBinaryFunctions();
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std::unordered_map<const MCSymbol *, const MCSymbol *> VeneerDestinations;
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uint64_t VeneersCount = 0;
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for (auto It = BFs.begin(); It != BFs.end();) {
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auto CurrentIt = It;
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++It;
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if (CurrentIt->second.isAArch64Veneer()) {
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VeneersCount++;
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BinaryFunction &VeneerFunction = CurrentIt->second;
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MCInst &FirstInstruction = *(VeneerFunction.begin()->begin());
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const MCSymbol *VeneerTargetSymbol =
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BC.MIB->getTargetSymbol(FirstInstruction, 1);
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// Functions can have multiple symbols
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for (StringRef Name : VeneerFunction.getNames()) {
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MCSymbol *Symbol = BC.Ctx->lookupSymbol(Name);
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VeneerDestinations[Symbol] = VeneerTargetSymbol;
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BC.SymbolToFunctionMap.erase(Symbol);
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}
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BC.BinaryDataMap.erase(VeneerFunction.getAddress());
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BFs.erase(CurrentIt);
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}
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}
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outs() << "BOLT-INFO: number of removed linker-inserted veneers :"
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<< VeneersCount << "\n";
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// Handle veneers to veneers in case they occur
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for (auto entry : VeneerDestinations) {
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const MCSymbol *src = entry.first;
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const MCSymbol *dest = entry.second;
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while (VeneerDestinations.find(dest) != VeneerDestinations.end()) {
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dest = VeneerDestinations[dest];
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}
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VeneerDestinations[src] = dest;
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}
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uint64_t VeneerCallers = 0;
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for (auto &It : BFs) {
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BinaryFunction &Function = It.second;
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for (BinaryBasicBlock &BB : Function) {
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for (MCInst &Instr : BB) {
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if (!BC.MIB->isCall(Instr) || BC.MIB->isIndirectCall(Instr))
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continue;
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const MCSymbol *TargetSymbol = BC.MIB->getTargetSymbol(Instr, 0);
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if (VeneerDestinations.find(TargetSymbol) == VeneerDestinations.end())
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continue;
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VeneerCallers++;
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if (!BC.MIB->replaceBranchTarget(
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Instr, VeneerDestinations[TargetSymbol], BC.Ctx.get()))
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assert(false && "updating veneer call destination failed");
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}
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}
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}
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LLVM_DEBUG(
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dbgs() << "BOLT-INFO: number of linker-inserted veneers call sites :"
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<< VeneerCallers << "\n");
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}
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} // namespace bolt
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} // namespace llvm
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