88 lines
2.9 KiB
C++
88 lines
2.9 KiB
C++
//===- bolt/Passes/PLTCall.h - PLT call optimization ----------------------===//
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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 file implements the PLTCall class, which replaces calls to PLT entries
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// with indirect calls against GOT.
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//
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//===----------------------------------------------------------------------===//
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#include "bolt/Passes/PLTCall.h"
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#include "llvm/Support/CommandLine.h"
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#define DEBUG_TYPE "bolt-plt"
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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 cl::opt<bolt::PLTCall::OptType>
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PLT("plt", cl::desc("optimize PLT calls (requires linking with -znow)"),
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cl::init(bolt::PLTCall::OT_NONE),
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cl::values(clEnumValN(bolt::PLTCall::OT_NONE, "none",
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"do not optimize PLT calls"),
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clEnumValN(bolt::PLTCall::OT_HOT, "hot",
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"optimize executed (hot) PLT calls"),
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clEnumValN(bolt::PLTCall::OT_ALL, "all",
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"optimize all PLT calls")),
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cl::ZeroOrMore, cl::cat(BoltOptCategory));
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}
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namespace llvm {
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namespace bolt {
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Error PLTCall::runOnFunctions(BinaryContext &BC) {
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if (opts::PLT == OT_NONE)
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return Error::success();
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uint64_t NumCallsOptimized = 0;
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for (auto &BFI : BC.getBinaryFunctions()) {
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BinaryFunction &Function = BFI.second;
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if (!shouldOptimize(Function))
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continue;
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if (opts::PLT == OT_HOT &&
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Function.getExecutionCount() == BinaryFunction::COUNT_NO_PROFILE)
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continue;
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for (BinaryBasicBlock &BB : Function) {
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if (opts::PLT == OT_HOT && !BB.getKnownExecutionCount())
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continue;
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for (auto II = BB.begin(); II != BB.end(); II++) {
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if (!BC.MIB->isCall(*II))
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continue;
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const MCSymbol *CallSymbol = BC.MIB->getTargetSymbol(*II);
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if (!CallSymbol)
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continue;
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const BinaryFunction *CalleeBF = BC.getFunctionForSymbol(CallSymbol);
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if (!CalleeBF || !CalleeBF->isPLTFunction())
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continue;
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const InstructionListType NewCode = BC.MIB->createIndirectPLTCall(
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std::move(*II), CalleeBF->getPLTSymbol(), BC.Ctx.get());
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II = BB.replaceInstruction(II, NewCode);
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assert(!NewCode.empty() && "PLT Call replacement must be non-empty");
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std::advance(II, NewCode.size() - 1);
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BC.MIB->addAnnotation(*II, "PLTCall", true);
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++NumCallsOptimized;
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}
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}
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}
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if (NumCallsOptimized) {
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BC.RequiresZNow = true;
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BC.outs() << "BOLT-INFO: " << NumCallsOptimized
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<< " PLT calls in the binary were optimized.\n";
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}
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return Error::success();
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}
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} // namespace bolt
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} // namespace llvm
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