a13bc9714a
`convertCallToIndirectCall` applies the PLTCall optimization and returns an (updated if needed) iterator to the converted call instruction. Since AArch64 requires to inject additional instructions to implement this pass, the relevant BasicBlock and an iterator was passed to the `convertCallToIndirectCall`. `NumCallsOptimized` is updated only on successful application of the pass. Tests: - Inputs/plt-tailcall.c: an example of a tail call optimized PLT call. - AArch64/plt-call.test: it is the actual A64 test, that runs the PLTCall optimization on the above input file and verifies the application of the pass to the calls: 'printf' and 'puts'.
94 lines
2.8 KiB
C++
94 lines
2.8 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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cl::opt<bolt::PLTCall::OptType>
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PLT("plt",
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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,
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"none",
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"do not optimize PLT calls"),
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clEnumValN(bolt::PLTCall::OT_HOT,
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"hot",
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"optimize executed (hot) PLT calls"),
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clEnumValN(bolt::PLTCall::OT_ALL,
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"all",
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"optimize all PLT calls")),
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cl::ZeroOrMore,
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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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*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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