| 1 | //===- bolt/Passes/PLTCall.h - PLT call optimization ----------------------===// |
|---|
| 2 | // |
|---|
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
|---|
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
|---|
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
|---|
| 6 | // |
|---|
| 7 | //===----------------------------------------------------------------------===// |
|---|
| 8 | // |
|---|
| 9 | // This file implements the PLTCall class, which replaces calls to PLT entries |
|---|
| 10 | // with indirect calls against GOT. |
|---|
| 11 | // |
|---|
| 12 | //===----------------------------------------------------------------------===// |
|---|
| 13 | |
|---|
| 14 | #include "bolt/Passes/PLTCall.h" |
|---|
| 15 | #include "llvm/Support/CommandLine.h" |
|---|
| 16 | |
|---|
| 17 | #define DEBUG_TYPE "bolt-plt" |
|---|
| 18 | |
|---|
| 19 | using namespace llvm; |
|---|
| 20 | |
|---|
| 21 | namespace opts { |
|---|
| 22 | |
|---|
| 23 | extern cl::OptionCategory BoltOptCategory; |
|---|
| 24 | |
|---|
| 25 | cl::opt<bolt::PLTCall::OptType> |
|---|
| 26 | PLT("plt" , |
|---|
| 27 | cl::desc("optimize PLT calls (requires linking with -znow)" ), |
|---|
| 28 | cl::init(Val: bolt::PLTCall::OT_NONE), |
|---|
| 29 | cl::values(clEnumValN(bolt::PLTCall::OT_NONE, |
|---|
| 30 | "none" , |
|---|
| 31 | "do not optimize PLT calls" ), |
|---|
| 32 | clEnumValN(bolt::PLTCall::OT_HOT, |
|---|
| 33 | "hot" , |
|---|
| 34 | "optimize executed (hot) PLT calls" ), |
|---|
| 35 | clEnumValN(bolt::PLTCall::OT_ALL, |
|---|
| 36 | "all" , |
|---|
| 37 | "optimize all PLT calls" )), |
|---|
| 38 | cl::ZeroOrMore, |
|---|
| 39 | cl::cat(BoltOptCategory)); |
|---|
| 40 | |
|---|
| 41 | } |
|---|
| 42 | |
|---|
| 43 | namespace llvm { |
|---|
| 44 | namespace bolt { |
|---|
| 45 | |
|---|
| 46 | Error PLTCall::runOnFunctions(BinaryContext &BC) { |
|---|
| 47 | if (opts::PLT == OT_NONE) |
|---|
| 48 | return Error::success(); |
|---|
| 49 | |
|---|
| 50 | uint64_t NumCallsOptimized = 0; |
|---|
| 51 | for (auto &It : BC.getBinaryFunctions()) { |
|---|
| 52 | BinaryFunction &Function = It.second; |
|---|
| 53 | if (!shouldOptimize(BF: Function)) |
|---|
| 54 | continue; |
|---|
| 55 | |
|---|
| 56 | if (opts::PLT == OT_HOT && |
|---|
| 57 | Function.getExecutionCount() == BinaryFunction::COUNT_NO_PROFILE) |
|---|
| 58 | continue; |
|---|
| 59 | |
|---|
| 60 | for (BinaryBasicBlock &BB : Function) { |
|---|
| 61 | if (opts::PLT == OT_HOT && !BB.getKnownExecutionCount()) |
|---|
| 62 | continue; |
|---|
| 63 | |
|---|
| 64 | for (MCInst &Instr : BB) { |
|---|
| 65 | if (!BC.MIB->isCall(Inst: Instr)) |
|---|
| 66 | continue; |
|---|
| 67 | const MCSymbol *CallSymbol = BC.MIB->getTargetSymbol(Inst: Instr); |
|---|
| 68 | if (!CallSymbol) |
|---|
| 69 | continue; |
|---|
| 70 | const BinaryFunction *CalleeBF = BC.getFunctionForSymbol(Symbol: CallSymbol); |
|---|
| 71 | if (!CalleeBF || !CalleeBF->isPLTFunction()) |
|---|
| 72 | continue; |
|---|
| 73 | BC.MIB->convertCallToIndirectCall(Inst&: Instr, TargetLocation: CalleeBF->getPLTSymbol(), |
|---|
| 74 | Ctx: BC.Ctx.get()); |
|---|
| 75 | BC.MIB->addAnnotation(Inst&: Instr, Name: "PLTCall" , Val: true); |
|---|
| 76 | ++NumCallsOptimized; |
|---|
| 77 | } |
|---|
| 78 | } |
|---|
| 79 | } |
|---|
| 80 | |
|---|
| 81 | if (NumCallsOptimized) { |
|---|
| 82 | BC.RequiresZNow = true; |
|---|
| 83 | BC.outs() << "BOLT-INFO: " << NumCallsOptimized |
|---|
| 84 | << " PLT calls in the binary were optimized.\n" ; |
|---|
| 85 | } |
|---|
| 86 | return Error::success(); |
|---|
| 87 | } |
|---|
| 88 | |
|---|
| 89 | } // namespace bolt |
|---|
| 90 | } // namespace llvm |
|---|
| 91 | |
|---|
