bolt/lib/Passes/ADRRelaxationPass.cpp

   1 //===- bolt/Passes/ADRRelaxationPass.cpp ----------------------------------===//
   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 ADRRelaxationPass class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "bolt/Passes/ADRRelaxationPass.h"
  14 #include "bolt/Core/ParallelUtilities.h"
  15 #include "bolt/Utils/CommandLineOpts.h"
  16 #include <iterator>
  17
  18 using namespace llvm;
  19
  20 namespace opts {
  21 extern cl::OptionCategory BoltCategory;
  22
  23 static cl::opt<bool>
  24     AdrPassOpt("adr-relaxation",
  25                cl::desc("Replace ARM non-local ADR instructions with ADRP"),
  26                cl::init(true), cl::cat(BoltCategory), cl::ReallyHidden);
  27 } // namespace opts
  28
  29 namespace llvm {
  30 namespace bolt {
  31
  32 void ADRRelaxationPass::runOnFunction(BinaryFunction &BF) {
  33   BinaryContext &BC = BF.getBinaryContext();
  34   for (BinaryBasicBlock &BB : BF) {
  35     for (auto It = BB.begin(); It != BB.end(); ++It) {
  36       MCInst &Inst = *It;
  37       if (!BC.MIB->isADR(Inst))
  38         continue;
  39
  40       const MCSymbol *Symbol = BC.MIB->getTargetSymbol(Inst);
  41       if (!Symbol)
  42         continue;
  43
  44       if (BF.hasIslandsInfo()) {
  45         BinaryFunction::IslandInfo &Islands = BF.getIslandInfo();
  46         if (Islands.Symbols.count(Symbol) || Islands.ProxySymbols.count(Symbol))
  47           continue;
  48       }
  49
  50       BinaryFunction *TargetBF = BC.getFunctionForSymbol(Symbol);
  51       if (TargetBF && TargetBF == &BF)
  52         continue;
  53
  54       MCPhysReg Reg;
  55       BC.MIB->getADRReg(Inst, Reg);
  56       int64_t Addend = BC.MIB->getTargetAddend(Inst);
  57       InstructionListType Addr =
  58           BC.MIB->materializeAddress(Symbol, BC.Ctx.get(), Reg, Addend);
  59
  60       if (It != BB.begin() && BC.MIB->isNoop(*std::prev(It))) {
  61         It = BB.eraseInstruction(std::prev(It));
  62       } else if (opts::StrictMode && !BF.isSimple()) {
  63         // If the function is not simple, it may contain a jump table undetected
  64         // by us. This jump table may use an offset from the branch instruction
  65         // to land in the desired place. If we add new instructions, we
  66         // invalidate this offset, so we have to rely on linker-inserted NOP to
  67         // replace it with ADRP, and abort if it is not present.
  68         errs() << formatv("BOLT-ERROR: Cannot relax adr in non-simple function "
  69                           "{0}. Can't proceed in current mode.\n",
  70                           BF.getOneName());
  71         exit(1);
  72       }
  73       It = BB.replaceInstruction(It, Addr);
  74     }
  75   }
  76 }
  77
  78 void ADRRelaxationPass::runOnFunctions(BinaryContext &BC) {
  79   if (!opts::AdrPassOpt || !BC.HasRelocations)
  80     return;
  81
  82   ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
  83     runOnFunction(BF);
  84   };
  85
  86   ParallelUtilities::runOnEachFunction(
  87       BC, ParallelUtilities::SchedulingPolicy::SP_TRIVIAL, WorkFun, nullptr,
  88       "ADRRelaxationPass", /* ForceSequential */ true);
  89 }
  90
  91 } // end namespace bolt
  92 } // end namespace llvm