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 // We don't exit directly from runOnFunction since it would call ThreadPool
  33 // destructor which might result in internal assert if we're not finished
  34 // creating async jobs on the moment of exit. So we're finishing all parallel
  35 // jobs and checking the exit flag after it.
  36 static bool PassFailed = false;
  37
  38 void ADRRelaxationPass::runOnFunction(BinaryFunction &BF) {
  39   if (PassFailed)
  40     return;
  41
  42   BinaryContext &BC = BF.getBinaryContext();
  43   for (BinaryBasicBlock &BB : BF) {
  44     for (auto It = BB.begin(); It != BB.end(); ++It) {
  45       MCInst &Inst = *It;
  46       if (!BC.MIB->isADR(Inst))
  47         continue;
  48
  49       const MCSymbol *Symbol = BC.MIB->getTargetSymbol(Inst);
  50       if (!Symbol)
  51         continue;
  52
  53       if (BF.hasIslandsInfo()) {
  54         BinaryFunction::IslandInfo &Islands = BF.getIslandInfo();
  55         if (Islands.Symbols.count(Symbol) || Islands.ProxySymbols.count(Symbol))
  56           continue;
  57       }
  58
  59       // Don't relax ADR if it points to the same function and is in the main
  60       // fragment and BF initial size is < 1MB.
  61       const unsigned OneMB = 0x100000;
  62       if (BF.getSize() < OneMB) {
  63         BinaryFunction *TargetBF = BC.getFunctionForSymbol(Symbol);
  64         if (TargetBF == &BF && !BB.isSplit())
  65           continue;
  66
  67         // No relaxation needed if ADR references a basic block in the same
  68         // fragment.
  69         if (BinaryBasicBlock *TargetBB = BF.getBasicBlockForLabel(Symbol))
  70           if (BB.getFragmentNum() == TargetBB->getFragmentNum())
  71             continue;
  72       }
  73
  74       MCPhysReg Reg;
  75       BC.MIB->getADRReg(Inst, Reg);
  76       int64_t Addend = BC.MIB->getTargetAddend(Inst);
  77       InstructionListType Addr;
  78
  79       {
  80         auto L = BC.scopeLock();
  81         Addr = BC.MIB->materializeAddress(Symbol, BC.Ctx.get(), Reg, Addend);
  82       }
  83
  84       if (It != BB.begin() && BC.MIB->isNoop(*std::prev(It))) {
  85         It = BB.eraseInstruction(std::prev(It));
  86       } else if (std::next(It) != BB.end() && BC.MIB->isNoop(*std::next(It))) {
  87         BB.eraseInstruction(std::next(It));
  88       } else if (!opts::StrictMode && !BF.isSimple()) {
  89         // If the function is not simple, it may contain a jump table undetected
  90         // by us. This jump table may use an offset from the branch instruction
  91         // to land in the desired place. If we add new instructions, we
  92         // invalidate this offset, so we have to rely on linker-inserted NOP to
  93         // replace it with ADRP, and abort if it is not present.
  94         auto L = BC.scopeLock();
  95         BC.errs() << formatv(
  96             "BOLT-ERROR: Cannot relax adr in non-simple function "
  97             "{0}. Use --strict option to override\n",
  98             BF.getOneName());
  99         PassFailed = true;
 100         return;
 101       }
 102       It = BB.replaceInstruction(It, Addr);
 103     }
 104   }
 105 }
 106
 107 Error ADRRelaxationPass::runOnFunctions(BinaryContext &BC) {
 108   if (!opts::AdrPassOpt || !BC.HasRelocations)
 109     return Error::success();
 110
 111   ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
 112     runOnFunction(BF);
 113   };
 114
 115   ParallelUtilities::runOnEachFunction(
 116       BC, ParallelUtilities::SchedulingPolicy::SP_TRIVIAL, WorkFun, nullptr,
 117       "ADRRelaxationPass");
 118
 119   if (PassFailed)
 120     return createFatalBOLTError("");
 121   return Error::success();
 122 }
 123
 124 } // end namespace bolt
 125 } // end namespace llvm