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//===- bolt/Passes/ADRRelaxationPass.cpp ----------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the ADRRelaxationPass class.
//
//===----------------------------------------------------------------------===//
#include "bolt/Passes/ADRRelaxationPass.h"
#include "bolt/Core/ParallelUtilities.h"
#include "bolt/Utils/CommandLineOpts.h"
#include <iterator>
using namespace llvm;
namespace opts {
extern cl::OptionCategory BoltCategory;
static cl::opt<bool>
AdrPassOpt("adr-relaxation",
cl::desc("Replace ARM non-local ADR instructions with ADRP"),
cl::init(true), cl::cat(BoltCategory), cl::ReallyHidden);
} // namespace opts
namespace llvm {
namespace bolt {
// We don't exit directly from runOnFunction since it would call ThreadPool
// destructor which might result in internal assert if we're not finished
// creating async jobs on the moment of exit. So we're finishing all parallel
// jobs and checking the exit flag after it.
static bool PassFailed = false;
void ADRRelaxationPass::runOnFunction(BinaryFunction &BF) {
if (PassFailed)
return;
BinaryContext &BC = BF.getBinaryContext();
for (BinaryBasicBlock &BB : BF) {
for (auto It = BB.begin(); It != BB.end(); ++It) {
MCInst &Inst = *It;
if (!BC.MIB->isADR(Inst))
continue;
const MCSymbol *Symbol = BC.MIB->getTargetSymbol(Inst);
if (!Symbol)
continue;
if (BF.hasIslandsInfo()) {
BinaryFunction::IslandInfo &Islands = BF.getIslandInfo();
if (Islands.Symbols.count(Symbol) || Islands.ProxySymbols.count(Symbol))
continue;
}
// Don't relax ADR if it points to the same function and is in the main
// fragment and BF initial size is < 1MB.
const unsigned OneMB = 0x100000;
if (BF.getSize() < OneMB) {
BinaryFunction *TargetBF = BC.getFunctionForSymbol(Symbol);
if (TargetBF == &BF && !BB.isSplit())
continue;
// No relaxation needed if ADR references a basic block in the same
// fragment.
if (BinaryBasicBlock *TargetBB = BF.getBasicBlockForLabel(Symbol))
if (BB.getFragmentNum() == TargetBB->getFragmentNum())
continue;
}
InstructionListType AdrpAdd;
{
auto L = BC.scopeLock();
AdrpAdd = BC.MIB->undoAdrpAddRelaxation(Inst, BC.Ctx.get());
}
if (It != BB.begin() && BC.MIB->isNoop(*std::prev(It))) {
It = BB.eraseInstruction(std::prev(It));
} else if (std::next(It) != BB.end() && BC.MIB->isNoop(*std::next(It))) {
BB.eraseInstruction(std::next(It));
} else if (!BF.isSimple()) {
// If the function is not simple, it may contain a jump table undetected
// by us. This jump table may use an offset from the branch instruction
// to land in the desired place. If we add new instructions, we
// invalidate this offset, so we have to rely on linker-inserted NOP to
// replace it with ADRP, and abort if it is not present.
auto L = BC.scopeLock();
BC.errs() << "BOLT-ERROR: cannot relax ADR in non-simple function "
<< BF << '\n';
PassFailed = true;
return;
}
It = BB.replaceInstruction(It, AdrpAdd);
}
}
}
Error ADRRelaxationPass::runOnFunctions(BinaryContext &BC) {
if (!opts::AdrPassOpt || !BC.HasRelocations)
return Error::success();
ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
runOnFunction(BF);
};
ParallelUtilities::runOnEachFunction(
BC, ParallelUtilities::SchedulingPolicy::SP_TRIVIAL, WorkFun, nullptr,
"ADRRelaxationPass");
if (PassFailed)
return createFatalBOLTError("");
return Error::success();
}
} // end namespace bolt
} // end namespace llvm
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