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//===- bolt/Passes/FixRelaxationPass.cpp ------------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "bolt/Passes/FixRelaxationPass.h"
#include "bolt/Core/ParallelUtilities.h"
using namespace llvm;
namespace llvm {
namespace bolt {
// This function finds ADRP+ADD instruction sequences that originally before
// linker relaxations were ADRP+LDR. We've modified LDR/ADD relocation properly
// during relocation reading, so its targeting right symbol. As for ADRP its
// target is wrong before this pass since we won't be able to recognize and
// properly change R_AARCH64_ADR_GOT_PAGE relocation to
// R_AARCH64_ADR_PREL_PG_HI21 during relocation reading. Now we're searching for
// ADRP+ADD sequences, checking that ADRP points to the GOT-table symbol and the
// target of ADD is another symbol. When found change ADRP symbol reference to
// the ADDs one.
void FixRelaxations::runOnFunction(BinaryFunction &BF) {
BinaryContext &BC = BF.getBinaryContext();
for (BinaryBasicBlock &BB : BF) {
for (auto II = BB.begin(); II != BB.end(); ++II) {
MCInst &Adrp = *II;
if (BC.MIB->isPseudo(Adrp) || !BC.MIB->isADRP(Adrp))
continue;
const MCSymbol *AdrpSymbol = BC.MIB->getTargetSymbol(Adrp);
if (!AdrpSymbol || AdrpSymbol->getName() != "__BOLT_got_zero")
continue;
auto NextII = std::next(II);
if (NextII == BB.end())
continue;
const MCInst &Add = *NextII;
if (!BC.MIB->matchAdrpAddPair(Adrp, Add))
continue;
const MCSymbol *Symbol = BC.MIB->getTargetSymbol(Add);
if (!Symbol || AdrpSymbol == Symbol)
continue;
auto L = BC.scopeLock();
const int64_t Addend = BC.MIB->getTargetAddend(Add);
BC.MIB->setOperandToSymbolRef(Adrp, /*OpNum*/ 1, Symbol, Addend,
BC.Ctx.get(), ELF::R_AARCH64_NONE);
}
}
}
Error FixRelaxations::runOnFunctions(BinaryContext &BC) {
if (!BC.isAArch64() || !BC.HasRelocations)
return Error::success();
ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
runOnFunction(BF);
};
ParallelUtilities::runOnEachFunction(
BC, ParallelUtilities::SchedulingPolicy::SP_INST_LINEAR, WorkFun, nullptr,
"FixRelaxations");
return Error::success();
}
} // namespace bolt
} // namespace llvm
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