1//===- bolt/Passes/FixRelaxationPass.cpp ------------------------*- C++ -*-===//
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#include "bolt/Passes/FixRelaxationPass.h"
10#include "bolt/Core/ParallelUtilities.h"
11
12using namespace llvm;
13
14namespace llvm {
15namespace bolt {
16
17// This function finds ADRP+ADD instruction sequences that originally before
18// linker relaxations were ADRP+LDR. We've modified LDR/ADD relocation properly
19// during relocation reading, so its targeting right symbol. As for ADRP its
20// target is wrong before this pass since we won't be able to recognize and
21// properly change R_AARCH64_ADR_GOT_PAGE relocation to
22// R_AARCH64_ADR_PREL_PG_HI21 during relocation reading. Now we're searching for
23// ADRP+ADD sequences, checking that ADRP points to the GOT-table symbol and the
24// target of ADD is another symbol. When found change ADRP symbol reference to
25// the ADDs one.
26void FixRelaxations::runOnFunction(BinaryFunction &BF) {
27 BinaryContext &BC = BF.getBinaryContext();
28 for (BinaryBasicBlock &BB : BF) {
29 for (auto II = BB.begin(); II != BB.end(); ++II) {
30 MCInst &Adrp = *II;
31 if (BC.MIB->isPseudo(Inst: Adrp) || !BC.MIB->isADRP(Inst: Adrp))
32 continue;
33
34 const MCSymbol *AdrpSymbol = BC.MIB->getTargetSymbol(Inst: Adrp);
35 if (!AdrpSymbol || AdrpSymbol->getName() != "__BOLT_got_zero")
36 continue;
37
38 auto NextII = std::next(x: II);
39 if (NextII == BB.end())
40 continue;
41
42 const MCInst &Add = *NextII;
43 if (!BC.MIB->matchAdrpAddPair(Adrp, Add))
44 continue;
45
46 const MCSymbol *Symbol = BC.MIB->getTargetSymbol(Inst: Add);
47 if (!Symbol || AdrpSymbol == Symbol)
48 continue;
49
50 auto L = BC.scopeLock();
51 const int64_t Addend = BC.MIB->getTargetAddend(Inst: Add);
52 BC.MIB->setOperandToSymbolRef(Inst&: Adrp, /*OpNum*/ 1, Symbol, Addend,
53 Ctx: BC.Ctx.get(), RelType: ELF::R_AARCH64_NONE);
54 }
55 }
56}
57
58Error FixRelaxations::runOnFunctions(BinaryContext &BC) {
59 if (!BC.isAArch64() || !BC.HasRelocations)
60 return Error::success();
61
62 ParallelUtilities::WorkFuncTy WorkFun = [&](BinaryFunction &BF) {
63 runOnFunction(BF);
64 };
65
66 ParallelUtilities::runOnEachFunction(
67 BC, SchedPolicy: ParallelUtilities::SchedulingPolicy::SP_INST_LINEAR, WorkFunction: WorkFun, SkipPredicate: nullptr,
68 LogName: "FixRelaxations");
69 return Error::success();
70}
71
72} // namespace bolt
73} // namespace llvm
74

source code of bolt/lib/Passes/FixRelaxationPass.cpp