03e1c8b8f9
Commit e4507fb8c94b ("bpf: disable DwarfUsesRelocationsAcrossSections")
disables MCAsmInfo DwarfUsesRelocationsAcrossSections unconditionally
so that dwarf will not use cross section (between dwarf and symbol table)
relocations. This new debug format enables pahole to dump structures
correctly as libdwarves.so does not have BPF backend support yet.
This new debug format, however, breaks bcc (https://github.com/iovisor/bcc)
source debug output as llvm in-memory Dwarf support has some issues to
handle it. More specifically, with DwarfUsesRelocationsAcrossSections
disabled, JIT compiler does not generate .debug_abbrev and Dwarf
DIE (debug info entry) processing is not happy about this.
This patch introduces a new flag -mattr=dwarfris
(dwarf relocation in section) to disable DwarfUsesRelocationsAcrossSections.
DwarfUsesRelocationsAcrossSections is true by default.
Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 326505
113 lines
3.7 KiB
C++
113 lines
3.7 KiB
C++
//===-- BPFTargetMachine.cpp - Define TargetMachine for BPF ---------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// Implements the info about BPF target spec.
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//
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//===----------------------------------------------------------------------===//
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#include "BPFTargetMachine.h"
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#include "BPF.h"
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#include "MCTargetDesc/BPFMCAsmInfo.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
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#include "llvm/CodeGen/TargetPassConfig.h"
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#include "llvm/IR/LegacyPassManager.h"
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#include "llvm/Support/FormattedStream.h"
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#include "llvm/Support/TargetRegistry.h"
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#include "llvm/Target/TargetOptions.h"
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using namespace llvm;
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static cl::
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opt<bool> DisableMIPeephole("disable-bpf-peephole", cl::Hidden,
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cl::desc("Disable machine peepholes for BPF"));
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extern "C" void LLVMInitializeBPFTarget() {
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// Register the target.
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RegisterTargetMachine<BPFTargetMachine> X(getTheBPFleTarget());
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RegisterTargetMachine<BPFTargetMachine> Y(getTheBPFbeTarget());
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RegisterTargetMachine<BPFTargetMachine> Z(getTheBPFTarget());
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PassRegistry &PR = *PassRegistry::getPassRegistry();
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initializeBPFMIPeepholePass(PR);
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}
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// DataLayout: little or big endian
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static std::string computeDataLayout(const Triple &TT) {
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if (TT.getArch() == Triple::bpfeb)
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return "E-m:e-p:64:64-i64:64-n32:64-S128";
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else
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return "e-m:e-p:64:64-i64:64-n32:64-S128";
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}
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static Reloc::Model getEffectiveRelocModel(Optional<Reloc::Model> RM) {
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if (!RM.hasValue())
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return Reloc::PIC_;
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return *RM;
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}
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static CodeModel::Model getEffectiveCodeModel(Optional<CodeModel::Model> CM) {
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if (CM)
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return *CM;
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return CodeModel::Small;
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}
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BPFTargetMachine::BPFTargetMachine(const Target &T, const Triple &TT,
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StringRef CPU, StringRef FS,
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const TargetOptions &Options,
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Optional<Reloc::Model> RM,
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Optional<CodeModel::Model> CM,
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CodeGenOpt::Level OL, bool JIT)
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: LLVMTargetMachine(T, computeDataLayout(TT), TT, CPU, FS, Options,
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getEffectiveRelocModel(RM), getEffectiveCodeModel(CM),
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OL),
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TLOF(make_unique<TargetLoweringObjectFileELF>()),
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Subtarget(TT, CPU, FS, *this) {
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initAsmInfo();
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BPFMCAsmInfo *MAI = static_cast<BPFMCAsmInfo *>(const_cast<MCAsmInfo *>(AsmInfo));
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MAI->setDwarfUsesRelocationsAcrossSections(!Subtarget.getUseDwarfRIS());
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}
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namespace {
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// BPF Code Generator Pass Configuration Options.
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class BPFPassConfig : public TargetPassConfig {
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public:
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BPFPassConfig(BPFTargetMachine &TM, PassManagerBase &PM)
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: TargetPassConfig(TM, PM) {}
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BPFTargetMachine &getBPFTargetMachine() const {
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return getTM<BPFTargetMachine>();
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}
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bool addInstSelector() override;
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void addMachineSSAOptimization() override;
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};
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}
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TargetPassConfig *BPFTargetMachine::createPassConfig(PassManagerBase &PM) {
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return new BPFPassConfig(*this, PM);
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}
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// Install an instruction selector pass using
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// the ISelDag to gen BPF code.
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bool BPFPassConfig::addInstSelector() {
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addPass(createBPFISelDag(getBPFTargetMachine()));
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return false;
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}
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void BPFPassConfig::addMachineSSAOptimization() {
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// The default implementation must be called first as we want eBPF
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// Peephole ran at last.
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TargetPassConfig::addMachineSSAOptimization();
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const BPFSubtarget *Subtarget = getBPFTargetMachine().getSubtargetImpl();
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if (Subtarget->getHasAlu32() && !DisableMIPeephole)
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addPass(createBPFMIPeepholePass());
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}
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