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963c5fad53
D34393 added MCCodePadder as an infrastructure for padding code with NOP instructions. It lacked tests and was not being worked on since then. Intel has now worked on an assembler patch to mitigate performance loss after applying microcode update for the Jump Conditional Code Erratum. https://www.intel.com/content/www/us/en/support/articles/000055650/processors.html This new patch shares similarity with MCCodePadder, but has a concrete use case in mind and is being actively developed. The infrastructure it introduces can potentially be used for general performance improvement via alignment. Delete the unused MCCodePadder so that people can develop the new feature from a clean state. Reviewed By: jyknight, skan Differential Revision: https://reviews.llvm.org/D71106
114 lines
4.0 KiB
C++
114 lines
4.0 KiB
C++
//===- MCAsmBackend.cpp - Target MC Assembly Backend ----------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/ADT/None.h"
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#include "llvm/ADT/STLExtras.h"
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#include "llvm/MC/MCELFObjectWriter.h"
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#include "llvm/MC/MCFixupKindInfo.h"
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#include "llvm/MC/MCMachObjectWriter.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/MC/MCWasmObjectWriter.h"
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#include "llvm/MC/MCWinCOFFObjectWriter.h"
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#include "llvm/MC/MCXCOFFObjectWriter.h"
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#include <cassert>
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#include <cstddef>
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#include <cstdint>
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using namespace llvm;
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MCAsmBackend::MCAsmBackend(support::endianness Endian) : Endian(Endian) {}
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MCAsmBackend::~MCAsmBackend() = default;
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std::unique_ptr<MCObjectWriter>
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MCAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
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auto TW = createObjectTargetWriter();
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switch (TW->getFormat()) {
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case Triple::ELF:
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return createELFObjectWriter(cast<MCELFObjectTargetWriter>(std::move(TW)), OS,
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Endian == support::little);
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case Triple::MachO:
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return createMachObjectWriter(cast<MCMachObjectTargetWriter>(std::move(TW)),
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OS, Endian == support::little);
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case Triple::COFF:
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return createWinCOFFObjectWriter(
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cast<MCWinCOFFObjectTargetWriter>(std::move(TW)), OS);
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case Triple::Wasm:
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return createWasmObjectWriter(cast<MCWasmObjectTargetWriter>(std::move(TW)),
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OS);
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case Triple::XCOFF:
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return createXCOFFObjectWriter(
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cast<MCXCOFFObjectTargetWriter>(std::move(TW)), OS);
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default:
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llvm_unreachable("unexpected object format");
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}
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}
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std::unique_ptr<MCObjectWriter>
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MCAsmBackend::createDwoObjectWriter(raw_pwrite_stream &OS,
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raw_pwrite_stream &DwoOS) const {
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auto TW = createObjectTargetWriter();
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if (TW->getFormat() != Triple::ELF)
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report_fatal_error("dwo only supported with ELF");
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return createELFDwoObjectWriter(cast<MCELFObjectTargetWriter>(std::move(TW)),
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OS, DwoOS, Endian == support::little);
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}
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Optional<MCFixupKind> MCAsmBackend::getFixupKind(StringRef Name) const {
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return None;
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}
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const MCFixupKindInfo &MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
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static const MCFixupKindInfo Builtins[] = {
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{"FK_NONE", 0, 0, 0},
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{"FK_Data_1", 0, 8, 0},
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{"FK_Data_2", 0, 16, 0},
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{"FK_Data_4", 0, 32, 0},
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{"FK_Data_8", 0, 64, 0},
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{"FK_Data_6b", 0, 6, 0},
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{"FK_PCRel_1", 0, 8, MCFixupKindInfo::FKF_IsPCRel},
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{"FK_PCRel_2", 0, 16, MCFixupKindInfo::FKF_IsPCRel},
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{"FK_PCRel_4", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
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{"FK_PCRel_8", 0, 64, MCFixupKindInfo::FKF_IsPCRel},
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{"FK_GPRel_1", 0, 8, 0},
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{"FK_GPRel_2", 0, 16, 0},
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{"FK_GPRel_4", 0, 32, 0},
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{"FK_GPRel_8", 0, 64, 0},
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{"FK_DTPRel_4", 0, 32, 0},
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{"FK_DTPRel_8", 0, 64, 0},
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{"FK_TPRel_4", 0, 32, 0},
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{"FK_TPRel_8", 0, 64, 0},
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{"FK_SecRel_1", 0, 8, 0},
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{"FK_SecRel_2", 0, 16, 0},
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{"FK_SecRel_4", 0, 32, 0},
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{"FK_SecRel_8", 0, 64, 0},
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{"FK_Data_Add_1", 0, 8, 0},
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{"FK_Data_Add_2", 0, 16, 0},
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{"FK_Data_Add_4", 0, 32, 0},
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{"FK_Data_Add_8", 0, 64, 0},
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{"FK_Data_Add_6b", 0, 6, 0},
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{"FK_Data_Sub_1", 0, 8, 0},
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{"FK_Data_Sub_2", 0, 16, 0},
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{"FK_Data_Sub_4", 0, 32, 0},
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{"FK_Data_Sub_8", 0, 64, 0},
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{"FK_Data_Sub_6b", 0, 6, 0}};
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assert((size_t)Kind <= array_lengthof(Builtins) && "Unknown fixup kind");
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return Builtins[Kind];
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}
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bool MCAsmBackend::fixupNeedsRelaxationAdvanced(
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const MCFixup &Fixup, bool Resolved, uint64_t Value,
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const MCRelaxableFragment *DF, const MCAsmLayout &Layout,
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const bool WasForced) const {
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if (!Resolved)
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return true;
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return fixupNeedsRelaxation(Fixup, Value, DF, Layout);
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}
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