e63455d5e0
On some architectures such as Arm and X86 the encoding for a nop may change depending on the subtarget in operation at the time of encoding. This change replaces the per module MCSubtargetInfo retained by the targets AsmBackend in favour of passing through the local MCSubtargetInfo in operation at the time. On Arm using the architectural NOP instruction can have a performance benefit on some implementations. For Arm I've deleted the copy of the AsmBackend's MCSubtargetInfo to limit the chances of this causing problems in the future. I've not done this for other targets such as X86 as there is more frequent use of the MCSubtargetInfo and it looks to be for stable properties that we would not expect to vary per function. This change required threading STI through MCNopsFragment and MCBoundaryAlignFragment. I've attempted to take into account the in tree experimental backends. Differential Revision: https://reviews.llvm.org/D45962
78 lines
2.8 KiB
C++
78 lines
2.8 KiB
C++
//===-- ARMAsmBackend.h - ARM Assembler Backend -----------------*- C++ -*-===//
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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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#ifndef LLVM_LIB_TARGET_ARM_ARMASMBACKEND_H
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#define LLVM_LIB_TARGET_ARM_ARMASMBACKEND_H
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#include "MCTargetDesc/ARMFixupKinds.h"
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#include "MCTargetDesc/ARMMCTargetDesc.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCSubtargetInfo.h"
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#include "llvm/Support/TargetRegistry.h"
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namespace llvm {
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class ARMAsmBackend : public MCAsmBackend {
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bool isThumbMode; // Currently emitting Thumb code.
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public:
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ARMAsmBackend(const Target &T, bool isThumb, support::endianness Endian)
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: MCAsmBackend(Endian), isThumbMode(isThumb) {}
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unsigned getNumFixupKinds() const override {
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return ARM::NumTargetFixupKinds;
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}
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bool hasNOP(const MCSubtargetInfo *STI) const {
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return STI->getFeatureBits()[ARM::HasV6T2Ops];
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}
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Optional<MCFixupKind> getFixupKind(StringRef Name) const override;
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const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
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bool shouldForceRelocation(const MCAssembler &Asm, const MCFixup &Fixup,
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const MCValue &Target) override;
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unsigned adjustFixupValue(const MCAssembler &Asm, const MCFixup &Fixup,
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const MCValue &Target, uint64_t Value,
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bool IsResolved, MCContext &Ctx,
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const MCSubtargetInfo *STI) const;
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void applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
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const MCValue &Target, MutableArrayRef<char> Data,
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uint64_t Value, bool IsResolved,
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const MCSubtargetInfo *STI) const override;
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unsigned getRelaxedOpcode(unsigned Op, const MCSubtargetInfo &STI) const;
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bool mayNeedRelaxation(const MCInst &Inst,
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const MCSubtargetInfo &STI) const override;
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const char *reasonForFixupRelaxation(const MCFixup &Fixup,
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uint64_t Value) const;
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bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
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const MCRelaxableFragment *DF,
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const MCAsmLayout &Layout) const override;
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void relaxInstruction(MCInst &Inst,
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const MCSubtargetInfo &STI) const override;
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bool writeNopData(raw_ostream &OS, uint64_t Count,
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const MCSubtargetInfo *STI) const override;
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void handleAssemblerFlag(MCAssemblerFlag Flag) override;
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unsigned getPointerSize() const { return 4; }
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bool isThumb() const { return isThumbMode; }
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void setIsThumb(bool it) { isThumbMode = it; }
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};
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} // end namespace llvm
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#endif
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