forked from OSchip/llvm-project
79 lines
3.4 KiB
C++
79 lines
3.4 KiB
C++
//===-------- PPCXCOFFStreamer.cpp - XCOFF Object Output ------------------===//
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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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//
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// This is a custom MCXCOFFStreamer for PowerPC.
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//
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// The purpose of the custom XCOFF streamer is to allow us to intercept
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// instructions as they are being emitted and align all 8 byte instructions
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// to a 64 byte boundary if required (by adding a 4 byte nop). This is important
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// because 8 byte instructions are not allowed to cross 64 byte boundaries
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// and by aligning anything that is within 4 bytes of the boundary we can
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// guarantee that the 8 byte instructions do not cross that boundary.
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//
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//===----------------------------------------------------------------------===//
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#include "PPCXCOFFStreamer.h"
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#include "PPCMCCodeEmitter.h"
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#include "llvm/BinaryFormat/XCOFF.h"
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#include "llvm/MC/MCAsmBackend.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCCodeEmitter.h"
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#include "llvm/MC/MCDirectives.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/MC/MCSectionXCOFF.h"
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#include "llvm/MC/MCSymbolXCOFF.h"
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#include "llvm/MC/TargetRegistry.h"
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using namespace llvm;
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PPCXCOFFStreamer::PPCXCOFFStreamer(MCContext &Context,
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std::unique_ptr<MCAsmBackend> MAB,
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std::unique_ptr<MCObjectWriter> OW,
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std::unique_ptr<MCCodeEmitter> Emitter)
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: MCXCOFFStreamer(Context, std::move(MAB), std::move(OW),
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std::move(Emitter)) {}
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void PPCXCOFFStreamer::emitPrefixedInstruction(const MCInst &Inst,
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const MCSubtargetInfo &STI) {
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// Prefixed instructions must not cross a 64-byte boundary (i.e. prefix is
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// before the boundary and the remaining 4-bytes are after the boundary). In
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// order to achieve this, a nop is added prior to any such boundary-crossing
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// prefixed instruction. Align to 64 bytes if possible but add a maximum of 4
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// bytes when trying to do that. If alignment requires adding more than 4
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// bytes then the instruction won't be aligned.
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emitCodeAlignment(Align(64), &STI, 4);
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// Emit the instruction.
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// Since the previous emit created a new fragment then adding this instruction
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// also forces the addition of a new fragment. Inst is now the first
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// instruction in that new fragment.
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MCXCOFFStreamer::emitInstruction(Inst, STI);
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}
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void PPCXCOFFStreamer::emitInstruction(const MCInst &Inst,
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const MCSubtargetInfo &STI) {
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PPCMCCodeEmitter *Emitter =
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static_cast<PPCMCCodeEmitter *>(getAssembler().getEmitterPtr());
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// Special handling is only for prefixed instructions.
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if (!Emitter->isPrefixedInstruction(Inst)) {
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MCXCOFFStreamer::emitInstruction(Inst, STI);
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return;
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}
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emitPrefixedInstruction(Inst, STI);
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}
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MCXCOFFStreamer *
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llvm::createPPCXCOFFStreamer(MCContext &Context,
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std::unique_ptr<MCAsmBackend> MAB,
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std::unique_ptr<MCObjectWriter> OW,
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std::unique_ptr<MCCodeEmitter> Emitter) {
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return new PPCXCOFFStreamer(Context, std::move(MAB), std::move(OW),
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std::move(Emitter));
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}
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