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//===-------- PPCXCOFFStreamer.cpp - XCOFF Object Output ------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This is a custom MCXCOFFStreamer for PowerPC.
//
// The purpose of the custom XCOFF streamer is to allow us to intercept
// instructions as they are being emitted and align all 8 byte instructions
// to a 64 byte boundary if required (by adding a 4 byte nop). This is important
// because 8 byte instructions are not allowed to cross 64 byte boundaries
// and by aligning anything that is within 4 bytes of the boundary we can
// guarantee that the 8 byte instructions do not cross that boundary.
//
//===----------------------------------------------------------------------===//
#include "PPCXCOFFStreamer.h"
#include "PPCMCCodeEmitter.h"
#include "llvm/BinaryFormat/XCOFF.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCDirectives.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSectionXCOFF.h"
#include "llvm/MC/MCSymbolXCOFF.h"
#include "llvm/MC/TargetRegistry.h"
using namespace llvm;
PPCXCOFFStreamer::PPCXCOFFStreamer(MCContext &Context,
std::unique_ptr<MCAsmBackend> MAB,
std::unique_ptr<MCObjectWriter> OW,
std::unique_ptr<MCCodeEmitter> Emitter)
: MCXCOFFStreamer(Context, std::move(MAB), std::move(OW),
std::move(Emitter)) {}
void PPCXCOFFStreamer::emitPrefixedInstruction(const MCInst &Inst,
const MCSubtargetInfo &STI) {
// Prefixed instructions must not cross a 64-byte boundary (i.e. prefix is
// before the boundary and the remaining 4-bytes are after the boundary). In
// order to achieve this, a nop is added prior to any such boundary-crossing
// prefixed instruction. Align to 64 bytes if possible but add a maximum of 4
// bytes when trying to do that. If alignment requires adding more than 4
// bytes then the instruction won't be aligned.
emitCodeAlignment(Align(64), &STI, 4);
// Emit the instruction.
// Since the previous emit created a new fragment then adding this instruction
// also forces the addition of a new fragment. Inst is now the first
// instruction in that new fragment.
MCXCOFFStreamer::emitInstruction(Inst, STI);
}
void PPCXCOFFStreamer::emitInstruction(const MCInst &Inst,
const MCSubtargetInfo &STI) {
PPCMCCodeEmitter *Emitter =
static_cast<PPCMCCodeEmitter *>(getAssembler().getEmitterPtr());
// Special handling is only for prefixed instructions.
if (!Emitter->isPrefixedInstruction(Inst)) {
MCXCOFFStreamer::emitInstruction(Inst, STI);
return;
}
emitPrefixedInstruction(Inst, STI);
}
MCXCOFFStreamer *
llvm::createPPCXCOFFStreamer(MCContext &Context,
std::unique_ptr<MCAsmBackend> MAB,
std::unique_ptr<MCObjectWriter> OW,
std::unique_ptr<MCCodeEmitter> Emitter) {
return new PPCXCOFFStreamer(Context, std::move(MAB), std::move(OW),
std::move(Emitter));
}
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