1 files changed, 112 insertions, 0 deletions
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFStreamer.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFStreamer.cpp
new file mode 100644
index 0000000000000..4373778cc96cc
--- /dev/null
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFStreamer.cpp
@@ -0,0 +1,112 @@
+//===-------- PPCELFStreamer.cpp - ELF Object Output ---------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This is a custom MCELFStreamer for PowerPC.
+//
+// The purpose of the custom ELF 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 aliging anything that is within 4 bytes of the boundary we can
+// guarantee that the 8 byte instructions do not cross that boundary.
+//
+//===----------------------------------------------------------------------===//
+
+
+#include "PPCELFStreamer.h"
+#include "PPCInstrInfo.h"
+#include "PPCMCCodeEmitter.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/MC/MCAsmBackend.h"
+#include "llvm/MC/MCAssembler.h"
+#include "llvm/MC/MCCodeEmitter.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCInstrDesc.h"
+#include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCSymbolELF.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/SourceMgr.h"
+
+using namespace llvm;
+
+PPCELFStreamer::PPCELFStreamer(MCContext &Context,
+                               std::unique_ptr<MCAsmBackend> MAB,
+                               std::unique_ptr<MCObjectWriter> OW,
+                               std::unique_ptr<MCCodeEmitter> Emitter)
+    : MCELFStreamer(Context, std::move(MAB), std::move(OW),
+                    std::move(Emitter)), LastLabel(NULL) {
+}
+
+void PPCELFStreamer::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. When emitting a code alignment
+  // a new fragment is created for this alignment. This fragment will contain
+  // all of the nops required as part of the alignment operation. In the cases
+  // when no nops are added then The fragment is still created but it remains
+  // empty.
+  emitCodeAlignment(64, 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.
+  MCELFStreamer::emitInstruction(Inst, STI);
+
+  // The above instruction is forced to start a new fragment because it
+  // comes after a code alignment fragment. Get that new fragment.
+  MCFragment *InstructionFragment = getCurrentFragment();
+  SMLoc InstLoc = Inst.getLoc();
+  // Check if there was a last label emitted.
+  if (LastLabel && !LastLabel->isUnset() && LastLabelLoc.isValid() &&
+      InstLoc.isValid()) {
+    const SourceMgr *SourceManager = getContext().getSourceManager();
+    unsigned InstLine = SourceManager->FindLineNumber(InstLoc);
+    unsigned LabelLine = SourceManager->FindLineNumber(LastLabelLoc);
+    // If the Label and the Instruction are on the same line then move the
+    // label to the top of the fragment containing the aligned instruction that
+    // was just added.
+    if (InstLine == LabelLine) {
+      AssignFragment(LastLabel, InstructionFragment);
+      LastLabel->setOffset(0);
+    }
+  }
+}
+
+void PPCELFStreamer::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)) {
+    MCELFStreamer::emitInstruction(Inst, STI);
+    return;
+  }
+  emitPrefixedInstruction(Inst, STI);
+}
+
+void PPCELFStreamer::emitLabel(MCSymbol *Symbol, SMLoc Loc) {
+  LastLabel = Symbol;
+  LastLabelLoc = Loc;
+  MCELFStreamer::emitLabel(Symbol);
+}
+
+MCELFStreamer *llvm::createPPCELFStreamer(
+    MCContext &Context, std::unique_ptr<MCAsmBackend> MAB,
+    std::unique_ptr<MCObjectWriter> OW,
+    std::unique_ptr<MCCodeEmitter> Emitter) {
+  return new PPCELFStreamer(Context, std::move(MAB), std::move(OW),
+                            std::move(Emitter));
+}