C++ AsmPrinter::EmitInt32方法代码示例

/// emitAssembly - Print the frametable. The ocaml frametable format is thus:
///
///   extern "C" struct align(sizeof(intptr_t)) {
///     uint16_t NumDescriptors;
///     struct align(sizeof(intptr_t)) {
///       void *ReturnAddress;
///       uint16_t FrameSize;
///       uint16_t NumLiveOffsets;
///       uint16_t LiveOffsets[NumLiveOffsets];
///     } Descriptors[NumDescriptors];
///   } caml${module}__frametable;
///
/// Note that this precludes programs from stack frames larger than 64K
/// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if
/// either condition is detected in a function which uses the GC.
///
void OcamlGCMetadataPrinter::finishAssembly(AsmPrinter &AP) {
  unsigned IntPtrSize = AP.TM.getTargetData()->getPointerSize();

  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
  EmitCamlGlobal(getModule(), AP, "code_end");

  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
  EmitCamlGlobal(getModule(), AP, "data_end");

  // FIXME: Why does ocaml emit this??
  AP.OutStreamer.EmitIntValue(0, IntPtrSize, 0);

  AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
  EmitCamlGlobal(getModule(), AP, "frametable");

  for (iterator I = begin(), IE = end(); I != IE; ++I) {
    GCFunctionInfo &FI = **I;

    uint64_t FrameSize = FI.getFrameSize();
    if (FrameSize >= 1<<16) {
      // Very rude!
      report_fatal_error("Function '" + FI.getFunction().getName() +
                         "' is too large for the ocaml GC! "
                         "Frame size " + Twine(FrameSize) + ">= 65536.\n"
                         "(" + Twine(uintptr_t(&FI)) + ")");
    }

    AP.OutStreamer.AddComment("live roots for " +
                              Twine(FI.getFunction().getName()));
    AP.OutStreamer.AddBlankLine();

    for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) {
      size_t LiveCount = FI.live_size(J);
      if (LiveCount >= 1<<16) {
        // Very rude!
        report_fatal_error("Function '" + FI.getFunction().getName() +
                           "' is too large for the ocaml GC! "
                           "Live root count "+Twine(LiveCount)+" >= 65536.");
      }

      AP.OutStreamer.EmitSymbolValue(J->Label, IntPtrSize, 0);
      AP.EmitInt16(FrameSize);
      AP.EmitInt16(LiveCount);

      for (GCFunctionInfo::live_iterator K = FI.live_begin(J),
                                         KE = FI.live_end(J); K != KE; ++K) {
        assert(K->StackOffset < 1<<16 &&
               "GC root stack offset is outside of fixed stack frame and out "
               "of range for ocaml GC!");

        AP.EmitInt32(K->StackOffset);
      }

      AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);
    }
  }
}

void RgcPrinter::finishAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) {
    MCStreamer &OS = AP.OutStreamer;
    unsigned IntPtrSize = AP.TM.getSubtargetImpl()->getDataLayout()->getPointerSize();

    // Put this in the data section.
    OS.SwitchSection(AP.getObjFileLowering().getDataSection());

    // For each function...
    for (GCModuleInfo::FuncInfoVec::iterator FI = Info.funcinfo_begin(),
            FE = Info.funcinfo_end(); FI != FE; ++FI) {
        GCFunctionInfo &MD = **FI;

        // A compact GC layout. Emit this data structure:
        //
        // struct {
        //   int32_t PointCount;
        //   void *SafePointAddress[PointCount];
        //   int32_t StackFrameSize; // in words
        //   int32_t StackArity;
        //   int32_t LiveCount;
        //   int32_t LiveOffsets[LiveCount];
        // } __gcmap_<FUNCTIONNAME>;

        // Align to address width.
        // AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);

        // Emit PointCount.
        OS.AddComment("safe point count");
        AP.EmitInt32(MD.size());

        // And each safe point...
        for (GCFunctionInfo::iterator PI = MD.begin(),
                PE = MD.end(); PI != PE; ++PI) {
            // Emit the address of the safe point.
            OS.AddComment("safe point address");
            MCSymbol *Label = PI->Label;
            AP.EmitLabelPlusOffset(Label/*Hi*/, 0/*Offset*/, 4/*Size*/);
        }

        // Stack information never change in safe points! Only print info from the
        // first call-site.
        GCFunctionInfo::iterator PI = MD.begin();

        // Emit the stack frame size.
        OS.AddComment("stack frame size (in words)");
        AP.EmitInt32(MD.getFrameSize() / IntPtrSize);

        // Emit stack arity, i.e. the number of stacked arguments.
        unsigned RegisteredArgs = IntPtrSize == 4 ? 5 : 6;
        unsigned StackArity = MD.getFunction().arg_size() > RegisteredArgs ?
                              MD.getFunction().arg_size() - RegisteredArgs : 0;
        OS.AddComment("stack arity");
        AP.EmitInt32(StackArity);

        // Emit the number of live roots in the function.
        OS.AddComment("live root count");
        AP.EmitInt32(MD.live_size(PI));

        // And for each live root...
        for (GCFunctionInfo::live_iterator LI = MD.live_begin(PI),
                LE = MD.live_end(PI);
                LI != LE; ++LI) {
            // Emit live root's offset within the stack frame.
            OS.AddComment("stack index (offset / wordsize)");
            AP.EmitInt32(LI->StackOffset);
        }
    }
}