lib/CodeGen/AsmPrinter/OcamlGCPrinter.cpp

   1 //===-- OcamlGCPrinter.cpp - Ocaml frametable emitter ---------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements printing the assembly code for an Ocaml frametable.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/CodeGen/GCs.h"
  15 #include "llvm/CodeGen/AsmPrinter.h"
  16 #include "llvm/CodeGen/GCMetadataPrinter.h"
  17 #include "llvm/Module.h"
  18 #include "llvm/MC/MCStreamer.h"
  19 #include "llvm/MC/MCAsmInfo.h"
  20 #include "llvm/Target/TargetData.h"
  21 #include "llvm/Target/TargetLoweringObjectFile.h"
  22 #include "llvm/Target/TargetMachine.h"
  23 #include "llvm/Support/Compiler.h"
  24 #include "llvm/Support/ErrorHandling.h"
  25 #include "llvm/Support/raw_ostream.h"
  26 using namespace llvm;
  27
  28 namespace {
  29
  30   class VISIBILITY_HIDDEN OcamlGCMetadataPrinter : public GCMetadataPrinter {
  31   public:
  32     void beginAssembly(raw_ostream &OS, AsmPrinter &AP,
  33                        const MCAsmInfo &MAI);
  34
  35     void finishAssembly(raw_ostream &OS, AsmPrinter &AP,
  36                         const MCAsmInfo &MAI);
  37   };
  38
  39 }
  40
  41 static GCMetadataPrinterRegistry::Add<OcamlGCMetadataPrinter>
  42 Y("ocaml", "ocaml 3.10-compatible collector");
  43
  44 void llvm::linkOcamlGCPrinter() { }
  45
  46 static void EmitCamlGlobal(const Module &M, raw_ostream &OS, AsmPrinter &AP,
  47                            const MCAsmInfo &MAI, const char *Id) {
  48   const std::string &MId = M.getModuleIdentifier();
  49
  50   std::string Mangled;
  51   Mangled += MAI.getGlobalPrefix();
  52   Mangled += "caml";
  53   size_t Letter = Mangled.size();
  54   Mangled.append(MId.begin(), std::find(MId.begin(), MId.end(), '.'));
  55   Mangled += "__";
  56   Mangled += Id;
  57
  58   // Capitalize the first letter of the module name.
  59   Mangled[Letter] = toupper(Mangled[Letter]);
  60
  61   if (const char *GlobalDirective = MAI.getGlobalDirective())
  62     OS << GlobalDirective << Mangled << "\n";
  63   OS << Mangled << ":\n";
  64 }
  65
  66 void OcamlGCMetadataPrinter::beginAssembly(raw_ostream &OS, AsmPrinter &AP,
  67                                            const MCAsmInfo &MAI) {
  68   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
  69   EmitCamlGlobal(getModule(), OS, AP, MAI, "code_begin");
  70
  71   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
  72   EmitCamlGlobal(getModule(), OS, AP, MAI, "data_begin");
  73 }
  74
  75 /// emitAssembly - Print the frametable. The ocaml frametable format is thus:
  76 ///
  77 ///   extern "C" struct align(sizeof(intptr_t)) {
  78 ///     uint16_t NumDescriptors;
  79 ///     struct align(sizeof(intptr_t)) {
  80 ///       void *ReturnAddress;
  81 ///       uint16_t FrameSize;
  82 ///       uint16_t NumLiveOffsets;
  83 ///       uint16_t LiveOffsets[NumLiveOffsets];
  84 ///     } Descriptors[NumDescriptors];
  85 ///   } caml${module}__frametable;
  86 ///
  87 /// Note that this precludes programs from stack frames larger than 64K
  88 /// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if
  89 /// either condition is detected in a function which uses the GC.
  90 ///
  91 void OcamlGCMetadataPrinter::finishAssembly(raw_ostream &OS, AsmPrinter &AP,
  92                                             const MCAsmInfo &MAI) {
  93   const char *AddressDirective;
  94   int AddressAlignLog;
  95   if (AP.TM.getTargetData()->getPointerSize() == sizeof(int32_t)) {
  96     AddressDirective = MAI.getData32bitsDirective();
  97     AddressAlignLog = 2;
  98   } else {
  99     AddressDirective = MAI.getData64bitsDirective();
 100     AddressAlignLog = 3;
 101   }
 102
 103   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
 104   EmitCamlGlobal(getModule(), OS, AP, MAI, "code_end");
 105
 106   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
 107   EmitCamlGlobal(getModule(), OS, AP, MAI, "data_end");
 108
 109   OS << AddressDirective << 0; // FIXME: Why does ocaml emit this??
 110   AP.EOL();
 111
 112   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
 113   EmitCamlGlobal(getModule(), OS, AP, MAI, "frametable");
 114
 115   for (iterator I = begin(), IE = end(); I != IE; ++I) {
 116     GCFunctionInfo &FI = **I;
 117
 118     uint64_t FrameSize = FI.getFrameSize();
 119     if (FrameSize >= 1<<16) {
 120       std::string msg;
 121       raw_string_ostream Msg(msg);
 122       Msg << "Function '" << FI.getFunction().getName()
 123            << "' is too large for the ocaml GC! "
 124            << "Frame size " << FrameSize << " >= 65536.\n";
 125       Msg << "(" << uintptr_t(&FI) << ")";
 126       llvm_report_error(Msg.str()); // Very rude!
 127     }
 128
 129     OS << "\t" << MAI.getCommentString() << " live roots for "
 130        << FI.getFunction().getName() << "\n";
 131
 132     for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) {
 133       size_t LiveCount = FI.live_size(J);
 134       if (LiveCount >= 1<<16) {
 135         std::string msg;
 136         raw_string_ostream Msg(msg);
 137         Msg << "Function '" << FI.getFunction().getName()
 138              << "' is too large for the ocaml GC! "
 139              << "Live root count " << LiveCount << " >= 65536.";
 140         llvm_report_error(Msg.str()); // Very rude!
 141       }
 142
 143       OS << AddressDirective
 144          << MAI.getPrivateGlobalPrefix() << "label" << J->Num;
 145       AP.EOL("call return address");
 146
 147       AP.EmitInt16(FrameSize);
 148       AP.EOL("stack frame size");
 149
 150       AP.EmitInt16(LiveCount);
 151       AP.EOL("live root count");
 152
 153       for (GCFunctionInfo::live_iterator K = FI.live_begin(J),
 154                                          KE = FI.live_end(J); K != KE; ++K) {
 155         assert(K->StackOffset < 1<<16 &&
 156                "GC root stack offset is outside of fixed stack frame and out "
 157                "of range for ocaml GC!");
 158
 159         OS << "\t.word\t" << K->StackOffset;
 160         AP.EOL("stack offset");
 161       }
 162
 163       AP.EmitAlignment(AddressAlignLog);
 164     }
 165   }
 166 }