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