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