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/MCAsmInfo.h"
  19 #include "llvm/MC/MCContext.h"
  20 #include "llvm/MC/MCSymbol.h"
  21 #include "llvm/MC/MCStreamer.h"
  22 #include "llvm/Target/Mangler.h"
  23 #include "llvm/Target/TargetData.h"
  24 #include "llvm/Target/TargetLoweringObjectFile.h"
  25 #include "llvm/Target/TargetMachine.h"
  26 #include "llvm/ADT/SmallString.h"
  27 #include "llvm/Support/ErrorHandling.h"
  28 #include "llvm/Support/FormattedStream.h"
  29 #include <cctype>
  30 using namespace llvm;
  31
  32 namespace {
  33
  34   class OcamlGCMetadataPrinter : public GCMetadataPrinter {
  35   public:
  36     void beginAssembly(AsmPrinter &AP);
  37     void finishAssembly(AsmPrinter &AP);
  38   };
  39
  40 }
  41
  42 static GCMetadataPrinterRegistry::Add<OcamlGCMetadataPrinter>
  43 Y("ocaml", "ocaml 3.10-compatible collector");
  44
  45 void llvm::linkOcamlGCPrinter() { }
  46
  47 static void EmitCamlGlobal(const Module &M, AsmPrinter &AP, const char *Id) {
  48   const std::string &MId = M.getModuleIdentifier();
  49
  50   std::string SymName;
  51   SymName += "caml";
  52   size_t Letter = SymName.size();
  53   SymName.append(MId.begin(), std::find(MId.begin(), MId.end(), '.'));
  54   SymName += "__";
  55   SymName += Id;
  56
  57   // Capitalize the first letter of the module name.
  58   SymName[Letter] = toupper(SymName[Letter]);
  59
  60   SmallString<128> TmpStr;
  61   AP.Mang->getNameWithPrefix(TmpStr, SymName);
  62
  63   MCSymbol *Sym = AP.OutContext.GetOrCreateSymbol(TmpStr);
  64
  65   AP.OutStreamer.EmitSymbolAttribute(Sym, MCSA_Global);
  66   AP.OutStreamer.EmitLabel(Sym);
  67 }
  68
  69 void OcamlGCMetadataPrinter::beginAssembly(AsmPrinter &AP) {
  70   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
  71   EmitCamlGlobal(getModule(), AP, "code_begin");
  72
  73   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
  74   EmitCamlGlobal(getModule(), AP, "data_begin");
  75 }
  76
  77 /// emitAssembly - Print the frametable. The ocaml frametable format is thus:
  78 ///
  79 ///   extern "C" struct align(sizeof(intptr_t)) {
  80 ///     uint16_t NumDescriptors;
  81 ///     struct align(sizeof(intptr_t)) {
  82 ///       void *ReturnAddress;
  83 ///       uint16_t FrameSize;
  84 ///       uint16_t NumLiveOffsets;
  85 ///       uint16_t LiveOffsets[NumLiveOffsets];
  86 ///     } Descriptors[NumDescriptors];
  87 ///   } caml${module}__frametable;
  88 ///
  89 /// Note that this precludes programs from stack frames larger than 64K
  90 /// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if
  91 /// either condition is detected in a function which uses the GC.
  92 ///
  93 void OcamlGCMetadataPrinter::finishAssembly(AsmPrinter &AP) {
  94   unsigned IntPtrSize = AP.TM.getTargetData()->getPointerSize();
  95
  96   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection());
  97   EmitCamlGlobal(getModule(), AP, "code_end");
  98
  99   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
 100   EmitCamlGlobal(getModule(), AP, "data_end");
 101
 102   // FIXME: Why does ocaml emit this??
 103   AP.OutStreamer.EmitIntValue(0, IntPtrSize, 0);
 104
 105   AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection());
 106   EmitCamlGlobal(getModule(), AP, "frametable");
 107
 108   int NumDescriptors = 0;
 109   for (iterator I = begin(), IE = end(); I != IE; ++I) {
 110     GCFunctionInfo &FI = **I;
 111     for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) {
 112       NumDescriptors++;
 113     }
 114   }
 115
 116   if (NumDescriptors >= 1<<16) {
 117     // Very rude!
 118     report_fatal_error(" Too much descriptor for ocaml GC");
 119   }
 120   AP.EmitInt16(NumDescriptors);
 121   AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);
 122
 123   for (iterator I = begin(), IE = end(); I != IE; ++I) {
 124     GCFunctionInfo &FI = **I;
 125
 126     uint64_t FrameSize = FI.getFrameSize();
 127     if (FrameSize >= 1<<16) {
 128       // Very rude!
 129       report_fatal_error("Function '" + FI.getFunction().getName() +
 130                          "' is too large for the ocaml GC! "
 131                          "Frame size " + Twine(FrameSize) + ">= 65536.\n"
 132                          "(" + Twine(uintptr_t(&FI)) + ")");
 133     }
 134
 135     AP.OutStreamer.AddComment("live roots for " +
 136                               Twine(FI.getFunction().getName()));
 137     AP.OutStreamer.AddBlankLine();
 138
 139     for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) {
 140       size_t LiveCount = FI.live_size(J);
 141       if (LiveCount >= 1<<16) {
 142         // Very rude!
 143         report_fatal_error("Function '" + FI.getFunction().getName() +
 144                            "' is too large for the ocaml GC! "
 145                            "Live root count "+Twine(LiveCount)+" >= 65536.");
 146       }
 147
 148       AP.OutStreamer.EmitSymbolValue(J->Label, IntPtrSize, 0);
 149       AP.EmitInt16(FrameSize);
 150       AP.EmitInt16(LiveCount);
 151
 152       for (GCFunctionInfo::live_iterator K = FI.live_begin(J),
 153                                          KE = FI.live_end(J); K != KE; ++K) {
 154         if (K->StackOffset >= 1<<16) {
 155           // Very rude!
 156           report_fatal_error(
 157                  "GC root stack offset is outside of fixed stack frame and out "
 158                  "of range for ocaml GC!");
 159         }
 160         AP.EmitInt16(K->StackOffset);
 161       }
 162
 163       AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3);
 164     }
 165   }
 166 }