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/ADT/SmallString.h" 16 #include "llvm/CodeGen/AsmPrinter.h" 17 #include "llvm/CodeGen/GCMetadataPrinter.h" 18 #include "llvm/IR/DataLayout.h" 19 #include "llvm/IR/Mangler.h" 20 #include "llvm/IR/Module.h" 21 #include "llvm/MC/MCAsmInfo.h" 22 #include "llvm/MC/MCContext.h" 23 #include "llvm/MC/MCStreamer.h" 24 #include "llvm/MC/MCSymbol.h" 25 #include "llvm/Support/ErrorHandling.h" 26 #include "llvm/Support/FormattedStream.h" 27 #include "llvm/Target/TargetLoweringObjectFile.h" 28 #include "llvm/Target/TargetMachine.h" 29 #include "llvm/Target/TargetSubtargetInfo.h" 30 #include <cctype> 31 using namespace llvm; 32 33 namespace { 34 35 class OcamlGCMetadataPrinter : public GCMetadataPrinter { 36 public: 37 void beginAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override; 38 void finishAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override; 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(Module &M, GCModuleInfo &Info, 70 AsmPrinter &AP) { 71 AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection()); 72 EmitCamlGlobal(M, AP, "code_begin"); 73 74 AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection()); 75 EmitCamlGlobal(M, AP, "data_begin"); 76 } 77 78 /// emitAssembly - Print the frametable. The ocaml frametable format is thus: 79 /// 80 /// extern "C" struct align(sizeof(intptr_t)) { 81 /// uint16_t NumDescriptors; 82 /// struct align(sizeof(intptr_t)) { 83 /// void *ReturnAddress; 84 /// uint16_t FrameSize; 85 /// uint16_t NumLiveOffsets; 86 /// uint16_t LiveOffsets[NumLiveOffsets]; 87 /// } Descriptors[NumDescriptors]; 88 /// } caml${module}__frametable; 89 /// 90 /// Note that this precludes programs from stack frames larger than 64K 91 /// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if 92 /// either condition is detected in a function which uses the GC. 93 /// 94 void OcamlGCMetadataPrinter::finishAssembly(Module &M, GCModuleInfo &Info, 95 AsmPrinter &AP) { 96 unsigned IntPtrSize = 97 AP.TM.getSubtargetImpl()->getDataLayout()->getPointerSize(); 98 99 AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getTextSection()); 100 EmitCamlGlobal(M, AP, "code_end"); 101 102 AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection()); 103 EmitCamlGlobal(M, AP, "data_end"); 104 105 // FIXME: Why does ocaml emit this?? 106 AP.OutStreamer.EmitIntValue(0, IntPtrSize); 107 108 AP.OutStreamer.SwitchSection(AP.getObjFileLowering().getDataSection()); 109 EmitCamlGlobal(M, AP, "frametable"); 110 111 int NumDescriptors = 0; 112 for (GCModuleInfo::FuncInfoVec::iterator I = Info.funcinfo_begin(), 113 IE = Info.funcinfo_end(); 114 I != IE; ++I) { 115 GCFunctionInfo &FI = **I; 116 if (FI.getStrategy().getName() != getStrategy().getName()) 117 // this function is managed by some other GC 118 continue; 119 for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) { 120 NumDescriptors++; 121 } 122 } 123 124 if (NumDescriptors >= 1 << 16) { 125 // Very rude! 126 report_fatal_error(" Too much descriptor for ocaml GC"); 127 } 128 AP.EmitInt16(NumDescriptors); 129 AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3); 130 131 for (GCModuleInfo::FuncInfoVec::iterator I = Info.funcinfo_begin(), 132 IE = Info.funcinfo_end(); 133 I != IE; ++I) { 134 GCFunctionInfo &FI = **I; 135 if (FI.getStrategy().getName() != getStrategy().getName()) 136 // this function is managed by some other GC 137 continue; 138 139 uint64_t FrameSize = FI.getFrameSize(); 140 if (FrameSize >= 1 << 16) { 141 // Very rude! 142 report_fatal_error("Function '" + FI.getFunction().getName() + 143 "' is too large for the ocaml GC! " 144 "Frame size " + 145 Twine(FrameSize) + ">= 65536.\n" 146 "(" + 147 Twine(uintptr_t(&FI)) + ")"); 148 } 149 150 AP.OutStreamer.AddComment("live roots for " + 151 Twine(FI.getFunction().getName())); 152 AP.OutStreamer.AddBlankLine(); 153 154 for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) { 155 size_t LiveCount = FI.live_size(J); 156 if (LiveCount >= 1 << 16) { 157 // Very rude! 158 report_fatal_error("Function '" + FI.getFunction().getName() + 159 "' is too large for the ocaml GC! " 160 "Live root count " + 161 Twine(LiveCount) + " >= 65536."); 162 } 163 164 AP.OutStreamer.EmitSymbolValue(J->Label, IntPtrSize); 165 AP.EmitInt16(FrameSize); 166 AP.EmitInt16(LiveCount); 167 168 for (GCFunctionInfo::live_iterator K = FI.live_begin(J), 169 KE = FI.live_end(J); 170 K != KE; ++K) { 171 if (K->StackOffset >= 1 << 16) { 172 // Very rude! 173 report_fatal_error( 174 "GC root stack offset is outside of fixed stack frame and out " 175 "of range for ocaml GC!"); 176 } 177 AP.EmitInt16(K->StackOffset); 178 } 179 180 AP.EmitAlignment(IntPtrSize == 4 ? 2 : 3); 181 } 182 } 183 } 184