1//===- OcamlGCPrinter.cpp - Ocaml frametable emitter ----------------------===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8// 9// This file implements printing the assembly code for an Ocaml frametable. 10// 11//===----------------------------------------------------------------------===// 12 13#include "llvm/ADT/STLExtras.h" 14#include "llvm/ADT/SmallString.h" 15#include "llvm/ADT/Twine.h" 16#include "llvm/CodeGen/AsmPrinter.h" 17#include "llvm/CodeGen/GCMetadata.h" 18#include "llvm/CodeGen/GCMetadataPrinter.h" 19#include "llvm/IR/BuiltinGCs.h" 20#include "llvm/IR/DataLayout.h" 21#include "llvm/IR/Function.h" 22#include "llvm/IR/Mangler.h" 23#include "llvm/IR/Module.h" 24#include "llvm/MC/MCContext.h" 25#include "llvm/MC/MCDirectives.h" 26#include "llvm/MC/MCStreamer.h" 27#include "llvm/Support/ErrorHandling.h" 28#include "llvm/Target/TargetLoweringObjectFile.h" 29#include <cctype> 30#include <cstddef> 31#include <cstdint> 32#include <string> 33 34using namespace llvm; 35 36namespace { 37 38class OcamlGCMetadataPrinter : public GCMetadataPrinter { 39public: 40 void beginAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override; 41 void finishAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) override; 42}; 43 44} // end anonymous namespace 45 46static GCMetadataPrinterRegistry::Add<OcamlGCMetadataPrinter> 47 Y("ocaml", "ocaml 3.10-compatible collector"); 48 49void llvm::linkOcamlGCPrinter() {} 50 51static void EmitCamlGlobal(const Module &M, AsmPrinter &AP, const char *Id) { 52 const std::string &MId = M.getModuleIdentifier(); 53 54 std::string SymName; 55 SymName += "caml"; 56 size_t Letter = SymName.size(); 57 SymName.append(MId.begin(), llvm::find(MId, '.')); 58 SymName += "__"; 59 SymName += Id; 60 61 // Capitalize the first letter of the module name. 62 SymName[Letter] = toupper(SymName[Letter]); 63 64 SmallString<128> TmpStr; 65 Mangler::getNameWithPrefix(TmpStr, SymName, M.getDataLayout()); 66 67 MCSymbol *Sym = AP.OutContext.getOrCreateSymbol(TmpStr); 68 69 AP.OutStreamer->emitSymbolAttribute(Sym, MCSA_Global); 70 AP.OutStreamer->emitLabel(Sym); 71} 72 73void OcamlGCMetadataPrinter::beginAssembly(Module &M, GCModuleInfo &Info, 74 AsmPrinter &AP) { 75 AP.OutStreamer->SwitchSection(AP.getObjFileLowering().getTextSection()); 76 EmitCamlGlobal(M, AP, "code_begin"); 77 78 AP.OutStreamer->SwitchSection(AP.getObjFileLowering().getDataSection()); 79 EmitCamlGlobal(M, AP, "data_begin"); 80} 81 82/// emitAssembly - Print the frametable. The ocaml frametable format is thus: 83/// 84/// extern "C" struct align(sizeof(intptr_t)) { 85/// uint16_t NumDescriptors; 86/// struct align(sizeof(intptr_t)) { 87/// void *ReturnAddress; 88/// uint16_t FrameSize; 89/// uint16_t NumLiveOffsets; 90/// uint16_t LiveOffsets[NumLiveOffsets]; 91/// } Descriptors[NumDescriptors]; 92/// } caml${module}__frametable; 93/// 94/// Note that this precludes programs from stack frames larger than 64K 95/// (FrameSize and LiveOffsets would overflow). FrameTablePrinter will abort if 96/// either condition is detected in a function which uses the GC. 97/// 98void OcamlGCMetadataPrinter::finishAssembly(Module &M, GCModuleInfo &Info, 99 AsmPrinter &AP) { 100 unsigned IntPtrSize = M.getDataLayout().getPointerSize(); 101 102 AP.OutStreamer->SwitchSection(AP.getObjFileLowering().getTextSection()); 103 EmitCamlGlobal(M, AP, "code_end"); 104 105 AP.OutStreamer->SwitchSection(AP.getObjFileLowering().getDataSection()); 106 EmitCamlGlobal(M, AP, "data_end"); 107 108 // FIXME: Why does ocaml emit this?? 109 AP.OutStreamer->emitIntValue(0, IntPtrSize); 110 111 AP.OutStreamer->SwitchSection(AP.getObjFileLowering().getDataSection()); 112 EmitCamlGlobal(M, AP, "frametable"); 113 114 int NumDescriptors = 0; 115 for (GCModuleInfo::FuncInfoVec::iterator I = Info.funcinfo_begin(), 116 IE = Info.funcinfo_end(); 117 I != IE; ++I) { 118 GCFunctionInfo &FI = **I; 119 if (FI.getStrategy().getName() != getStrategy().getName()) 120 // this function is managed by some other GC 121 continue; 122 for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) { 123 NumDescriptors++; 124 } 125 } 126 127 if (NumDescriptors >= 1 << 16) { 128 // Very rude! 129 report_fatal_error(" Too much descriptor for ocaml GC"); 130 } 131 AP.emitInt16(NumDescriptors); 132 AP.emitAlignment(IntPtrSize == 4 ? Align(4) : Align(8)); 133 134 for (GCModuleInfo::FuncInfoVec::iterator I = Info.funcinfo_begin(), 135 IE = Info.funcinfo_end(); 136 I != IE; ++I) { 137 GCFunctionInfo &FI = **I; 138 if (FI.getStrategy().getName() != getStrategy().getName()) 139 // this function is managed by some other GC 140 continue; 141 142 uint64_t FrameSize = FI.getFrameSize(); 143 if (FrameSize >= 1 << 16) { 144 // Very rude! 145 report_fatal_error("Function '" + FI.getFunction().getName() + 146 "' is too large for the ocaml GC! " 147 "Frame size " + 148 Twine(FrameSize) + 149 ">= 65536.\n" 150 "(" + 151 Twine(reinterpret_cast<uintptr_t>(&FI)) + ")"); 152 } 153 154 AP.OutStreamer->AddComment("live roots for " + 155 Twine(FI.getFunction().getName())); 156 AP.OutStreamer->AddBlankLine(); 157 158 for (GCFunctionInfo::iterator J = FI.begin(), JE = FI.end(); J != JE; ++J) { 159 size_t LiveCount = FI.live_size(J); 160 if (LiveCount >= 1 << 16) { 161 // Very rude! 162 report_fatal_error("Function '" + FI.getFunction().getName() + 163 "' is too large for the ocaml GC! " 164 "Live root count " + 165 Twine(LiveCount) + " >= 65536."); 166 } 167 168 AP.OutStreamer->emitSymbolValue(J->Label, IntPtrSize); 169 AP.emitInt16(FrameSize); 170 AP.emitInt16(LiveCount); 171 172 for (GCFunctionInfo::live_iterator K = FI.live_begin(J), 173 KE = FI.live_end(J); 174 K != KE; ++K) { 175 if (K->StackOffset >= 1 << 16) { 176 // Very rude! 177 report_fatal_error( 178 "GC root stack offset is outside of fixed stack frame and out " 179 "of range for ocaml GC!"); 180 } 181 AP.emitInt16(K->StackOffset); 182 } 183 184 AP.emitAlignment(IntPtrSize == 4 ? Align(4) : Align(8)); 185 } 186 } 187} 188